TACTICAL MULTISENSOR RECONNAISSANCE VOL. 5 SYSTEM CONCEPT
Document Type:
Collection:
Document Number (FOIA) /ESDN (CREST):
CIA-RDP67B00657R000300220001-3
Release Decision:
RIFPUB
Original Classification:
K
Document Page Count:
274
Document Creation Date:
December 22, 2016
Document Release Date:
July 8, 2009
Sequence Number:
1
Case Number:
Publication Date:
June 15, 1965
Content Type:
REPORT
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845 2-65-43
TM-65- 5
COPY NO. I
TACTICAL MULTISENSOR
RECONNAISSANCE
VOL. 5
SYSTEM CONCEPT
15 JUNE, 1965
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Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
1. Synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
2. Engineering Summary . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.1 Mission Analysis and Performance Requirements. . . . . . . . . 2-2
2.2 Sensor Integration . . . . . . . . . . . . . . . . . . . . . . 2-13
2.3 Optimized Multisensor System Utilizing Keying. . . . . . . . . 2-18
2.4 Typical Sensors and their Parameters . . . . . . . . . . . . . 2-24
2.5 Observer . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24
2.6 Photography . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25
2.7 Infrared . . . . . . . . . . . . . . . . . . . . . . . . . 2-28
2.8 High Resolution Side Looking Radar . . . . . . . . . . . . . . 2-29
2.9 ELINT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-30
2.10 Key System . . . . . . . . . . . . . . . . . . . . . . . . . . 2-31
2.11 Display System . . . . . . . . . . . . . . . . . . . . . . . . 2-32
2.12 Data Management . . . . . . . . . . . . . . . . . . . . . . . . 2-33
2.13 Data Preparation . . . . . . . . . . . . . . . . . . . . . . . 2-33
2.14 Priority.Analysis . . . . . . . . . . . . . . . . . . . . . . . 2-34
2.15 Mission Analysis . . . . . . . . . . . . . . . . . . . . . . . 2-35
2.16 Viewing System . . . ... . . . . . . . . . . . . . . . . . . . 2-36
2.17 Data Storage and Retrieval . . . . . . . . . . . . . . . . . . 2-37
2.18 Mission Materials . . . . . . . . . . . . . . . . . . . . . . . 2-37
4. Optimized Multisensor System . . . . . . . . . . . . . . . . . . . . 4-1
4.1 Target Data Gathering Requirements . . . . . . . . . . . . . . 4-1
4.2 Sensor Operating Characteristics . . . . . . . . . . . . . . . 4-16
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CONTENTS (Continued)
4.3 Sensor Operating Procedures . . . . . . . . . . . . . . . . . . 4-106
4.4 Observer Display and Control Operations. . . . . . . . . . . . 4-117
4.5 Airborne Data Processing . . . . . . . . . . . . . . . . . . . 4-134
4.6 Data Links . . . . . . . . . . . . . . . . . . . . . . . . . . 4-142
4.7 Data Management . . . . . . . . . . . . . . . . . . . . . . . . 4-183
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2-1. Time Response Cycle . . . . . . . . . . . . . . . . . . . . . . . 2-4
2-2. Target Class Distribution in Parameter Space . . . . . . . . . . 2-9
2-3. Imaging Sensors . . . . . . . . . . . . . . . . . . . . . . . . . 2-12
2-4. Sensor Capabilities . . . . . . . . . . . . . . . . . . . . . . . 2-14
2-5. Airborne System Concept . . . . . . . . . . . . . . . . . . . . . 2-19
4-1. Solar Horizontal Plane Illuminance as a Function of Solar
Altitude in Average Clear Weather . . . . . . . . . . . . . . . . 4-3
4-2. Constant Solar Horizontal Plane Illuminance as a Function of
North Latitude and Time of Year (time: local apparent noon) . . 4-4
4-3. Constant Solar Horizontal Plane Illuminance as a Function of
North Latitude and Time of Year (time: local apparent noon
?2 hours) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
4-4. Constant Solar Horizontal Plane Illuminance as a Function of
North Latitude and Time of Year (time: local apparent noon
?5 hours) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
4-5. Reflected Radiation Useful for Near Visual UV and IR
Photography as Restricted by Atmospheric Absorbtion. . . . . . . 4-7
4-5(a). Plot of Soviet Radar over 2500 to 6000 Megacycle Frequency
Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
4-6. Typical Survivability vs Operating Altitudes for High
Performance Aircraft Tactical Reconnaissance . . . . . . . . . 4-17
4-7. Frame/Strip Camera - 44 mm EFL, 5" Sq. Format (vertical)
(1 permanent) (2 optional) . . . . . . . . . . . . . . . . . 4-21
4-8. Frame Camera - 3-6" EFL, 5" Sq. Format (side oblique). . . . . . 4-23
4-9. Panoramic Camera - 3" EFL, 70 mm or 5" Format (vertical) . . . . 4-25
4-10. Frame or Panoramic - Constant Scale Pan 2" - 4" EFL, 70 mm
Format (forward oblique) . . . . . . . . . . . . . . . . . . . . 4-27
4-11. Urban Area - Black and White Print . . . . . . . . . . . . . . . 4-29
4-12. Urban Area - SO-121 Color Film . . . . . . . . . . . . . . . . . 4-30
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FIGURES (Continued)
4-13. Urban Area - Additive Color from Black and White Negatives . . 4-31
4-14. Urban Area - Additive Color Camouflage Detection from Black
and White Negatives . . . . . . . . . . . . . . . . . . . . . . . 4-33
4-15. Forest Area - Black and White Print . . . . . . . . . . . . . . . 4-34
4-16. Forest Area - S0-121 Color Film . . . . . . . . . . . . . . . . . 4-35
4-17. Forest Area - Camouflage Detection Film . . . . . . . . . . . . . 4-35a
4-18. Constant Scale Pan - 6-12" EFL, 70 mm Format Vertical
(high-med altitude) . . . . . . . . . . . . . . . . . . . . . . . 4-36
4-19. Panoramic - 24" EFL, 5" Format, Vertical (high alt.) . . . . . . 4-38
4-19(a) Example Mounting for IR Panoramic Sensor . . . . . . . . . . . . 4-41
4-20. Infrared Scanner Optical Configuration . . . . . . . . . . . . . 4-44
4-21. Signal Channel Block Diagram . . . . . . . . . . . . . . . . . . 4-46
4-22. Airborne Signal Processing Block Diagram . . . . . . . . . . . . 4-50
4-22(a) Idealized Video Waveform (end of mirror scan). . . . . . . . . . 4-51
4-23. Carrier Based Data Processing . . . . . . . . . . . . . . . . . 4-55
4-24. Interconnection Between Requirements and System Parameters for
a Synthetic Arrary Radar . . . . . . . . . . . . . . . . . . . . 4-59
4-25. Parameter Derivation Flow Chart Synthetic Array Radar Imagery. . 4-61
4-26. Possible Radar Sensor Subsystems . . . . . . . . . . . . . . . . 4-64
4-27. Radar Unit Block Diagram . . . . . . . . . . . . . . . . . . . . 4-65
4-28. Dual Channel Airborne Recorder . . . . . . . . . . . . . . . . . 4-66
4-29. Range Coverage . . . . . . . . . . . . . . . . . . . . . . . . . 4-74
4-30. Segmented Recording. . . . . . . . . . . . . . . . . . . . . . . 4-76
4-31. Total Range Swath per 100 Pounds of Recorder . . . . . . . . . . 4-78
4-32. Real Time Storage Tube MTI Processor . . . . . . . . . . . . . . 4-79
4-33. Real Time Storage Belt Processor . . . . . . . . . . . . . . . . 4-83
4-34. System Weight for Different Configurations . . . . . . . . . . . 4-84
4-35. ELINT Subsystem Block Diagram . . . . . . . . . . . . . . . . . 4-91
4-36. Basic Receiver Electronics . . . . . . . . . . . . . . . . . 4-93
4-37. Range Accuracy as a Function of Time and Azimuth . . . . . . . . 4-96
4-38. Forward-Looking Monopulse Antenna (multi-mode spiral). . . . . . 4-98
4-39. Projected 4) - 0 Grid . . . . . . . . . . . . . . . . . . . . . . 4-99
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FIGURES (Continued)
4-40. Coverage Diagram of DF Systems . . . . . . . . . . . . . . . . . 4-101
4-41. Multisensor Components Fields of View . . . . . . . . . . . . . 4-107
4-42. ELINT Situation Display . . . . . . . . . . . . . . . . . . . . . 4-125
4-43. Sensor Coverage Areas (500 feet altitude). . . . . . . . . . . . 4-128
4-44. Airborne System Concept . . . . . . . . . . . . . . . . . . . . 4-139
4-45. Data Processing Flow Diagram . . . . . . . . . . . . . . . . . . 4-141
4-45(a) Conceptual Data Link . . . . . . . . . . . . . . . . . . . . . . 4-144
4-46. Imagery Sensor Resolution . . . . . . . . . . . . . . . . . . . . 4-148
4-47. Commercial TV Frequency Spectra . . . . . . . . . . . . . . . . . 4-155
4-48. Estimated Spectra of the HRSLR Sensor . . . . . . . . . . . . . . 4-156
4-49. Estimated S/N in a KC Band South Vietnam - March, 1965 . . . . . 4-161
4-50. Multiplexing - Modulation Technique (straight-forward analogue). 4-171
4-51. Multiplexing - Modulation Technique (multiple RF carriers) . . . 4-171
4-52. Multiplexing - Modulation Technique (straight-forward digital) 4-172
4-53. Multiplexing - Modulation Technique (hybrid analogue-digital). 4-172
4-54. Multiplexing - Modulation Technique (multiple digital
transmitters) . . . . . . . . . . . . . . . . . . . . . . . . . . 4-173
4-55. Detailed Breakdown of Signal Flow in the Reconnaissance Center . 4-187
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2-1. Targets and Data . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2-2. Information Requirements with Respect to Targets. . . . . . . . . 2-7
2-3. Report Time and Resolution for Various Target Types . . . . . . . 2-8
4-1. ELINT Input Data Requirements . . . . . . . . . . . . . . . . . . 4-15
4-2. Example Scanner Parameters . . . . . . . . . . . . . . . . . . . . 4-43
4-3. Weight Estimates - Airborne Data Processing Equipment . . . . . . 4-49
4-4. Comparison of Radar Characteristics . . . . . . . . . . . . . . . 4-69
4-5. Weight Estimates for "A" Design . . . . . . . . . . . . . . . . . 4-72
4-6. Weights for Storage Tube Processor . . . . . . . . . . . . . . . 4-81
4-7. Weights for Storage Belt Processor . . . . . . . . . . . . . . . 4-81
4-8. Receiver Characteristics . . . . . . . . . . . . . . . . . . . . . 4-94
4-9. Typical Miniature Aerospace General Purpose Computers
(December 1964) . . . . . . . . . . . . . . . . . . . . . . . . . 4-103
4-10. Miniature Airborne Computer - Typical Characteristics . . . . . . 4-105
4-11. System Resolution versus Data Link Resolution . . . . . . . . . . 4-153
4-12. Summary: Wide Band Link Parameters . . . . . . . . . . . . . . . 4-157
4-13. Digital Data Format . . . . . . . . . . . . . . . . . . . . . . . 4-159
4-14. Wideband Link Characteristics Summary . . . . . . . . . . . . . . 4-163
4-15. Signal Power at Receiver, PR, for Three Frequency Bands . . . . . 4-166
4-16. Receiver Noise Temperatures for Three Frequency Bands . . . . . . 4-167
4-17. Resulting Receiver S/N Ratios Three Frequency Bands . . . . . . . 4-168
4-18. Transmitted Power Required - Modulation System B-1. . . . . . . . 4-177
4-19. Transmitted Power Required - Modulation System B-2. . . . . . . . 4-177
4-20. Transmitted Power Required - Modulation System B-3. . . . . . . . 4-179
4-21. Transmitted Power Required - Modulation System B-3 (PCM/M'FSK). . 4-179
4-22. Typical Operational Characteristics of Disc Storage Systems . . . 4-205
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The multisensor system which is conceptually delineated here is based on
the cooperative effort of the technical specialists from each sensor area.
Sensors treated were photography - by Itek Corporation; infrared (IR) -
by Baird Atomic; high resolution side looking radar (HRSLR) - by Conductron,
Inc.; and electronic intelligence (ELINT) - by Airborne Instruments Laboratory,
with Itek Corporation managing the overall multisensor system effort.
In considering the optimization of the system for minimum interpretation
time, the following two factors were paramount in the study.
1. Simplicity - For an operational, combat system, it is recognized that
only the essential tools will be fully utilized by men under extreme pressure.
2. Man/Machine Relations - In a fast moving and changing environment,
man's limited ability to deal with vast amounts of simultaneous data is recog-
nized, and the system has been conceived to utilize to the fullest the data
handling capability at the man/machine interface by using automatic systems to
preselect information and bring to the man a volume of data which can be handled
quickly to produce effective timely decisions.
The optimized multisensor system which is presented has been purposely
divorced from existing systems and vehicles, and is based on parallel studies
of the basic elements on which system requirements are founded. The sensor
technology is current capability suitable for prototype hardware by 1967, and
does not represent nebulous advances in the state-of-the-art. Some of the
systems concepts are new, but they utilize available components, ingeniously
combined to enhance the utilization of the multisensor system.
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The multisensor system has resulted in the compilation of six documents,
which are as follows:
Volume 1 - Naval Doctrine
Volume 2 - Target Characteristics
Volume 3 - System Characteristics
Volume 4 - Technology Survey
Volume 5 - System Concept
Volume 6 - Summary
The next section is a summary of the information presented in Volume 5 -
System Concept.
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The multisensor system conceived in this study combines a small number of
unusual state-of-the-art sensors to arrive at the airborne equipment complement,
and adds a wideband data link for real-time relay of selected information.
Photographic Data is considered as the prime record, since it produces high
resolution imagery having the highest information content.
The aircraft systems will produce prime records, and transmit secondary
records. Thus, redundant records will be generated to cover two possibilities:
first, the need for image information prior to the return of the aircraft;
second, to provide image information should the aircraft be lost or the records
damaged in combat.
The system will provide adaptive analysis by keying all records with a
locator to indicate the detection of an active or potential target as auto-
matically determined from the SLR, ELINT and IR sensors or the observer.
A real-time electro-optical operator display is provided which presents
keyed, geographically located, probable targets and moving targets on an up-to-
date Order of Battle representation.
The operator display will be designed to utilize the 4 to 5 bit per second
visual data rate of man, but it will also have a IR image mode for navigation,
and night reconnaissance.
A simultaneous wideband and narrowband data link are suggested to relay
information to the analysis center. For real-time analysis, the same display as
is in the aircraft is considered proper, so that areas of high interest can be
set up for detailed analysis of the prime records. The wideband link, perhaps
requiring a relay system, could provide real-time IR imaging, SLR imagery and
ELINT locators for those target systems with very short timeliness requirements.
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The records, prime or secondary, will be analyzed using the keys to
correlate the areas of high target probability. A viewer which has available
on call all the image records, and displays only two major and two historical
records is recommended to best utilize the interpreters' viewing capability.
The record handling system is designed to use machine aids wherever
possible, but is configured for manual operation in an emergency.
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The derivation of a system usually a complex compromise, based on the
operational and design tradeoffs which have to be made. The simplest and most
reliable designs will result when there is a thorough understanding of the
purpose for which the system is ultimately to be used. Unless there is a deep
appreciation of the user's problems, and the system technology, it is difficult
for the design to evolve into a useful system.
In designing a tactical multisensor reconnaissance system, such as is
presented in this study, an attempt was made to gain such an understanding and
to apply the knowledge obtained to the derivation of the system. This has led
to a philosophy of design which stresses the use of automatic equipment to
accomplish functions which are beyond the data rate capabilities of man, but
which take full advantage of man's subjective capabilities to recognize patterns,
evaluate situations, make decisions, and to take responsive action.
The system, however, retains the use of manual modes to backup automatic
equipment, of course, accepting the performance reduction thus caused. The
concept provides for simple designs, and for the incorporation of redundant
records and flow paths throughout the system. The flexibility thus introduced
also provides for a priority intelligence path to speed up the processing of
vital real time data.
During the study, only the design concept has been prepared, using hardware
examples to provide explanations for some of the system arrangements.
Before examining the capabilities of the sensors and data processing
systems, it is necessary to evaluate the needs and priorities of the intelligence
cycle of tactical multisensor reconnaissance.
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2.1 MISSION ANALYSIS AND PERFORMANCE REQUIREMENTS
An optimized tactical multisensor reconnaissance system is conceived by
first developing a set of performance requirements. These, _in turn, are derived
from the operational requirements arising out of the basic reconnaissance
mission(s). This discussion will therefore begin with an analysis of the
intelligence objectives pertinent to the full range of tactical situations,
then proceed to a specification of the physical data that must be reported to
the air intelligence officer, and conclude with technical performance require-
ments on the sensors and means of communication. A comparison is made between
these requirements and the performance obtainable by conservative extrapolation
of current state of the art to a time not later than mid-1967. This comparison
yields an optimum choice of the sensors to perform each of the defined recon-
naissance functions, and leads to a requirement for mutual reinforcement of the
data output, especially between image and non-image classes of data. Sensors
considered for this task are visual (observer), photographic (,cameras) infrared
(IR), high resolution side looking radar (HRSLR), and electronic intelligence.
The tactical environments of greatest significance in which air reconnais-
sance will be performed are represented by operations against hostile land
forces. These will be assisted in some cases by small surface craft and sub-
marines. Typical examples are an amphibious operation and a continued series
of carrier-based interdiction strikes. Intelligence is required in support of
two distinct functions: strike direction and prevention of tactical surprise.
For the purpose of identifying reconnaissance targets, strikes can be classified
in three classic missions: winning and holding air superiority, interdiction,
and close support of friendly ground forces. Tactical surprise prevention is
concerned with threats to both the fleet and friendly ground forces.
For strike direction, reconnaissance is performed to determine:
1. Identity and location of strike targets.
2. Hostile air defense capability (location and strength of air defense
units).
3. Effectiveness of previous strikes (damage assessment).
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For tactical surprise prevention, reconnaissance is performed;
1. To detect the existence of threat forces.
2. To evaluate the nature, degree and imminence of the threats.
Consider now the reconnaissance targets that are associated with each of
the missions, and specific types of information that is to be collected from
each. Table 2-1 shows the classes of targets by missions. Table 2-2 shows the
information required with respect to each target in support of the mission.
These tables are not exhaustive, but include most of the targets of major
importance. An examination of Table 2-3 shows that, with few exceptions, the
sensory data required is imagery that can be interpreted by visual inspection.
Non-image data, consisting of ELINT, moving target indication (MTI) and radio-
metric highlights ("hot spots") are in almost all cases inadequate to provide
the clues necessary for target identification when used without imagery. The
principal exception lies in the class of radars associated with air defense
units, where ELINT by itself can provide high confidence identification, subject
to the condition of active radiation by the radars. However, location accuracy
achieved by this means alone is less than that desirable for strike direction,
though it can be used.
Therefore, the first conclusion is that the system must be capable of
collecting and presenting imagery data of quality sufficiently high to permit
identification and assessment of condition of the targets. While "quality" is
a complex concept, for the purpose of defining order of magnitude performance
requirements, and choosing between sensors, it is suitable to measure it by
the single parameter resolution. Table 2-3 lists the range of resolution for
each class of target. (Ref. Vol. II, Target Characteristics).
The other parameter of the collection-reporting process that must be
specified is timeliness. This quality may be measured by a parameter defined
in the context of the complete response cycle, beginning with the instant of
collection of the sensory data and ending with completed action (e.g., weapon
delivery, evasion accomplished, redeployment completed), which is illustrated
in simple form in Fig. 2-1. Since the end product of the multisensor system is
delivered to the air intelligence officer, the appropriate parameter is the
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Battlefield
(Targets)
Launch
Aircraft
Fig. 2-1 - Time response cycle
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Table 2-1. Targets and Data
Strike Direction: Air Superiority
Air Interception:
Missiles:
AAA:
Strike Direction: Interdiction
Airfields, parked aircraft, GCI and TARC
complexes
SAM complexes, launchers, missile storage,
radars
Batteries, guns, radars
All Air Superiority Targets (for evasion)
Transportation Bottlenecks: Bridges, railroad junctions, tunnels,
marshalling yards, docks
Tactical Supply Concentrations: Fuel stores, vehicle parks, ammunition
stores
Communication Nodes: Transmitters, telephone centers
Power Facilities: Central stations, substations, transmission
lines
Industrial Facilities: Factories, warehouses
Strike Direction: Close Support
Artillery
Armor
Troops
Fortifications and entrenchments
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Table 2-i. (Cont.)
Tactical Surprise Prevention; Threat to Fleet
Attack and Bombing Aircraft (primarily parked)
SSM
Torpedo or Missile Boats
Submarines - principal responsibility is in other hands
Tactical Surprise Prevention: Threat to Ground Forces
Artillery SSM troops, armor, machine gun emplacements
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Table 2-2. Information Requirement with Respect to Targets
Airfield: Location, capability, condition structures
Parked Aircraft: Location, type, condition, number
GCI Complex: Location, type, radar components
SAM Complex: Location, type, condition (readiness)
AAA: Location, type of guns, radar, size, condition
Transport Bottleneck: Location, identity, size, orientation, surroundings,
distinguishing features, condition
Same as for Transport Bottleneck
Communication Nodes: Same as for Transport Bottleneck
Power Facilities: Same as for Transport Bottleneck
Industrial Facilities: Same as for Transport Bottleneck
Artillery: Type, location, number of guns, revetments, auxiliary
components, surroundings, motion
Armor: Type, location, number, condition, motion
Troops: Number, vehicles, motion, equipment
Fortifications,
Trenches: Location, description, size, ordnance
SSM: Same as Artillery
Boats: Location, type, number, armament, motion
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Table 2-3. Report Time and Resolution
for Various Target Types
Target Type
Resolution Range (feet)
Report Time Range (hours)
25
- 100
5
- 10
2
- 30
0.5
- 2
3.
GCI Complex
6
- 20
5
- 10
4.
SAM Complex
5
- 50
3
- 5
5.
AAA
3
- 25
0.5
- 2
6.
Transport Bottlenecks
15
- 100
5
- 10
Tactical supply
concentrations
10
- 100
5
- 10
Communication
nodes
5
- 50
5
- 10
Power facilities
50
- 100
5
- 10
Industrial facilities
50
- 100
5
- 10
7.
Artillery, SSM
0
- 0.5
8.
Armor
2
- 8
0
- 0.5
9.
Troops
Fortifications
(passive defense)
0.5
- 5
Warcraft (small)
0- 1
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Fig. 2-2 - Target class distribution in parameter space
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"report time", defined as beginning at the instant of collection and ending at
the instant of delivery to the air intelligence officer, either as hard copy or
visual display. Table 2-3 lists the range of allowable maximum report times for
the targets. These are derived from the two basic functions (strike direction
and tactical surprise prevention). For strike direction, the important consid-
erations are the perishability of the data as determined by mobility and
changeability of the target, and the time required to interpret the data, make
a decision, order, prepare and deliver the strike. For surprise prevention, the
important considerations are the time required for a threat to materialize and
the time required to interpret the data, make a decision, and take counteraction.
Figure 2-2 shows how the target classes are distributed in the parameter
space defined by report time and resolution. While the target list is not
exhaustive and the report time and resolution requirements depend to some extent
on judgment, the plot of Fig. 2-2 nevertheless reveals certain major features
of the requirements. There is a rough correlation between the resolution ele-
ment size and the report time. Furthermore, taking the mean time from data
collection to return to carrier to be between one and two hours. There is a
substantial set of targets requiring imagery reporting inflight. Some of these
(e.g., artillery, armor, troops, and warcraft), generate a requirement for
imagery to be reported almost in real time (maximum delay of a few minutes
only). This set of targets is for the most part associated with ground combat
and hence with the close support strike mission and prevention of tactical sur-
prise to ground forces. Required resolution is 8 feet or less, and extends down
to 1 foot. This target set is called Class A.
A second set of targets - Class B - consisting of parked aircraft and
anti-aircraft artillery has slightly less exacting imagery requirements in both
resolution and report time. Some effective intelligence is gained by reporting
after landing, but much is lost unless reporting inflight is done.
Finally, the class of fixed or slow moving structures (Class C) that in-
cludes most of the interdiction targets and the less mobile elements of air
defense does not in general require reporting during flight, and resolution
below 5 feet is not required to obtain intelligence of major utility.
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Consider now the capabilities of the various types of sensors answering
these requirements. Figure 2-3 shows the resolution dependence on altitude of
two typical cameras, an infrared imaging system, and high resolution side look-
ing radar. The resolution as limited by a cathode ray tube dynamic display
(priority viewer) and a flying spot scanner for readout from film in the air-
craft are also shown. The delays of inflight processing for these sensors are
as follows:
1. Photography (exposure to processed film) - 1 to 15 minutes.
2. Radar (reception to processed film) - 2 to 15 minutes first correlation.
3. IR (reception to transmission of video modulated signal) - effectively
zero.
(NOTE: It is not considered feasible, in light of the 1967 cut-off for
state-of-the-art to transmit raw radar data, because of bandwidth
limitations.)
Examination of Fig. 2-3 and the above delay table shows that for Class A
targets only the IR image former will meet all the requirements, and then only
on a low altitude flight path. Resolution is limited by the viewer, which is
required if near real time reporting is to be done. If line of sight limita-
tions preclude the use of wideband data link, the one remaining method for
achieving real time reporting of imagery is its presentation to the observer in
the aircraft, with report by voice or narrowband link. This is a last resort,
since the capability of the observer to perform this task is likely to be con-
siderably less than when the observation is done on the carrier. The radar
resolution falls short of that required for this class of targets, so that it
cannot be expected to contribute much even when a delay of half an hour or more
is tolerable. Since resolution achievable by photography is limited in this
case by the scanner used to generate data link modulation, there is no improve-
ment to be expected over the IR resolution, even when the processing delay can
be tolerated.
For Class B targets, the IR sensor again answers best to the requirement
for inflight transmission. As noted above, some amount of timely intelligence
is deliverable after the aircraft lands on the carrier. Here, hard copy imagery
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/
T
/a
IR
e/mm
0.5 milliradian P
Resoluti
I .400
Camera
120 Cone Angle
60 lines/mm resolution'
Shipboa
rd
/
Cathode
ray tub viemer
Vis
ual
20 lines
/mm - from
Ob
ervation
/
s
camera
r IR as noted*
(Static) /
+
I I Its Lit
I I RS LII
60 lines; mm
Over data link
20 lines;' m m
(scanner limi-
Visual Observation
tation)
/
010 K Range (min.)
?1000 ft/sec - Dynami
Fig. 2-3 - Imaging sensor
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from all three sensors may be used in a cooperative way. Photography will sat-
isfy all resolution requirements at both high and low altitudes, IR has limited
capability at high altitude, and radar is limited at all altitudes. For Class
C targets, all sensors provide usable resolution.
The final consideration relating to timeliness has to do with the time
required for interpretation of the imagery aboard the carrier. Because of the
large quantity of detail, this time is likely to be intolerably long. A strong
requirement therefore exists for presorting the imagery hard copy to reduce
substantially the amount of material that need be examined by the interpreters.
This requirement can in large measure be met by the non-image data. The
properties of high temperature and motion, while not having a one-to-one
correspondence with the targets, do show a highly useful correlation. ELINT
data is very highly correlated with priority targets. Thus, by keying the
total imagery take with these data items, the time for interpretation can be
very significantly reduced, and in some cases by orders of magnitude.
Examination of sensor coordination and integration will first be discussed
realizing of course that each of the five sensors has an outstanding capability
not possessed by the others. Figure 2-4 indicates these functions, and it should
be noted that although man has a spectral sensitivity which duplicates the
photographic regime, no other device can recognize, identify and evaluate with
the judgment possessed by an observer.
Briefly, the basic characteristics of the various sensors are as follows:
The observer and the photographic sensors, operating in the visual and/or
near visual range, evaluate and record detail -
Observer - judgment, valuation, very limited data rate
Photography - shape and texture; limited by atmospheric conditions.
The IR sensors detect activity through heat radiation -
IR - imagery, good resolution, operative in darkness; limited by atmos-
pheric conditions.
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The SLR sensors detect moving and man-made objects through reflective
characteristics -
SLR - imagery, poor resolution, operative in darkness, all weather
operation foliage penetration; limited by poor resolution, specular
reflections.
The ELINT sensors detect radiation from man-made emitters -
ELINT - long range, identification; limited locating ability.
The ability for real time target detection is automatic and inherent in
IR, SLR, ELINT, and the observer; however, there is not such a capability for
the photographic sensor due to the complex nature of the technology, and the
complexity of the target characteristics. There is, however, the capability of
rapid inflight processing and electronic readout, which together will enable,
if desired, near real time evaluation of a record.
To be of increased value, a multisensor system must meet the obligations
of data priority and timeliness of response as outlined previously. This is
accomplished by integrating the individual sensor operations so that they func-
tion cooperatively co assist in sorting the data, and producing the necessary
response. Integration alone is not the answer, even though the complementary
data will permit extended evaluation. The sheer volume of data thus produced
forms a more potent barrier to timely interpretation than any lack of data ever
could. A technique must be found which enables the sensor array to achieve data
priority selection, real time data reduction, and overall efficient data
management.
A variety of techniques were investigated to evolve the data produced by
an airborne multisensor system. Some of the basic methods considered were the
following:
1. Cueing
2. Controlling
3. Pointing
4. Annotating
5. Display
6. Scaling
7. Moding
8. Screening
9. Targeting
10. Keying
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There is a similiarity between some of these techniques which becomes
evident in the following brief discussion. The system finally chosen has
borrowed features from several to form the final configuration.
Cueing - A technique involving the -alerting of one sensor by another so
that features of the alerted sensor may be changed for maximum effectiveness
(sensitivity, scale factor, focal length, etc.).
Controlling - An active cueing function wherein the alerted sensor is
automatically changed by logic in the alerting sensor. This assumes an ability
for target detection somewhat advanced beyond present capabilities.
Pointing - A controlling function in which the alerted sensor is not
optimized but pointed in the direction of a detected alarm, thus utilizing very
high resolution, small field systems rather than broad field systems.
Annotating - A technique in which the sensor alarm is r-ecorded on the
sensor record as a point indication, which calls special attention to that area
during analysis.
Display - A system of converting imagery to an electronic or visual format
for presentation in near real time. This can include simultaneous display of
several sensor outputs.
Scaling - A technique of image manipulation to provide a common scale in
the sensor records.
Moding - A technique for sensor operation which provides for effective
sensor parameters with changing operating environments, such as high and low
altitude operations. Simple parameter changes by the operator would be classed
in this category.
Screening - A popular concept in which the alerting sensor causes a brief
operation of the alerted sensor, this decreasing the data record volume to those
areas in which an automatic alarm is sensed.
Targeting - A complex technique, requiring computer memory and manipula-
tion, in which major tactical "targets" would have a multisensor "fingerprint",
and the system would detect the signature and automatically annote a record,
precluding analysis. Thus the total multisensor output would be continuously
monitored and the readout of targets computed automatically.
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Keying - A composite technique in which a sensor threshold or alarm is
annotated with an identifier and locator on each sensor record, and/or a
separate, high density "key record" to promote quick evaluation of records for
high priority areas in which sensor alarms have occurred. Since the value of
the multisensor concept is inherent in this technique, this "combination of
ingredients" scheme has great merit in providing an adaptive analysis method
that is simple, .and easily implemented.
The keying system correlates the alarm data capability of IR, SLR and
ELINT with the precise detail available in the prime record - the photograph.
