of the aircraft on approach to, and departure from the gamma radiation field in the free air surrounding the cloud was negligible and that the flight time for each penetration through the cloud was brief relative to the elapsed time since the explosion, scientists were able to formlate an equation to correlate the amount of cloud debris collected by a sampling aircraft with the radiation exposure received by the crew and with the other important flight variables, Quantitatively, the equation predicted that the amount of explosion debris collected was a maximm for a particular sampling aircraft, and its associated sampling equipment. Assuming equally effective filtering equipment and otherwise similar conditions, it indicated that a high speed aircraft collected more debris than a slow one in direct proportion to their relative speeds, It indicated, also, that the quantity of debris collected was not explicitly dependent upon the expected yield of a test explosion, but that the fraction of the. total debris collected under given conditions was inversely ( or hyper=-‘ - bolicly) dependent upon the yield, At early penetration times, therefore, a high radiation exposure was necessary to collect the required sample but. if penetration time was delayed enough it was theoretically possible to collect any sample at a negligible cost of exposure. In addition, at too early a penetrationtime a serious risk existed in that an acceptable radiation exposure might be exceeded when the aircraft was in the cloud the least possible time. As penetration delayed, on the other hand, the cloud | dispersed and the radiation flux within it decreased, Project officials met an increasing risk if delaying in that the cloud probably could not 208 APHHe SWEH~2-003); yo saleee