AERIAL PHOTOGRAPHY AT LOWER ALTITUDES

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP62B00844R000200080039-3
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 3
• Document Creation Date: December 14, 2016
• Document Release Date: December 2, 2002
• Sequence Number: 39
• Publication Date: April 17, 1958
• Content Type: MFR

Att to SAPC A2gmved Fo elease 2003/01/24 CIA'RDP62B00S ,8000200080039-3
17 April 1958
SUBJECT: Aerial Photography at Lower Altitudes
1. PROBLEM: To evaluate capability of the U-2 aircraft to descend
to an alt ttude'below high cirrus and/or middle deck cloud cover to obtain
aerial photography during marginal weather conditions.
2. FACTORS BEARING ON THE PROBLEM:
a. Without modification, existing camera configurations will
produce acceptable quality photography, with adequate overlap, at
the following minimum altitudes:
Camera Ground Speed* Altitude;
6+, cartographic 240 Kts 35,000 feet
220 Kts 32,000 feet
24? camera 240 Kts 36,000 feet
220 Kts 33,000 feet
B camera not considered for reasons indicated below.
*Ground speed dependent upon wind direction and velocity.
b. Since the U-2 system was designed specifically for a high
altitude reconnaissance role, there are certain inherent design
limitations in the existing camera configurations which will restrict
or have an adverse effect upon the quality of photography accomplished
at lower altitudes. There are also other factors, not attributable
to design, which must be considered:
(1) On letdown from a higher (colder) to a lower (warmer)
altitude, extreme amounts of condensation must be anticipated.
This will adversely affect quality of photography if camera
lenses or port glasses are fogged. In addition, high condensa-
tion or humidity increases probability of film jams, transport
problems, etc., caused by film emulsion sticking when wet.
(2) As altitude is decreased, photographic scale is
increased - larger scale photography is desirable, especially
for tactical interpretation of targets such as troop concen-
trations, convoy movements, etc. However, as altitude is
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decreased, photographic coverage (the area covered by a
single photograph or single flight line) is also decreased.
For example, at K plus 20, the A-2 system covers an area on
the ground 36 nautical miles in width; the same camera at
20,000 feet, covers an area only 7.5 nautical miles wide.
(3) Design limitations, which may be remedied by modifi-
cation, include:
(a) Fixed interval setting of existing cameras.
Since it was assumed that all missions would be flown
at maximum altitude and airspeed, no provision was
incorporated for changing interval settings of cameras.
(Except for the tracker, on which scan rate may. be
varied.) In order to obtain adequate (50%) forward
overlap of photography, the time between exposures must
be decreased as the altitude of the aircraft is decreased.
An alternative, but less desirable procedure, would be to
slow the speed of the aircraft. For example, the A-2
camera set interval is one exposure every 15 seconds. If
a mission were flown at 20,000 feet, the proper interval
would be one exposure every 9.2 seconds at 225 knots.
Provisions for selecting various interval settings could
be incorporated into existing A-2 system by modifying the
system programmer. Modification would include provisions
for inflight changes in interval by the pilot as the in-
terval settings would vary dependent upon flight line
altitude and ground speed of the aircraft.
(b) Image Motion Compensation ratio. I.M.C. was
designed for a specific altitude and airspeed range to
compensate for forward movement of the aircraft during
exposure. Redesign and rework of this system would entail
considerable effort. Photography could be accomplished
without modifying I.M.C. system, however, quality would
be degraded. Higher shutter speeds would help, but we
are then faced with the problem indicated in the next
paragraph.
(c) Hycon has stated that reliability of shutters
will decrease at higher speeds and presently recommend
use of only the mid range shutter speed with the A-2
camera system. Higher shutter speeds would be required
at lower altitudes.
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(d) Existing Project camera systems utilize a pressure
differential vacuum system. Camera manufacturers (Hycon)
state this system would be ineffectual at altitudes under
17,000 feet. A new or supplementary vacuum system would be
required below that altitude.
NOTE: The 6"-A-1 camera system is not recommended for tactical
photography since the scale produced, even at lower altitudes,
would be too small for interpretation of the majority of tac-
tical type targets. The "BU camera would require a more complex
and extensive modification than would the A-2 to permit low
altitude photography. This is especially true since the Mini-
vib (vibration compensating device) has been removed from the
"Btt system. It is believed that the "B" would be unacceptable
due to increased turbulence and consequent vibration which
would be-expected at lower altitudes.
3. RECOMMENDATIONS
a. Recommend using a system (i.e., etc.) designed 25X1
for low altitude (tactical) reconnaissance. Severa resently assigned
"drivers" have been previously checked out in the 25X1
b. If the U-2 and existing equipment is to be used for lower
altitude reconnaissance, the following modifications would be required:
(1) A pilot selective intervalometer
(2) A supplementary or redesigned vacuum system
(3) A recalibrated Image Motion Compensating ratio, or
(fit) A "beefed up" shutter which would withstand stresses
imposed by-utilizing higher shutter speeds required at lower
altitudes.
c. If a decision is reached to utilize the U-2 for this purpose,
ree anmend mission planning specify approach to target area at, or as
close to as practicable, the target run altitude. This procedure will
reduce comdensation problem.
RSQ:bm
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