It is an extremely flexible system which does not degrade the performance of
any sensor, or rely on the proper operation of a particular sensor for continu-
ity. The key system functions with one sensor, or any combination, with no
preference or interdependence. Its greatest advantage is that the keys greatly
facilitate the data management in surface based equipment.
The logic on which the selection of this concept has been made is now
described.
1. The unique outputs from the IR, HRSLR and ELINT sensors (hot spots,
moving targets and emitter activity) respectively are recognized as extremely
important identification parameters for highly significant targets.
2. Each sensor by itself cannot always reliably identify and locate these
significant targets from its unique output signal, nor can its output signal be
easily correlated with photographic records.
3. If the unique high-priority signals from the observer, IR, HRSLR, and
ELINT sensors are used to "key" the outputs from each other, and jointly to key
the output from the photographic sensor, important targets will be highlighted
from the viewpoint of all the sensors. False alarms can be reduced and unknown
targets identified and located with a much higher degree of reliability.
4. The keying signals are the kind of information most useful to an
observer in the aircraft in a "situation type" display. They are high-priority
data, which have been heavily filtered by each sensor, and they are available
in a useful format.
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5. The keying signals, being activity-based signals (and not map-like
imagery), consist of information whose content has a very low data rate and can
be transmitted within a relatively narrow bandwidth. This information can be
transmitted over standard high frequency (HF) air-to-ground links, and be
available on the carrier in real time.
6. The low data rate key signals are of the type which can be readily
encoded digitally and stored on tape. The tape, of course, is an ideal medium
for the control of data link transmission, visual displays, and shipboard data
management.
7. The key signals from the three sensors are similar in function to the
keying signals which will be interjected by the observer in the aircraft.
Therefore, comments and annotation by the observer (observer "keys") would also
be entered on the key tape with the sensor keys to assist further in the sensor
output correlation. These would likely be derived from operator's "pushbuttons",
and would certainly be digitized for the tape, and for immediate transmission
to the ground via the narrow band data link, since they normally would constitute
high priority information.
2.3 OPTIMIZED MULTISENSOR SYSTEM UTILIZING KEYING
A block diagram of the airborne portion of the optimized multisensor system
is illustrated in Fig. 2-5. As the signal flow paths in this diagram are re-
viewed, the advantages of the data integration keys, already discussed, will
become even more apparent. In Fig. 2-5, the sensor signals originate on the
left hand side of the diagram, the observer's display is at the lower right,
and the data-link is in the upper right quadrant. The keying control tape is
in the center of the diagram.
The margin burden of organization of material, and the basic steps in data
management that make this concept workable, fall to the airborne system. The
delineation of the methods which form the data management base is thus accom-
plished in the discussion of the data collection system.
As an aid to the interpretation of Fig. 2-5, it would be as well at this
point to summarize the salient features of the optimized airborne system. No
attempt is being made to delineate specific hardware, only the data flow, and
basic configuration of the subsystems are shown.
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1. Keying of imagery by MTI and high reflectivity targets of the HRSLR,
hot spots of the IR, emitters of ELINT and comments of the observer are to be
the primary method of integrating the airborne sensors. Photographic sensors
will not key any of the other sensors.
2. No cueing of one sensor by another will be done - sensor pointing will
be fixed for all sensors, and the missions set up ahead of time to cover the
target areas desired.
3. A "keying" or "control" tape will be generated in the air to store keys
from the three sensors, and the observer, and allow them to be transmitted to
ground via a data link. Keying data will be put on the same tape with naviga-
tional data and timing signals, so that the tape may be used in the air or on
shipboard for complete sensor media synchronization.
4. Keying of the photographic, IR, HRSLR, and ELINT recording media will
be done in parallel with the recording of the keys on the keying-control tape.
However, because of the difficulty in obtaining the keys in precise real time,
the keys placed on the imagery may be displaced from the proper nadir points.
This will not alter the use of these imagery keys as a backup to the control
tape, since both the keying and the imagery will be referenced to the airborne
timing pulses.
5. The key/control tape could be used in the air to control the trans-
mission of keyed data over the data link when the aircraft is returning, thus
restricting the transmission to selected, highly-significant data.
6. Side looking radar will have an MTI processor so that MTI data in
digital form will be available for keying, for the data link, and for the onboard
observer's display. In the MTI mode, the HRSLR can look forward at approximately
a 45-degree angle.
7. The IR sensor will have a real time output of thresholded hot spots for
use in keying, display, and data transmission. The map image will also be pro-
vided to the observer's display for auxiliary navigation at night, etc., and
also to the data link for transmission to the ground. An IR image will be
recorded on film, using the tape readout as a source. This film is redundant
but provides the prime IR image on film for the interpreter immediately on the
return of the aircraft.
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8. ELINT will use an onboard processor to provide real time identification
and location data for a maximum of 20 emitter functional types. Data will go to
the keying tape, data link, and observer's display. Data on all emitters inter-
cepted will be stored on the magnetic tape.
9. The observer will be able to report on significant MTI, hot spots, or
ELINT targets from real time displays presented to him. He will also have IR
map display for auxiliary nighttime navigation, target location, etc.
10. The airborne observer's display is envisioned as a split optical viewer
fed by superimposed sensor images and projected map/battle order synthetic
image. The sensor images will be on a storage type of cathode-ray tube and will
consist of ELINT type and location, IR thresholded hot spots, HRSLR, MTI targets,
and an IR map display. An identical display is suggested for the Priority
Analyst on the carrier.
11. Rather than using a microphone for reporting information, the observer
will have a "pushbutton" keying device which will encode important data into
digital codes for immediate transmission over the data link (or HF link), inser-
tion on keying control tape, etc. These data will consist of the observer's
evaluation of the overall situation and the progress of the mission, his con-
firmation of target identity, suggested actions, and any other information
deemed necessary.
12. Limited mode switching of some of the sensors can be done by the
observer.
13. A wide band data link will be provided to enable the IR map, the HRSLR
data, and the processed ELINT data to be sent to the carrier in real time.
14. The data will be sent back on the data link in real time, if a line-of-
sight path or relay exists, or on the return trip of the aircraft, if a line-of-
sight path or the relay do not exist. Control of transmission will be at the
discretion of the observer.
15. Transmission of the photographic sensor imagery over the data link will
not be done. This because for the rapid assessment of real time imagery re-
quired on the carrier, the IR image would serve as well as the photographic
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image. In addition, the IR map image is available at night, and conserves
bandwidth in the data link. Processors will still be included with the cameras
so that processing time can be saved onboard the carrier.
16. Since the keying and observer's report data occupy a relatively narrow
bandwidth, they will be sent over the high frequency (HF) aircraft communication
link, thereby providing a data transmission capability beyond the line of sight
for the highest priority information.
Utilizing the background of system operation just presented, a more
detailed examination of Fig. 2-5 is now in order. Starting with the camera
sensors at the upper left hand corner of the diagram, it will be noted that the
film output is processed immediately in the aircraft, but that no outputs are
sent to the keying tape, observer's display, or the data link. There are a
number of excellent reasons for the omissions. From the standpoint of keying,
the photographic sensor cannot, within the present state-of-the-art, conveniently
recognize targets and generate appropriate signals therefrom. Target recognition
studies and development programs have been underway for a number of years and
operational systems may someday become available, but not within the 1967 state-
of-the-art. In this system, the photographic imagery will be keyed, but will
not generate keys.
The photographic image is not sent to the observer's display because
virtually the same information is available from the IR sensor as an electronic
analog signal (IR map), and can be easily displayed. The IR sensor will have
nearly the ground resolution capability of the camera, but for an observer's use
in a real time situation display, it is not felt that the slight loss in resolu-
tion would be detrimental. It is interesting to note that an important added
feature gained by the use of the IR signal for display is that it can "see" in
the dark as well as in daylight.
Photographic transmission is not recommended since the IR image will suffice
for rapid assessment of real time imagery on the ship and processed film will be
back with the aircraft within an hour after it could have been sent back by the
data link. Using the data link would force a minimum 3:1 resolution degradation
due to readout.
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The IR sensor stores the detail thermal mapping information on tape as
shown, a resolution degraded image is read out for use in the display system,
and a simultaneous high resolution film record is made. The tape is used for
interpretation only when thermal detail, not recorded adequately on the film,
is required. The IR imagery becomes high priority information when the time-
liness factors of a target fall into a time period less than that required for
the aircraft return. Thus the carrier-stored image will be extremely useful.
The image display will also serve as an adjunct to navigation and flight path
orientation. Either a vertical or forward looking IR image can be viewed at
the operators choice.
Derivation of the HRSLR high resolution map requires the additional proc-
essing of film imagery by an optical correlator. Therefore the output from
the HRSLR must be film, and the film must be processed rapidly before being
scanned by a flying-spot scanner (FSS) and transmitted to the ground over the
data link. The HRSLR MTI processor is a thresholding device, similar in func-
tion to the IR threshold processor, and produces moving target keys for the
keying tape and observer's display. The data on this key are target velocity
and heading, target cross range location, and time.
The ELINT sensor block located at the bottom left of Fig. 2-5 uses a small
general purpose computer as its digital processor, and stores digital data from
every emitter received on the airborne magnetic tape. Data processed by the
computer for apriori targets of interest are sent from the computer in digital
form to the keying tape and to the observer's display, similar to the priority
keys from the IR and HRSLR sensors.
Before leaving the sensor blocks in Fig. 2-5, it should be pointed out that
the tape readers and the flying-spot scanner used to remove data from the sen-
sor records and keying tape are configured to permit immediate readout as the
data are being stored and also, to permit readout of the data later in the
flight. This feature is deemed necessary to permit transmission by the data
link after the intelligence mission is completed and the aircraft is on its
return to the carrier.
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Two data links are shown in Fig. 2-5. The wideband data link is the
primary link for all data sent from the multisensor system, and will be used for
that purpose whenever there is a satisfactory propagation path from the recon-
naissance aircraft to the carrier (either line-of-sight or a suitable relay).
The narrowband link represents one of the standard communication links provided
with the reconnaissance aircraft. A link in the HF region is recommended since
it can provide a beyond-the-horizon capability for the transmission of high
priority data. This link is only to be used when the primary wideband link is
unusable, and., because of the bandwidth limitations, can only handle the
observer's keys, and the data from the keying tape, if required.
The concept on which the solution to the problem of handling multisensor
data is based has been delineated in general. Now to illustrate the concept,
the typical sensors and their parameters will be briefly outlined with a
justification for each.
2.4 TYPICAL SENSORS AND THEIR PARAMETERS
For adaptive analysis, there is a requirement for wide, high resolution
coverage from each sensor, over as large an area as is required by the mission.
A parallel need is the reduction of the number of records to be handled, with-
out reducing their data content. Where possible, high acuity systems covering
a wider angle than normal are specified, particularly to maintain correlative
cover for the keying system.
The sensor systems will be laid out by technology showing the coverage and
typical performance required from each.
2.5 OBSERVER
The role of man in exercising judgment against the key system, and per-
forming correlation on a limited basis, justifies expenditure of some effort
in providing a clear forward and limited side view for the observer. This
indicates that a side by side seating arrangement is preferable if the man is
to perform any valuable evaluation of the passing scene.
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The limitations of the observer are based on some very real visual limits.
Moving targets further degrade ground resolution with the following general
relationships.
1. Visual Ground Resolution - Under static conditions human vision has
about 1 minute of are resolution on high contrast targets - this is equivalent
to 4 inches at 1000 feet distance.
2. Motion Limits - Dynamic conditions impose severe restrictions on human
vision. When a relative motion greater than 6 to 8 degrees per second exists,
human vision is impared, leading to nausea or disorientation. It is necessary
then to extend the target range to the point where the relative motion is less
than 8 degrees per second. At 1000 feet altitude, traveling at 1000 feet per
second ( Mach 1) a minimum range for useful vision is 10,000 feet. Therefore
the ground resolution becomes 3 feet apparent, which at low obliquity may mean
30 feet on the ground. (The range refers only to the distance from the observer
to the target on a direct line.)
It can be seen from this treatment that clear forward view is vital for low
level observation, with the side view becoming more important and feasible as
altitude increases.
In keeping with the concept of reducing the record count, the sensors out-
lined in the following paragraph have been selected as typical of the require-
ments.
2.6.1 Low Level Operational Envelope
2.6.1.1 Forward Oblique
Constant scale panoramic camera with an f/3.5, 2 to 4-inch zoom lens using
70 millimeter film. This camera will have a 120-degree cross-track scan and
60-degrees along the flight line set at a 25-degree depression angle. The
ground resolution will be 1.2 feet from 500 feet to 1000 feet per second.
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The forward oblique coverage is wider than normal, emphasizing the addition-
al coverage judged valuable in this position. The forward oblique in tactical
use is felt by many to be the most valuable single camera for low level work.
Frame/strip camera with T/8, 1.75-inch Super Aviogon lens using 5-inch film.
This convertible camera will have a strip or stereo frame capability covering
110-degrees cross-track and 110-degrees along the flight line. The ground reso-
lution from 500 feet at 1000 feet per second will be 4 inches at nadir, and less
than 12 inches at the edge of the format.
The wide angle frame camera will provide maximum coverage with a single
record, and still maintain simplicity. Stereo is available from adjacent frames
when 55 percent overlap is used. The coverage is designed to coincide with the
coverage of the vertical IR sensor, which will have virtually the same ground
resolution.
Panoramic camera with f/3.5, 3-inch focal length lens on 70 millimeter
film. This camera will have a 180-degree cross-track coverage, and cover 40-
degrees along-track. The ground resolution will be less than 12 inches from
500 feet at 1000 feet per second.
This camera is selected to provide near horizon coverage which will corre-
spond with the coverage of the IR hot spot detector, the SLR and the ELINT,
along the flight line, without need for scale conversion. It is particularly
needed since the key system is based on the flight line cross-track coordinate
system, and horizon-to-horizon photographic coverage on one record will be
useful in correlation.
2.6.1.4 Side Oblique
Frame camera with a f/2.-8, 6-inch lens using 5-inch film, This camera
will complete the fan array with the vertical - with a 40-degree field cross-
track and a 40-degree field along-track set at a 20-degree depression angle.
The ground resolution of this camera will be 6 inches on axis.
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This camera is suggested for fulfilling beach running and road survey mis-
sions, and as a prime oblique record for tactical analysis along the flight path.
It can be used as correlative material, with the other sensors, with scale
adjustment.
2.6.2 High Level Operational Envelope
Constant scale panoramic camera with f/3.5, 6 to 12-inch zoom lens using
70 millimeter film. This camera will provide high level basic mapping cover
with a 120-degree cross-track and 20-degree coverage along the flight line.
From 60,000 feet at a velocity of 2000 feet per second, a ground resolution of
6 to 8 feet can be expected across the entire format.
This camera is intended to provide reference imagery, with wide coverage
without the penalty of weight and need for high light level common with high al-
titude wide angle frame cameras. The camera can be set up to cover up to 140-
150? cross-track, should this be desirable.
2.6.2.2 Vertical
Panoramic camera with f/3.5, 24-inch Petzval lens using 5-inch film. This
camera will provide high level detail, with a ground resolution of 9 inches from
60,000 feet at 2000 feet per second. The coverage is selected for 90-degree
cross-track (20 nautical mile swath) and 10 degrees along-track to maintain high
resolution imagery. Scale changes and atmospheric effects beyond a 45-degree
elevation angle will degrade the imagery, and the swath width is judged adequate
for tactical use at the 90-degree field angle. For operational requirements
where extreme coverage is mandatory, this camera can be utilized up to 140-150?
cross-track coverage with some resolution degradation.
Stereo coverage is possible from either high altitude camera by use of 55
percent overlap. The constant scale camera also is useful as a mid-altitude
camera down to 5000 feet altitude, and the 24-inch pan camera is useful down to
10,000 feet, filling the midrange requirements if such operations should be
needed.
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2.6.3 Optional Photo Systems
2.6.3.1 High Altitude
Stand-off camera - this is a pod-mounted external system employing long
focal length optics and stabilizing mounts to allow 70 to 100 nautical miles
stand-off photography. This system is an add-on since there is no justification
for carrying rarely needed equipment on the normal mission.
Additional 1.75-inch focal length frame cameras, vertical - An additional
two cameras for identical coverage on spectrally separated black and white high
resolution coverage. This configuration would provide additive color and
camouflage detection color (near IR) in a simple operational system requiring
no special color processing equipment. Color has proven to be an invaluable
tactical tool as detailed in the final report.
The photographic systems are considered to provide the prime image records.
They produce the best detail, and the images fall into more familiar recognition
patterns. For data management purposes, all imagery will be processed on air-
craft to be available immediately as transparent positives on recovery. The
very high resolution films will be viewed in the negative for fast work, and
duplicated for leisurely interpretation due to processing limitations.
2.7 INFRARED (IR)
The infrared sensors will produce imagery and detail thermal patterns to
reinforce the photographic system, and to make records under cover of darkness.
It is expected that most night reconnaissance will be done with IR, but that an
electronic illumination system will be provided for photographic detail if
required.
The IR system is configured for a low and high altitude envelope
simultaneously.
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2.7.1 Vertical
A multidetector "sweep broom" array utilizing an f/8, 80-inch optical
system and a rotating mirror scanning system. The sensor will record on 2-inch
video tape, and has a potential ground resolution of 0.25 milliradians or
3 inches at 500 feet altitude and a speed of 1000 feet per second. The resolu-
tion limit is 0.125 milliradians for use at high altitudes where image blur
(V/h) is not a major factor. Thus at 60,000 feet, the ground resolution is
7 1/2 feet, comparing directly with the corresponding photographic system.
The IR sensor will have a cross-track coverage of 120 degrees and produce a
strip record. In addition, the sensor will produce hot spot indicators out
to 170-degrees cross-track coverage.
2.7.2 Forward Oblique
A multidetector array, used in "push broom" fashion will be mounted in the
forward oblique position. It will utilize an f/8 optical system and has a
dynamic resolution of 1 milliradian or about 1 1/2 feet, a direct correlation
with the photographic system. The IR system, however, is limited to a 90-degree
cross-track coverage. The value of the forward oblique imagery has been estab-
lished, and this system provides for optional observer display and real time
relay.
The IR system will be used to generate "hot spot" keys by thresholding in
a signal processor. The record tape will be read out to produce an IR image on
film by modulating a light source. That imagery will be the prime IR RECORD
FOR INTERPRETATION, with the tape detail available for interpretation in depth.
The thermal sensitivity of the sensors is about 1?C.
Either IR image can be presented on the operator display, and either can be
transmitted in real time. The images are recorded simultaneously on the IR tape
record.
2.8 HIGH RESOLUTION SIDE LOOKING RADAR (HRSLR)
The radar system is independent of altitude for function, and produces
imagery and more important, MTI (moving target indication) data for the key
system.
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2.8.1 Vertical
A side looking radar system utilizing a synthetic array antenna, and
coherent beam techniques. Of the sensors recommended, this system is the most
advanced, and the ground resolution is dependent on the operational era. Current
systems (AN/APQ-108) can resolve 8 feet out to 100 nautical miles, with 1970 era
systems capable of 2 feet at 50 nautical miles and 8 feet at 100 nautical miles.
The cross-track coverage of the HRSLR is from 30 degrees to 97 degrees eleva-
tion - with degraded resolution from 5 to 30 degrees.
The MTI capability will utilize a cross-track scan or a 45 degree forward
"squint" for more efficient determinations. The movement detection is about
4 miles per hour cross-track and 10 miles per hour along-track with a direc-
tional vector determined above 15 miles per hour. The processed key information
will be available about I to 2 seconds after detection in the squint mode.
The imagery produced by a synthetic array -system requires an intermediary
imaging and optical correlation step. The first image is formed on the aircraft
on 5-inch film, processed, and read out over a data link if imagery is required
quickly. The aircraft system for optical correlation is not justifiable on the
basis of the operational analysis and timeliness criteria.
An optional foliage penetration system, as an external pod system, is
suggested for that special purpose task. The frequency requirements are such
that the same system cannot perform imagery and foliage penetration effectively.
The ELINT system is independent of altitude, and operates passively,
limited by the radio horizon. The system also provides key data, through an
airborne computer processing step.
The ELINT sensor consists of an array of antenna collectors, each tuned to
a different frequency range. The total range for this system is 60 megacycles
to 18 gigacycles, which encompasses all the currently known hostile radars. By
computed triangulation of signal intensity as received by the antenna array, the
ELINT system is capable of locating an emitter to within 3 percent of its range
to the aircraft. The location and emitter type computed on the aircraft are the
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keys processed for the display and key system. The total ELINT record is
maintained on magnetic tape for analysis at leisure for new emitters and other
manifestations.
Conventionally, ELINT is a "side looking" device, covering a sector from
45 degrees aft. For the tactical mission, especially at low level, a forward
looking system has been incorporated, so that the system can now be warned of
emitters ahead, an important survival feature for the electronic countermeasure
components, and an important coverage area for the reconnaissance mission,
correlating with the forward oblique sensors of IR and photo.
The ELINT data will identify 20 basic emitters and can be programmed against
any combination of emitters prior to a.mission. These 20 emitters cover all
known tactical systems adequately, not allowing for special purpose sorties. An
airborne computer will be required for the ELINT system, and it will be cross-
utilized by the display system and navigation system for airborne computations
and integration of key data.
In order that data management can be controlled, and a two-hour data
analysis period can be maintained, the key system has been instituted. As
noted, judgment indicates that potential danger exists in neglecting ground
areas not causing alarms in automatic equipment. Therefore, a complete ground
coverage with annotations of alarms is considered safer from tactical surprise,
and easier to manage because of coherence and easy correlation from all sensors.
The key system is briefly a record, on the margin of each record, and on a
separate "key and control" record of an alarm from an IR hot spot, an SLR MTI
signal, an ELINT detected emitter, or an observer report on visual detection of
screened data or visual sightings. The data analysis, whether in real time by a
"priority analyst" or on return of the aircraft, is made against the key annota-
tions. The keys are noted on each record so that manual backup analysis without
special equipment can be made on a simple light table.
The keys are generated as follows:
1. Photo - none
2. Observer - activity, identification, shape, texture
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3. IR - temperature (threshold adjustable to 1?C), location
4. ELINT - emitter identification, location
5. HRSLR - MTI (speed and vector), location (2 second delay at 45 degree
squint)
Each key is noted as an 18-bit digital word, man readable, giving sensor,
location, and time. All records are correlated against a time standard, thus
reducing location confusion.
A key and control record separate from all other records is made on magnetic
tape. It contains a separate channel for each key and the observer comments, as
well as time, and location from the navigation system. This tape is used in the
viewer to allow control of the records, and recall against the keys, thus
eliminating the need for a film reader in the viewer, where occasional overlap
of keys could result from extremely high density alarms.
A practical, simple, display system has been selected for the operator/
observer, which presents only screened, high density information to relieve the
strain of high data presentation rates. The keys are displayed as a symbol,
in proper location, overlaid on a-moving map image, on which the aircraft is
correctly located. The map is a current order of battle status map, so that
new alarms can readily be distinguished from old. It is automatically scaled
for altitude, and has a momentary stop action mode as needed. An IR image from
either the forward looking, or the vertical system can be overlaid on the map
for gross analysis, or navigational updating. This mode will be particularly
useful for low level night reconnaissance, for both the operator, and the
aircraft commander.
The operator/observer will use a simple coded report keyboard to annote
the key record, and that key record will be read out in real time over the HF
data link (not horizon limited). The data links, if both are operative, will
allow a complete replay of the display for the priority analyst on the carrier.
If the HF link alone is operative, the display without imagery will be in real
time allowing cumulative plot of the keys and determination of detail analysis
priority.
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The basic problem in multisensor reconnaissance can be classed as a data
management problem, as the collection methods are well established. The multi-
sensor theory contends that corroborative data on the same area will reinforce,
and ease the interpretive effort with reference to a given target. This is
true; however, the multiplicity of records on the same target inserts a complex-
ity into the management of data, to maintain quick, timely analysis. The key
system is an important part of the concept which provides for timely data
handling. The other basic points of the system are outlined here.
2.13 DATA PREPARATION
In order that all records be available on return of the aircraft, thus
eliminating ground processing delays, all image records will be airborne
processed. The photographic sensors will each have processing magazines, pro-
ducing negatives and transparent positives ready for immediate use. The nega-
tives will remain as backup spooled records, and the positives, usually of
adequate resolution (maximum 80 lines per millimeter) will become the viewing
record.
The infrared images, formed on film in the aircraft will be processed in a
like manner, and be available as positive transparencies. The IR tape record
will be maintained for use as required for detail temperature data, not record-
able film.
The HRSLR record will be handled differently to conserve weight and space
on the aircraft. The operational analysis indicates that a delay from real
time is acceptable for the SLR image, due to its low comparable resolution.
Therefore the first data reduction, a non image photo record, will be made on
the aircraft processed, read out and relayed on the wideband data link for
optical correlation on the carrier, where the imagery will be produced.. This
record then will be available on return of the aircraft as a second generation
positive transparency.
The ELINT record will be maintained as a backup tape record, with the
prime ELINT data processed into the key and control record tape. The ELINT tape
will be processed for new emitters by the carrier-based computer systems.
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The key and control tape, containing all the key annotations, is available
as a complete separate record, both as an airborne record and as a relayed record
maintained on the carrier for backup. Either record tape will be read into a
disc storage system for use in cumulative plots of the aircraft progress and key
alarms. The disc storage system will also maintain order of battle (OB) status
and ELINT data for ECM systems on a quick access/change format for use by sev-
eral downstream systems.
The first innovation in the data management concept involves the use of a
real time analyst. This individual will monitor the key and display records
relayed in real time. As noted, this may include imagery if the wideband data
link is operative.
The priority analyst has two functions.
First, he will evaluate the key alarms for target activity levels. This
will be done against an order of battle (OB) status map in real time, a dupli-
cate of the airborne display, and a cumulative plot. This will possibly
generate new status information, but definitely will allow programming of the
analysis of the prime records. Second, the priority analyst may be able to
evaluate IR imagery, which can be recorded and replayed if desired, for real
time order of battle (OB) status information. The data r-ate, which is the limit
of man's real time evaluation capability, is limited to 5 to 10 bits per second,
thus generating the need for prescreening data for real time use. Without this
feature, the man is overloaded and rapidly falls behind the real time situation
to the point where the evaluation breaks down.
Since the analyst working in "real time'"' cannot use imagery, a second
operator should be associated with the priority analysis whose sole function
is relayed imagery evaluation. This analyst may utilize the IR imagery, either
forward oblique or vertical, or a selective video presentation keyed to a sector
of the real time display by either the analyst or the airborne operator. Thus
the capability to work with limited imagery is incorporated, allowing target
and opportune sighting evaluation.
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The records used by the priority analyst, those relayed over the data links,
are secondary records, and consist of the key and control record and degraded IR
imagery. The SLR record relayed for processing only, is also available should
the aircraft fail to return.
The next critical phase of data management occurs in the preparation for
and analysis of the prime records. As shown by the operational analysis, time
here is critical, so that command decisions can be timely, and based on con-
firmed data. The records for analysis consist of the total record take of the
aircraft:
1. Photography - positive imagery from 7 cameras
2. IR - positive imagery from 2 sensors
3. HRSLR - positive imagery from 1 sensor
4. ELINT - emitter plot
5. KEY AND CONTROL - key annotations and time/navigation data
Each image record will redundantly carry the key annotations from all
alarms should manual viewing be required.
There is need for reference imagery and text to establish a data base for
updating, and to allow change detection, which is the critical parameter. The
"historical" imagery and text will be maintained in aperture and file form for
quick retrieval. A card deck, representing the imagery and text required for
the analysis will be assembled on the basis of: 1) the assigned flight path and
target areas, and 2) the activity and real flight path as determined by the
priority analyst. Records will be maintained, and computer indexed by geo-
graphic coordinates and target type. The card system will maintain imagery in
the original format (70 millimeters or 5 inch) to reduce handling problems
under extreme time pressure. Text and reference material will be format reduced
to microfile and standard microstorage systems, but maintained in the 6 by 9-inch
standard aperture card as is the imagery.
An order of battle (OB) plot and overlaid key plot will be maintained, with
aircraft location as determined from the key and control tape or the imagery data
blocks for use as reference for the analysts.
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The heart-of the analysis system will be the viewer. The viewer should
have the following major capabilities:
1.
Two analyst stations
2.
Two prime viewing screens
3.
Two reference viewing screens
4.
Ten parallel image channels with operator selection (five for each
screen)
5.
Stereo capabilities with binocular view module on two channels
only
6.
Key and control tape for target or areal selection
7.
Tie-in with computer for mensuration and data index information
Associated with the viewer, but not a part of it, should be the key and
order of battle (OB) plot and aircraft location indicator. The operation of
this viewer complex will be on the following basis.
From the order of battle (OB) plot, an analysis area will be selected, and
a computer identification of the index code will be established from coordinate
read-out. The reference card deck, in the viewer will be searched and the last
imagery presented on the reference screen, the key tape will be searched for the
same reference, and the records clewed to the proper area by data block time
read out. The analyst can optically select the prime record photograph, IR,
SLR; etc., read the keys from the tape AJN display and make an interpretation in
a short time. If required a simultaneous record can be switched to the other
view screen for point to point comparison. Image magnification from 4X to 20X
will be required as well as image rotation capability for orientation purposes
(as with panoramic coverage versus frame coverage).
The analyst will make his report and requests orally to avoid delays, and
an operator associated with him will communicate with the automatic systems with
conventional keyboard systems. A computer will be utilized to perform mensura-
tion conversions and communicate with the disc storage, and index reference
systems.
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A punchcard backup will be generated for the disc and index stores, as
part of the reporting cycle. The new order of battle (OB) status or detail
reports can be automatically plotted on the flag order of battle (OB) display,
or they can be manually posted there from the punchcard readout.
2.17 DATA STORAGE AND RETRIEVAL
The data base update, provided by the new intelligence will take two basic
forms. First will be the selection of the new imagery by the analyst from the
sortie records. Second will be the selection of the order of battle (OB) status
reports, in punchcard, text and disc file format.
The new imagery will be directly placed in the aperture card system and
filed as original imagery in an index system for manual retrieval on call. The
card file backup will be automatically sorted and stored to back up the fast
access disc storage systems. By maintaining the original image format, several
advantages occur. The manipulations of reduction, processing, storage, and
reproduction are eliminated, and image resolution is not degraded as is
inevitable with duplication processes.
Original negatives in spool storage, will be retained for duplication and
archival uses as required, only for such periods as are reasonable, due to the
time perishability in a dynamic environment.
The magnetic tape records will be stored for 36 hours then erased and
reused.
The materials for mission folders will be extracted from the imagery files
and disc storage printouts and provided as hard copy along with maps and target
lists.
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The concept outlined above has been gaged to fulfill the intelligence
requirements of the operational analysis. It is based on collecting all
available data, and screening it by use of key annotations generated uniquely
by the observer, and the IR, ELINT and SLR systems. It provides for aircraft
display of important data and real time relay of priority information to the
carrier.
The concept provides a system of data analysis utilizing a minimum of
records, and the key information. The interface with automatic data handling
equipment is limited to speed up functions, which do not in any way attempt
evaluation or decision making.
The storage system is based on a minimum of manipulations, and utilizes
the human capability for rapid random access.
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In developing the system concept, a basic environment has been used that
specifies the conditions in which the system must operate, and the requirements
which it must fulfill. These represent as realistic an operational environment
as is possible, with the parameters based on the reconnaissance doctrine discus-
sed in Volume 1, Naval Doctrine.
1. Reconnaissance Support of the Task Force - The system must perform all
the reconnaissance for the task force regardless of the operation, ranging from
peaceful maneuvers to total combat support.
2. Self Contained - The system must operate alone, and perform all collec-
tion and interpretation with no support outside the task force.
