Chopter 9 CLOUD PHOTOGRAPHY Following the Ivy-Mike test in 1952, there was considerable controversy as to the rate of rise and stabilization time of the Mike cloud. Concern was expressed by the aircraftdelivery group that strike and supporting aircraft might be faced with a critical escape problem from high-yield weapons. In view of this, the Air Force presented a requirement for a photogrammetry project which would determine the various parameters of nuclear clouds as a function of time and attempt to establish approximate scaling (yield) relationships. First in importance was dctermination of the initial rate of rise of the cloud and height at time of stabilization. Second in importance was determination of the lateral dimensions and drift as functiovis of time after the cloud had reached its maximum altitude. It was further suggesteJ that should aerial photography prove successful on this project, analysis of the negatives would most likeiv provide yaluable information pertaining to felloutdistribution, long-range-detectior, and meteorological studies. In July 1953, the requirement was incorporated into the Castle program and given project stutus. Participating agencies were Edgerton, Germeshausen & Grier. Inc. (EG&G) and Lookout Mountain Laboratory. EG&G was assigned responsibility for the analysis and reporting of the data and as a technical advisor to the Program Director and Lookout Mountain personnel. Lookout Mountain performed all aspects of the project relating tc the taking and processing of the pictures, scheduling of aircraft, training of crews, and the procurement and modification of cameras and camera mounts. Back~up terrestrial photography from ground stations was supplied by EG&G under Project 13.2. The project involved the participation of four aircraft: One RB-36 operated at an altitude of 35,000 to 40,000 feet and conducted photography through H + 10 minutes; three C-54's operated from H-hour through the time required for cloud dispersal. Aircraft position ranges from ground zero at H-hour varied from 50 to 75 nautical miles, depending on expected yields. All aircraft were identically equipped with a K-17-C aerial} camera and an Eclair 35-mm motion-picture camera. In order to analyze the data from the cloud photography, it was of prime importance to know the spatial orientation of the photographic axis during every exposure and the time of every exposure. This was accomplished by mounting the K~17-C camera ard the Eclair motion picture camera on a modified A-28 gyro-stabilized mount. All cameras were modified to record time-clock, tilt, and azimuth readings of the camera heuding on the lower third of the negative frame. The instrumentation of the cameras worked out very well on all events. Minor mal- functions occurred on the time clocks, such as slow starts and time lags, during the operating period. These errors were generally able to be compensated for in the analysis of the negatives. In addition, it was also necessary to know within +2 miles in horizontal coordinates the location of all aircraft from H~hour throughout the required mission time. The results on this portion of the mission were not too aatisfactory. Owing to constantly changing flight patterns, navigation was extremely difficult, and at timesit was impoasible to maintain to the required accuracy. All four aircraft flew on every shot. Of the 24 missions, 6 were spoiled because of 102