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ABSTRACT
Project 9.1 was organized to document the cloud-rise phenomena during Operation Castle
by means of photographs exposedfrom aircraft. This supplements Program 13.2, a LosAlamos Scientific Laboratory study of the early cloud~rise by means of ground-based
' Cameras.
Four aircraft were used: One RB—36 operating at 40,000 feet, and three C—54's
working at 10,000 to 14,000 feet. The planes were 40:'to 100 miles from ground zero,
usually at the 50-mile range at H-hour. Aerial cameras were installed on A-28 Stabilized Mounts and operated by the Lookout Mountain Laboratory, U.S. Air Force. Photographs were taken of the visible cloud, from several directions, as a function of time.
Supporting data were photographed antomatically, and the aircraft furnished navigation
logs to documenttheir position at everyinstant. These logs were rather less complete
and less accurate than had been expected; this is attributed primarily to the difficulties
in flying under unaccustomed conditions.
All four aircraft flew on every shot. Of the 24 missions, six were spoiled because
of interference bynatural clouds. Four of these were on Shot 3, which was fired under
such bad weather conditions that good photography from the ground or from the air was
impossible.
'_ The data obtained are more complete and more accurate than any obtained during
previous operations. - Good measurements of cloud heightand diameter over a 10-minute
interval were obtained for the five shots which were photographed. It has been found
possible to apply suitable corrections for the effects of earth curvature and-atmospheric:
refraction, the slight tilt of the camera platform, and the altitude of the plane. The re‘sulting data agreé well from one plane to the other, and it has been possible to assign
smaller uncertainty to the results than had been anticipated. With a few exceptions, it has
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SECRET