0018933 It was planned to fire a total of eighteen rockets on each shot at zbout H # 10 minutes from launching platforms spaced at various dis- tances from ground zero, Two rockets were to be fired along each trajectory, one programmed to collect a sample from the base to the top of the debris and the other to collect from the top half of the cloud only. 1, 3.3 Aircraft Sampling of Clouds, A condition necessary for use of the gzs-partiéle sampling technique for the determination of device p2rtition is that the samples be collected from a region which is losing materia] by fallout but not receiving particles from any other section of the clord. The portions of the cloud which are suitable for this type of sampling are dependent on the wind structure existing at the time of burst, For one type of structure which occurs fairly frequently at the proving grounds, the tcp and bottom pzrts of the cloud are blewn off rapidly in different directions leaving a layer 2pproximztely one mile thick that experiences only light and variable winds, Hence this stratum, which is located between 50,000 and 60,000 feet, will soon be isclated irom the rest of the clovd and may remain fairly closely over grcund zero for a day or more. It is called the'light and variable wind layer" and is sifisfactory for coincident sampling since it can not receive fallout from higher cloud levels. 36 a ae e ene med ars