3. Reconnaissance Aircraft - The system will be based on a 6 to 8 vehicle
complement, and assumes that only one carrier is so equipped. Further, the air-
craft are specially configured for multisensor reconnaissance, and are not as-
signed any other function.
4. Targets Assigned - It is assumed that each reconnaissance sortie is
assigned between 10 and 20 targets, and that further "targets of opportunity"
will be recorded on the judgment of the observer.
5. Simultaneous Sorties - A maximum of 2 sorties will be simultaneous and
1 sortie in the air at all times will be standard procedure under normal con-
ditions.
6. Sortie Cycle - The launch/retrieve cycle will be 2 hours, with a launch
occurring at each retrieval.
7. Interpretation Cycle - The information recovered from a sortie should
influence the targeting of the next-off sortie, thus a maximum interpretation
time of 2 hours from touch-down is assumed.
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4. OPTIMIZED MULTISENSOR SYSTEM
4.1 TARGET DATA GATHERING REQUIREMENTS
In any complex system, the input characteristics heavily affect the design
concept of the system. The considerations on which the conclusions reached here
are based are discussed in detail in Volume 2, Target Characteristics, and the
results are further delineated in this section. Each sensor is evaluated for its
ideal environment, but it must be realized that any deviation from this condition
will modify the results.
The requirement on the system for technical detail on request, and tactical
Order of Battle data under all circumstances leads to the conclusion that each
sensor must operate to its maximum capability. The basic system concept is shown
in Block Diagram A.
4.1.1 Photography
The study of target characteristics, and the comparison of sensor systems
resolution capability, leads to the realization that photographic imagery will
provide the most detailed information on a target, regardless of the altitude or
speed of the aircraft.
The photographic systems, recording in the visual and near visual spectrum,
are passive sensors since they utilize reflected light for forming images. Nor-
mally, of course, that light is solar radiation, and good quality images can be
produced at light levels as low as 100 foot lamberts. In the absence of solar
illumination, photographic systems require either electronic light amplification
(passive) or artificial illumination (active).
Since the multisensor system has infrared sensors, which require no illumi-
nant source for producing imagery, light amplification systems can be considered
redundant. The IR systems can produce an image of the same resolution as that
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is produced with light amplification systems, thus eliminating the latter from
consideration at this time.
The use of artificial illumination systems should be restricted in the multi-
sensor system to those situations where low -altitude detail is required which can-
not be recorded by the infrared system. In order to minimize logistic and pyro-
technic problems, the use of electronic flash systems is recommended. The loss
of shadow detail will result, and the system will be restricted to low altitude
(below 1500 feet), but it is not anticipated that the flash mode for night recon-
naissance will be a major system because of the presence of the wide range infra-
red systems which fill most night requirements in combination with HRSLR and ELINT.
The available solar illumination for photography can be illustrated by the
illuminance charts shown in Figs. 4-1, 4-2, 4-3 and 4-4. The reflected radiation
useful for near visual UV and IR photography is restricted by absorption charac-
teristics of the atmosphere as shown in Fig. 4-5. However, dye sensitized silver
halide emulsions are available which have sensitivity in the near visual ranges
so that the range from 300 millimicrons to 1.2 microns can be used to form images
on aerial photographic films.
The selection and use of photographic films for aerial photography is not
discussed in this report; however, "Photographic Considerations for Aerospace"
published by Itek treats this subject in detail. The factors which affect the
selection are basic, and are as follows:
Illumination
Lens characteristics (f/number)
Spectral range
Atmospheric factors
Exposure time
System motion
As a basis then for the evaluation of data requirements for the photographic
system, there is established adequate illumination and proper film selection,
based on the mission parameters. The analyst should be provided with photographs
having a resolution level determined by the task. The primary requirement of the
analyst is to generate an order of battle status; detailed interpretation maybe
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called out at any time. Therefore, the resolution should be to the level re-
quired for detail analysis. The photographic target characteristics, discussed
in Volume 2, Target Characteristics, show that a ground resolution of 1 to 2 feet
will be sufficient for detail work on 95 percent of tactical targets. There are
isolated targets, such as gun emplacements, which may require 3-inch resolution
to determine detail such as caliber, and model. Therefore, a requirement for
tactical photography should be a basic 1-foot ground resolution, with a 3 to
4-inch requirement on low altitude missions. It is well recognized that this
level is not necessary for most analysis; however, it should be provided since
there is no prior knowledge of what target area will require detail work.
4.1.2 Infrared
Analysis of the reconnaissance missions in terms of types of targets, mis-
sion time-altitude evelopes, and generic sensor capabilities has indicated that
an infrared sensor can produce useful information both for visual interpretation
and for automatic keying of certain types of targets. The first of these implies
data having sufficient spatial resolution that the target size and shape may be
recognized visually; the latter implies that an adequate variation and emitted
energy occur to permit automatic threshold decisions without excessive inter-
ference from the background (anything not a target). Target studies presented in
Volume 2, Target Characteristics, show that adequate imagery for visual inter-
pretation is obtained with a ground resolution of 1 to 5 feet for the majority of
missions. Sensitivity requirements for useful imagery of ambient temperature ob-
jects imply a noise equivalent temperature of the order of 0.25?C.
Automatic keying may be performed by selecting a field of view approximately
matching the size of the target and automatically thresholding the output signal.
Temperature variations averaged over the field of view should be at least 10?C
for reliable keying.
Adequate imagery should be obtained for a total -angular coverage of ?60?
from the aircraft nadir. Keying data however may be useful from horizon to hori-
zon. The high resolution coverage can provide both interpretive backup for the
photographic data and keying to enable the air intelligence officer to select
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areas for high detail priority analysis. Geometrical range variation reduces the
interpretive utility of the infrared data at elevation angles much greater than
60?, but thermal variations may be observed which can be correlated with the SLR
and ELINT data.
Because the infrared sensor produces imagery of the thermal radiation emit-
ted from the scene, it is useful under both daytime and nighttime conditions.
However, obscuration by clouds and inclement weather may prevent obtaining useful
imagery.
4.1.3 High Resolution Radar
The present operational requirements for tactical reconnaissance include a
high altitude mode for general reconnaissance and surveillance and a low altitude
mode for survival or for detailed reconnaissance of preselected targets. There
can be up to 20 preselected target areas for the low altitude mission. The mis-
sion duration will allow a nominal one half-hour of actual data gathering. The
following tables give estimates of the aircraft performance for the high and low
altitude missions:
High Altitude:
Aircraft Velocity Mach 2 - 3
Altitude 40,000 - 80,000 feet
Maximum Radar Range 100 - 150 nautical miles
(one side coverage)
50 - 75 nautical miles
(both side coverage)
Aircraft Velocity Mach 0.8
Altitude 500 - 5000 feet
The raw data requirements are set by the mission duration, number of target
areas, and type of target. A study of typical tactical targets has indicated
that a radar sensor requires a resolution of 20 to 50 feet for the larger targets
such as bridges, buildings, etc., while resolutions of down to a few feet are
advantageous for smaller targets. The target radar characteristics can vary from
strong, high contrast targets such as vehicles to low backscattering, low contrast
targets such as roads and runways surrounded by grass fields.
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4.1.4 Electronic Intelligence (ELINT)
Airborne ELINT systems can identify and locate sources of electromagnetic
radiation within the "radio" spectrum by intercepting signals, analyzing their
characteristics, and taking bearings on them. Although information concerning
all radiating systems is of value, the most valuable information gathered by
ELINT systems has been obtained from the interception and analysis of radar sys-
tem emissions. Therefore, the majority of ELINT systems have concentrated on
these signals. The radiations from radar emitters are usually characterized by
repetitive pulse transmission of low duty cycle which are very amenable to de-
tailed analysis by intercept equipment. Some of the radars, however, radiate a
continuous-wave (CW) signal. The frequency range employed by radar systems ex-
tends from 30 megacycles to 30 gigacycles but the systems are usually clustered
in small bands throughout the total range.
Target radiation characteristics which may be detected and measured by ELINT
systems are discussed in detail in Volume 2, Target Characteristics. The refer-
enced study discusses two signal environment models which were constructed to
enable signal parameters and -statistical data to be ascertained. One of the en-
vironments postulates a carrier task force operation inthe Baltic Sea near the
Soviet mainland during the years 1967-70. The second covers a task force oper-
ation near the country of North Vietnam in the year 1967. The Soviet environ-
ment is representative of a very dense signal environment, because of the presence
of both strategic (permanently located) and tactical emitters. The Vietnam en-
vironment, on the other hand, is representative of a very light signal environ-
ment, since the radiations originate from a small population of fixed emitters
located throughout the country. In both environments, the classes of equipments
expected to be used are similar.
From the information presented in the target characteristics study, particu-
larly the postulated signal environments, conclusions can be drawn concerning the
characteristics of the raw signal data input to an ELINT system, which can be
used to optimize the multisensor system. A tabulation of ELINT target identifi-
cation and location characteristics points out that the primary usefulness of the
ELINT sensor is activity detection, and that target complexes with associated
radar and communication equipments can be identified and located. The keying
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potential of the ELINT sensor pertaining to its use in keying other sensors in
the system, is extremely high, especially where emitters are associated with de-
sirable targets.
The target characteristics study mentioned above also contained plots of RF
frequency versus pulse repetition frequency for Soviet radars over the complete
frequency range of their operation. Figure 4-5(a)shows one of these plots, cover-
ing the frequency range of 2500 to 6000 megacycles and illustrates the signifi-
cance of these parameters in identifying the functional type of an unknown emit-
ter. In this figure, the abscissa coordinates represent emitter rf carrier fre-
quencies, while the ordinates are emitter pulse repetition frequencies. Each
small rectangle in the field of the plot represents the envelope of frequency
versus prf known to exist for a particular functional class of radar equipments.
In areas where rectangles overlap the possibility of ambiguous emitter identifi-
cation exists. There is very little overlap of the frequency-prf envelopes, even
though the frequency range between 2500 and 3500 megacycles (S-band) has the high-
est density of Soviet emitters in any portion of the spectrum. It may be observed
from the figure that a large gap in the distribution of Soviet emitters appears
in the region from about 3300 to 4900 megacycles. Such gaps are common in other
portions of the spectrum.
It is apparent from the frequency versus prf plots that Soviet emitter func-
tions, for the most part, are grouped in separate frequency-prf regions and can
be successfully identified on the basis of this signal parameter set. Where dif-
ficulties exist because of the overlapping of the rf-prf envelopes, other signal
parameters can be utilized to resolve the ambiguities.
The complete frequency spread of these radar sets occurs within the range
of 70 megacycles to 10 gigacycles, and it is not expected to differ much in the
next few years. Although no intercepts have been received from any operational
emitters at frequencies above 10 gigacycles, the Soviets are doing development
work in the K-band region, and there may be future traffic in this band. In ad-
dition, some traffic may appear within the present frequency gaps. Based on the
information now available, the present frequency range of tactical ELINT systems,
approximately 60 megacycles to 18 gigacycles, appears entirely adequate for an
optimized system. The addition of a 30 to 60 megacycle receiver will extend the
system into the VHF communication range, which may provide valuable intelligence.
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frequency range.
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A characteristic of ELINT intercept data, which has a considerable bearing
on the design of a system, is the signal traffic density. Traffic studies dis-
close that the density of just the tactical emitters associated with a Soviet
Combined Arms Army (CAA)can be as high as 179 emitters radiating in an 8000 mile
square area, This does not include the permanently located radar sets (strategic
emitters), the communications systems, or airborne emitters. An area of 8000
square miles (nautical) is a circular area of approximately 50 nautical miles
radius, and corresponds to the radio line-of-sight horizon for an aircraft flying
at 1500 feet. For an aircraft at 500 feet, the radio horizon is approximately
30 nautical miles in radius, enveloping an area of approximately 3000 square miles
around the aircraft. A total of 67 tactical radar emitters would be detectable
within that area. At the higher altitudes, the signal traffic densities become
proportionally higher. A peak density of 1000 emitters of all types across the
entire frequency spectrum has been estimated for high altitude flights in dense
areas.
There is a tremendous redundancy in the information content of intercepted
radar pulse trains. Contrary to what might be expected, the high signal densities
do not create a problem in the rate of data handling, even if real time analysis
is desired. The problem is rather one of data sorting - separating the trains of
interleaved pulses and correlating them with their emitters. A discussion of this
problem, and its impact on the airborne and ground computer requirements is con-
tained in Volume 4, Technology Survey. Real time analysis, as required by the
optimized multisensor system, calls for a small general purpose computer to be
located aboard the aircraft. By the insertion of apriori data on emitters of
interest, such a computer can identify by function and locate up to 20 different
kinds of emitters at a rate of 2 to 5 per second, thus satisfying the require-
ments of a tactical mission in the densest of environments.
Although the raw data input to the ELINT system in the form of emitter sig-
nal parameters is fairly well defined in a tactical situation, changes to existing
emitters and new equipments can be introduced. The design of an ELINT system for
an optimized multisensor system must take this into account, and provide a flexi-
bility which can adapt to anticipated changes. Here is where the general purpose
airborne computer can be highly valuable, because of its extreme versatility.
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Simply by programming changes, the overall system response can be revised to keep
up with changes in emitter characteristics or to fit almost any conceivable multi-
sensor integration or mission plan. By proper programming, the ELINT system can
accomplish such functions as alerting on specific emitter threats, identifying
peculiar emitter combinations, searching for emitters in particular locations
assigning priorities, preparing statistical plots, and so on.
Countermeasure activity will be attempted to prevent the identification and
location of battlefield emitters by ELINT systems. Two standard techniques are
rapid frequency shifts in a random manner (frequency-jump radars) and jittered
pulse repetition frequency. Frequency-jump radars employing rotating vane magne-
trons are relatively simple to implement, and it is expected that there use will
increase. Their greatest effectiveness is against a slow-scanning receiver be-
cause of the time required to accumulate enough samples over a number of scans
to make a positive identification. Once again, it is the tremendous redundancy
in pulses which makes the solution possible. Contemplated improvements in wide-
open and rapid-scan receivers are expected to minimize the effects of this subter-
fuge. Pulse jitter, likewise, only serves to increase the processing time. The
location of an emitter, determined by monopulse angular fixes, is not-particularly
affected by most countermeasure techniques.
A summary of the raw data input requirements for an ELINT subsystem in an
optimized multisensor reconnaissance system can now be made. These requirements
are imposed on the system by the nature of the radiated signals and their expec-
ted densities in a battlefield environment. The requirements are given in Table
4-1. These requirements for an optimum multisensor system are no different from
those levied against today's ELINT systems, and which presently-programmed ELINT
systems are capable of meeting.
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Table 4-1. ELINT Input Data Requirements
Frequency Range
PRF Range
Pulse Width
Pulse Amplitude
Geographical Coverage <
Pulse Density
Within-pulse modulation
Modulation Characteristics
(non-pulse)
60 mcs - 18 gcs
(30 mcs - 60 mcs optional)
100 pps - 5000 pps
0.1 sec - 29 sec
30db in 4db steps
To radio horizon
forward and sides
106 pulses per second max
Detectable
Type Detectable
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For a reconnaissance aircraft to collect the necessary data, either of two
major installations schemes can be used. First, the sensor complement can be
configured to collect all the information from high and low altitudes with no
modular equipment changes for sortie parameter modification. Second, the sensor
complement can be configured in a modular fashion, and high and low altitude
components can be exchanged as required by the sortie parameters.
The evaluation of these basic systems has included consideration of mainte-
nance, mission readiness, and versatility. It has been concluded that the sen-
sors should be permanently carried for both altitude envelopes with provision
for special purpose systems such as photographic stand-off cameras or foliage
penetration radar as modular add-on units. The reasons for this conclusion are:
1. A quick response to sortie change on the carrier is required.
2. Sortie requirements may dictate both high and low coverage.
3. A modular maintenance/replacement system can be utilized to advantage.
4. The adaptive characteristic of the well-equipped aircraft will enhance
the ability for mid-sortie changes in situations of opportunity.
5. There is no major requirement for different systems except for the
photographic sensor.
The overriding reason is the simplicity and lack of logistic problems in
meeting the need for flexibility under time pressure. The launch/retrieve cycle
of a tactical mission dictates almost instant readiness, on the decision of the
air intelligence officer, of the aircraft for either high or low altitude
operation.
4.2.1 Photographic Sensors
It has been developed that the photographic sensors should collect image
data on normally pre-assigned target areas to a ground resolution level of 1
foot or less. As shown in Fig. 4-6, most sorties will likely be flown at either
low altitude (500 to 1000 feet) or high altitude (30,000 to 60,000 feet) for
reasons of aircraft survival. It is recognized that in a non-combative situation
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0
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Anti-Air
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Fig. 4-6 - Typical survivability versus operating altitudes for high
performance aircraft tactical reconnaissance.
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the altitude can be selected freely, where an altitude on 3000 to 5000 feet and
30,000 feet would be representative of the low and high altitude regime,
respectively.
Each region of altitude provides collection of specialized data. The high
altitude region will be used for large area, basic cover, with specialized stand-
off requirements on occasion. The low altitude region will be used to acquire
detail cover, and perspective cover when using oblique sensors. In tactical
operations, the oblique views, when used with vertical views for geographical
orientation, are highly valuable. Normally, low oblique angles will not provide
useful information from high altitude for lack of resolution. The long range
stand-off camera, however, is a specialized low oblique camera, useful for long
range work from high altitude; it is limited in coverage, and is very sensitive
to orientation problems, and cannot be classed as a tactical device except as a
special tool for covert observations.
4.2.1.1 Photo Sensor Requirements
To attain the required ground resolution, established as less than 1 foot,
and to provide useful information in the views required, the following low
altitude cameras are considered necessary:
1. A short focal length, wide field frame/strip camera - vertical.
2. A moderate focal length, 180-degree panoramic camera - vertical.
3. A moderate focal length frame camera - side oblique.
4. A wide angle, moderate focal length frame or panoramic camera -
forward oblique.
The capability of these cameras to provide basic information will be dis-
cussed in paragraph 4.2.2. In addition, the versatility of the photographic sys-
tem can be increased by adding the following sensors:
1. A short focal length vertical strip/frame for additive color (identical
coverage).
2. A short focal length vertical strip/frame for camouflage detection
(identical coverage - near visual IR).
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The theory of additive color and camouflage detection with spectral sepa-
rated, identical coverage black and white photography is discussed in Volume 3,
System Characteristics. Briefly, the concept is that the spectrally separated
identical images can be superimposed in two or three color projections to pro-
vide a high resolution real color or camouflage detection color image. This is
similar to the familiar Technicolor process.
Color for interpretation or camouflage detection is extremely valuable. In
black and white photography, detail is lost since the conventional grey tones are
not keyed as to their real color content. However, there is a penalty of redun-
dant equipment, which classes this system as optional for a basic sensor package.
The use of color films has been discussed in Volume 3, System Characteristics,
and while a possibility, it is not felt that the prime record can safely be a
color image, thus sensor redundancy for color is necessary, and it is felt that
the higher resolution additive color system is superior from an operational stand-
point.
The usefulness of stereo coverage, especially in the vertical imagery, is
also extremely valuable. The frame camera, and the panoramic camera, operating
in the vertical can provide stereo for interpretive viewing by simply allowing
greater than 50 percent overlap along the flight path from frame to frame. Pro-
vision should be made at the viewing station to allow stereo viewing from a single
record when it is required. The option of carrying a redundant record for the
sole purpose of providing stereo is considered an excessive penalty of the oper-
ational efficiency of the total system.
The need for a high altitude capability, concurrent with a low altitude sys-
tem, requires more sophisticated cameras in order to achieve the one foot ground
resolution. The equipment suggested for the high altitude mode is as follows:
1. A frame or panoramic camera to provide a large area, distortionless,
basic photo map. A 120-degree maximum field angle is required, with a moderate
focal length lens resolving 6 to 8 feet from 60,000 feet altitude.
2. A panoramic camera, with a long focal length to provide a field angle of
90 degrees with 1 foot ground resolution from 60,000 feet.
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Both high altitude cameras should have 55 percent overlap for stereo cover-
age. The option of 10 percent overlap should be available to increase coverage
on long missions at the loss of stereo.
Optional high altitude equipment considered for the multisensor mission is
a camera for special long range oblique photography. Since the stand-off re-
quirement is a rare one, this camera should be considered as an exterior store
system, probably a self-contained pod unit for ease of use. In this way the very
long focal length system needed for 60 to 100 nautical miles stand-off will not
occupy needed aircraft space. The use of frequency is expected to be low for
this item, and it will be a physically large optical system, so that the pod
concept has many advantages.
4.2.1.2 Typical Camera Systems
The characteristics of several camera systems which fulfill the general re-
quirements for coverage and resolution outlined previously is presented here for
evaluation of their parameters.
An attempt has been made in evaluating the camera systems to standardize
formats. This has been carried only to the point where no penalty is incurred
by way of increased system complexity, weight, or volume. The cameras therefore
utilize 5 inch and 70 millimeter film only, and the selection is often on the
basis of existing camera equipment.
Low Altitude Photo Systems - The following cameras fulfill the require-
ments for photographic operation at 500 feet altitude and a ground speed of 1000
feet per second, these conditions being taken as standard.
1. Frame/Strip Camera - A frame camera, similar to the KA-51, mounting a
44 millimeter f/5.6 Wild Super Aviogon lens could be used for the vertical, wide
angle coverage. The camera should have a focal plane -shutter, modified to con-
vert the operating mode from frame to strip, by stationing an adjustable slit
across the center of the format. The normal IMC drive system, operating continu-
ously would permit use of the frame camera as a strip camera (see Fig. 4-7(a)).
The camera would normally be operated as a frame camera, with a 60 percent over-
lap for stereo (see Fig. 4-7(b)). In this mode a frame cycle time of 1/2 second
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(a) (b)
Strip
Typical Ground Coverage
Fig. 4-7 - Frame/strip camera - 44 mm EFL, 5" Sq. format (vertical)
(1 permanent) (2 optional)
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is required for the worst mission profile considered. The resolution performance
of this system can be described as follows. The lens/film static resolution of
the Super Aviogon lens has been measured at 160 lines per millimeter. Degrading
that performance to 50 lines per millimeter for dynamic use on Plus-X aerial film
(4401), calculations indicate that with an illumination of 200 foot lamberts, an
exposure time of 1 millisecond (1/1000 second), and at 2:1 contrast, a ground
resolution of 3 inches can be obtained. This camera can be hard mounted and
provide ground resolution of less than one foot from altitudes of up to 2000
feet.
For this reason, the value of a wide field angle camera with good resolution
cannot be overlooked. The 55-degree slant range at the edge of the field is at
about the maximum angle for meaningful photography. Beyond this point, perspec-
tive problems, scaling, and shadowing effect begin to seriously degrade the
image quality. At low altitude, the effect of increased atmospheric path length
is not as important as for high altitude systems.
The wide angle coverage of the vertical camera is designed to correspond
with the cross-track coverage of the vertical IR sensor. In thisway the records
from the two sensors will be easily compared. It is felt that the wide field
angle is a superior solution to the coverage problem, as compared with any kind
of selective or multiplexed coverage, because of its simplicity, and the knowl-
edge that no important, unknown target will be missed.
2. Vertical Panoramic Camera - A panoramic camera, similar to the Perkin-
Elmer or Fairchild rotating prism pan, is suggested to complement the cross-track
coverage of the frame camera. The slightly longer focal length of 3 inches will
provide better theoretical resolution. The primary purpose of this camera,
which can cover a 180-degree cross-track field angle with 40 degrees forward
coverage (Fig. 4-8), will be to provide photographic imagery of the marginal
areas beyond the frame camera limits. This is important to the system concept
in order that the areas seen by the IR hot spot system, the SLR, and the ELINT
will have photo coverage. It is recognized that the coverage will not be of
primary use beyond the 60 degree elevation angle; however, target indications
from one or more of the other sensors can be compared to imagery and some
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Typical Ground Cover
Fig. 4-8 - Frame camera - 3-6" EFL, 5" Sq. format (side oblique).
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valuable intelligence may well result. The system ground resolution should be
on the order of 3 inches at nadir from a hard mounted camera operated under the
same conditions as the frame camera previously discussed. The camera will use
a 70 millimeter format, and have a cycle rate of 6 to 8 frames per second at the
standard altitude and speed selected.
3. Frame Cameras - Side Oblique - Frame cameras mounted in the side
oblique position to form a fan array with the vertical provide a valuable tool
for the interpreter. A camera similar to the KA-51 with a 6-inch f/2.8 lens,
mounted at a 20-degree depression angle will provide coverage to the horizon,
and will overlap the vertical field by 10 degrees (lens field angle of 41
degrees - see Fig. 4-9). This coverage is redundant to the pan camera and
some justification of the separate functions is required. The pan camera pro-
vides an unrectified, but complete swath from horizon to horizon for direct
comparison with other sensor records which are keyed along the flight path.
The side oblique frames will be of different scale from the vertical, and to
determine keyed locations along the flight path may require some scale adjust-
ment. The oblique record could be used, however, to do comparisons with other
sensors by properly setting up the viewing system. The primary use of the side
oblique is for beach and road surveys and similar operations where perspective
photographs are desired along a long path, most easily covered by parallel
flight.
The resolution capability of the 6-inch system in this side oblique camera
is about 4 to 6 inches under standard conditions on axis (20-degree depression
from horizon).
4. Panoramic Camera - Constant Scale-Forward Oblique- A panoramic camera
has been selected to illustrate the required coverage for the forward oblique.
A normal pan system with its scale changes and scan induced degradations would
produce a distorted view from this position. The use of a constant scale pan
camera, in which the effective focal length varies with the scan, produces a
nearly distortionless wide angle frame. This is accomplished using a zoom lens
and a stationary film plane. The wide angle coverage will be quite important,
since it allows a valuable low level interpretation which nearly represents the
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7 0 ?
Fig. 4-9 Panoramic camera - 3" EFL, 70 mm or 5" format (vertical).
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fieldof view of the pilot/observer. The perspective advantage, and cover
penetration available in this view are often more valuable in gaining intelli-
gence than the vertical imagery. When combined, the pair offer tremendous
interpretive possibilities. Therefore, the field of view (120 degrees) has been
selected to give as wide, identical ground coverage as possible.
The lens system selected for this camera is a compromise between resolution
and ground coverage. Because the IMC varies across the format due to the vary-
ing range in the oblique position, a determination has been made to provide only
an average IMC correction for the axial position. Therefore the resolution over
the format will be limited by image blur caused by the aircraft speed. Since
worse resolution will be limited to anywhere from 8 to 12 inches, a 2 to 4-inch
zoom lens system has been selected to maximize areal coverage.
The use of a panoramic system also carries the advantage of a lower f
number for the system which, in turn, allows faster exposure and less image
blur from motion. The lens selected in a 2 to 4-inch, f/3.5 zoom system which
will image on a 70 millimeter format. Thus the -field of view (see Fig. 4-10)
is 50 degrees forward and 120 degrees cross-track with no resolution fall off
at the edge of the format. As noted, the resolution will vary across the format
(the forward aircraft direction) from 6 to 12 inches depending on the IMC error
at the format point.
5. Optional Frame Cameras - Vertical - It has been stated that spectrally
separated identical coverage can yield highly valuable intelligence. Using this
system for color and camouflage detection systems now appears to have great
interpretive value. Figures 4-11 through 4-14 show the comparison between black
and white, color film, and spectrally reconstituted color and camouflage detec-
tion. The resolution and information content can readily be seen. The black
and white photograph which is shown is the normal aerial filtered image, and
the reconstituted images are made by adding a near visual IR and a blue-green
image. Thus the original interpretation can be made on the black and white,
with detail, comparative work utilizing the color or camouflage detection views
when required. It is strongly suggested that the three camera array in the
wide angle vertical is a very valuable innovation for tactical reconnaissance.
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Fig. 4-10 - Frame or panoramic - constant scale pan
2" - 4" EFL, 70 mm format (forward oblique).
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Vrban area - Add i Ci of col or from black and white I,(, :,,q! i ,,c S
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This can be demonstrated by observing the features which are not noticeable on
the black and white scene, Fig. 4-15, or the color scene (SO-121) Fig. 4-16
which become immediately evident in camouflage, Fig. 4-17. As has been demon-
strated, color film processing does not currently lend itself to time pressured
operations, conversely the black and white images in the spectral separation
system are easily handled, even to inflight processing.
The reconstitution problem can be handled in viewing equipment which is
currently available.
High Altitude Photo Sensors - The following camera systems are suggested
to fulfill the requirements for photographic operations at up to 60,000 feet
altitude and ground speeds of up to 2000 feet per second, these conditions
being taken as illustrative standard.
1. Panoramic Camera - Constant Scale-Vertical - The camera requirements
for high altitude fall into two basic categories; the need for properly scaled,
large-area mapping imagery and the need for high ground resolution (1 foot or
better). The constant scale panoramic camera with a 6 to 12-inch focal length
lens system which can cover a 120-degree cross-track area is suggested to yield
the mapping imagery which is required. Cross-track coverage can be increased to
140? if required. Wide angle frame cameras, split vertical cameras, or fan arrays
could be used, but impose a weight and complexity problem. The constant scale pan
camera can use a fast lens (f/3.5) and normal IMC features and record imagery
sometimes unavailable to wide angle lens systems due to light conditions. The
vertical pan camera will have a ground resolution of 6 to 8 feet, which will pro-
vide good reference mapping capability. The field of view of this camera is il-
lustrated in Fig. 4-18 and is 25 degrees along the flight path and has 120-degree
cross-track coverage. The camera should utilize 70 millimeter film to minimize
volume and weight and, under the standard conditions, it will have a 12 cycle per
minute rate with 55 percent overlap for stereo viewing if required.
The cycle times and ground resolution for this camera indicate that it
will be an excellent mid-altitude camera which can operate satisfactorily and
with constantly improving performance at altitudes down to 5000 feet.
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Fig. 4-18 - Constant scale pan - 6-12" EFL, 70 mm format
vertical - (high-med altitude).
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Fig. 4-19 - Panoramic - 24" EFL, 5" format, vertical (high alt.)
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2. Panoramic Camera - Vertical - The major camera installation suggested
for the photographic equipment complement is a vertical standard panoramic
camera, similar in operation to the HYAC camera, that is, with stationary film
and a high resolution lens rotated about its nodal point to sweep the image.
A lens similar to the f/3.5 Petzval with a lens-film resolution of 150 to
200 lines per millimeter is required to attain the 1 foot ground resolution which
is possible under good atmospheric conditions.
With a 500 foot-lambert average light level and a 2:1 contrast using a
yellow-orange filter to reduce haze effects, a ground resolution of less than 1
foot can be expected from such a lens. The exposure time of 1/500 second and 3
percent error in IMC dictate the film resolution on S0206 would be about 130
lines per millimeter, which from 60,000 feetis the calculated resolution. At
this resolution level, the performance of any camera system is at the mercy of
the atmospheric conditions between the lens and the terrain. The contrast level
is reduced to 2:1 or 1.6:1 and turbulence cell size becomes important. On an op-
erational basis, the camera system suggested will provide the calculated resolu-
tion. From 60,000 feet, the field of view should be a 90 degrees cross-track and
10 degrees along the flight path (see Fig. 4-19) using a 24-inch f/3.5 lens on
5-inch film. Thus, a single frame will be 36 inches long and cover a 20-nautical
mile swath. With 55 percent overlap, the cycle time will be about 2 1/2 seconds,
becoming faster as altitude decreases. If operational requirements dictate a
very wide swath, the angular coverage can be increased to 140-150?, and even to
180?. Resolution, degradation, and distortion will be a problem at the higher
elevation angles however. The imagery produced by this camera will require rec-
tification if it is to be used for mosaic purposes. However, for tactical intel-
ligence purposes, there should be no need for rectification, if a proper viewing
grid can be provided for target location purposes.
