EFFECTS OF WEATHER ON PHOTOGRAPHIC RECONNAISSANCE OVER NORTH VIETNAM

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP68B00724R000100050012-3
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 4
• Document Creation Date: December 15, 2016
• Document Release Date: April 19, 2004
• Sequence Number: 12
• Publication Date: April 11, 1966
• Content Type: MF

SECRET
Approved For Release 2004/05/21 : CIA-RDP6'8B9O724R000100050012-3
25X1
Copy /d'
1 1 APR 1966
MEMORANDUM FOR: Director of Central Intelligence
SUBJECT: Effects of Weather on Photographic
Reconnaissance over North Vietnam
1. This memorandum is for the information of the
Director of Central Intelligence. It is in answer to the
question posed by the Director of Central Intelligence
concerning weather conditions over North Vietnam for the
next three-month period.
2. To properly evaluate the effect of weather on
photographic reconnaissance, it is necessary to differentiate
between high-level and low-level reconnaissance. High-level
is divided into aircraft/drone and satellite platforms. Low-
level includes all tactical aircraft and certain drone con-
figurations. Pertinent operational criteria and associated
weather restrictions are presented below.
(1) Flight path is normally in the lowest
10,000 feet of the atmosphere.
(2) Maneuverability to and from the target
area, plus the latitude of variance in acceptable
photographic altitudes over the target, result in
a high probability of satisfactory weather conditions
during any month of the year. -
(3) Reaction time is short and utilization-of
the 417 Meteorological Satellite readout at Saigon
presents the user with an excellence of cloud cover
data prior to launch.
(4) The primary weather. restrictions which could
preclude mission success are:
(a) Reduced vertical visibilities due to
precipitation, fog or heavy haze/smoke over the
target.
25X1
GROUP 1 SECRET
Excluded from automatic
downgredirig and KIWI reVI W s corn Ieted
I I
p
I3 sri
- -- X}'& ti-r~ elease 2004/05/21 : CIA-RDP68B00724R000100050012-3
 SECRET
AApprove& r Release 2004/05/21 : CIA-RDP68B09i-"t4R000100050012-3
I I
Page
(b) Hazardous flying conditions resulting
from low-lying, terrain-obscuring clouds and
25X1
(c) Turbulence associated with thunderstorm
activity enroute to, from and in the vicinity
of the target area.
b. High-level (Aircraft/Drone)
(1) Flight path over target area above 60,000
(2) Actual flight plan optimizes target coverage
over forecast good weather areas.
(3) Flexibility in target selection and route
development, based on existing and forecast weather,
coupled with a 24/12 hour unit reaction time insures
maximum target coverage with each mission.
(4) The primary weather restriction is total
cloud cover in excess of 25 percent over the target
area. Targets become partially to wholly obscured
by clouds and/or shadows when 50 percent or greater
total cloud cover exists.
c. High-level (Satellite)
(1) Flight path over target area is above
approximately 85 nautical miles.
(2) Orbital characteristics determined by pre-
planning based primarily on priority targets to be
covered in the USSR. The number of N-S?swath cuts
through South China and North Vietnam is dependent
upon the orbital parameters and the mission length.
25X1
(3) As with high-level (aircraft/drone), the
primary weather restriction is total cloud cover
over the target area.
Approved For Release 2004/05/21 : CIA-RDP68B00724R000100050012-3 25X1
 SECRET
Appro yi?For Release 2004/05/21 : CIA-RDP6815OCf724R000100050012-3 25X1
Page
3. The following data indicates the number of days
satisfactory weather conditions normally exist for high-level
(less than 25 percent total cloud cover) and low-level (no
clouds below 2,000 feet) over Hanoi.
JAN FEB MAR APR MAY
JUN
High-level
5 6 6 8 6
1
Low-level
18 16 13 16 19
20
High-level
JUL AUG SEP OCT NOV
2 2 5 6 10
DEC
8
Low-level
19 18 18 22 23
22
25X1
days in June and two days in July.
In 1965, weather favorable for high-level reconnaissance
over Hanoi occurred four days each in April and May, zero
ALBERT D. WHEELON
Deputy Director
for
Science and Technology
Signature is recommended.
25X1
25X1
Approved For Release 2004/05/21 : CIA-RDP68B00724R000100050012-3
 SECRET
ApproFor Release 2004/05/21 : CIA-RDP0724R000100050012-3
I
Page
WS/OSA/
Distribution:
#1 - DCI
#2 - DCI
#3 - DD/S&T
#4 - DD/S&T Reg.
#5 - DD/S&T Chrono
#6 - DD/I
#7 - D/SA
#8 - D/FA/OSA
#9 - WS/OSA
#10- RB /OSA
#11- Chrono
11 April 66
25X1
25X1
Approved For Release 2004/05/21 : CIA-RDP68B00724R000100050012-3