The operational rehearsals necessary to test plans, proce- dures, and communications for Operation CASTLE were conducted during January and February. Each of the task groups participated in those rehearsals relative to its participation in the detonations. CTG 7.1, with participation by supporting task groups, conducted practice loadings of devices and shot barges in late January and early February. The LST 762 and the BELLE GROVE made three trial runs prior to actual movement of the first test device from Eniwetok to Bikini. The tugs, APACHE and SIOUX, also rehearsed the laying and recovery of fallout collector buoys at both Eniwetok and Bikini. CTG 7.4 conducted a rehearsal on 16 February in preparation for air participation in the initial shot. The aircraft partici- pating were essentially those which would take part in SHor% The Air Operations Center (AOC) on Eniwetok and the AOC in the ESTES were fully manned for actual control of aircraft. The rehearsal was a success from the Task Group 7.4 standpoint and bet- ter prepared that unit for successful participation in the sHor/ detonation. A general Task Force rehearsal for[Sfo7/ was executed on 23 February with H~hour set at 0645. TG 7.4 participated with a max- imum air effort and TG 7.3 had all vessels except the GYPSY and the COCOPA participating. TG 7.1 took part to the maximum extent pos~ sible in view of instrumentation readiness,. and evacuation procedures were tested although complete evacuation was not effected. 11g