3. Optional Stand-Off Camera - The mission requirements of the stand-off
sortie are not established sufficiently in the analysis made for this system
concept to allow a particular selection. In general, the long focal length lens
system useful for this mission have relatively small fields of view, ranging
from 5 degrees down to I degree or less. It is suggested that systems with a
60 to 70-inch focal length can typically resolve 2 to 3 feet at distance of
500,000 feet (80 nautical miles). A fast f/4 lens with a 5-inch format to yield
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a 4-degree field, mounted axially with sophisticated tracking mirrors and motion
stabilization, would mount nicely as an exterior-pod store. In this way the
attachments for the equipment and the control systems could be permanently
assembled, without requiring fuselage space, and relieving the dead weight
problem on normal missions.
The stand-off camera then, which can be required on some task force assign-
ments, is suggested as a pod-mounted external system, with permanently installed
control systems for quick add-on.
The photographic sensors have been selected to cover the useful fields of
view in their entirety. The concept of "cueing" or directing the photographic
sensor or any other system from another has been discarded because of the lack
of image or information continuity which this concept imposes. Each photographic
sensor will contain a standard data block system, and a key data system which
will be described in Section 4.7. The sensor complement has been reduced to
maintain all the necessary data in as few records as possible to reduce the
material handling problem. No attempt will be made to realize real time infor-
mation from any of the photo systems since other sensors on the aircraft are
better adapted to this function.
4.2.2 Infrared Sensors
In order to obtain the data described in Volume 2, Target Characteristics,
an infrared sensor must have angular resolution of the order of 0.1 milliradians
for the high altitude envelope and 1 milliradian for the low altitude envelope.
The required resolution can be obtained by a sensor having an entrance aperture
diameter of 8 to 10 inches. It will be necessary to employ an array of detec-
tors in the focal plane to achieve the required temperature sensitivity and
information rate. Hence, the field of view may be selected electronically to
correspond to the mission profile. It will be necessary to provide variable
scan rates for the optical scanner. This type of sensor will be capable of
gathering information at the maximum required rate on a continuous basis,
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limited only to the data storage and/or transmission capability. No interaction
with any other sensor is required during data gathering, although keying infor-
mation from the other sensors will appear on the infrared sensor record. In
addition, time and navigational data will be recorded.
Keying data from the infrared sensor will be quantized to provide the
coordinates on the image display plus thermal radiation amplitude. This will
form a digital word containing approximately 18 bits. It will be recorded on
the infrared record and made available to the operator display and other sensor
records.
4.2.2.1 Optimized Infrared System (Example Configuration)
Two types of infrared sensors are suggested for inclusion in the optimized
multisensor system. One of these is a forward looking device similar to a unit
presently being built by Texas Instruments Company. This unit is particularly
useful for low altitude missions and as a real time navigational aid. Its
resolution is limited to approximately 1 milliradian.
The panoramic scanner is best mounted below the aircraft in an aerodynamic
designed housing which prevents direct contact of ram air upon the optical
window. This type of mounting will also permit a minimum of 120 degree scan
angle with extension to 170 degrees if keying data near the horizon is desired
to correlate with that from the SLR. This type of mount is illustrated in
Fig. 4-19(a).
The second sensor is of the panoramic type designed for both high altitude
and low altitude missions. It is capable of 0.125 milliradians and is provided
with a real time display.
The forward looking infrared sensor scans a field 10 degrees in elevation
by 45 degrees in azimuth with a spatial resolution of approximately 1 milli-
radian. The scan is two-dimensional at rates such that six complete frames are
produced per second. The elevation angle of the center of the frame may be
altered for use during a particular mission.
The signals produced by this scanner may be recorded directly on film or
processed as described in Section 4.2.2.3.
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Recessed window rotating
with scan mirror
Fig. 4-19(a) -- Example mounting for IR panoramic sensor.
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Infrared Scanner Configuration - The infrared scanner consists of several
basic elements. Incoming infrared energy from the scene is directed into a
primary optical system by a scanning 45-degree mirror which directs the field
of view along a path perpendicular to the aircraft motion. A secondary mirror
directs the energy upon an array of mercury doped germanium detectors whose
spectral response is determined by cooled filters. These detectors are cooled
to 30?K by a closed cycle heat engine. The outputs of the detector array are
preamplified by matching electronics adjacent to the detector to the detector
dewar. The entire assembly is approximately 14 inches in diameter and 60
inches long. A summary of its pertinent parameters is given in Table 4-2.
1. Optical Configuration - A single configuration which is useful for
both high altitude and low altitude missions is illustrated in Fig. 4-20. A
10-inch diameter collecting beam is directed by a rotating 45-degree mirror.
This mirror rotates continuously in one direction, but is switched 90 degrees
twice each revolution. This provides a highly efficient scan. A 80-inch f/8
Cassegrain primary optical system forms an image upon a detector array. Two
arrays of detectors are provided; one having an elemental field of view of 1.25
x 10-4 radians and the other having an elemental field of view of 0.5 milli-
radians. The first array to be used during a particular mission is selected
by a 45-degree mirror just behind the primary.
2. Detector Configuration - Two separate arrays of mercury doped germa-
nium are located in a single dewar. One array consists of 96 elements, each
0.01 by 0.01 inch. The elements are arranged in a single line with approxi-
mately 0.002 inch spacing between elements. The technique for fabricating
arrays of this nature has been developed at Baird Atomic. A second array of
detectors, parallel to the first, consists of 24 elements, each 0.04 by 0.04
inch, with 0.004 inch spacing between elements. All detector leads are brought
out radially through the dewar wall using a 0.002 inch diameter low thermal
conductivity copper-nickel wire. The detectors are cooled to 30?K by a closed
cycle heat engine, probably employing Stierling technique. The particular
choice of cooler will depend upon the technology at the time final design
decisions must be made.
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NOTES FOR TABLE 4-4:
BWO Backward Wave Oscillator
TWT Traveling Wave Tube
CFA Crossed Field Amplifier
Paramp Parametric Amplifier
A Design Reasonable extrapolation to 1968 to 1970 time era
(weight estimates based on A system)
B Design More advanced system
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Table 4-5. Weight Estimates for "A" Design
Weight
Pounds
Transmitter 350
Receiver 225
Antenna 350 (both sides)
Recorders (see Recorder Section)
Phase Correction Computer and Synchronizer 50
Self-Test, Controls, Junction Boxes and Cables 300
TOTAL (exclusive of recorders 1275
or data link)
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range swath width again be 6 nautical miles the maximum range will be 13 miles
which occurs at a depression angle of 27.4 degrees.
From the above discussion we will establish a geometry for this mission.
Let the aircraft altitude be 6.92 nautical miles. The depression angles will be
set as those which lie between 27 and 60 degrees. A diagram illustrating this
geometry for both sides of the aircraft is shown in Fig. 4-29.
System Parameters
PRF = 1200 pps (one side), 2400 pps (both sides).
R = Maximum Range = 13.2 nautical miles = 7.92 x 104 feet.
TR = Noise Temperature = 1110? Kelvin.
v = Maximum Velocity = 1000 feet/second.
8 = Resolution = 15 feet.
S/N = Signal to Thermal Noise Ratio = 15 db.
F = System losses + Foliage loss = 4 db + 10 db = 14 db.
G = Antenna Gain = 12 db.
T = Wavelength = 3 feet.
or = Target Cross-Section = 0.5 square meters.
Pa = Average Power = 25 watts.
POD EQUIPMENT SIZE AND WEIGHT
(Including Recorders)
Volume (ft3) Weight (lbs) Power Cons. (watts)
Radiate Both Sides 22 cu. ft. 1300 lbs
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This system is designed to look for jeep size vehicles. Our best estimate
of the root mean square cross-section of a jeep for an RF wavelength of 1 meter
is 0.5 square meters which is equivalent to about 5 square feet. The receiver
noise temperature shown above allows for a 4.5 db noise figure looking into the
receiver terminals and an antenna temperature of 290 degrees Kelvin. There is
a duplexing network interconnecting the receiver and transmitter to the antenna
which has transmission losses. We must allow for the two-way loss encountered
when traversing the foliage. We will allow for a two-way foliage loss of 10 db
which is 6 db higher than the average foliage attenuation measured in the
Conductron measurements program.
Recorder Description - Space and weight limitations usually preclude re-
cording of the entire swath illuminated by the radar. Each five inch film covers
a separate range segment, and these segments may be made to lie adjacent to each
other to provide continuous coverage.
The modular design of the recording process also permits segmented recording
as shown in Fig. 4.30. Here the recorders first map a continuous range swath to
cover one target area, then map two non-adjacent areas at other ranges, and sub-
sequently map a third, continuous swath. This recorder switching can be pre-
programmed into the navigator if desired. Not shown in Fig. 4-30, but equally
simple to implement, is switching of recorder coverage to map returns from the
opposite side of the aircraft. Since this switching can be done singly or in
groups, optimum use of the total recording capability can be achieved at all
times.
Airborne recorders for synthetic-array radars have been designed, fabricated,
and tested on the Conductron Corporation AN/APQ-108 (XA-1) radar program. An
engineering evaluation has been performed to determine the feasibility of utili-
zing the concepts and key components of this design for a miniaturized dual chan-
nel broadband recorder. The recording unit which is described immediately below
can be made today with the present state-of-the-art components. The character-
istics are summarized in the following table:
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Recording Channels two 5 inch films
Volume 4 cu.ft.
Weight 150 lbs
Recording Density 40 line pairs per millimeter
Total Recording Capacity 8000 range resolution elements for the
two films plus data block information
By 1970 it is expected that this present day capability will be extended to
80 line pairs per millimeter recording density and that the weight will be re-
duced to approximately 100 pounds. These improvements in performance are illus-
trated by the graphs given in Fig. 4-31.
The dual channel recorder records video frequency signals over a wideband
width on 5-inch photographic recording film. The film is exposed by passing it
at a specified rate over the curved fiber optics face plate of a cathode ray
tube which has a linear sweep and is intensity modulated by the video input sig-
nal. Two 5-inch film recordings are made from two CRT's. The dual channel re-
corder configuration is shown in Fig. 4-28. A single capstan motor with dual
coaxial output shafts drives both recording films at a film speed proportional
to the frequency of an input pulse train which in turn is made proportional to
the aircraft velocity.
The electronics required for signal amplification, CRT sweeps, and the
power supplies are built into the basic recorder. The film spools are situated
such that they can be easily removed at the carrier without the necessity of
removing the entire recorder. Inflight film developing units and flying spot
scanner readout units can be incorporated into the recorder design at the ex-
pense of additional weight and volume.
Moving Target Indicator Processor, -- The moving target indication processor
can be mechanized with currently existing 2-gun storage tubes as shown in
Fig. 4-32. The capability of the storage tubes is approximately 600 range ele-
ments. This corresponds to 1 nautical mile swath coverage at 10 feet resolution,
or 5 nautical mile swath coverage at 50 feet resolution.
The coherent radar video data from the receiver is recorded on electrostatic
storage media in the tube. Orthogonal scanning of the readout electron beam
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PRO-j'EcTe:p F6R 1970
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Fig. 4-31 - Total range swath per 100 pounds of recorder.
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HIC114 MIME
FOWER
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Fig. 4-32 - Real time storage tube MTI processor.
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PROO'KAMNIED
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GENERp,TOR
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effectively range gates the video data. This data is translated into the proper
frequency range for the filters by a programmed mixer. The detection of a sig-
nal in one of the filter channels will give the range, azimuth and closing rate
of the moving target. This data is put into digital form in the proper format
by the coordinate computer. The output of the coordinate computer is then sent
via data link and recorded on the keying tape. The estimated weight for such a
processor is given in Table 4-6.
There is presently under development by Westinghouse Corporation a dielectric
storage belt tube which has approximately four times the range coverage of the
storage tube. This corresponds to 4 nautical miles range coverage for 10 foot
resolution, or 20 nautical mile range coverage for 50 foot resolution. The block
diagram of this processor is shown in Fig. 4-33, and the weight estimates are
given in Table 4-7.
4.2.3.4 Weight for Different Configurations
Figure 4-34 compares the weights for the radar configurations which have
been discussed in the sections above.
Comparison of Real and Synthetic-Array Radar Mapping Systems - The current
real antenna radar reconnaissance mapping systems operate at either X-band (some
with moving target indication - MTI) or at Ka-band (without MTI). This latter
category is typified by the AN/APD-7 side-looking radar in the RA-5C. This is
a "brute force" Ka-band radar built by Westinghouse. The following are approxi-
mate characteristics:
1.
Beamwidth
0.150
2.
Pulsewidth
0.1 microseconds
3.
Range
15 nautical miles
4.
Range Resolution
50 feet
5.
Azimuth Resolution
(see figure 4-32a)
The advantages and disadvantages of X-band versus Ka-band for MTI and
reconnaissance mapping are summarized in the following table.
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Table 4-6 - Weights for Storage Tube Processor
High Voltage Power Supply
2-Double Gun Storage Tubes
75 lbs
60
Programmed Reference Generator
10
5
Amplifier
1
Mixer
10
Filter Channels
Sweep and Intensity Circuits
40
50
Low Voltage Power Supply
20
Synchronizer
Table 4-7 - Weights for Storage Belt Processor
High Voltage Power Supply
Storage Belt Tube
75 lbs
20
Belt Drive System
15
Sweep and Intensity Circuits
25
Mixer
1
Amplifier
5
Filter Channels
10
Programmed Reference Generator
10
50
Low Voltage Power Supply
Synchronizer
20
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Fig. 4-32(a) - Azimuth resolution of K8-band real antenna -napping system.
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Vftw Nor
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Table' 4-10 Miniature Airborne Computer - Typical Characteristics
Physical
Size
Weight
Power
Operational
Type
Command Structure
Word Length
Memory
0.21 cubic foot (outside dimen-
sion including cooling fins)
21 pounds
High-speed, general-purpose,
stored-program, binary, parallel
Single address, 40 instructions,
three index registers
16-bit, instruction and 24-bit
data
Metallic thih film, Random access
4096 24-bit words holding 6144
16-bit instructions, electronically
alterably, BICORE film expandable
to 14, 336 24-bit words
512 24-bit words; expandable to
1024 words
Maximum Short-Instruction Operation 125,000 instructions/second
Guidance Program Operation
Instruction Execution Time
65,000 instructions/second
Single Precision Add, Substract 8 microseconds (24-bit operand)
Double Precision Add, Subtract
Multiply
Divide
Square Root
Shift
Scale (or normalize)
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12 microseconds (48-bit operand)
40-72 microseconds (48-bit product)
104 microsecond (24-bit quotient)
192 microsecond (24-bit root)
8 + 1 - 1/3N microsecond (48-bit
word)
8 + 1 - 1/3N microsecond (48-bit
word)
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4.3 SENSOR OPERATING PROCEDURES
4.3.1 Photographic Sensors
The sensor complement has been described for each of the basic systems
suggested for the multisensor mission. With the variety of equipment now avail-
able to the observer, the use of those systems can be described.
The operator should be given the responsibility for deciding on the correct
selection of sensors on a sortie. The AIO will have set up a flight path and
target list which the sortie is responsible for following. Under normal cir-
cumstances that flight plan should not be deviated from except in emergency.
The problem of "targets of opportunity" will be handled by acquiring data on
those which are in "view" with no changes in the flight plan. The systems fields
of view are shown in composite in Fig.4-41. It is felt that the AIO is responsi-
ble for the data collection and priority assignment of targets, and deviation from
an assignment must be at his discretion. He is furnished with crew observations
and fragmentary automatically classified information which may justify a change,
plus a real time IR or SLR image and the "key" data by the system, so that his
scope of action now includes redirection of a sortie based on a correlated need.
The sensor package is so conceived that the maximum useful coverage area
is included under normal operating conditions. The operator function in a target
area or between targets will be to assess the local atmospheric and flight para-
meters, and select and control those sensors which can gather useful information.
To aid in this task, the observer will be provided with a display system which
covers the area surrounding the aircraft to the limits of the sensor fields of
view. The display will have the latest order of battle status map as base in-
formation, with the aircraft position indicated on it so that. key inputs can be
instantly noted as new or old identifications. The keys refer to the threshold
indications of IR hot spots, SLR moving target indications, and reflective tar-
gets, and identified ELINT targets. These keys will be properly geographically
located on the display. The operator will also have the option of displaying
the vertical or forward IR imagery in real time for gross analysis or navigation
purposes.
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It is intended that the data link in the aircraft will relay the display
information plus operator comments via keyboard to the priority analyst associ-
ated with the air intelligence officer. The priority analyst then will have a
real time IR or SLR image, as well as the key and observer reports to guide the
analysis team in preparation for the return of the reconnaissance data itself.
The problem of display to the observer has been extensively studied and the con-
clusions are that the observer cannot perform sufficiently detailed analysis.
However, he can exercise considerable judgment on fleeting targets, and do a
gross determination of target identification which can be very valuable. The
gating factor on his performance is the human data rate, which is limited to
5-10 bits/second. By providing a reporting keyboard, and key information on a
display, the sensor system reduces the data display to the operator to a level
where he can utilize his full capability without saturation. It will be neces-
sary to provide imagery at times for navigation or analysis, and the study shows
that the IR input, already electronic and not as weather limited as photography,
is the best choice for display.
Especially at low altitude the operator would be faced with an impossible
task if required to view the very rapidly passing terrain in real time. The
features and discussion of the display system are discussed in detail in the
following section.
With the display available in real time, the operator function is greatly
eased for he can determine when a "target of opportunity" which is beyond the
scope of the flight plan is in view. He is then able at his discretion to
activate the photographic sensors, which will be the limited collection sensor.
It is suggested that the IR, SLR and ELINT records should be maintained for the
entire sortie with their reduced resolution capability. The high resolution IR,
and the photographic systems gather so much information that their use should
be delegated to the portion of the sortie of assigned and opportune value. It
is assumed that the photographic records are the prime records when available;
however, the system is designed to depend on the best resolution record that is
obtained. For example, under darkness or extreme weather conditions, the IR and
SLR, in that order, may represent the best or prime record.
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It will bethe function of the operator/observer to control and checkout
the operation of the sensors. Each device will have a control panel and check-
out panel when required. There will also be a master selective/operation panel
for the entire system close to the display system.
4.3.2 Infrared Sensors
During a mission, the operator will be able to control the infrared sensor
only insofar as he may select an on, standby, or off mode plus semi-automatic
equipment checkout. If operation considerations require it, he may in addition
be given manual override on the scan rate and sensor gain controls. Normally
these would be automatically adjusted by a V/h sensor and automatic gain control
circuitry.
A synthetic display will be provided the observer which will include a
mission map or photograph plus OB data, and keying information from the infrared,
SLR and ELINT sensors. The operator may select the thresholding levels for the
IR key data and the effective field of view of the IR sensor for keying purposes.
This does not affect the field of view of the raw data being recorded.
The key information, in addition to appearing on the sensor records and on
the synthetic display, may also be recorded in a temporary hLgh priority data store.
This information may be transmitted directly back to the carrier, or alternative-
ly, to a user at the battle line. This allows transmission of artillery direct
information, or indication of areas of high activity with a minimum delay time
and minimum interpretation requirements. Correlative data from the SLR and
ELINT sensors is also transmitted to provide additional confidence. Because of
the relatively infrequent occurrence of high priority key data, a narrow band
width communication link may be employed with extensive coding to prevent
jamming.
The observer may elect to display the IR imagery data directly rather than
the synthetic display. The mission map and OB data will be retained and the IR
imagery will be in essentially real time so that the observer may compare the
map and the imagery to aid navigation and/or target recognition.
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4.3.3 High Resolution Side Looking Radar (HRSLR) Sensor
Radar sensor operating parameters can be divided as follows:
1. Preflight
2. Inflight
3. Post-flight
These phases can, in turn, be divided into systems check-out, mode selection,
parameter selection, and data handling procedures. Each phase is discussed
below.
4.3.3.1 Preflight
The preflight check-out procedure includes sequential tests utilizing
self-test features of the radar in conjunction with the airborne computer
and observer display. A synthetic signal generator will be used to give an
output on the observer display which will indicate operation of the basic
radar, MTI processor, and radar imagery raw data scanner. These three outputs
will serve as a go no-go subsystem test. As part of the inertial system gyro
erection and alignment, the inertial inputs for motion compensation can be
checked.
If the system is configured to have additional modules (for example,
additional recorders or a low frequency radar pod), then these modules are
installed when missions and weather justify their use. Radar parameters and
recorder switching sequencing can be stored along with navigation data in the
computer or can be included in the briefing material of the observer depending
upon whether automatic or manual techniques are employed.
4.3.3.2 Inflight
After take-off and before entering the initial target area, the radar
system is turned on and sequenced through the warm-up cycle. The observer
decides when to transmit based on the mission requirements. Transmitting
periods are minimized to avoid alerting enemy defenses. For each target area,
the recorder and MTI processor range segments are chosen. The observer can
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also select the MTI processor output for the observer display. A priority
range segment to be recorded for output scanning and telemetry can also be
selected. At the time range segments are selected, other parameter changes
such as antenna pointing, PRF, and one or two side operations of the aircraft
are also chosen.
4.3.3.3 Post-flight
Upon aircraft return to the carrier, the recorder raw data film recorders
and the MTI keying data (on the data key and navigation tapes) are removed from
the aircraft and taken to the data analysis center aboard ship. The keying
data can be immediately used by the priority analyst or interpreter. The raw
data films are photoprocessed and then output image maps are made in the ship-
board optical correlator. These output images are then photo-processed and
used for image interpretation and change detection. This sequence is maintain-
ed as a higher resolution image back-up to the SLR data which may have been
transmitted, and already be in analysis when the aircraft SLR imagery is
available.
4.3.4 ELINT Sensor
4.3.4.1 Mission Planning and Briefing
The multisensor reconnaissance mission is designed to meet the data re-
quirements of the carrier air intelligence officer. Depending on the type of
data needed, the terrain to be overflown, the known threats to be encountered,
and other factors, the air intelligence officer prescribes the flight para-
meters, the target areas, and the sensor application. All key flying and non-
flying personnel receive briefings and instructional material to coordinate
the preparations and assure a successful flight.
4.3.4.2 Data Loading
In addition to the information required by the air crew, data must be
loaded into the ELINT system and its airborne computer, depending on the type
of mission and tactics to be employed. Some of these data are as follows:
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1. Special Signal Table - parameters describing emitters of special
interest, known to be in the environment.
2. Computer Instructions - stored program for the computer - includes
processing modes, dwell times, self-check routine, etc.
3. Radar order of battle along the route.
The above information is loaded into the ELINT computer by means of
magnetic tape using a portable magnetic tape reader. The radar order of
battle along the route is automatically prepared by the central data pro-
cessor on the carrier, utilizing the planned route and altitude and the
complete ROB as input data.
4.3.4.3 Preflight Checkout
A combination of Aerospace Ground Equipment (AGE) and built-in test
equipment is required to ensure that the operational requirements of the
ELINT system will be met.
For flight-line testing, to determine flight readiness, the ELINT sensor
system will contain semi-automatic, built-in test facilities. Also, facilities
will be provided to prepare the system for specific mission objectives. To
supplement the fault-isolating capability of the built-in equipment, a minimum
of portable flight-line AGE in required.
Built-in test facilities are required to perform, on the flight line, a
rapid qualitative, self-assessment of the state of readiness of the ELINT
system to perform its assigned task. These facilities will provide for a
rapid, semi-qualitative check of almost all the functions of the system in-
cluding all channels of all receivers. The test time for performing a semi-
automatic functional checkout is estimated to be 10 minutes. For possible
preflight, an abbreviated version of the complete test, limited to particular
bands and word types, can be made in significantly less time. In addition,
by the use of the ELINT airborne computer for programming and data analysis,
the complete self-test time can be considerably reduced. However, unless the
possible savings in test time warrant the additional expense and complexity
of automating completely, it is felt that the semi-automatic approach to
testing is adequate.
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The preflight check of the ELINT subsystem consists of injecting simulated
emitter signals into the system from broad-band interference generators mounted
in the vicinity of the antennas and, at the same time feeding a simulated navi-
gation output to the computer. The airborne and carrier displays are energized
and a short simulated flight is flown, using cable for link transmission. To
save time, only the factors most critical to the success of the specific mission
are preflighted.
4.3.4.4 Inflight Check
Depending on the extent of preflight testing, some cursory checks may be
desirable after take-off. The carrier itself provides an excellent target for
MTI and infrared checkout. In addition, unless strict electronic silence is
being maintained, it will provide one or more emissions for the airborne ELINT
subsystem. Consequently, it would be profitable to energize the multisensor
system immediately after take-off and if radio transmission is authorized, to
transmit sample data on low power to the carrier. Obviously, if minimum opera-
tion for the mission is not obtained at this point, the aircraft should be
immediately recalled.
4.3.4.5 Reconnaissance Run
The observer readies for the run by turning on his passive sensors and
noting the displays. When the reconnaissance area is reached, the recording
equipment is energized and keying data are available for the narrow band link.
At low altitudes, the wide band data link is out of line of sight from the
carrier, and hence is not used until the aircraft climbs out of the recon-
naissance run.
The observer monitors his multisensor display and used his observer
push buttons to interject his own keys, and otherwise follow the status of the
mission. He also maintains a watch for threats, both visually and on the dis-
plays and informs the pilot accordingly, using his ECM if required. In addition,
he may perform navigation fixes by map-matching the terrain overlay with the IR
map image, or by visual observation of the terrain.
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The observer exercises his judgment when required, by overriding the
computer to freeze images, to set display scale factors, to give transmission
priority to a particular target, to shut down a poorly performing sensor, and
to accomplish a host of other details.
4.3.4.6 Wideband Data Transmission
The resumption of line-of-sight with the carrier can be detected by
acquisition of the reconnaissance aircraft on the carrier radar, computation
from navigational data, monitoring a signal transmitted from the carrier, etc.
When line-of-sight is indicated, the IR, ELINT and HRSLR data take is trans-
mitted to the carrier, giving the air intelligence officer a lead on the data
processing and evaluation task which must be performed before the follow-up
mission is launched.
On the return flight to the carrier, the airborne computer could be used
to process the pulse word data which was not reduced to keying symbols. Any
additional keys generated during this operation can be immediately transmitted
on the narrow band link. It may be profitable to widen the list for this phase
of operation to include more than the original 20 priority emitters.
On request, portions of the narrow and wideband transmissions which were
not satisfactorily received by the carrier are re-transmitted. It is advisable
to secure a complete transfer of data to the carrier as quickly as possible to
hedge against the possibility of loss of the aircraft on the return flight.
4.3.4.8 Post-Flight Operations
The data delivered by the aircraft after landing on the carrier consist of:
1. Photo-reconnaissance film (already processed).
2. IR map and tape (W).
3. ELINT pulse word tape.
4. Keying tape (N) (W).
5. HRSLR film already processed (W).
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An (N) or (W) following a data item means that the data has already been
transmitted via the narrow band or wide band link, respectively.
The data cannisters are immediately unloaded by carrier personnel and
rushed into the appropriate processing and display areas, while the flight
crew is debriefed for intelligence and equipment performance information.
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To provide tactical reconnaissance under all weather conditions, in
day or night flight, it is required to use multisensor reconnaissance
systems that provide target information from infrared, radar, photo, and
ELINT sensors. Although each of these sensors provides unique information
that can serve to supplement an observer's intelligence evaluation, the
variety and quantity of information could easily overload, or degrade,
the observer's capacity to use it, if it were indiscriminately displayed.
Suggestions for presenting the different forms of data range from
a separate display for each sensor, to some combination or superposition
of all available sensors. A more realistic technique would fall somewhere
between these two extremes.
In the multisensor system recommended in this study, a "situation"
type of real-time display has been advocated as a powerful method of
integrating the reconnaissance observer into the multisensor data manage-
ment loop. As pointed out earlier in this study, the aircraft observer
is a "fifth sensor" with unique capabilities which should be exploited
in optimizing the overall intelligence system. Certainly his capabilities
for monitoring, evaluating and applying judgment to a rapidly changing
set of stimuli are unmatched by any computer or machine. To ignore these
capabilities would be to remove from the multisensor system a valuable
source of dynamic intelligence.
It is imperative, therefore, to design the observer's real-time
situation display so that its output matches his data handling capability.
Complicated displays, rapidly changing data, fancy overlays, and the
excessive use of controls to be actuated, must be minimized. This is the
justification for the elementary display recommended herein--sensor activity
"keys", against map-type image backgrounds when desired.
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The multisensor information available for display is likely to be
more than the observer can use of interpret at certain phases of the
mission. Consequently, some degree of filtering before presentation is
essential. Any filtered reconnaissance data should be classified and
coded with respect to target signatures and threats to the aircraft.
ELINT data lends itself readily to such categorizing and coding, as
do the HRSLR and IR returns which can be coded according to moving tar-
get or heat intensity patterns. When scanning techniques can be used to
intercept pictorial information, as in the case of the IR, identifiable
terrain features or desired target signatures could also be displayed.
The coding should clearly differentiate targets from one another, as well
as from threats, and give some indication of the level of priority for
each.
Before examining techniques for displaying multisensor information,
it would be of value to consider briefly the problems of display for each
available sensor. The manner in which reconnaissance data are to be pre-
sented is greatly influenced by the nature of the energy source and the
sensor itself. For example, the photo, IR and radar mapping images pro-
vide a "literal" pictorial representation of a ground target, but IR hot
spots, radar MTI and ELINT emitters constitute only a "symbolic" relation
to the real target. The transfer of target appearance to luminance values
on a display also varies considerably for different sensors.
To these variations can be added characteristic differences in dynamic
range, resolution, and distortion inherent in a given sensor. The dis-
play properties that can influence the obderver's interpretation of the
information presented by each of three types of sensors to be displayed
will be briefly considered: IR mapping, ELINT, and high-resolution side-
looking radar (HRSLR).
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4.4.1 Infrared Mapping
This sensor is optimum at large depression angles below the hori-
zontal with the aircraft directly over the target area. At long range,
the image suffers from perspective distortion and loss of resolution.
The pictorial image presented by an infrared sensor can differ in form
and outline when compared with optical sensors, but it heightens the
detectability of certain targets that possess distinctive temperature
gradients. Infrared is better able to penetrate haze than optical sensors,
and functions well in total darkness. Also, local "hot spots" such as
vehicle engines, warm building, etc., can be seen through conventional
camouflage. However, infrared is severely hampered by heavy cloud cover.
Infrared mapping obtained by a line-scan transverse to the vehicle
track, combined with scaled motion of the integrating medium (tape) along
the vehicle ground track offers high sensitivity and resolution. However,
the integrated map, thus generated, suffers from both overlapped data and
degraded resolution in parts of the display during yaw turn maneuvers.
In the optimized multi-sensor system, keying signals which exceed
the amplitude of preestablished amplitude "thresholds" will be generated
from exceptionally hot targets and presented to the real-time display, in
addition to the map image. At the time the "hot spots" are separated from
the threshold, a time signal and cross-range location code will be added
and the entire "key" digitized for use by the display, the keying tape
and the data link.
4.4.2 Radar
Since the range capability of radar is greater than optical or infrared.
it provides a tactical reconnaissance advantage because it can supply
ground target information at distances of 50 to 100 miles. The high
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resolution capabilities of HRSLR anywhere within its range can provide
target characteristics close to those of a pictorial display. However,
the displayed radar image does vary from optical and infrared images in
target and background relationships because of differences in distribution
of signal strength. Since radar operates best at relatively low grazing
angles, shadowing effects will also influence target and background display.
A primary advantage of the radar display in comparison to optical
sensors is its capability of providing ground target returns in any
weather. A disadvantage is that it is an active system, which is of some
concern when entering a hostile environment.
