0018933 In the rocket samplers some breakup of the fallout particles was thought to be likelyin passing through the shock front in the diffuser throat. A series of experiments carried out by NRDL on the shock tube at the University of California Engineering Experiment Station indicated that coral fallout grains were not fractured by Mach 2 shock waves (Reference 58). Impact with the filter is another possible cause of particle breakup in all the sampling devices, but little or nothing is known aboutthis effect. 2.3 DESCRIPTION OF FIELD OPERATIONS 2.3.1 Meteorology. It was indicated in section 1.3.3 that samples to be used for the determination of fallout partition by the UCRL method should be collected from the light and variable layer, if well defined, or from higher locations in the cloud. The cloud heights and wind structure in the upper atmosphere are therefore important characteristics to consider in devising operational plans. It is known from previous work that the clouds rise toa maximum altitude in the first few minutes and then settle back to a 'stabiliz- ed" level. Based on height-yield curves derived from photographic data on earlier shots (Reference 21), it was estimated that the stabilized altitudes ETED would be around 72,000 feet for Koa PSY""™ (Reference 59). and 99, 000 feet for Oak The altitudes observed by project aircraft were considerably lower (Reference 60). A radar record for shot Koa indicated that the cloud rose to 72,000 feet at 5 minutes and then settled rapidly (Reference 61). The light and variable layer existed for all the shots, being possibly: 50 SAN BRUNO FRO