0018933 Oe It was plannedto fire a total of eighteen rockets on each shot at about H ¢ 10 minutes from launching platforms spaced at various distances 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 gas-particle sampling technique for the determination of device partition is that the samples be collected from a region which is losing | material by fallout but not receiving particles from any other section of. the cloud, 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 top and bottom parts of the cloud are blown off rapidly in different directions leaving a layer approximately 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 isolated from the rest of the cloud and may remain fairly closely over ground zero for a day or more, It is called the'light and variable wind layer" and is satisfactory for coincident sampling since it can not receive fallout from bp O FRG can BROS higher cloud levels. 36