In addition to the capability of the HRSLR to generate a map-type
image, it also has the. unique capability of providing indication of
moving targets. The spot images produced by the moving target indicator
(MTI) result from the component of target motion normal to the broadside
direction of the radar antenna in the reconnaissance aircraft, and can
be compared to a threshold as in the case of the IR hot-spot signals.
The MTI threshold, however, is a velocity threshold, instead of an
amplitude threshold, and allows only moving targets above a prescribed
velocity (in the vicinity of 5 mph) to be passed. The key to be displayed
by this sensor consists of the target velocity and heading as well as
its time of arrival and cross-range location. Because of the large
amount of airborne equipment required to derive the high resolution radar
map in the reconnaissance aircraft, and the doubtful value of the map
display to the reconnaissance observer, only the radar MTI keys will be
displayed.
ELINT sensor information has traditionally been confined to operator
analysis displays. The ELINT operator has been the intelligence device
for identifying radars. The proposed ELINT output data are the identification
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of prescribed emitter functional types and the symbolic display of emitter
targets. Thus, prescribed emitter functional types and their location
become the keys presented to the situation display.
4.4.4 Display Combinations
Rapid, precise identification and location of significant targets
requires that information be presented to the observer using the several
sensors cooperatively in a multisensor display. Simultaneous use of
several or all of the available sensors suggests: (1) the separate display
of each form of information Atmultaneously, {2) the presentation of one
sensor at a time in some desired sequence, or (3) the combination of
sensors by controllable display superposition.
The first approach is obviously limited by the number of separate
displays to which the observer can attend, the display size and number
permissible in a cockpit. It is almost certain that the observer could
not correlate data from such an arrangement satisfactorily because of
data rate limitations.
The second approach allows flexibility of sensor selection at any
phase of the mission. However, it forces the observer to relate the different
sources of information to one another over a period of time. Scale factors
also have to be kept in mind by the observer from one presentation to
another.
The last alternative, with some degree of variation, is recommended
as the most attractive approach, since it permits the sensor displays to
complement one another. Thus, information from one sensor may be super-
posed or added to the display of another, at the observer's option, to
enhance target recognition or to extend geographical coverage.
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4.4.5 PHOTO/Infrared
Since these sensors provide literal display data of nearly equal
resolution, and since optimum pictorial information is achieved when the
vehicle is near or directly over an area of interest, one or the other
is sufficient for the observer's map display. However, since the IR sensor
provides as good a return at night as it does in daylight, it has a
slight advantage in this respect. A final advantage of the IR sensor
over the PHOTO, for the real-time observer's display, is the fact that
the real-time IR display is much simpler to generate and requires less
equipment in the aircraft than the photographic display. The conclusion
reached is that the use of only the IR map-type display is preferred for
the map-like image on the observer's display.
4.4.6 Radar/ELINT
These sensors should provide a highly compatible combination, since
both can be used at considerable distances from a hostile area. ELINT
target information and MTI information will enhance the identification
and location of potential threats or desired targets.
4.4.7 ELINT/IR
ELINT also would be compatible with the map image or hot-spot Coded
information of the infrared sensor, since it can continue to provide
symbolic indications of the electronic environment and potential threats
when close to the target area.
4.4.8 Radar/Infrared
This combination is desirable in that the infrared returns display
both map and "hot" objects (unique targets) for superposition with the
radar MTI information.
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4.4.9 Display Coding
Coding of the display to identify targets can be based on target
type, and target priority. The code dimensions may include: numerals,
letters and/or symbols for target identification; shape coding (geometric
figures) for priority coding with no more than 15 priority levels; and
possibly color to augment the basic coding scheme. If compound coding
is required, the numerals (or letters) could be surrounded with an
appropriately colored geometric figure.
In a dense target environment, the display of many target signatures
and threats could tax operator search and decision making. To minimize
this the optimum brightness level and contrast ratio are required, with
a clear definition of coded symbols.
Numerals or letters should be no smaller than 5 minutes of visual
angle, with the maximum dimension of any geometric code symbol subtending
no less than 10 minutes of visual angle. Symbol density should be kept
to a minimum on the display because the search time required to find a
numerical symbol has been shown to increase rapidly as the number of
symbols exceeds 25..
4.4.10 Physical Display Characteristics
Assuming optimum display location (about 15 to 30 inches from the
observer's eyes), the more critical aspects of combining display infor-
mation will be concerned with the following:
Display Size and Scale Factor
The larger the display, the greater the increase in observer
search time. However, the optimum display sizes and scale factors may
vary depending on the technique used. For example, radar recognition has
been found to be best for a 12-inch display, and decreases rapidly as the
5-inch display size is approached.
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and by any control actions he may be capable of performing. An adjunct to the
real-time display must be provided, therefore, to enable his tactical "keys" to
be inserted into the data chain with the other sensors, and to provide him with
the sensor controls required. A "push-button" type of keyboard is recommended
for his communication outlet. By proper attention to the human-factors engineering
involved in the design of the keyboard, it could be made to handle the observer's
comments and observation, (keys) plus the control of sensor data transmission to
the carrier over the data link and HF channels. The keyboard lends itself readily
to the instrumentation of the digitally-coded communications link. By formating
the output of the keyboard in the same digital language being placed on the keying
tape, the observer's contributions on the tape will function in identically the
same manner as the other sensor keys, to expedite and control the ultimate separa-
tion of the highly significant data from the total take.
4.4.14 Typical ELINT Display
This section describes an ELINT display concept which facilitates the
correlation of ELINT with MTI keys and with IR mapping. The guidelines estab-
lished in the previous discussion were used in the derivation of the display
concept.
The conceptual ELINT display is shown in Fig. 4-42, The display is sta-
bilized about the aircraft position with the projected ground track vertical.
The range scales are a function of altitude, with the appropriate display cir-
cuit parameters and scale numerals selected by the CLINT computer.
Each emitter is identified by a single letter descriptive of its function,
i.e., "M" for missile control, "S" for surveillance, and so forth, and is dis-
played at its computed position relative to aircraft. The emitter location is
updated several times as the aircraft approaches it, the fresh location printouts
being bright, gradually fading away as they are superseded by new printouts. The
most accurate location data is printed as the aircraft passes the emitter, because
of the favorable relative bearing and the large number of previous bearing fixes
obtained.
MTI and IR hot-spot keys are also printed on the display, with special
symbols used for each (circles for all moving targets and squares for all hot-
spots, for example). The map image from the IR sensor appears in the background
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w -)
2S zo
10 5 0 5 to
?.Ata(E -NA.U T. t.J t l -E S
1:i' zO
Fig. 4-42 -- ELINT situation display.
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4.4.11 Luminance and Contrast
Minimum resolvable visual angles depend upon brightness level
and contrast ratio. Summations of brightness may prove beneficial to
detection, using display combination or superposition,-but contrast
changes are likely to affect symbol detection adversely if not properly
adjusted.
4.4.12 Orientation and Navigation Display
If the multisensor activity information is displayed over a map
pattern analogous to the terrain below, there is an advantage in showing
target signatures or threat indications in geographic relation to the
aircraft and to one another. This makes possible more immediate and
accurate responses to threats and targets. The map-type display is most
effective when only the significant data from each sensor (heavily filtered
and coded) are superimposed on the map background.
It is likely that much of the observer's interest will be ahead
and to the side of the reconnaissance vehicle. But enough interest should
remain for threats and overlooked areas to warrant the use of almost a
full 360-degree map display. If the aircraft symbol is positioned some-
what near the center, with the moving terrain and target symbols changing
beneath it (that is, a plan view), a realistic "situation" display will
result.
4.4.13 Observer Keying
The primary reason for the observer's display is to assess him of
the tactical situation at hand. Through the instantaneous display of
the high-priority data being collected, he can contribute to the intelli-
gence being gathered by the addition of his own observations and evaluations,
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of the display plus a synthetic map of the battlefield area to be covered by the
flight. The synthetic map would be moved in synchronism with the aircraft flight
path by signals from the aircraft navigational equipment. Each map image can be
independently faded into the background at the convenience of the observer.
The most difficult problems associated with the presentation of the super-
imposed sensor displays occurs at low flight altitudes because of the disparity
in the coverage areas of the three sensors and the speed at which the area is
overflown. The problem in coverage area is illustrated in Fig. 4-43 for a flight
altitude of 500 feet. At this altitude the ELINT system can "see" to the radio
horizon, which is approximately 30 miles. The IR sensor, however, can only dis-
cern its map image and hot-spot keys, with any degree of reliability, to a range
if 0.5 nautical miles while the high-resolution side-looking radar can see with
good fidelity to 1.5 nautical miles.
These ranges for the IR and radar sensors are based on usable angles of 80
degrees and 87 degrees, as shown in Fig. 4-43. A value of 60 degrees is custom-
arily used as the outer limit for recognizable imagery for the IR, but for hot-
spot keying, angles as large as 80 degrees may be usable. The radar can see fur-
ther, and will display approximately an 8 nautical mile strip of range. Therefore,
its minimum range scale is shown as 4 nautical miles on Fig. 4-43. Values of R
versus a for other flight altitudes are also tabulated for each sensor on Fig.4-43.
The difficulty in display at the low altitudes is thus apparent. If very
short range scales are employed to favor the IR, full advantage will not be taken
of the forward looking keys from the radar and ELINT sensors. If larger range
scales are employed to favor the radar and ELINT, the IR hot-spot keys will be
crowded in the center of the display. At high altitudes, all sensors will cover
a large view, as may be seen from the values of R versus altitude tabulated for
each sensor on Fig. 4-43, and the correlation of keying will be excellent.
A number of solutions are practical to solve this scaling problem at the low
altitudes, and the following will be discussed here:
1. Multiple scales
2. Off-scale annotation
3. Logarithmic scales
4. Dual plots
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IR
cr 80?
cr - 87 ? I
(Flat-Earth)
Assumption
ELINT
Horizon
Alt. Range
500 - 0.5 NM
1 K - 1
2 { - 2
5 K - 5
10 K - 10
25 K - 25
50K- 50
500 - 1.5 4
1 K - 3 4
2 K - 6
5 K - 15
10 K - 30
25K- 75
50 K - 150 NM
500 30 NM
1 K 40
2K- 60
5 K - 100
10 K - 130
25 K 200
50 K 300
Fig. 4-43 - Sensor coverage areas (500 feet altitude).
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In the multiple-scale display, the observer will have three range scales
labeled IR, Radar, and ELINT respectively. When set to one of these positions
the range scale will be automatically adjusted as a function of altitude (by the
airborne computer) but will follow the program for the sensor selected, as shown
in the small tables of Fig.4-43. All sensor keys will be displayed at their correct
location, regardless of which scale function is being used, but will be favored
according to the observer's selection. If the ELINT scaling should be selected,
for example, a thirty mile full scale will be displayed at 500 feet altitude and
the display will look like Fig. 4,42. In this display IR hot-spot keys will be
crowded in the center 1-mile rectangle as shown, while the radar moving target
keys will be contained within the large 10 mile rectangle, looking forward.
Conversely, if the IR display scaling were selected, the full scale range at 500
feet altitude would be only 1 nautical mile (?0.5), automatically varying with
altitude as shown in the IR table of Fig. 4-43. Some of the radar, and most ELINT
keys would fall outside the displayed view (perhaps in the margin so that they
will not be lost to the observer) and the display will favor the IR sensor.
Although the multiple-scale system will not completely correlate the observer's
display for low altitude multisensor viewing, the keying signals will not be lost
or distorted on the keying tape and full correlation can be done on board ship.
The aim is to provide the observer with a simplified display useful for overall
evaluation of the situation.
In the off-scale annotation type of display the range is automatically pro-
grammed with a short range scale at the low altitudes, and off-scale keys are
displayed in the margin. The same function can be achieved by one of the switch
positions in the multiple-scale technique.
Logarithmic scales appear to be a useful solution for this application, since
they expand the inner and compress the outer portions of the scale in exactly the
manner desired. However, polar plots must be used to maintain the true angular
bearing relationship of targets to the aircraft with the log coordinate, and
severe X-Y distortions exist with this type of display.
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In a dual-plot arrangement of displays, a small display would be supplied
just for long-range ELINT targets, and the proportionally-scaled displays re-
served for the IR and radar. Short-range ELINT keys would still be present on
the IR radar display.
To make the low-altitude IR map image useful to the operator, it must be
stopped for examination. This can be done by depressing a stop button at the
correct moment. However, the image moves so fast at low altitudes that the
normal reaction time makes timely action difficult. One solution available to
aid the operator in this respect is to automatically "freeze" the display when-
ever specific keys from any emitter appear on the display. Target keys produced
ahead of the aircraft by the radar and ELINT would be used for control of the
display. However, the keying tape (in conjunction with the airborne computer)
could be employed in a number of ways to control the observer's display. Since
automatic freezing of the display is not necessary at altitudes above 3000 feet
or so, because of the greater amount of time available to the observer, a manual
freeze can also be used.
Note the freezing of the IR map data will result in missing data frames.
Keying data continue to be supplied to the keying tape and to the data links.
Since forward looking keys are used to control data framing, the operator, (in
conjunction with visual reconnaissance), is better able to assess the mission
situation. Thus, improved operator keying plus better data priority ordering
and data linking to the carrier will result.
It should be emphasized at this point that when the keying tape data is
being transmitted to the carrier by either the wideband and/or narrow-band data
link, a real time display, identical to the observer's display in the air will
also be functioning on the ship. Thus, identical "freeze" functions are also
available to the reconnaissance analyst.
A valuable reconnaissance contribution can be provided by applying the
analytical judgment available in the observer. In applying this capability in
the context of high performance aircraft, one must consider the problems as well
as the advantages of direct visual observation.
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In a dual-plot arrangement of displays, a small display would be supplied
just for long-range ELINT targets, and the proportionally-scaled displays re-
served for the IR and radar. Short-range ELINT keys would still be present on
the IR radar display.
To make the low-altitude IR map image useful to the operator,it must be
stopped for examination. This can be done by depressing a stop button at the
correct moment. However, the image moves so fast at low altitudes that the
normal reaction time makes timely action difficult. One solution available to
aid the operator in this respect is to automatically "freeze" the display when-
ever specific keys from any emitter appear on the display. Target keys produced
ahead of the aircraft by the radar and ELINT would be used for control of the
display. However, the keying tape (in conjunction with the airborne computer)
could be employed in a number of ways to control the observer's display. Since
automatic freezing of the display is not necessary at altitudes above 3000 feet
or so, because of the greater amount of time available to the observer, a manual
freeze can also be used.
Note the freezing of the IR map data will result in missing data frames.
Keying data continue to be supplied to the keying tape and to the data links.
Since forward looking keys are used to control data framing, the operator, (in
conjunction with visual reconnaissance), is better able to assess the mission
situation. Thus, improved operator keying plus better data priority ordering and
data linking to the carrier will result.
It should be emphasized at this point that when the keying tape data is being
transmitted to the carrier by either the wide band and/or narrow-band data link,
a real-time display, identical to the observer's display in the air will also be
functioning on the ship. Thus, identical "freeze" functions are also available
to the reconnaissance analyst.
A valuable reconnaissance contribution can be provided by applying the
analytical judgment available in the observer. In applying this capability in
the context of high performance aircraft, one must consider the problems as well
as the advantages of direct visual observation.
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The observer's keying display will be in constant operation from the GCI
line until departure from hostile territory. The observer will constantly
monitor this display to -ascertain combinations of superimposed keying data
indicative of critical fleeting target activity. Activation of those sensors
limited to intermittent operation will, in large measure be initiated by the
observers analytical judgment of the meaning of data on the keying display.
Diversion of the observers attention from this display could disrupt his con-
centration and increase the probability of missing important data for sensor
activation.
In the context of high performance aircraft, direct visual target observation
in both the high and low operating envelops cause severe problems. In the low
mode at a velocity approaching Mach 1, the period a point target remains under
observation even if the observer has been alerted to its presence and picks it up
immediately, is too short to perform reliable identification much less activity
analysis. Without some external cueing assistance, there is a high probability
that a point target will pass totally unobserved. Operating at Mach 2 or more
in the high envelop, the observer can only perform a gross target analysis with
the unaided eye. A more detailed target evaluation will require considerable
magnification using optical or electro-optical devices. A number of possibilities
have been considered to aid the observer in direct visual observation as follows:
1. An optical or electro-optical viewer with automatic pointing controlled
by the keying data vector information generated for the display and activated at
specific thresholds of key data activity.
2. An optical or electro-optical viewer automatically pointed by the keying
data vector information activated at the observers option to points selected
from the keying display.
3. An instantaneous video recording of a target selected by techniques
described in 1 and 2 above, to be:
a. viewed by the observer
b. transmitted to the carrier for analysis
c. both the above options
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Considering human limitations as well as operational problems options 1, 2
and 3(a) would divert the observers attention from the keying display. In addi-
tion at law and high altitude option 1 in an active hostile environment the
system would tend to change from target to target at a very high rate, totally
confusing the observer. Option 2 has limited merit for high altitude operation
provided the input optical system could be made to track a point for a sufficient
time to permit analytical judgment. At low altitude option 2 becomes ineffective
because of the extremely short time the target remains in line of sight. Option
3(a) under observer control would provide the necessary target image persistence,
but while the observers attention was diverted to permit image analysis, the
acquisition of additional images based on the keying display would cease option
3(a) under automatic control could produce a volume of imagery which would exceed
the observers capability to keep abreast of the current environment. Option 3(b)
under observer control is the only combination of techniques and equipment
permitting selective acquistion of meaningful imagery and providing these data
to an environment where proper analysis and correlation can be applied and where
the analysis can result in appropriate command action.
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4.5 AIRBORNE DATA PROCESSING
The general conclusion regarding timeliness as derived from the operational
analysis clearly emphasizes the requirement for shortening the time required for
providing viewable material to the analyst. In this area then, the case becomes
clear for airborne processing of all records to the point of viewability. With
the IR, SLR and photographic material, onboard, in mind that the number of
records were reduced to a minimum. An additional problem is present if the
coherent radar system is used. The radar system requires an optical correlation
-step between the first film record and a viewable image. The weight/volume
requirements of such equipment suggest that it be ground based, thus the SLR
processed film should read out over the wide band data link if possible, to
shorten the availability time of the imagery so that it is ready when the
aircraft returns.
The ELINT information will be processed in flight so the data will be
available on tape when the aircraft returns from the mission.
Because the need for IR detail arise only during intensive analysis of a
small area, a redundant record will be made from the primary IR magnetic tape.
The imagery film record will be produced from the tape on the aircraft, and
inflight processed to produce a readable film upon recovery of the aircraft.
This image will be the prime IR record for analysis, with the tape containing
the fine temperature information available for detail work as required.
There is electronic format imagery available from the IR and the SLR
system; however, the photographic imagery would not add significantly to the
available records for real time use. Because of the degradation from the real
data content required for transmission in near real time, and the complexity
of the equipment required to produce this degraded transmission, there is no
suggestion for photographic imagery transmission in the system concept.
4.5.1 Airborne Photographic Processing
The case for airborne processing has been discussed and it was determined
that the processing scheme of such a system would produce 1) a positive image
and a negative, 2) maximum film resolution and 3). minimum system complexity.
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The purpose of airborne processing is to save time, and while producing a
negative is such a saving, the final desired product is a positive transparency.
Under this requirement, the processing system utilizing a saturated film material
which forms a positive by diffusion has been selected as meeting the requirements.
This system is typified by the Eastman Kodak Bimat process, although other
similar materials are available.
Each of the photographic sensors then will incorporate a processing
magazine so that the positive imagery is available on return of the aircraft.
There is no significant degradation in resolution on the films in probable
use with the system.
4.5.2 Airborne Infrared Processing
The electronic signals from the infrared scanner are processed to obtain
keying data and to provide high resolution imagery. The high resolution
information is recorded for interpretation in the intelligence data processing
center. This data is also transmitted in essentially real time by a wide band
data link. Low resolution imagery is displayed upon request by the observer.
The keying information is displayed to the observer and also recorded on a
separate keying tape which is transmitted in real time on a separate data link.
The data processing includes combining the detector channels to obtain
required resolution element size, amplitude threshold, and formatting for
transmission or display.
Prior to thresholding or decision making, the data remains in analog form.
Signals exceeding threshold are converted to digital format which includes
position, amplitude, and time information. The infrared imagery remains in
analog format, and the keying information is presented in the digital format.
The IR signal may be recorded directly on magnetic tape for delayed
transmission and/or permanent storage. If it appears desirable from the stand-
point of correlation with the photographic sensor, the IR data may, alternatively,
be recorded on film and processed in a similar fashion to the photographic record.
The disadvantage of employing film is that the quantitative nature of the IR
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data is impaired. The advantages of high storage density and comparable record
handling and data transmission equipment may out weigh the quantitative
considerations, particularly if the primary use of the IR imagery is for visual
interpretation and the only automatic processing is that performed in near real
time under control with the operator.
The bandwidth of the IR video data is sufficiently narrow (5 megacycles)
so that it can be handled on a real time microwave transmission link. Alter-
natively transmission may be delayed and altered in time scale by including
a storage medium such as magnetic tape or photographic film.
4.5.3 Airborne SLR Processing
Electronic or coherent optical signal processing techniques may be
employed to process the synthetic array radar raw data to obtain imagery maps
or to process the data for moving target indication. With the present state-
of-the-art, electronic processing has proved less efficient than coherent
optical processing, in terms of the weight and power required for processing
at a specified data rate (in resolution elements per second). Further develop-
ments in storage media and electron beam technology may make electronic pro-
cessing attractive in the 1970 era. Even with the present state-of-the-art,
electronic processing can be used for moving target indication while in flight,
although the number of range resolution elements is restricted.
There appear to be very good reasons to perform inflight signal processing
to obtain moving target indications, since this indicator can be used as an
alerting and keying device for the radar imagery and other sensors. However,
there appears to be little reason for doing in-flight image processing just for
the purpose of presenting the output to the aircraft observer, since the
observer does not have sufficient time to absorb the information at the sensor
output data rates from even one of the imagery sensors. Therefore, the principal
reason for doing in-flight processing of imagery is to shorten the time involved
in transferring the imagery from the aircraft to the carrier, and then to the
reconnaissance analyst. It is not clear whether this time saving is commensurate
with the additional amount of airborne equipment required, with the resulting
problems in weight, power, complexity, reliability, and cost.
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4.5.4 ELINT Airborne Data Processing
The airborne data-processing elements are depicted in three blocks at the
bottom left-hand side of the Optimized Multisensor System Diagram, Figure 4-44.
These blocks are labeled Signal Process, Recorder and Storage.
The signal process block consists of several units depending on the exact
configuration of the system. Typically the units are: (1) the logic and control
system (computer), and (2) an auxiliary data converter with a digital clock.
The logic and control function is applied by a high speed, microminiaturized,
general-purpose digital computer. Typical characteristics for such a computer
are a 1-mc clock rate, a word size of 30 bits with a memory expandable to
32,000 bits in 8K modules, and an access time for conventional (core) memory
of 2 usec with a cycle time of 6 microseconds. The normal add time is 6
microseconds. There is also a 256-word thin-film memory having a 1 microsecond
cycle time. The computer has 7 index registers. It provides no indirect
addressing and no wired-in, floating-point arithmetic. The 89 instruction
complement includes block transfer and block mask-and-compare instructions,
and cumulative summation. Asynchronous, simultaneously-buffered I/O channels
can be provided with a total maximum transfer rate of 160-thousand 30-bit words
per second. The machines are fully ruggedized.
The auxiliary data converter is required to change the format of the data
obtained from the auxiliary data-handling system within the aircraft. The
signals are usually supplied from the data-handling system in excess-3 binary-
coded decimal. The computer uses a straight binary code. The converter will
change the code of the signals supplied, and assemble 30-bit computer words
for quick and efficient transfer into the machines. In the same unit with the
auziliary data converter is the digital clock. It consists typically of a 1-Mc
crystal-oscillator counter and other required logic to produce a 17-bit binary
time code. This will be read in with the parameter data from the receiver
as time-of-arrival (TOA).
The recording and storage function is performed by a magnetic-tape digital
data recorder. A typical recorder has a 16-track tape deck designed specifically
for severe environments. It uses a 1-inch tape and has a capacity of up to
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2400 feet. The recording is on 16 tracks, and the density can be made as high
as 1000 frames per inch, though only 500 per inch is typically used.
Figure 4-45 is a diagram illustrating data flow in the signal processing
equipment. Pulse words from the receiver enter the auxiliary data converter
where time-of-arrival information is affixed. Navigation data is also
transmitted to this unit where it is formatted for recording. The output of
the converter unit is transmitted to a buffer store, and then to the recorder.
The buffer output is also sent to an Ax-El filter that selects all pulse
words that are received in the forward sectors. These selected pulse words
then undergo correlation, which converts the series of pulses received from an
emitter on each receiver scan into a single word representing the complete pulse
train. Deinterleaving is also formed at this point.
In deinterleaving, an attempt is first made at separation of the pertinent
sorting parameters such as frequency, direction, pulse width, and pulse ampli-
tude. The test for a successful data reduction is pulse-repetition-interval
coherence in a sorted pulse train. The deinterleaving technique recommended
is one that Airborne Instruments Laboratory has used in other data processing
systems. It depends on a hypothesis-testing procedure in which test pulse-
repetition-intervals are formed by computing time-of-arrival differences be-
tween neighboring pulses; these time intervals are tested to see whether they
will correlate with any pulses in the train. The test interval is stepped
through the pulse train to determine the correlation. If correlation is
achieved, the correlated train is extracted from the signal sample, and the
remainder has the same procedure applied to it repetitively, until no further
reduction can be achieved.
Correlated pulse trains are then checked with the key-threat parameters,
which have been loaded in the computer before the mission. If a match is found,
a signal is sent to the mode-control logic section which initiates the high-
scan-rate mode of operation required for real-time emitter location. Intercepts
from key emitters are also stored to provide a history from which the location
is computed by observing bearing rate. Located emitters are stored in an out-
put buffer, which sends information on the key emitters to other components of
the multisensor system.
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In the optimized multisensor system concepts, there exists a need for a
very rapid system response time for some types of data. This can be accom-
plished by the addition of a real-time data transmission capability. Such a
transmission link is not only important for the instantaneous reporting of
"activity" information, observer's comments and data on fleeting targets (such
as sensor "keying" signals), but it also can serve to reduce the overall intel-
ligence processing cycle, under some circumstances, by getting sensor imagery
back to the carrier before the reconnaissance aircraft itself returns. For
signals and data of the very highest priority, it would be desirable to have
such a link, even when the reconnaissance aircraft is beyond the line-of-sight
to the carrier.
To fulfill this task, such a data link must transmit data of sufficient
quality and quantity to reliably support tactical decisions at the intelligence
center on the carrier. Since the reconnaissance aircraft, under most circum-
stances, will returnto the carrier in I to 2 hours with the original high-
resolution data collected by the sensors, the output resolution quality of the
link can be sacrificed, to some degree, for a more reliable, longer range, real-
time link. The acute need for the real-time imagery at the carrier is not for
the high-resolution content of the imagery, but for the timeliness of critical
data. In fact, all available information indicates that an output resolution
of approximately 20 line-pairs per millimeter at the real-time display equip-
ment on the carrier is adequate for the purpose. Consequently, the design of
the wideband data link is based on that level of performance at the output
displays.
To extend the range capability of a wideband data link to over-the-horizon
transmission, as is necessary when the reconnaissance aircraft is beyond the
line-of-sight path to the carrier, a relay repeater must be used. However, the
problems involved in providing such a relay, even when the relay platform is
only a conventional high-flying aircraft, are so severe that no operational
multisensor data links are available today. These problems are concerned
primarily with the pointing of the antennas between the reconnaissance aircraft
and the relay aircraft (or platform) as they maneuver, but propagation multipath,
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and many other factors, also contribute to the difficulties involved. Therefore,
for purposes of this study the relay vehicle or equipment will not be considered;
however, the system should be configured so that its operation with a relay in
the future would be possible without changes being made.
Since the high priority, activity-type data is of a low data rate, an
investigation was made to determine whether these data could be sent over a
standard aircraft communication link. The supporting analysis, which is con-
tained in this section, demonstrates that these data, including the keying
signals, can be accommodated as digital data within the voice channel of a
single sideband transmitter. If a high-frequency transmitter can be made avail-
able on the aircraft, a beyond-the-horizon capability will be provided for these
important data.
The presence of the data link equipment on the reconnaissance aircraft
should in no way constrain the maneuverability of the aircraft, or significantly
degrade its performance. These, and the previous considerations, have delineated
the guidelines to be used in the design of the airborne data link equipment.
4.6.1 Data Link Concept
A conceptual presentation of the data link's role in the overall multisensor
system is given in Fig. 4-45a.. This concept includes optional features which can
be traded-off against such system characteristics as communications reliability,
operational versatility and technological realizability. The reconnaissance air-
craft carries the data collection subsystems, data processors, data storage
units, a narrowband data transmitter and a wideband data transmitter. The system
handles two categories of data:
1. Keying Data which are generated by the onboard sensors and observer, and
which is considered of prime interest and of high priority.
2. Bulk Data which comprise the main body of the sensor data to which key-
ing data have been added.
The narrowband data link provides a real-time capability beyond the line of sight
for the keying data. The other link provides wideband transmission of the bulk
data to receivers within line of sight (or beyond, if a suitable repeater relay
is employed).
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For the bulk data, two cases are of interest.
Case 1 - Delayed transmission in which the reconnaissance aircraft stores
the wideband data until it is within a favorable line-of-sight condition with
respect to the receiver, and then transmits it.
Case 2 - Real-time transmission in which the data are transmitted as soon
as collected, with the reconnaissance aircraft within line-of-sight: of the re-
ceiver. This case includes operation in which the line-of-sight is extended by
means of a repeater relay on a high-flying aircraft or other airborne platform.
Case 1 requires onboard data storage, and does not achieve minimum system-
response time of Case 2. Nevertheless, Case 1 has several important advantages
over Case 2.
1. Transmission is delayed until the aircraft is a few degrees above the
radio horizon, thereby avoiding the higher level of system complexity and trans-
mitter power required to combat multipath, selective fading and inband frequency
perturbations.
2. A deeper penetration into enemy territory can be achieved without using
an airborne repeater.
3. The active portion of the mission can be flown independently of trans-
mission requirements.
4. The aircraft on its return flight can virtually aim itself at the re-
ceiver (presumed to be at the carrier), and effect a fair and highly useful
antenna gain. In addition, with a nose-mounted antenna, there is no shadowing
or reflections from the aircraft itself, and undesirable pattern lobing is
minimized.
Concerning delayed transmission, consideration has been given to speeding
up the playback of the stored data to permit trading reduced readout time for
increased transmission bandwidth. The feasibility of this technique depends on
the system bandwidth required at the normal playback rate. Both the data stor-
age and the data link itself impose constraints on the maximum bandwidth which
can be accommodated by the system.
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About a three-to-one speedup (with the subsequent transmission time
reduction to one-third its normal value) would have to be used for the speedup
technique to be significant. When video and rf bandwidth figures are compared
to airborne recorder and wideband transmitter capabilities, even a two-to-one
speedup appears difficult to achieve. Therefore, for the time being, the speed-
up technique will not be considered further..
Based on the foregoing discussion, a preliminary data link concept has been
formulated to provide a logical structure for more detailed considerations. The
basic system aboard the reconnaissance aircraft includes the following equip-
ments:
1. Means for storing and reproducing the bulk data at its normal rate.
2. Narrowband transmitter for the real-time transmission of keying data
within line-of-sight and beyond the horizon.
3. Wideband transmitter for transmitting bulk data at its normal rate.
The input to this transmitter can be either the sensor data being generated for
real-time transmission, or the sensor data already stored for delayed trans-
mission. This equipment is to be compatible with both direct path and airborne
repeater operations.
