of testing whether fractionation has occurred, made that no fractionation will occur," A silent prayer is then Fractionation occurring naturally within the cloud and that caused by the characteristics of the sampling device employed, constituted two types of fractionation, Manned sampling was at some disadvantage in the first type because of the necessarily later penetrations. One method of testing for fractionation, Rubinson added, was with samples collected by radio-operated drone boats. Soon after the CROSSROADS detonations, drone boatswould move in to collect water samples, After a period of time, other drone bnats would go into the target area to collect more samples, If the later samplesmatched the earlier ones, Mr. Rubinson reported, ". . . then we could be sure that no fractionation had oceurred between the time of the shot and time the first samples were collected,” Under the circumstances, Rubinson wished for as many cloud samples as could be taken, For the airburst, he asked that cloud samples be taken from eight different altitudes with only four altitudes during the water detonation, Task Unit 1.5.3. The Instrumentation and Test Requirement Unit, Task Unit 1.5.3, was charged with taking samples from the atomic clouds during Operation CROSSROADS. * The unit organized at Clovis Army Air Field, . . ° Results of the water sample tests indicated that some fractionation had taken place, 5 APYLUHG SWEH-2-003L a “0.