4.6.2 System Engineering Aspects
Data Characteristics - The data link may handle data from six sources,
three of them scanned imagery signals and the other three digitized outputs
from the onboard data processors. Although the photographic sensor data are
not presently assigned to the data link, they are included in the system
engineering considerations for the sakeof completeness. All references cited in
text are given at the end of this section.
Analog Data - The three analog signals are the outputs of the HRSLR, the
IR and the photographic sensors. Although these sensing processes are fundamen-
tally different, the electrical signals which are supplied to the data link are
each generated by a line-scanning process applied to a two-dimensional scene,
which permits discussing them together.
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Since the data link is a series element between the analog outputs of the
imaging sensors and the recorder-processor-viewing equipment on the aircraft
carrier, it is necessary to consider the inherent resolution capabilities of
the sensors and the viewer when determining the amount of data link bandwidth
required for satisfactory image reproduction. The data link should have only
enough bandwidth to provide the output resolution required as limited by the
sensors or viewer, since data link implementation is easier, and the resulting
system reliability higher, when the video bandwidth requirements are kept to a
minimum.
The ground resolution of the camera and IR sensors is a function of the
reconnaissance altitude, as may be seen from Fig. 4-46, which is a plot of
ground resolution versus flight altitude. In this figure, the lines labeled
IR SENSOR and PHOTO represent the ground resolution available on the airborne
records of these sensors, respectively, as a function of the flight altitude.
The IR system, with a detector resolution angle of at least 0.5 milliradians,
for example, can resolve a 30-foot object at 60,000 feet altitude or a 0.25-foot
object at 500 feet altitude, with corresponding values inbetween. A camera
suitable for use with the data link has a field of view of 120 degrees and a
resolution of 60 line pairs per millimeter on 5-inch wide film. At 60,000 feet
altitude, this corresponds to a ground coverage of 208,000 feet and a resolution
of 35 feet, as shown on the PHOTO curve in Fig. 4-46, The resolution figure is
based on 2000 line pairs for 4 inches of usable film width (which equals 20 line
pairs per millimeter). Because of the constant 120-degree camera coverage angle,
the ground resolution for a given film resolution is also a function of altitude,
being 0.35 feet at 500 feet altitude, as shown.
The ground resolution capability of the HRSLR is not a function of altitude,
because a constant range scale is used for all altitudes. The HRSLR curve, shown
at 8 feet ground resolution on Fig. 4-46, corresponds to the HRSLR capability
when using an 8-mile range scale and 60 line-pairs per millimeter resolution on
5-inch film.
The curve labeled REAL TIME VIEWER on Fig. 4-46 indicates the ground resolu-
tion capability of cathode-ray tube type viewers which can be used for real-time
displays onboard ship. The resolution of these displays is limited by approxi-
mately a 0.001-inch beam spot size to 20 line pairs per'millimeter. This
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Fig. 4-46 - Imagery sensor resolution.
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corresponds to a ground resolution of 104 feet at 60,000 feet altitude, and
0.87 feet at 500 feet altitude, if the ground coverage is equal to the 120-degree
field of view provided by the IR and photographic sensors. It is obvious from
this curve that if he real-time viewer is used it will limit the resolution of
the IR and photographic sensors at all flight altitudes. However, as shown in
an early portion of this study, the ground resolution provided by a 20 line pair
per millimeter viewer is in close agreement with the ground resolution require-
ments for tactical .ntelligence, except at the very high altitudes. Therefore,
if the data link bandwidth can be tailored to match the resolution characteris-
tics of the viewer, it will not limit the resolution capabilities of the overall
system.
The vertical 1Lne labeled HRSLR PROCESSED & SCANNED, at 24 feet ground
resolution, represe}its the resolution available from the HRSLR airborne
processor-scanner ireal-time transmission of data is required. It indicates
the degradation froii 60 line pairs per millimeter to 20 line pairs per milli-
meter resulting froiI p the rapid film processor and cathode-ray tube scanner
required in the air to provide a real-time radar map image. Since further proc-
essing of this image is required onboard ship before a final image is available,
the display of this imagery on a real time viewer will not be accomplished.
Therefore, the data link bandwidth required for the HRSLR map image must be
based on the 24-foot resolution limitation of the airborne processor-scanner.
The video bandwidths required to be handled by the data link in order not to
degrade the resolution of the real-time viewer for photo or IR imagery, or the
24-foot resolution requirement for the HRSLR, are calculated from the number of
resolution elements in the ground map image covered per second. For the case of
the IR or photographic sensors, where the ground coverage changes with altitude,
the bandwidth required is a function of aircraft altitude and speed. In the
case of the radar image, where the ground coverage is the same for all altitudes,
the bandwidth required is only a function of the aircraft speed. Because of
these relationships, the ground resolution versus altitude delineated by the
REAL TIME VIEWER line of Fig. 4-46, is not a constant bandwidth relationship,
whereas the ground resolution depicted by the 24-foot HRSLR line is. The deri-
vation of the video bandwidth required for the IR or photo map image is, there-
fore, slightly more complicated than for the radar map image.
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If the video bandwidth required to be handled by the data link for the IR
(or photo) real-time viewer were calculated at the high-altitude end of the
real-time viewer curve (point A1), for an aircraft speed of Mach 2 and a ground
resolution of 104 feet, it would be found to be 0.55 megacycle. However, if
this bandwidth were held constant (as would exist in practice), the resulting
ground resolution at lower altitudes would follow the square-law curve Al- A2,
and the overall system resolution would degrade appreciably below the viewer
resolution desired, as shown. Conversely, if the bandwidth were calculated at
an altitude of 500 feet and a speed of Mach 1 (point S1 on the viewer curve) the
ground resolution would be 0.85 feet and the bandwidth 7.8 megacycles. A good
compromise, and the one finally selected, is a bandwidth corresponding to 1.75
feet resolution at 1000 feet altitude and Mach 1 speed, which is 3.9 megacycles
(approximately 4 megacycles). The resolution provided by this bandwidth will
deteriorate slightly below the desired viewer curve as shown at C1- C2, but the
slight loss in resolution at 500 feet altitude (C2 instead of B1) is a small
penalty to pay for the two times reduction in bandwidth obtained. The final IR
(or photo) ground resolution obtainable from the 4-megacycles video bandwidth
data link for a speed-of Mach 2 at 60,000 feet altitude, and a speed of Mach 1
at 500 feet altitude, is closely approximated by the line A1- C1- C2.
It should be noted, at this point, that the ground resolution of 1.75 feet
indicated at the break-point in the curve at point C1 will be modified slightly
upward because of the series effect of a 20 line pair per millimeter data link
and a 20 line pair per millimeter viewer. The effect rounds out the curve at
the break-point, and allows the curve to approach the line segments as asymptotes
at altitudes removed on either side of the break-point.
The video bandwidth required for the HRSLR radar is obtained from the eight
mile total range coverage at a maximum speed of Mach 2. The calculations yield
a bandwidth of approximately 1 megacycle required to provide the 24 foot resolu-
tion, allowing for the slight degradation caused by using the link in series
with the viewer.
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We now detail the scanning parameters required to achieve 20 cycles per
millimeter resolution for the IR or photographic sensor processes. The condi-
tions assumed for these computations are:
Aircraft altitude 1000 feet
Aircraft speed 1000 feet per second (Mach 1)
IR or photographic cross-track
viewing angle
120 degrees
A frame of data is defined as one in which the cross-track coverage is
equal to the coverage along the flight path (i.e., a square picture, or unity
aspect ratio) for a flat earth. This corresponds to an area of 100 by 100
millimeter (assuming 4 inch usable width) on the real-time viewer. For equal
resolution in the horizontal and vertical directions, a resolution requirement
of 2000 cycles per frame is imposed on the data link.
One cycle of resolution perpendicular to the scan lines corresponds to
2.8 (= 2/0.715) video scan line or "TV lines". The factor (0.715) is referred
to as the Kell factor, and is a measure of the average loss of vertical resolu-
tion which occurs because the scan lines are not in perfect registration with
the horizontal lines in the scanned scene (see reference 2). Therefore, 5,600
TV lines per frame are required to give an equivalent data link resolution of
20 cycles per millimeter.
The maximum frequency required for these channels (see reference 3) is
given by:
k
fmax= 2Kmn2 f()(
h)
K = Kell factor (= 0.715)
m = horizontal-to-vertical resolution ratio (1)
n = TV lines per frame (5,600)
f = frames per second (depends on speed and altitude)
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w/h - aspect ratio (- 1.0)
kv - fraction of field scanning time which is active (= 1.0)
fraction of total line which is active (0.83)
The numbers in parenthesis have been adopted for this application; some of
them are estimates based on standard practices in commercial TV.
For the IR and photographic sensors, a 120-degree viewing angle at 1000 feet
altitude covers 3464 feet. At Mach 1, this distance is covered in 3.46 seconds
by the aircraft, thus providing a value of f = 1/3.46 frames per second. Using
this value of f, the video bandwidth required for the IR or photographic sensors
is calculated to be 3.9 megacycles.
For the high resolution side looking radar, the conditions assumed for the
bandwidth computations are:
Aircraft altitude 60,000 feet
(doesn't enter into computations)
Aircraft speed 2000 feet per second (Mach 2)
Range segment 8 nautical miles
Under these conditions, a frame is covered in the time taken for the air-
craft to fly 8 nautical miles (48,000 feet), i.e., 24 seconds at a speed of 2000
feet per second.
Using these assumptions and figures the video bandwidth required is calcu-
lated to be 0.56 megacycle for a resolution of 20 line pairs per millimeter in
the data link itself. However, as discussed earlier, in order to achieve an
overall system resolution close to that imposed by the real-time viewer, the
equivalent resolution capability of the data link must be somewhat higher than
20 cycles per millimeter because of the deterioration in resolution from both
sources. This is, however, a tradeoff situation because the video bandwidth
required for the data increases in proportion to the square of the equivalent
resolution of the link and becomes intolerably high if too high a link resolution
is used. Using an rms rule for the summation of "irresolutions" (see reference
1 - reciprocal resolution in millimeters per cycle) the system resolutions that
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can be achieved are tabulated in Table 4-11. The video bandwidth Expansion
Factor in the table is the increase in video bandwidth required as a function
of the square of the link resolution, as noted above, with unity as the refer-
ence for a 20 cycles per millimeter link.
Table 4-11. System Resolution versus Data Link Resolution
Resolution of
RPV - *Cycles
Per Millimeter
Resolution of
Data Link - Cycles
Per Millimeter
Video Bandwidth
Expansion
Factor
Overall System
Resolution
Cycles Per Millimeter
20
20
1
14.2
20
28.3
2
16.3
20
40
4
17.8
20
60
9
19.2
20
80
16
19.4
*Cycles per millimeter = line pairs per millimeter.
From Table 4-11 we see that a data link resolution of 60 cycles per milli-
meter or higher is desirable to meet the 20 cycles per millimeter overall system
resolution. However, 60 cycles per millimeter entails a video bandwidth expan-
sion of 9 times the amount required for a 20 cycles per millimeter data link, or
4.95 megacycles. If a bandwidth of 1 megacycle is used the data link equivalent
resolution is approximately 27 cycles per millimeter resulting in an overall
system resolution of approximately 16 cycles per millimeter, or 29 feet ground
resolution. Since it is felt that the airborne processing will produce data
slightly better than the 20 cycles per millimeter resolution assumed, the 1
megacycle bandwidth link will provide close to the 24 foot ground resolution.
At speeds less than Mach 2, the 1 megacycle bandwidth will be more than adequate.
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Because each of the three video signals is derived by an image line-scan
process, the resulting spectral distributions of energy are expected to strongly
resemble that of commercial TV. Using a typical TV spectrum (see reference 4)
as a basis, (Fig. 4-47), a more conservative estimate of the video spectrum
shape has been selected for subsequent computational purposes. For the ratio
of fm/?i - 66.7, the estimated spectra of the HRSLR sensor is shown in Fig. 4-48.
For the IR sensor, the spectrum consists of 25 double-sideband frequency-division
multiplexed channels. For computational purposes, this spectrum is assumed to
be "white".
For image quality, a signal-to-noise ratio is defined as:
20 log10 Vp-p -20 log10 Vrms
Vp-p = peak-to-peak video signal voltage
V rms = rms noise voltage
On the basis of many subjective tests on commercial TV, a S/N ratio (as defined
above) of 46 db is considered to be noiseless (see reference 5). For our pur-
poses, the 46 db figure will be used as the minimum acceptable quality. Where
digital modulation approaches are considered, the quantization noise will like-
wise be set at 46 db. In addition, a maximum binary error rate of 10-4 is
selected as a design value for these systems.
Table 4-12 is a summary of the pertinent data parameters.
The foregoing analyses present several bandwidths for the various sensor
configurations. In the system considerations of subsequent sections, the
photographic data is assumed to be excluded from the data link, the IR signal
is taken to occupy a video bandwidth of 4 megacycle and the HRSLR bandwidth as
1.0 megacycle.
4-154
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Digital Data - The keying data, generated in digital form, consists of the
following:
1. processed ELINT data
2. "hot spot" indications from the IR sensor
3. moving-target indications from the HRSLR
4. observer's comments
5. navigation and timing data
The first four types are generated and transmitted at random, interleaved
among navigation and timing words, which are transmitted periodically. It is
estimated that the random words occur at an average rate of one word per second.
A buffer store may be required to smooth the occurrence of bursts of such words.
The periodic words are transmitted once in 10 seconds.
Table 4-13 gives the data format for each of these words, and an estimate
of the number of bits which must be used.
The narrowband link can operate in the HF band (3 to 30 megacycle) using
ionospheric reflections or at a higher frequency with a line-of-sight repeater.
Because of the relatively low data rate and the desirability of operating this
link independently of an airborne repeater, HF operation was chosen with sky-
wave reflections from the F2 layer of the ionosphere. The actual frequency
selection depends in a complex way on:
1. A complete path description.
2. Geographical location of the transmitter and receiver.
3. Phase of the solar cycle.
4. Season of the year.
5. Time of day.
In addition, since the sky-wave path via the ionosphere is characterized
by parameters which are random variables, the problem is approached on a sta-
tistical basis, and the communication reliability is stated as a statistical
function. Methods and data (see references 6, 7 and 8) for predicting HF
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propagation and noise characteristics have been developed at the National Bureau
of Standards and need to be applied on an hour-by-hour basis for a specific
situation.
For the sake of illustration, a representative set of circumstances is
assumed and the link performance computed. The conditions and assumptions are:
Path length 300 nautical miles
Path location South Vietnam
(midpoint of path at 13?30'N and 108? OOE)
Time period
Airborne transmitter
Transmitter power
Transmitting antenna gain 0 db
Transmitting antenna 15 percent at 2.5 megacycle
efficiency 55 percent at 7.0 megacycle
Absence of manmade
interferring signal
Receiver (near sea level)
Receiving antenna Half-wave dipole at the height for
maximum gain
Receiver sensitivity Limited by external noise
The resulting S/N ratio at the receiver is plotted for a 1 kilocycle
bandwidth for a 24 hour period (Fig. 4-49). For this example the optimum
traffic frequency (FOT) is 7.0 megacycle during the daylight hours and 2.5
megacycle at night. Figure 4-49 is applicable only for the path length of
300 nautical miles. Since HF propagation is markedly dependent on path length,
it may be necessary to change frequencies even during a relatively short mission
of an hour or less.
The example chosen here is a particularly difficult one because of the high
incidence of thunderstorms in South Vietnam in the early sprang gives rise to
severe atmospheric noise conditions.
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Consider now the error rate performance of a digital data link operating
under the specified conditions within a voice channel of a single sideband trans-
mitter. Assume a 75 bit per second data rate and the use of frequency shift
keying (FSK) modulation. For this narrower data bandwidth the S/N ratio of
Fig. 4-49 must be increased by 6 db. In addition, assume a dual frequency
diversity within the same 4 kilocycle voice channel to provide communications
redundancy and combat selective fading. Under these conditions a bit error rate
of 10-4 or less is achieved throughout the 24 hour period for the median curve.
However, when the lowest decile of hourly S/N's is exanined, the need for
some further improvment is indicated. Several approaches can be used simul-
taneously. Because the early morning (01 to 04 hours) drop in S/N is not
coincident with the occurrence of the minimum FOT, the selection of a higher
frequency than 2.5 megacycle would result in lower atmospheric noise, and a
better S/N for 01 to 04 hours. Also, an additional diversity can be provided
to the system by the addition of another HF transmitter to repeat the narrowband
data. So long as the repetitions are separated in time by one second or greater
there will be no correlation in the atmospheric noise effects which dominate the
hours of interest here.
It is estimated that by using the indicated frequency diversity all of the
time, and the time diversity as well as a third transmitting frequency for the
early morning hours, the overall system performance will give fewer than 10-4
bit errors for 20 hours of the day, and for 90 percent of the early morning
hours under the severe atmospheric noise conditions for the assumed mission in
South Vietnam.
The system engineering procedure for the wideband link begins with the
selection of an rf band, then the design of a multiplexing-nodulation combina-
tion, and finally, an estimation of system performance. The details of this
procedure are described in detail in Sections 4.6.4.1, 4.6.4.2 and 4.6.4.3,
respectively. Table 4-14 is a summary of the results of the wideband link
design study.
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Table 4-14. Wideband Link Characteristics Summary
Primary Mode of Operation
Airborne Transmitter
Carrier Frequency
Antenna Gain
Multiplexing
Modulation
Delayed Transmission
60,000 feet-altitude
C-Band (5 gigacycle)
12 db
Frequency Division at rf
Frequency Modulation of 2 rf carriers
by the 2 analogue data channels
Sea Level Receiver
Range
Antenna Gain
Front End
System Noise Temperature
RF power margin for
meteorological losses and
fading at low elevation
angles
Demodulated signal quality
with margin expended,
20 log (Vp )
rms
46 megacycle
240 nautical miles
46 db
Uncooled Parametric Amplifier
326?K
9 db
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Briefly considering the multipath problem, the receiving antenna has a
half-power beamwidth of approximately 0.8 degrees, and its main lobe is down
6 db at a point about 1.1 degrees from the boresight. For antenna elevation
angles greater than 1.1 degrees, the signal fading due to destructive inter-
ference between the direct ray and the reflected ray of the received signal
cannot depress the signal level by more than 6 db. Therefore, a 6 db fade
margin is sufficient to provide for operation down to 1.1 degrees elevation.
Likewise, other multipath problems such as frequency perturbations are not
significant above this angle and such system sophistication, as diversity
reception, is not yet required. Fortunately, the 1.1 degree angle corresponds
to a range of 252 nautical miles which is greater than the design range of
240 nautical miles.
Each of the techniques explicitly (and components implicitly) chosen in
this design is feasible. A vast amount of experience exists in the design,
development and operation of the selected circuit techniques, in spite of the
scarsity of operational experience for this system application. The results
of this study indicate that the required data link equipment does not pose
any technological problems which require separate exploratory programs. How-
ever, many design and development problems do await the hardware designer.
4.6.4.1 Wideband Link Frequency Selection
The selection of the radio frequency for the wideband data link under
consideration is of fundamental importance. The discussion which follows
considers primarily the technical parameters involved in such a selection.
For the wideband link, the relative merits of the UHF band (300 megacycle
to 3 gigacycle) and the SHF band (3 to 30 gigacycles) is first considered. The
lower portion of the UHF band does not offer sufficient bandwidth capability,
and the extrapolated-future needs of military data links are such that even
S-band (around 2 gigacycles),may not be adequate. Therefore, for the sake of
technological compatibility with receiving equipment likely to be contemporary
with this data link, the UHF band is dropped from further consideration.
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In the SHF band, portions of three sub-bands are of current interest:
1. 4.4 to 5.5 gigacycles in C-band
2. 7.4 to 8.4 gigacycles in X-band
3. 14 to 18 gigacycles in Ku-band
Above Ku -band frequencies, atmospheric attenuation becomes so severe that
long range wideband links may not be feasible.
The performance of data links in these three bands is now compared in terms
of the S/N ratio at a remote receiver, for a fixed transmitter power. The
following system parameters are assumed:
RF Power 1 watt (0 dbw)
Antenna Gain 12 db
Coupling Losses 2 db
Altitude 60,000 feet
Range 240 nautical miles
Receiving Antenna 16 foot parabola
The signal power at the receiver is then given by:
PR = PT - LC + GT - LP - AT - AC - AP + GR
PR = receiver power, dbw
PT = transmitter power, dbw
LC = coupling losses in the transmitter; db
GT = transmitting antenna gain, db
LP = free space loss, db
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AT - attenuation due to oxygen and water vapor along the
atmospheric path, db
AC - attenuation due to the condensed water droplets in clouds
along the path, db
AP - attenuation due to precipitation along the path, db
GR = receiving antenna gain, db
A summary of the PR computations is given in Table 4-15.
Table 4-15. Signal Power at Receiver, PR, for
Three Frequency Bands
Band
f
Gc
PT
dbw
LC
db
GT
db
LP
db
AC
db
AP
db
GR
db
PR
dbw
C
5
0
2
12
159.3
1.3
0.9
0.2
46
-105.7
X
8
0
2
12
163.4
1.5
1.4
0.7
50
-107.0
K
16
0
2
12
169.4
2.0
5.0
3.4
56
-113.8
The first two loss factors (LC and LP) in the table, are straight-forward
computations. The factor AT (see reference 9) is relatively uniform and static
for the frequencies considered here. AC has been computed (see reference 10)
for an extensive cloud cover (associated with frontal zones) in the temperature
zones. The db values indicated can get to be about three tLmes greater under
high humidity conditions, therefore, operating margins of 1.8, 2.8, and 10 db
should be considered for C, X, and Xu-bands, respectively, to ensure the
required performance.
AP has been computed to account for 99 percent of the hours in a temperate
zone (see reference 10), where greater communications reliability is required,
or in areas of greater precipitation, these figures must be raised accordingly.
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The noise performance of the receiver is dominated by the ENT (equivalent
noise temperature, ?K) of the external environment as viewed by the antenna, and
by the ENT of the receiver front end. Some interesting cases are tabulated in
Table 4-16.
Table 4-16. Receiver Noise Temperatures for
Three Frequency Bands
Noise Temperatures Total Noise Temperatures
ENT (?K) ENT( ?K)
Band
Antenna Antenna
Receiver
Receiver
At
Sea
On Land
Parametric
Amplifier
Cryogenic
Maser
C
126
153
200
6
326
132
353
159
X
129
154
290
7
419
136
444
161
Ku
152
172
440
9
592
161
612
181
In calculating the antenna temperatures in Table 4-16, the antenna sidelobe
characteristics assumed are for an "average" antenna, not for one with suppressed
sidelobes designed specifically for low noise operation (see references 11 and
12). It is felt that this more nearly describes the actual situation.
Although both a parametric amplifier at 290?K and a maser at liquid helium
temperature are considered here, the difficulty of operating the cryogenic maser
under field conditions precludes its use in most situations.
Continuing with the evaluation, the S/N ratio for each frequency band is
computed for a 1 cps bandwidth, and the 1 watt transmitter power. However,
since the shipborne receiver is of greatest interest here, only the noise
temperature of column (A+C) from Table 4-16 was used. The S/N ratios are
tabulated in Table 4-17.
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Table 4-17. Resulting Receiver S/N Ratios
Three Frequency Bands
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Band PR (dbw) PN (dbw/cps) S/N (db)
-105.7 -203.4
-107.0 -202.3
-113.8 -200.8
Ku
For the assumed conditions, the C-band link is 2.4 db more efficient than
the X-band link, and 10.7 db better than the Ku-band link. When one adds the
safety factor required for clouds, these figures become 3.4 db and 18.7 db,
respectively. Another consideration is that greater rf power is available at
C-band than at the other two bands. Therefore, from a technical point of view,
the C-band link is the best, with X-band a fairly close second, and Ku-band a
poor third. However, such other considerations as a pre-emptive frequency
allocation, an electronically-steerable high-gain antenna for the reconnaissance
aircraft, and ultrawideband data requirements could force these results to be
reshuffled.
4.6.4.2 Wideband Link Multiplexing - Modulation Techniques
In engineering the wideband data link, the selection of a multiplexing-
modulation technique is secondary in importance only to the selection of the rf
carrier. The characteristics of the individual data channels handled by this
link are discussed in Section 4.6.2. In the following discussion, various
techniques are considered, and their relative merits judged on the basis of
their contribution toward the goal of reducing the required transmitter power
while achieving the specified signal quality. The fundamental tradeoff applied
here is that of increased bandwidth for reduced transmitter power. Of course,
for the sake of system feasibility, this tradeoff is bounded by what is
realizable in such areas as modulation linearity, accurate and high rate signal
sampling, and so forth.
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At the transmitter terminal of a data link the modulator is usually
preceded by the multiplexer which reduces the system hardware. However, when
a component becomes exceedingly difficult to build, or unfeasible because of
the wideband requirements imposed by this approach, a greater number of less
difficult components may offer the better solution. This tradeoff of more
hardware for better performance is applied wherever it removes a stumbling
block from the successful conclusion of the data link design.
The broad categories of techniques (see reference 13) considered here are
as follows:
Baseband Techniques 1. Vestigial Sideband (VSB)
2. Digital Subcarriers (DSC)
3. Pulse-Code Modulation (PCM)
Multiplexing 1. Time-Division (TDM)
2. Frequency-Division (FDM)
1. Frequency (FM)
2. Mary Frequency-Shift Keying (M'FSK)
3. Phase-Shift Keying (PSK)
The baseband techniques are those required to prepare the baseband signals
for the multiplexing and modulation processes. The analog channels are derived
from scanned images. Typically for these data, the low frequency components
(down to dc) are important; to preserve image quality these should not be re-
moved or distorted. Whenever it becomes necessary to shift the baseband spec-
trum of a video signal, the VSB technique is used to minimize the bandwidth
without seriously affecting image quality.
Similarly, when digital signals are to be frequency-multiplexed with non-
coherent signals, or time-multiplexed with other pulse trains, it is often
desirable to shift their spectra or gate them into correct time sequence, by
mixing the digital signal with a higher frequency digital subcarrier. We refer
to this process as DSC.
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Furthermore, to convert an analog signal into a digital signal, the PCM
technique is used here. While the previous two processes approximately pre-
served the base bandwidth, the PCM technique multiplies the bandwidth by two
factors: 1) the number of samples per cycle, and 2) the number of binary
digits per sample.
Time-division multiplexing (TDM) interlaces digital data pulses from
different channels such that the channels occupy the same bandwidth, but are
separable in time. Frequency-division multiplexing (FDM) is a method whereby
individual channels are added together to form a composite signal. In order
to permit separation of those signals, they are each assigned to a separate
frequency band.
Frequency modulation (FM) is considered here in preference -to other methods
of carrier modulation by an analog signal, because it permits a significant and
efficient increase in rf bandwidth occupancy, with a subsequent reduction in
transmitter power requirements.
For digital data, a choice must be made between phase-shift keying (PSK)
and Mary frequency-shift keying (M'FSK, sometimes referred to as multi-
frequency tone signaling). It can be shown that relative to PSK, an M'FSK
signal uses wider bandwidth, requires less transmitter power, and simultaneously
increases the length of the signaling elements. The latter two characteristics
are highly desirable in wideband data link applications. However, the principle,
that of increasing hardware for the sake of easing the technical problems, has
been stated. The M'FSK is tentatively chosen over PSK for this application.
The tasks remaining is the consideration of the foregoing techniques in
various combinations, and the selection of that combination which is both
feasible and theoretically most efficient. These combinations (wideband data
link concepts) are shown in Figs. 4-50 through 4-54.
The combination in Fig. 4-50 is the straight-forward analogue approach
commonly used in microwave relay links. For wideband signals the non-linearities
in the FM modulator, and in the receiver's discriminator, impose a bound on the
amount of FM improvement in signal-to-noise ratio which the system can achieve
through wide frequency deviation.
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Fig. 4-50 - Multiplexing-modulation technique (straight-forward
analogue).
vs
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b ,j
I
` FM
E
FPM
'POWER
AMP.
Analogue Channels Digital Channels
Fig. 4-51 - Multiplexing-modulation technique (multiple RF carriers).
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B
Tp1A
0:51(
Fig. 4-52 - Multiplexing-modulation technique (straight-forward
digital).
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I
4Y5s
Y55
E
FPM
YcWftt
AMP,
Fig. 4-53 - Multiplexing-modulation technique (hybrid analogue digital).
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PCM 1M' P5K
PCM M' FSK
M'FSK
Powert
AMP.
Fig. 4-54 - Multiplexing - modulation technique (multiple
digital transmitters).
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The approach in Fig. 4-51 circumvents this difficulty by assigning an
individual modulator to each analog channel and an orthogonal set of frequency
tones to each of the digital channels. These are then frequency multiplexed
at rf to form a composite signal which is amplified by a wideband linear
amplifier, like a TWT, and transmitted.
The combination in Fig. 4-52 is a straight-forward digital approach, in
which each of the analog signals is digitized directly and interlaced with the
other digital signals. The composite pulse train is then coded and the appro-
priate multi-frequency tones are keyed, amplified, and transmitted. For wide
bandwidths the time-multiplexed code elements become as short as a few nano-
seconds and, therefore, become difficult to handle. This problem is not as
critical in the M'FSK circuit, since several short code elements are combined
to give longer output pulses.
Figure 4-53 shows a variation of Fig. 4-52 in which the analog signals are
first frequency-multiplexed to produce a composite wideband signal. This signal
is converted to PCM by a high-speed sampler/digitizer. This PCM signal is com-
bined with the other digital signals and processed by the M'FSK coder, ampli-
fied, and transmitted. This approach time-shares the PCM equipment among the
three analog channels and, thereby, compounds the difficulty of converting
wideband analog signals to nanosecond pulse digital signals. Although an
apparent equipment saving has resulted, the high-speed digitizing required may
be beyond the state-of-the-art.
Another variation of Fig. 4-52 is seen in Fig. 4-54. Here each analog
channel is individually digitized and multifrequency coded for transmission.
Although this approach uses more hardware than the others, it also permits the
greatest frequency spreading, and uses the longest duration signaling elements.
With microminiaturization, the additional hardware may not be a significant
disadvantage. The independence of each channel represents a desirable system
redundancy, and permits greater system flexibility, which is true for the system
in Fig. 4-51.
Finally, the choice must be made between Figs. 4-51 and 4-54. This should
be made on the basis of analog signaling, versus digital signaling. Should the
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requirements for secure communications be imposed on the data link, the choice
would be clearly for the digital system. On the other hand, the techniques
employed in Fig. 4-51 have had significantly more trial in operational systems.
From a theoretical viewpoint, Fig. 4-54 offers the greatest potential reduction
in transmitter power, especially if higher signal-to-noise ratios are required.
Furthermore, a close examination of the technique employed in Fig. 4-54, indi-
cates that the circuit techniques are well developed in spite of the fact that
little operational system experience is available.
This qualitative discussion of the relative merits of these multiplexing-
modulation combinations can only serve as general guidelines in the preliminary
selection of system techniques. In Section 4.6.4.3, the evaluation of some of
these multiplexing-modulation combinations is carried out specifically for the
data channels of interest.
In this section, the transmitter power required by the data link is
computed. Preporatory to this, detailed computations are done for the perform-
ance of the multiplexing-modulation approaches discussed in the previous section.
Since the digital signals (channels d, e, and f) occupy a relatively insignifi-
cant bandwidth, they are not included in these analyses for the sake of
simplicity. The following conditions are assumed:
Path Length 240 nautical miles
Transmitting Antenna Gain 12 db
Carrier Frequency 5 gigacycles
Losses from Transmitter 164 db
to Receiver
Loss Margin 8 db
Receiver (near sea level)
Receiving Antenna 16 foot parabolic - 46 db gain
Receiving System ENT 326?K
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Receiver Noise Power -203 dbw/cps
Data Channels See Section III A
For the system shown in Fig. 4-50, two arrangements of the two channels in
the frequency-division multiplex are possible. Both were evaluated, and the
arrangement with channel d (IR composite signal) at the low frequency and
channel b at the higher frequency, minimizes the required power. For this
arrangement emphasis networks were designed (see reference 15) to further
reduce the carrier power required to attain the 46 db signal-to-noise ratio.
In commercial TV, subjective tests have shown that interference by a low-
frequency tone (or low-frequency, narrow-band noise) is much more disconcerting
than interference by a high-frequency tone of equal power. This has led to the
use of noise weighting functions which rate low-frequency noise more disturbing
than high-frequency noise. However, for a reconnaissance application, the key
requirement is the preservation of fine detail, and slight large-area distor-
tions in the picture do not reduce the value of the data. Therefore, in the
emphasis network optimization procedure, a uniform noise weighting function was
used.
Next, the peak frequency deviation required for each channel was computed,
as the means for allotting the optimum carrier power to each channel. Finally,
the required transmitter power was computed. This design is summarized in
Table 4-18.
For the system shown in Fig. 4-51, each channel frequency modulates its own
rf carrier. Each of the channels is treated individually in the design of
channel emphasis, peak deviation, and carrier power, with due respect to the
full improvement threshold signal-to-noise ratio of the receiver. A summary of
this design follows in Table 4-19.
For the system of Fig. 4-52, each analog channel is converted to a PCM
format. To reduce the quantization noise (assumed to be "white") introduced
by the digitization process, emphasis is applied to the signal spectrum prior
to sampling (see reference 15). For channel jt, 13.7 db improvement is obtained.
This is equivalent to greater than 2 bits of quantization. To meet the 46 db
quality requirement, a 6-bit quantization would ordinarily be needed, but the
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Table 4-18. Transmitter Power Required -
Modulation System B-1
Trans.
Base
FDM
Peak
Emphasis
RF
Power
Channel
Bandwidth
Band
Deviation
Improvement
Bandwidth
'Required
a
4 me
0 to 4 me
+18 me
1.2 db
b
lmc
4to5mc
?4.7 me
13.7 db
Total
0 to 5 me
?18.6 me
-
45 me
27.5 dbm
563 mw
Table 4-19. Transmitted Power Required -
Modulation System B-2
Base
Emphasis
Peak
RF
RF
Channel
Bandwidth
Improvement
Deviation
Bandwidth
Power
a
4.0 me
1.2 db
? 18 me
44 me
550 mw
b
1.0 me
15.5 db
? 2 me
6 me
28 mw
50 me
578 mw
Total
-
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emphasis allows this to be reduced to 4 bits. A word of caution at this point;
the assumption that quantization noise is "white" becomes questionable for such
a coarse quantization level, so that experimental verification of the actual
effects of emphasis and 4 bit quantization is desirable before proceeding to
design operational hardware. For channel A, no improvement is obtained by
emphasis, because both the signal and noise spectra are assumed to be "white"
and, therefore, already matched to each other.
A sampling rate of 3 times the maximum frequency of channel b, and of the
subchannels of g, was chosen. A value as low as 3 samples per cycle, under
these circumstances, does not introduce excessive biasing or distortion errors,
because the signal spectrum at the nominal band cutoff is conservatively esti-
mated to be 36 db below the power level of the low-frequency spectrum. For the
typical TV spectrum, it is 57 db down. Therefore, it is estimated that, using
a 4-section Butterworth filter for post-decoding interpolation, the processing
error (-see reference 16) at this sampling rate will be below the noise level
when the 46 db picture quality level is achieved. The use of emphasis networks
does not alter these estimates significantly, because the additional high-
frequency errors, thereby introduced, are attenuated by the de-emphasis network.
The resulting PCM parameters are summarized in Table 4-20, and the rf require-
ments for a PCM/PSK transmitter are also included for a bit error probability
of 10-4.
Taking the output of the TDM (Fig. 4-52) in which the PCM signals are
encoded in 5-bit blocks, we generate a pulse at one frequency, out of a possible
32 frequencies, for each 5-bit block. This constitutes a 32-level M'FSK en-
coding. The signaling element length is thereby reduced by a factor of 5, and
the total rf bandwidth is increased by a factor of 6.4 over PCM/PSK (see
reference 17). The M'FSK characteristics are given in Table 4-21 for a bit
error rate of 10-4.
A summary of the rf power required for the four optimized system designs
considered here is:
FDM/FM (System B-1)
27.5 dbm
0.56 w
2-Carrier FM (System B-2
27.7 dbm
0.59 w
PCM/PSK (System B-3)
29.7 dbm
0.93 w
PCM/M'FSK (System B-3)
27.2 dbm
0.53 w
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Table 4-20. Transmitted Power Required -
Modulation System B-3 (PCM/PSK)
PCM/PSK
Base
Emphasis
Samples
Bits/
Bits/. RF RF
Channel
Bandwidth
Improvement
Cycle
Samples
Second Bandwidth Power
a
4 me
0 db
3
6
72 mbps - -
b
1 me
13.7 db
3
4
12 mbps - -
Total
-
-
-
-
84 mbps 126 me 29.7 dbm =
930 mw
Table 4-21. Transmitted Power Required -
Modulation System B-3 (PCM/M'FSK)
Frequency tones
32
Frequency pulses/second
M'FSK rf bandwidth
Rf power required
16.8 mbps
813 mcps
525 mw =
27.2 dbm
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Using rf power as the figure of merit, leads to the selection of the PCM/M'FSK
approach. However, since all of the above rf powers are well within the reach
of practical airborne C-band power amplifiers, this criterion becomes less
important, and other norms must be applied. The 2-carrier FM system has the
fewest number of circuit blocks, is the least critical in terms of component
linearity, has the greatest flexibility and is well within the state-of-the-art.
Therefore, the 2-carrier FM system is the approach recommended for this data
link design. The keying data can be easily inserted as a third carrier or as a
digital subcarrier multiplexed with channel a after the emphasis network.
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1. G.C. Higgins, "Methods for Engineering Photographic Systems," Vol. 3, p. 1,
Applied Optics, 1964.
2. D.G. Fink, "Television Engineering," p. 26, McGraw-Hill Book Company, Inc.,
New York, 1952.
3. D.G. Fink, op cit., p. 32.
4. D.G. Fink, "Television Engineering Handbook," p. 10-22, McGraw-Hill Book
Company, Inc., New York, 1957.
5. D.G. Fink, op cit., p. 256.
6. G.W. Hayden, D.L. Lucas, and R.A. Housen, "Technical Considerations in the
Selection of Optimum Frequencies for High-Frequency Sky-Wave Communication
Services," N.B.S. Report No. 7249, 1 November 1962.
7. "Ionospheric Predictions for March 1965," N.B.S. Report No. 24, December
1964.
8. CCIR Report No. 65, Los Angeles, 1959.
9. D.C. Hogg, "Effective Antenna Temperature due to Oxygen and Water Vapor in
the Atmosphere," pp. 1417 to 1419, Journal of Applied Physics, Vol. 30,
No, 9, September 1959.
10. W. Holzer, "Atmospheric Attenuation in Satellite Communications," pp. 119
to 125, Microwave Journal, March 1965.
11. R.C. Hansen, "Low Noise Antennas," pp. 19 to 24, Microwave Journal,
June 1959.
12. R. Gardner, "Antenna Noise Temperature Study," Final Report 3304-11 on
Contract DA-49-1 70-SC-1547, Airborne Instruments Laboratory,
November 1957.
13. H.S. Black, "Modulation Theory," D. Van Nostrand Co., Inc., 1953.
14. E.J. Baghdady, "Lectures on Communication Theory," McGraw Hill Book
Company, Inc., New York, 1961.
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REFERENCES (Cont.)
15. R.A. Bruce, "Optimum Pre-Emphasis and De-Emphasis Networks for Transmission
of Television by PCM," pp. 91 to 96, IEEE Transactions on Communications
Technology, September 1964.
16. D.G. Childers, "Study and Experimental Investigation on Sampling Rate and
Phasing in Time-Division Telemetry Systems," pp. 267 to 283, IRE Trans.
on Space Elect. and Telemetry, December 1962.
17. V.A. Kotelnikov, "Optimum Noise Immunity," pp. 48 to 52, McGraw Hill Book
Company, Inc., New York, 1959.
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Background
"General-purpose display consoles, which were originally
developed to facilitate the man-machine interaction in command and
control information systems, have not found wide acceptance and use
in this application. Instead, the greatest success in the use of general-
purpose display consoles has occurred in scientific applications.
Early in 1958, in what was then the Ramo-Wooldridge Corporation,
the Data Systems Project office design team was faced with the problem
of designing a man-machine subsystem to aid in the analysis and inter-
pretation of large quantities of reconnaissance data. Proper interpreta-
tion could be done only by correlating new data with older data contained
in a large, highly structured computerized data base. Both men and
machines were required in the interpretation. The computer could be
programmed easily to perform routine data-conversion and filekeeping
functions, and to perform rough file selection for data correlation, how-
ever, the analyst was essential for the final interpretation. A rapid
means for displaying data and for recording the analyst's interpretation
were required. Also, since they had to perform other system control
functions as well as interpretation, the analysts in the system needed
current information on the state of the system itself, and the system
needed a facility for accepting instructions from the analysts.
The solution which was adopted was that of developing a general-
purpose display console (called the Display Analysis Console) to func-
tion as a man-system interface. The console (the forerunner of the
Bunker Ramo TRW 85 console) could display graphical and alpha-
numeric data, and had capability for input of data from the analyst
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using control keys, crosshairs, and light pen. A time-shared
digital computer, the TRW 400, was intended in the system design
to serve to format the output displays, and to operate subroutines in
response to user inputs.
Since the same console was to perform many different tasks,
the meaning of the console keys could be changed by overlays on the
keyboard, just so long as the computer was appropriately informed,
by a coded input, as to which subroutines were to be used. Since pro-
grams could be changed more easily than hardware, a system designed
in this way could readily be adapted to changing needs.
We thought that we had solved the problem, and that general-
purpose consoles and this system philosophy would find extensive use
in command and control or other man-machine information systems in
which large data bases were involved and displays were essential.
This has not occurred. It is now nearly seven years later, and
general-purpose consoles, although effective in particular military
applications, are not widely used and are not used with the versatility
that was originally envisioned. It turned out that the equipment design
philosophy was good and fit the user-machine interface very well. How-
ever, nobody has been able to implement an information system using
general-purpose consoles such that programs allow sufficient flexibility
to meet actual and changing requirements of the operating systems.
Some of the desired capabilities for a general-purpose display
system are:
simplicity - the system should be easy to use for non-
programmers;
a language for accessing (retrieval and storage) data in
a data base;
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compatibility with a wide class of data bases, requiring
only that the data base be described properly to the system;
full arithmetic and logical manipulative capability;
on-line programming capability;
capability for accepting inputs from different types of
devices, e.g., keyboard, light pen, and RAND Graphic
Input Tablet;
output on CRT display (alphanumeric and line drawing),
teletype, line printer, and plotter;
ability to interface with other programs and to operate
within a time-sharing environment; and
provision for supplying cueing and prompting information
flexibly to the user."
-- from SP-1688 - S.D.C.,
General-Purpose Display System,
23 September 1964
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0
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4.7.1 Introduction
The multisensor concept as put forth here, takes note of the inherent diffi-
culty in the proper maintenance of the man/machine interface in a dynamic, flex-
ible system as is required in an operational task force. The varied task force
assignment or mission spectrum presents a unique problem, for which there may be
no unique answer. In evaluating all the vast data manipulation concepts avail-
able in modern technology, it has been decided that the emphasis must be placed
on man aids, rather than replacements. This has been done for the purpose of
manual back-down when required, and with the realization that the man alone is
the most adaptive and flexible means of maintaining continuity in a tense, time
restricted environment. The broad concept which will be discussed is shown in
Fig. 4-55.
The multisensor system records are more extensive over a time base, than the
returns from other reconnaissance systems. By their nature, there are redundant
records of the same targets and areas from several sensor types to be maintained.
In addition, a viewer must be provided which allows correlative viewing of any
of the prime records, and the reference imagery. In order that the viewer pro-
vide flexibility, and utilize the keys, a concept is presented which permits
viewing of two prime records and two reference records, while maintaining up to
ten switchable parallel channels in the viewer. The records can be slewed and
are controlled by the time reference from the key tape, and the corresponding
data blocks on the imagery. The wide spectrum data collection system has been
evolved on the basis that technical detail, such as identification of 37 versus
57 millimeter artillery may be requested at any time, and further, that a sortie
may be required to collect from various altitudes, thus requiring full spectrum
onboard capability.
4.7.2 Data Reduction
In the system evaluation between adaptive data collection and adaptive ana-
lysis, the conclusion reached in this study has been overwhelmingly in favor of
analysis.
In explanation, there is a need to collect sufficient detail, at the time of
original cover, to allow for technical determinations which may be pertinent to
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the tactical situation, such as weapon caliber. This need implies detail not
normally required for tactical status reconnaissance. Further, there is implicit
in the flexibility of a task force a requirement for a wide spectrum sensing
capability, in that the sortie profile may range over many extremes. The air-
borne sensors, and data management systems, must have an inherent ability to
deal with combat and peaceful missions, and with a variety of information needs
within a sortie framework. Thus, the justifications for decision must rest on
these basic requirements, realizing that attendant to the operational environment
must be the knowledge that little time is available to make physical changes to
the system in a dynamic situation.
The attendant problems of selective sensing appear complex beyond the needs
of the problem. The basic tenet of selectivity is an ability to automatically
locate and identify a target as requiring coverage. This implies that the recon-
naissance task has been virtually completed just in the collection. There is
considerable doubt that any automatic sensing system could cope with the false
alarm rate which would be a part of such a system in order that it avoid missing
borderline information. Rather, it seems logical to collect more information,
and look at it less. To accomplish this the automatic detection systems are re-
quired only to indicate the type and geographical location of a detected or thres-
holded target. This is well within the capability of the observer and of the IR,
SLR and ELINT systems, and virtually impossible for the photographic systems.
The keys so generated are designed to place on each record an indication of type
and location of alarm, so that the analyst can ignore the mass of information
not pertinent to his job. This screening can be referred to as adaptive analysis,
in that the major problem of data volume is handled by pinpointing areas of high
target probability. This concept is the basis of the data reduction system sug-
gested for the multisensor system.
For priority analysis - a real time function dealing with key alarms and
IR and selected photo imagery, for the purpose of evaluating the take of the
sortie, and setting up the historical records required for interpretation. The
records utilized are:
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1. Key alarm indications of IR hot spots, SLR reflective targets and MTI
indication and ELINT source
2. Observer/operator reports on visual observation and display evaluation
3. Optional IR imagery forward or vertical
4. Optional selected photo imagery, or video imagery
For interpretive analysis - a function of trained photo analysts, using
high quality prime records in concert to provide timely intelligence. The
records utilized are:
1. Cumulative key, ELINT and Order of Battle map display with aircraft
indicator
2. Observer reports
3. Prime aircraft records, which may include:
7 photographic records
2 IR records
1 SLR record
4. Historical and reference imagery
The principle of adaptive collection has been discussed earlier in this
document. The proposed system bases its effectiveness very heavily on principles
of adaptive analysis but also incorporates some of the characteristics of adap-
tive collection.
A sortie is launched having been assigned responsibility for the coverage
of up to twenty predesignated targets. The observer is responsible for activating
the appropriate sensors to provide the required information. However, those
sensors providing data for the keying display must operate and therefore record
and transmit during the entire mission. Only the photographic system is acti-
vated intermittently on the preassigned targets. Where point targets are as-
signed, keying the photographs for selective analysis provides only limited bene-
fits. However, a large percentage of the missions are assigned tasks of area,
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route, beach or battle-line surveillance. In this case, limiting analysis to
keyed photographs reduces the volume of effort and the time for completion of
critical sortie analysis.
Were activation of the photosensors limited to the preassigned targets,
implementation of the keying display would not be justified. However, the keying
display provides the observer with a category of data permitting him to operate
the full range of sensors when he identifies signatures of critical fleeting tar-
gets on his display. This element of adaptive collection reduces the probability
of overlooking targets, not previously assigned, which fall along the mission
route. In addition, the availability of an identical keying display in the com-
mand environment permits realistic mission diversion and enables real time com-
mand requests for photo system activation.
The data reduction from raw material to intelligence will be accomplished
as two distinct operations. The priority analysis will be performed in near
real time, the detail analysis will be performed after return of the reconnais-
sance aircraft. The viewing requirements are distinctly different, and affect
the data management concept.
The real time transmission of keying data to the priority analyst and its
display on a duplicate of the viewer available to the observer provides an ex-
cellent analytic capability to support command decisions on actions to be taken
to counter fleeting threats to friendly ?orces. However, keying data alone may
not be sufficient to identify the nature of the target. Lacking these specific
data, the commander may hesitate to commit available resources for its destruc-
tion until positive identification can be established. The system provides IR
imaging for this purpose whose resolution is adequate for target identification.
Although best IR image resolution is obtained at low altitude, current detectors
make possible the acquisition of imagery from high altitude with sufficient reso-
lution to permit gross target identification. Sensing in the IR frequencies has
the added benefit of reduced signal attenuation by atmosphere. The sensed data
is electromagnetic and can be transmitted without transduction,
Considering the alternative of using a photographic image to confirm and
identify fleeting targets there are two options available.
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Number 1 - Airborne processing, and transmitting images preselected on
keying data for reconstitution and veiwing aboard the carrier. Using this tech-
nique imposes considerable equipment and system sophistication and a significant
time delay from sensing to analysis.
Number 2 - Selective, instantaneous acquisition of a video image and real
time transmission to the carrier where it is recorded and displayed.,
The degradation in image quality suffered in option 1 above regardless of
the quality of the original image will result in a received image equal in quality
to the IR image or the video image, offering nothing more in information while
adding to system complexity and delay in analysis. Option 2 offers an excellent
backup to the IR image in the event of IR system failure but will not equal the
IR system capability in the event of haze or other obscuration to visual image
formation. In either case, both IR and video imagery are available in "real time"
permitting immediate configuration of targets posing a threat to friendly forces.
4.7.2.1 Priority Analysis
The installation of the priority information channel has been made for the
reasons of short time data requirements, as indicated in the operational analysis.
The intelligence most useful to a tactical commander, is that which is most up-
to-date. In particular, fleeting and transient targets are of high importance,
and the information on their location and activity rapidly decays to the point
of uselessness in about an hour. This is far less than the normal data reduction
time from a reconnaissance mission. In order to extract some value from the real
time acquisition/data transmission system, and still not overload the data rates
of the analyst, the key display over the current OB status map will be used by
the priority analyst.
The viewer then becomes a screen display of the key alarms, operated off
a tape recorded from the HF data link in real time. The tape is used to provide
the input signals to the electro-optical viewer, which duplicates the observers
display already described. It maintains the stop action feature and moving OB
map with the aircraft locator superimposed on it.
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In addition, using the carrier computer and a disc storage system, the
key and control transmitted tape will be used to generate a cumulative plot of
aircraft flight path, and the keys, on a current OB status map.
The correlative use of these displays will allow the analyst to provide
the following intelligence.
OB Status - By direct use of the current OB map and correlation with new
alarms, fleeting targets and activity from IR and MTI can indicate action areas
of high interest. The knowledge of targets in the area could indicate what the
hostile intent is, certainly such indications will call up examination of imagery
when available to identify the active elements. ELINT detections in themselves
constitute OB material, and are part of the key record and available in near
real time.
Activity Reports - In parallel with determining gross OB status by corre-
lation, the analyst will be able to indicate areas to be diligently examined for
activity of an unknown nature. The MTI, SLR reflection keys plus the IR and
ELINT will be supplemented by the observer reports and these will clearly indi-
cate in the cumulative plot, high alarm density areas, with sufficient infor-
mation to determine OB status.
Alerting for Detail Analysis - As a part of the activity report, the ana-
lyst sets up the format for the detail analyst by listing the areas to be covered
first, even to the point of pre-empting the sortie target list priority. The
communicator for the analyst may draw up a supplementary list of references
probably required to support the detail analysis. This information may come
from changes in flight path activity or detection of innocuous areas.
To further support these functions of the priority analyst requires some
imagery analysis to confirm either the observer's reports; to identify further
new alarm areas; and to present visual confirmation on the assigned targets. As
noted previously, the photo sensors will be activated on "targets of opportunity"
in addition to the assigned targets and there is considerable time to be won on
fleeting targets by having some imagery available.
In this respect, it is necessary to provide a priority analyst whose sole
function is selected image analysis. This must be in parallel to the real time
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work, so that the current situation is covered, as well as the delayed evaluation
of imagery. The imagery may be time delayed by minutes due to transmission me-
chanics, and it will be selected on the judgment of the airborne operator and
the priority analyst who are operating in the broad field, and need not stop to
evaluate and thus loose new material during the change of attention.
The spot analysis of imagery, whether IR, selected photo, or video, will
now form a better basis for OB up-date on fleeting or transient targets, within
the useful time range.
The communicator associated with the analysts at the priority station is
vital in relieving the need for attention shift from analysis to communication.
With the communicator, an oral report by the analyst can be made, without shif-
ting attention even momentarily.
In summary, the priority analysts will view in real time the key display,
a duplicate of the airborne system, and selected imagery. Their reports will be
oral, and communication with the OB status plot and the rest of the data reduc-
tion complex will be through the communicator.
4.7.2.2 Mission Analysis
With the inclusion of the priority analyst in the data reduction system,
the job of the detail analysis is eased slightly. Consider the case when the
wideband data link has been operative, which is to be the preferred operational
mode. The time pressure on the detail work is relieved in that the short term
information has either been utilized or has now decayed, thus allowing the first
through the records to be a working run, not a frantic search for some hidden
major threat.
The analyst now will utilize the prime records of the flight. In detail
they are comprised of the following items.
1. Photographic imagery, in the processed transparent positive, with the
negative available.
2. IR imagery, as transparent processed positive, and a magnetic tape with
full detail as back-up.
3. SLR imagery, as a transparent positive, prepared on the carrier from a
transmitted non-image film record. A high resolution positive will be produced
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15 minutes after the return of the aircraft.
4. Key and Control record, a magnetic tape carrying key annotations, ob-
server report, navigation data, and time record.
5. ELINT record, as a magnetic tape, not to be used in interpretation as
the ELINT information is already on the key record. The tape will be processed
for emitters outside the set 20 already programmed on the aircraft.
These records will be in numbers governed by the sortie profile. For a low
level sortie there will be five maximum photo records, two IR, one SLR and the
key tape to be handled and viewed. From a high level sortie, there will be two
photo records, one IR, one SLR and the key tape to be handled. The information
density from the high level sortie will be greater, due to the coverage and reso-
lution in the photo system particularly.
The control of the data for viewing will be from two sources. First, the
geographic priority locations set up as assigned targets and as determined from
priority analysis as "hot areas". The viewer then should have a capability of
reading the data blocks and slewing records to -a desired location (as determined
from geographic readout or correlated time readout). Second, the priority of the
keys versus unkeyed areas, thus passing by areas of record which have not shown
alarm areas to concentrate on high probability areas for analysis.
These two methods should reduce the time to a minimum for a first OB status
report. It will be necessary to rework the records to cover the areas not keyed,
to locate margined information, which may be vital, or to provide detail tech-
nical information as requested by the air intelligence officer.
4.7.2. 3 Detail Analysis
The instrument which displays the data to the analyst assumes a vital role
in data management. For multisensor viewing it must have flexibility, while not
overloading the analyst with peripheral information not vital to the task. It is
suggested that the viewer be manned by two analysts, for this is the most useful
compliment. There are some missions best analyzed by one man, some best handled
by two, thus we must configure for two, to maintain usefulness. The best use of
these highly trained analysts, is in viewing and working with the records. There-
fore, again it is suggested that all requests for information, reports and com-
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munication with the rest of the system be through a communicator, associated
with the analysts to avoid attention shifting.
The viewer itself should be capable of simultaneously carrying the records
from a sortie, which may run to eight film records and the key tape. For best
human utilization only one prime viewing screen should be provided each analyst.
The parallel record channels should be optically switchable, so that the two re-
cords displayed can be any pair from the eight in the machine. The standard
features of frame translation and rotation should be included, and a magnifica-
tion range from 4 to 20 times will be useful.
The analyst now has the basic tool for viewing. It displays the two records
of choice, it has a data block readout, data block alphanumeric display, key con-
trol, key tape readout (alphanumeric), priority list display, and the necessary
viewing tools such as high magnification stereo eyepieces and mensuration facili-
ties, to enable the analyst to work the prime records.
The viewer must also display reference material, either text or imagery. The
reference store configuration now becomes. important. It is suggested that each
analyst have a reference view screen, now making a total of four screens on the
viewer. This should be sufficient, with the switching capability already men-
tioned.
The reference material will have been assembled from storage, based on the
targets assigned, and the flight path. The priority analyst will have added to
the reference those records called for based on his analysis including "targets
of opportunity". It is suggested that the reference material be in a 6 by 9 inch
card store format, thus utilizing the stored cover to its utmost. The use of the
imagery in its original format (thus the 6 by 9 inch standard size to accommodate
5-inch film in aperture cards) reduces the storage system record manipulations
and retains the maximum resolution in the material. All of the original formats
fit this record size in one combination or another, and only removal from the
film roll and insertion in the card aperture is required to update the image
base file.
The predesignated 6 by 9 inch aperture card is designed to accommodate a
5 by 8 inch image. This format has been selected to enable storage of selected
sensor records at full size. The images used in these aperture cards can be die-
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cut from the original material or can be reproduced selectively in a variety of
special devices. Because of the variety of applications for these records con-
sideration should be given to storing them both as positive and negatives. Most
desirable, providing the material has no further use, die-cutting the original
positive to form the primary graphic record should be considered. Alternatively,
use of diazo or kalvar material should be considered to form the primary record
if the original negative must be retained in its original form. These materials
are suggested because of their ease and speed of handling as well as avoiding
the use of wet chemical processes made necessary by silver halide material. Re-
production of graphics for use in mission folders, and analytical viewers would
be greatly simplified by the use of dry or near dry rapid processing duplicating
material. Rapid scanning viewer printers would permit reproduction of reference
graphics within the retrieval area eliminating the need for support from a photo
laboratory for this area of effort.
Photographs are regularly taken of the most current OB status board. The
photographs are processed and stored in the graphic file of the data base. These
records are retrieved and reproduced to become part of the mission folder and
are used as input material to the airborne keying display and the priority ana-
lysts display.
To handle the reference material in the viewer a concept: which uses a card
deck composed of all the reference material either text or imagery is suggested.
The viewer will accept the card deck, sort and display a card utilizing a mag-
netic edge strip index, imposed on each card. Thus, random access to the refer-
ence material allows the analyst to rearrange his priority list at any time, and
also add information on request during analysis which he may require.
The magnetic index can also be used to recall from the storage file if that
system is automated. But both systems are alphanumeric-indexed so that degrada-
tion of the recall and reference viewing can be manual if required.
Further, although the key tape is the basic record of annotations used in
analysis, each prime record has a digital record of the keys in its margin.
Should the system be required to operate with such a simple reliable viewer as
an emergency light table, then the keys are still available for use.
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As useful to the detail analyst as to the priority analyst will be a supple-
mentary display system. This will be a cumulative key and current OB status dis-
play, maintained from the computer disc storage, and updated to dynamically lo-
cate the aircraft position represented by the record being viewed.
The photograph of the OB plot, which is used as base material in the air-
craft observer display, and the priority analysts display is produced from time
to time as a basic reference image on 5-inch square high resolution film.
If system design permits, there is value in using 3 by 3 foot monitor'
display as noted above, for the analysts, and a larger 6 by 6 or 8 by 8 foot die
play for the command/decision display, operating simultaneously, deleting the
aircraft indicator for the command display.
The reporting function will be handled as with the priority analyst. Human
factors study clearly indicates a difficulty and loss of continuity from an
attention change. The analyst in reporting or communication should be allowed
to maintain his full attention on the records he is viewing, rather than rever-
ting to the communicator role. Therefore by utilizing a third man on the ana-
lysis team, the attention shift is avoided.
The tasks of translating from the oral report to digital format and requests
for information from the interpretation complex are easily handled by the com-
municator. In function, the update reports are maintained in a data card system
as well as in the disc memory.
The detail analysts file reports in the following major categories:
1. OB Status Update, with a direct address to the disc storage system
backed up by the simultaneous card file, read out either automatically or manually
posted.
2. Graphic File Update, with selected target and areal coverage directed
into the image store.
3. Digital File Update, with OB status changes and generation, simultane-
ous input to the disc storage-and card file maintains the digital file, which
can be searched regularly for OB update in command and control display systems.
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4. Special Reports, as called for by the air intelligence officer, detail
intelligence and technical data from the records in a repeat or original viewing.
5. Briefing Material, selected by the analysts for use in target briefing
for strike and reconnaissance crews, areal and target imagery and data earmarked
for briefing folders and reproduced by the photo laboratory on request of the
air intelligence officer.
6. Mission Folder Material, selected by the air intelligence officer, for
mission/sortie folders from the material provided by the analysts.
In detail, the analysts annotate the viewed material or notify the communi-
cator of selection, so that the storage system receives marked positives for
direct index annotation and file. From that point the air intelligence officer
can call up on a separate viewer/printer, the image or text required for further
use, whether in mission material, press releases, or "show me" hard copy for
command and control.
In summary, the mission/detail analysis will deal with the prime record
materials. The analysis priority will be determined-from the assigned target
list, modified by the priority analyst report for additions and reorder. The
analysis will be performed on a two station viewer, with a prime screen and a
reference screen for each analyst, The system will use the key and control tape
to note key locations and/or control the record selection. The records will be
contained in parallel channels, switchable at the operators option. The system
will magnify, provide stereo viewing (adjacent frames) rotate and translate the
imagery as required. The reference material will be supplied as full format
aperture cards, magnetically keyed for index, geographical location and target
type. The viewer can randomly select the material by a card search and display
it for reference.
All reporting and other communications will be through a third operator/
communicator, who will use a standard keyboard communications system to report
OB status, and request new material, The OB cumulative plot with key indicators,
flight path, and aircraft position will supplement the viewer, providing refer-
ence for the analysts. A repeater of the OB status plot will be used for com-
mand/control display. All reports will be made through-the communicator, gener-
ating a disc record and a back-up punch card. The original viewer material
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(spooled positives) forms the basis for imagery update, through analyst annota-
tion for file. Original negative material is retained for disposition.
Mission/briefing material is generated from annotated original imagery in
a separate viewer/printer associated with the storage facility.
4.7.3 Data Storage, Processing and Retrieval Center
The data base for the air intelligence operations consists of a large vol-
ume of data, occasionally in heavily clustered natural units, such as a multi-
megabit photograph. The keying concepts developed previously make it expedient
to store this material essentially in its natural form, and to process and re-
trieve it by manipulation and rearrangement of the associated low volume key
data. This primitive distinction is of vital importance in outlining an opti-
mum system, as it permits a clear division between the main memory requirement
of the data store and the sorting and recombination requirements of the key data
processor and its associated low volume memory store. The system which follows
this distinction is a compact store for say 105 records, (each occupying less
than 0.0025 cubic feet, or something like a 6 foot cube for 100,000 records)
utilizing a small general purpose digital computer with I/O units matched to the
data sort requirements, and alternate electromechanical and manual access sys-
tems to obtain the listed material from the data store.
The main data store, as it is formed, is composed of data base collateral
information and update material, all processed and stored against a target type
and geographical index. In configuring the storage system for manual back-up,
the index system will generally be geography based, with target type as an add-on
annotation. The computer index dictionary will perform the cross file conversion
from target type to geographic location, so that a single storage base system
can be used.
More specifically, the bulk data store, or record store, should have a ran-
dome drum store as those used for large volume correspondence filing. Such a
store can be organized to provide a slightly stylized representation of the ter-
rain covered by the data base; this is a rule of "right hand drum is East, clock-
wise rotation of a drum moves the records North" would permit the rapid orienta-
tion for anyone required to pull material from store without the benefit of the
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data processing facility. Similarly, edge coding of the aperture cards which
carry the data base records (photographs, etc.) with colors to represent dominant
targets found on the record would expedite the manual operation of the store.
This initial emphasis on manual operation is deliberate; it is necessary if the
system is to achieve a high reliability and graceful degradation under operational
conditions which might include the lack of computer power or the unavailability
of the especially skilled data processing personnel.
The actual controls of the store should consist of unitized sensor records
(e.g., films cut into frames) or other representations scaled as nearly as pos-
sible to the size and format of the current sensors and uniformly mounted on
aperture cards. This is both to minimize the number and complexity-of process
steps between first acquisition of operational records and their availability as
additions to the data store, and to simplify the equipment (which may be naked
eyes in extreme cases) required to compose current and fact records, and to ease
the complexity of the task of making meaningful comparisons.
The capacity of the record store should be sufficient to accommodate the
largest expected required data base, plus all records which might be acquired
throughout an operational tour, say 72 hours. While it is recognized that under
good conditions the records should be systematically culled, and records whose
contexts are wholly updated by more recent coverage should be deleted, it is un-
fortunately true that most records are incomplete, and do not constitute an exact
match in percentage cloud free area, shadow conditions, best achieved resolution,
or distance of principal target from frame center. Failure on any of these
counts can and should justify retention of both old and current imagery. Of
course, whenever this is done, the old record should be annotated with a record
of -the availability of more recent cover (which may be in an adjacent drum because
of center separation).
In summary, this bulk data store should contain a complete set of regional
records, map card and all images, in geographic order, with the cards color coded
for quick visual location of key target and sensor type records. This store
would normally be manned by a specially indoctrinated file clerk, who could as-
sist and guide professional manual users as necessary.
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Fully automated operation of this store is not anticipated. However, its
manual operation could be considerably expedited by using the output from the
key data processor, which may be cards or paper tape, to drive the store. When
so driven, the store would sequentially present each called-out record to the
operator for quality check and extraction at a standard working level. Extrac-
tion could be accompanied by the insertion of a use reference card prepared by
the key data processor, and mating the pulled record with a reference card which
recorded the reason for presenting this particular record. These operations, of
course, assume such an arrangement as magnetic edge strip control of the record
aperture cards and use reference cards. The magnetic strip system will be man-
datory if the viewer random access card deck concept is used.
The true computer associated with this store is the key/data processor.
This machine would accept as input from an analyst (typically at a viewing station)
a series of descriptors of required reference material making use of the geo-
graphic or target index system, and instructions to sort its records for the
best matched records in main record store. The volume of its output from such
a request would be a function of the degree of post sort judgment permitted in
the (aided) manual extraction of main store material, which would in time depend
on the type of data requirements which the analyst is faced with making the re-
quest. Thus, a man analyzing a particular building complex may want reference
material relating'to the particular buildings at a known location, which is rela-
tively unambiguous; or he may want to see other examples of weapons storage faci-
lities of the type which he suspects he is examining, backed by some central
records of innocuous buildings of the same apparent class. Unless judgment and
evaluation is exercised in the latter cases, he may be flooded with an unneces-
sary volume of reference material. To avoid such distractions of the working
analyst, subordinate judgment should be exercised by the main store file clerk,
aided by meaningful printouts of the descriptors which led to the callout of
each record. Such considerations as these lead to the need for a high speed
printout device for the key data processor. The characteristics of several disc
storage/retrieval systems are.found in Table 4-22.
The key data processor should be of the same general type as used in com-
mercial inventory file and transaction record systems, typically, a small central
processor and a multidisc system to permit prompt and efficient sorts and up-
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dating operations. Multiple access and real time time-sharing should be asses-
sed; there is no cause for concern if there is discernible flicker in response
to each user, because unit response and action times for working professional
analysts are represented by minutes rather than milliseconds. While input must
be accepted from each of several user stations, there is probably need for only
one high speed output device. However, each user should have low speed return
facilities, typically, the same electric typewriter as he uses for input. His
low speed output channel should simply inform him of the gross results of his
requests - for example - "none available" or "96 printed out to main store" or
"3 approximations found - do you want them?" The last entry is inserted to raise
the issue of the general lack of precision in callouts from such data stores.
We should not fail to produce a record when the nominal center called for is
slightly away from the nearest on file, nor should we present one only record
when several have the required photographic coordinates each in a different
corner. Programming around these problems of operational common sense is pain-
fully slow, and leads to results which convince everyone but the programmer
(who already knows) that the machine is a high speed idiot; we recommend the
retention of a junior man in the record pulling operation, because of the judg-
ment available from him, and the confidence that he represents a truly adaptive
link in the data processing sequence.
The insertion of new data evidently takes place at two levels. The master
file of the key data processor system can be updated directly by the readout of
the prime record data block, plus any annotations by the examinations analyst.
This operation does not require the physical transfer of any material. The bulk
data store is updated by a combination of copy from the prime record, as indexed
and annotated by the key data processor. This indexing operation takes input
from the data block, analyst, the master file, and the record store index. The
key data processor uses a separate program to combine these inputs and to pro-
duce aperture card sticker outputs proper for each frame (or other unit record)
and an indication of other records which should be examined for possible calling
after insertion of the current frame. These aperture cards are made up in the
photo reproduction section, and inserted into the bulk data store as soon as con-
venient. After insertion, a record of insertion and availability is entered as
to the index memory and working file via a set of transaction cards which was
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prepared concurrently with the aperture card stickers. The phasing of the oper-
ations calls for close control to prevent undue delays in access on one hand,
and undue interruption to operational use of the main-store onthe other. A
well-defined system of priorities and a careful design of the input system is
called for to minimize aperture card insertion time.
The transmissions of reference material from the bulk data store should in-
volve minimum time and minimum personnel movement. A high-speed spring or pneu-
matic tube system is favored for this task. This system would also enable the
analyst to bypass the computer and feed graphic requests to the file clerk in
cases where formal descriptions would evidently produce a large volume ambiguous
reply. A back-up system of bulkhead apertures and hand passage should be set up
to ensure continued operation at degraded speeds in the event of operational
damage to the hard copy tube system.
With the analysis viewer set up to accept-the reference material as a ran-
dom access card deck, new information can be added during the analysis without
regard to sequence. As previously noted, the magnetic edge coding, imposed when
the aperture card is annotated with the index sticker, now provides the means
of random access by the analyst. The use of a communicator to perform the com-
puter/data store interface function is reiterated here, to relieve the analyst
of detail functions not pertinent to the task for which he is trained.
A detailed discussion of data handling for the side looking radar, ELINT,
and infrared outputs are discussed in sections 4.7.5, 4.7.6 and 4.7.7, respec-
tively.
4.7.4 Support Facilities
As an adjunct to the storage and retrieval problem there is a need for sup-
port facilities to perform routine photographic work which will be associated
with the data management process.
Photographic Laboratory There are a number of applications for a photo-
graphic laboratory aboard the carrier primarily to finish material processed
aboard the reconnaissance aircraft, to process HRR correlated images, reconsti-
tuted IR and video images, material generated for graphic storage, and printed
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products from graphic storage for use in mission folders, detailed analysis and
keying or priority displays. Printing equipment for these applications fall into
the continuous printer, step-and-repeat printer categories. Reproduction of re-
cords from the graphic files would be accomplished essentially by viewer - prin-
ters obviating the need for laboratory services for this application. The normal
complement of support equipment to enable chemical mixing, titling, inspection,
splicing, cleaning and quality control will be required.
Duplicators - Until recently, with limited exception, military duplicating
equipment was generally configured around designs originated for commercial use.
Recent advances in mechanics and optics are leading to duplicator designs par-
ticularly applicable to military reproduction problems. Previous devices were
limited to one type of operation while this new generation incorporates many
capabilities. These devices are now configured to perform any combination of
tasks from the following:
1. Dodging
2. Non-dodging
3. Continuous, enlarging
4. Continuous contact
5. Step-and-repeat enlarging
6. Step-and-repeat contact
7. Automatic exposure and contrast control
These duplicators, which operate at high production rates, enable a .wide
variety of printing tasks to be accomplished with a lesser equipment complement.
Processors - The predominant military processor has been the deep tank
immersion or spray processor. A wide variety of devices falling into this cate-
gory are in current military inventory. There have been recent developments of
a new straight-path rapid processor which is particularly applicable to tactical
operations. These processors operate to a greater or lesser extent on the liquid/
air bearing principle, minimizing the amount of mechanical contact imposed on the
film. These devices are self threading compact and simple to operate and main-
tain. More recent developments will result in a modular processor with the capa-
bility for any type of material, black and white or color, simply by assembling
the appropriate number of modules and connecting chemical delivery to the proper
number of applicators in the proper sequence. Production speed can also be in-
creased by adding modules. Current processors require fresh water for washing
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at up to 45 gallons per minute. Recent developments in resin de-ionizers permit
recirculation wash systems requiring very little new fresh water.
Duplication of the high quality high altitude photography will be required
to a limited degree. In this event the quality of the duplicators and the pro-
cessor must be such that a minimum amount of detail is lost in the duplication
process. To support these devices the facility must have a controlled environ-
ment with regard to temperature, humidity, dust and contaminants. Strict quality
control procedures will be required to provide a full range of quantitative sensi-
tometric data as a measure of product quality.
Automaticity in operation is desirable when production requirements are high,
and space and personnel are limited. Recently developed techniques can permit a
fully automatic printingsystem which operates from data marked on the edge of
each negative which controls all aspects of printer magnification positioning,
exposure and volume. Such a system includes an editing console and automatic
printer/processor. Such a printer/processor combination would be valuable to
support high volume, short term duplication requirements for the graphic data
base as well as serving other requestors for duplicating services.
4.7.5 Side Looking Radar Data Handling
It is anticipated that the processing of high resolution radar pictures
aboard the carrier will use the basic procedures, equipment, and storage method
that is used for the other image systems. For example, the film viewer has the
capability to look at enlarged sections of film, measure the distance between
two points on the film, perform restitution and coordinate conversion and trans-
formation in order to obtain ground coordinates, and compare two film views of
the same area. The storage media which employs film "chips" mounted in cards
can be used for the storage, classification, and annotation of radar data from
the high resolution side-looking radar.
It is proposed that the film taken by the high resolution radar be anno-
tated along its edge as taken, in the same manner that the film from aerial
cameras is now annotated. That is, information concerning latitude and longitude
of the aircraft, radar pointing angles, altitude of aircraft and time would be
put on a data block on the side of the-film, Also, the priority key will be im-
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printed along the edge at appropriate locations.
4.7.5.1 Priority Target Indicators
A priority target could be caused by:
1. moving target indication,
2. cross section threshold indication,
3. IR hot spot indication,
4. ELINT indication of preselected type,
5. indication given by the aircraft observer for any reason.
It is suggested that these priority keys be sent back to the carrier via
data link and also be placed on the radar film when appropriate. These keys are
used to indicate that priority viewing should be given to the portions of the
film where the priority key is present. These keys are used aboard the carrier
for several different purposes:
1. performing some data interpretation before the aircraft returns to the
carrier,
2. selecting pictures and data from the data store to compare with the
reconnaissance data just taken,
3. scheduling film reading and interpretation.
4. planning the mission of reconnaissance sorties which will take off
in the near future.
This real time interpretation aboard the carrier could, for example, indicate
unusual traffic on a given road as the moving target indicators are plotted on a
map; or the presence of a new type of emitter and its location. It: should be
noted that even if this priority keying information is not sent back to the carrier
via data link, the priority keys are still present on the film and can be of great
value.
4.7.5.2 Automated Changed Detection
The use of automated change detection techniques is possible when two radar
pictures of the same area are compared. These pictures must be taken from the
same flight path, altitude, and aspect angle but are independent of time of day.
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This occurs because the radar carries its own illumination and thus shadowing
effects just depend on position of the radar.
Automated change detection can take several forms. The first is a blinking
system as used in astronomy. In this system two views of the same area are
alternately shown to the observer and areas which disagree tend to blink on and
off, much like a blinking light. This blinking effect then indicates the por-
tion of the reconnaissance area at which a change has occurred.
The grey spot method can be used also, in which a positive and negative
image are overlaid.
An optical target-matching and target change detection technique which
greatly simplifies area contrast correlation has been developed at Conductron on
a company sponsored program. This technique has been applied in several propo-
sals to problems of high resolution map matching and moving target indication.
The application to target tracking is also simple and direct and gives the de-
sired effect of area tracking without complex computation.
Another approach to the change detection process is to bring the two picture
areas under study into a close match by scanning them with a flying spot scanner
and performing a multiplication correlation on the outputs of the photo-tubes.
Once the areas are matched, they are scanned and photo-tube outputs are sent to
a subtractor, whereby any difference in the areas in question will appear as
electrical outputs. The difference signals are then filtered and processed. The
processed output places an indication of change on a radar photograph identical
to either photograph (as selected by the operator).
4.7.5.3 Discussion of Change Detection
The detection of changes requires that the area under consideration was
covered more than once so that the sensor records obtainedon different missions
can be compared. The detection of changes can be accomplished in several ways.
1. In the case of point surveillance when one looks for changes at nartowly
defined locations, the detection, description, and interpretation of changes is
easily accomplished and reported.
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2. In the case of area-surveillance when one must scan the entire record
to find changes, the detection becomes a formidable task. Because. the changes
tend to get lost in the mass of image information which must be reviewed in area
surveillance, the automatic extraction of differential changes is extremely help-
ful.
The outputs from change detection can be manual isotime plots of change
locations and identifications, for example on sliding Plexiglass panels, or they
can consist of automatically derived change records which then have to be anno-
tated. The automatically derived change records can be on transparencies and
appropriately scaled so that the transparencies can be superimposed onto area maps
or projections. While it will be possible to selectively plot positive changes
(additions) or negative changes (deletions) when manual change compilation is
practiced, the automatically derived records will show both positive and negative
changes, which, however, can be printed in different colors.
The use of change of position of tactical detail as a discriminating parame-
ter provides a most valuable capability for distinction between dead and live
detail. Such things as destroyed tanks and trucks, disabled railroad equipment,
etc., eliminate themselves from judgment by disappearing from the presented pic-
ture of "changes". This fact does not reduce the systems capability for pro-
ducing an integrated picture of the operational situation through sensing the
positive and negative changes as they occur. Positive and negative changes are
separately presented as influx into or outflux from an existing permanent ter-
rain pattern.
It is anticipated that many times when tactical intelligence will be urgently
needed only the side-looking radar records and the attack radar scope photography
will be available for deriving the called for information. Although the detec-
tion of small tactical targets such as vehicles, missile launchers, tanks, etc.,
is assured by the "resolution" of the proposed side looking radar set, the radar
returns from the vehicles will appear as "blobs" on the record just like those
caused by the returns from isolated houses, rocks, or similar permanent corner
reflectors in the terrain. The recognition of certain "blobs" as important
mobile tactical targets rather than as fixed terrain corner reflectors is diffi-
cult if repetitive coverage of the area by SLR is not available. However, the
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deployment of large numbers of vehicles will generally follow systematic patterns
related to the road and rail net, waterways, harbors, airports, etc. Further-
more, large numbers of military vehicles will always form patterns compatible
with established military behavior and doctrine. Thus, interpretation of tac-
tical targets must rely heavily on the recognition and exploitation of patterns.
The changes recorded during the previous data reduction step represent all
machine-recognizable differences in the compared SLR imagery. Therefore, the
change records will contain not only true changes, but also psuedo changes that
are caused by differences in aspect angle, terrain clutter, scintillation, mal-
functions, etc. In general, the distribution of the psuedo changes is_ non-sys-
tematic while the true changes, particularly those caused by returns from large
numbers of vehicles, will follow systematic patterns related to the road and
rail net, terrain, and established military behavior and doctrine. Hence, it will
be possible to eliminate quickly from further considerations the majority of
psuedo changes. The changes found are of two types: positive (new returns are
found) and negative (returns formerly observed but now absent).
A piece of equipment which can be used to examine areas of change is es-
sentially a projecting measuring device which permits examination of the change
record and the radar terrain imagery from which the change record was derived.
Provision is made for a number of magnifications and for optically superimposing
the SLR records in any chosen combination. The radar terrain imagery then can
be used for the analysis of the changes of comparison with norms for the area
under consideration.
During interpretation the individual SLR change records are analyzed in
order to extract information found on these records. These data can be in the
form of target numbers, and distribution and changes in patterns. From these
data the interpreter applies meaning to produce intelligence information. Once
positioned, correlation of SLR changes with terrain transportation nets and cul-
tural detail can be made. Verification of changes is also accomplished at this
step, permitting only the significant changes to go to multisensor interpretation.
4.7.5.4 Multisensor Interpretation
Changes can now be evaluated jointly in terms of probable enemy intention
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and/or the establishment of an order of battle. This function is called Multi-
sensor Interpretation (MSI). Norms are kept current for area elements by con-
sidering over a period of time, both quantitatively and qualitatively, such fac-
tors as landforms, terrain trafficability, population density, industrialized
areas, traffic schedules and patterns, time of day, and other daily variations
of field forces. The operational patterns for differing numbers of vehicles and
different types of emitters are established and maintained up-to-date by tech-
nical intelligence, the study of military doctrine, and the continuous analysis
of enemy tactics, training procedures and posture. All of these inputs to MSI
are part of a systems file that contains map transparencies, texts, graphics,
and imagery.
The radar records are also processed for defined doppler frequencies as
caused by vehicle motion, thus automatically eliminating all stationary infor-
mation and producing a separate MTI record showing detail in motion only. Using
color differentiation, this record can be divided into a desirable number of
speed intervals. The scale of the motion record can be compatible with that of
the record of changes to enable overlay viewing.
The store of imagery, maps, text and graphics is contained in microfilm and
transparencies in order to minimize space and weight considerations. Map trans-
parencies are used in the positioning function of the SLR data. Technical and
general information from the file is furnished during interpretation and MSI.
Information and graphics (previous change records) are taken from the file and
used during comparison in the data reduction sequence.
4.7.5.5 Carrier Based Equipment
Much of the current carrier based equipment is consistent for use with the
synthetic array radar system discussed in this report. However, some additional
pieces of equipment would be required which are as follows:
1. Coherent optical processor for the reduction of the raw data films
received from the aircraft.
2. A special purpose piece of equipment to perform change detection on
processed signal films.
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3. A method of storing and obtaining the precise navigation information
required for repetitive cover runs - needed if automated change detection is
used.
4. A data link receiver and data handling equipment to expedite the hand-
ling of the keying information and relaying it to the priority analyst.
5. The addition of a priority analyst display station in addition to the
present reconnaissance stations.
4.7.6 ELINT Data Handling
Basically, the data handling system for ELINT involves processing of a mag-
netic tape removed from the aircraft on a large general-purpose computer. The
outputs from the system are printed lists of emitters (with characteristics and
locations) from a teletypewriter, and an annotated plot of the same emitters on
a large automatic map plotter. There are several different computer programs
available to permit printout and plots of the output data from a number of stati-
stical viewpoints, but correlation with other sensor records is done by the ana-
lysts and operators.
In the optimized system, these same data flow paths and techniques exist
for the low priority ELINT data, but additional capabilities and facilities have
been added to separate-the high-priority data rapidly from the total ELINT col-
lection, and to correlate the ELINT data reduction and outputs with similar high-
priority data from the other sensors. These additional capabilities arise pri-
marily from the use of the ELINT real time computer in the aircraft, and the
availability of the sensor keying and control tape on the carrier. The airborne
computer accomplishes much of the ELINT processing presently being done on the
ship, identifying by function and locating preselected types of emitters. The
keying tape contains this predigested ELINT data from the computer and, in addi-
tion, contains similar predigested high-priority data from other sensors and the
observer. The keying tape, therefore, provides the means for correlating the most
significant ELINT information with the most significant (and unique) moving-
target, hot-spot target, and observer data, collected by the HRSLR, IR and ob-
server, respectively. Furthermore, since the digital information denoting each
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keyed target on the keying tape also contains the location of the target in time
and in cross range, the ELINT and other sensor keys can be cross checked against
the photographic and IR map imagery (which do not provide keys for the keying
tape).
The improved multisensor data correlation process made possible by these
innovations can be speeded up and improved to even a greater extent, when the
reconnaissance aircraft is able to use its wide-band data link to send sensor
imagery to the ship in real time. Here again, however, it is the use of the
sensor keying data transmitted with the imagery which enables the greatest im-
provements to be realized. It is of little use to obtain a great deal of sensor
imagery in real time if there is no indication as to what might be valuable and
what might not, or what the priority of viewing should be. By scheduling the
viewing and cross checking of target locations through the use of the keying
tape, however, reduction of even the real time data processing and analysis
cycle will be improved considerably. For example, as soon as the data starts
coming over the link a permanent plot of the location of all keys will auto-
matically begin, the ELINT keys being identified as to type of emitter. At the
same time, the attention of the reconnaissance analyst and his staff will be
directed toward the examination of those IR and HRSLR map images being produced
at the locations dictated by the keying tape. Even though final confirmation of
any results obtained from this early screening would probably have to be deferred
until it could be checked against the photographic imagery when the aircraft
returned, the amount of prefiltering already accomplished would undoubtedly re-
duce the subsequent cycle time appreciably. When the data link is being used, a
duplicate of the aircraft observer's real time situation display is also avail-
able in the Priority Analysis Center of the carrier. This display is derived
from the same signals used in the aircraft to produce the observer?s display
namely the keying tape and IR map, and which are transmitted to the ship.
Finally, one of the most important advantages to be gained in the shipboard
data processing cycle through the use of the keying-control data is that the
signal contents of the tape can be transmitted over long distances beyond the
line-of-sight by using a high frequency (HF) air-to-ground communications link.
This is technically feasible because the information content of the keying sig-
nals (bits per second) is low enough to allow very reliable transmission within
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standard HF channel allocations. Now the intelligence center on the carrier has
access to the observer's real time display and the keying data, even when the
reconnaissance aircraft is beyond the line-of-sight. The amount of data received
is smaller than when the wide-band link is being used (the IR map image cannot
be handled by the narrow-band link), but the aircraft flight path, complete ELINT
data, and other sensor key data can automatically be plotted, and advance prepar-
ations begun. In fact, rather complete intelligence on high priority enemy ac-
tivities will be available at a very early point in the overall reconnaissance
cycle, and will include a considerable amount of sensor cross-correlation on
significant targets.
4.7.6.1 Subsystem Description
The shipboard data reduction and processing system for the ELINT subsystem
must meet the following requirements:
1. Rapid data processing and release of information to mission planners.
Priority information should be -available within seconds of receipt by radio
link; all but low priority, data-base type of information should be available
within one-held hour after the reconnaissance aircraft has landed.
2. Rapid correlation of ELINT keys with the high priority keys of the
other sensors so that meaningful data will be screened and processed first.
3. Correlation of ELINT data with Radar Order of Battle and known radar
parameter lists, to confirm the presence of specific emitters at precise loca-
tions.
4. Flexible filtering of output data to restrict teletypewriter printouts
and plots to emitters with specified characteristics, or to emitters located
within prescribed geographical areas.
5. Printout of selected data on plotting boards, teletypewriter, and
magnetic tapes.
6. Correction of ELINT location data by information from the reconnais-
sance analyst. The latter obtains this information by location data from the
photo, IR and HRSLR sensor records.
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Since the airborne computer has done important presorting of the ELINT
intelligence aboard the reconnaissance aircraft, the important ELINT flow path
becomes the data-link path, which starts with the keying control tape and pro-
ceeds through the Data Correlation Center to the Priority Analysis Center.
Here ELINT signals are displayed on the priority viewer, or plotted on the ana-
log key data plotting board. This is the flow path for the ELINT data which
have been predigested in the airborne computer and is available on the keying
tape in the form of emitter locations and functional types.
If the data link is not used, the keying tape record removed from the air-
craft becomes the starting point for the ELINT priority path, and flow-wise
progresses through the computer to the teletype printer and the analog plotting
board. The ELINT tape removed from the aircraft is not needed for the high-
priority analysis and can be used to do the conventional ELINT reduction at a
later time. Since the keying and control tape contains ELINT data which have
already been reduced in the air, plus all of the other high-priority sensor keys,
it is the starting point for all of the high priority data reduction on the
carrier, whether the data links are used or not.
If the HF data link is being used (aircraft beyond line of sight to the
carrier), a keying tape is made in the Priority Analysis Center from data being
received. The same data are used to operate the priority viewer in the Priority
Analysis Center, and can be fed to the ELINT computer in the Data Storage, Pro-
cessing and Retrieval Center, while the tape is being made. The output from the
computer will then operate the two plotting boards, one next to the reconnais-
sance analyst in the Data Analysis Display and Interpretation Center, and the
other next to the priority analyst in the Priority Analysis Center. Thus, all
high priority key data will be presented in real time on a viewer and plotters,
and a keying tape will be available to control the processing and viewing of the
imagery data when it becomes available.
When the wideband data link is being used, there is no change as far as the
processing of ELINT data is concerned. ELINT data filtered by the airborne com-
puter, and placed on the keying and control tape, still is displayed on the
viewer and operates the two plotters. When the keying and control tape is re-
produced on the ship, however, it can be used immediately to filter and display
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the IR and HRSLR imagery received over the wideband link.
If no data link is used, the ELINT data on the keying and control tape,
and the ELINT data on the ELINT tape, are removed from the aircraft. The keying
tape, however, has the high-priority data and would be processed through the
computer immediately in the Data Storage, Processing and Retrieval Center. The
ELINT tape removed from the aircraft contains a record of every pulse word re-
ceived from emitters during the mission, and can be processed in the same manner
as present ELINT tapes are processed to derive complete ELINT intelligence on
all emitters intercepted.
An additional flow path exists for ELINT data reduction when both the ELINT
tape and keying tape are available after a flight.. If the keying tape is used
to control the reduction of the ELINT tape in the computer, there is a possibility
of identifying emitters keyed by the IR or HRSLR (moving vehicle or rotating an-
tenna) which may not have been identified and processed by the airborne ELINT
computer.
The remaining flow paths for ELINT data retrieval and storage are discussed
later in this report with the other sensor library materials.
4.7.6.2 Detailed Data Flow
The computer on the reconnaissance aircraft has the capacity to completely
process a maximum of approximately 20 priority emitter types, and to write their
identities and locations on the keying tape. As soon as narrowband communications
with the carrier becomes feasible, the keying tape is transmitted.
The shipboard receiver output is fed to the processing location in the Data
Correlation Center so that a keying tape can be prepared for subsequent corre-
lation of the sensor imagery. In real time, however, the output from the re-
ceiver will also operate the priority viewer (in the Priority Analysis Center)
and, through the computer and D/A converter the two plotting boards.
When the keying tape is completed it can be run through the computer (if
the computer is not "on line" for real time plotting) to correlate ELINT data
with the other sensor keys, and the ELINT ROB library tape which is entered into
the computer. When emitters whose identity and location correlate with the other
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sensor keys or the ROB tape are found, they are printed out on the ELINT tele-
typewriter output. Since the keying tape constructed from data received over
the narrowband link contains ELINT data, ELINT processing can be done as soon as
the computer is free.
Although the use of the computer has been indicated to process the ELINT,
MTI and hot-spot targets for real time plotting, it is probable that the plotting
will be able to be done directly from the received digital signal. The outputs
from the data link receivers will then go directly to the D/A converter, and the
computer will not be used for "on line" work.
When the wideband link is used, IR and HRSLR imagery are also received on
the carrier, and will be processed while the keying tape is being made. The
keying tape then will be used by the computer to control the display of the IR
and HRSLR imagery on the main image viewer at the reconnaissance analyst posi-
tion to locate the significant targets keyed.
Processing of the complete ELINT record tape will be as described in
Volume 2, Target Characteristics, with the additional assistance of the keying
tape for multisensor correlation. All of the computer programs for special fil-
tering of the output plots and printouts will be available and should be used as
required. This filtering has the advantage of unburdening the processors and the
operator of data which is not applicable to the specific mission in process.
Samples of programs which might be used in special situations are as follows.
Location Selection - Data are processed only for emitters within a given
region. The region can be specified in the following terms:
1. latitudes and longitudes of the boundaries
2. location of center and radius of circular area
3. locations of points defining a polygon
4. locations of points defining a flight path and the range covered on
each side of the flight path..
If it is desired to restrict the data processing to the area covered by
other sensors, the range from the flight path can be automatically computed from
the altitude.
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Characteristic Selection - Data is processed only for emitters designed
for specified functions. For example, if printout is desired only on anti-air-
craft fire-control radars, the data would be filtered for the parameters of Whiff,
Firecan, and other AAA radars, and printed out.
Emitter data, filtered as required by the appropriate location and charac-
teristic selection can be plotted on transparent map overlays. Theplotting
board includes digital-to-analog conversion of the location coordinates, and a
head capable of printing the essential information about the emitter, such as
the type and identifying number. In addition, the teletypewriter provides a
printout of the filtered emitter activity for visual analysis and for record
purposes.
4.7.7 Infrared Data Handling
Upon landing of the reconnaissance aircraft, the magnetic tape and the pro-
cessed film containing the high resolution infrared imagery is taken to the Data
Correlation Center. The film is loaded into the PI viewer, and the imagery is
interpreted visually inconjunction with the information from the other sensors.
The keying tape may be used to select specific imagery for priority analysis or
to cue the PI to objects of interest on a given frame.
The magnetic tape containing the high resolution infrared quantitative data
may be employed to produce secondary keying tapes by synthesizing fields of view
and threshold levels other than those originally-selected by the aircraft obser-
ver. These key tapes may then be used to provide additional cueing information
to the photointerpreter. In addition, the tape may be processed to obtain quan-
titative information regarding the size and temperature difference of particular
objects as requested by the photointerpreter. This information is extracted auto-
matically by digitizing a region upon re-quest from the PI and providing the infor-
mation either as symbol display by CRT or as typewriter printout.
Priority analysis aboard the carrier may be performed during the data gather-
ing mission by making use of the infrared imagery combined with the cueing infor-
mation on the priority data link.
The display provided to the priority analyst is essentially identical to
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that provided to the aircraft observer. It is a synthetic display which incor-
porates a photographic presentation of the expected flight path, plus the imagery
transmitted from the IR and SLR sensors. The keying data is displayed in a sym-
bolic form to aid the interpreter. He may elect to display only information
from selective geographical locations or information for which several sensors
indicate high priority.
The infrared data is stored in both film and magnetic tape format. Selec-
ted imagery or quantitative data may become part of the intelligence data base.
The remainder of the data is discarded at the end of its tactical lifetime.
The data stored on magnetic tape remains in analog format but the digital
data block associated with each scan permits ready access to the analog infor-
mation through the use of digital tape search routines. Analog to digital con-
version is performed by conventional methods and the resulting data, both ampli-
tude and position, may be printed or displayed numerically.
The film records of the infrared imagery are essentially identical to the
photographic records and are similarly stored and retrieved.
The output of the infrared reconnaissance equipment is in the form of visual
display and OB status presentation during a tactical situation. In addition, it
may be used to provide supporting interpretive information as required.
Data selected by the air intelligence officer may become part of the perma-
nent data base in either digital or film format as requested by the PI.
SPECIAL HANDLING
Approved For Release 2009/07/08: CIA-RDP67B00657R000300220001-3
Approved For Release 2009/07/08: CIA-RDP67B00657R000300220001-3
SPECIAL HANDLING
SPECIAL HANDLING
Approved For Release 2009/07/08: CIA-RDP67B00657R000300220001-3