retained the snap-bag gas-sampling devices used in IVY. The B-36s were Fitted with a filter installed in the cabin pressure system and each received both a double-squeegee gas-sampling system and a particulatesampling device. One of these B-36s was equipped with an array of elec- tronics to serve as backup to the primary B-36 controller, which, like the F-84Gs, was also used in IVY (Reference 29, pp. 97~98). were equipped to perform “heavy nuclide" sampling. The WB-29 aircraft The WB~29s carried a "shoe box" in each wing; each box had two filter panels but the aircraft had no special instrumentation, controls, or sampling indicators. The only proof of sample collection while airborne was the aircraft background as measured by a T1-B radiac meter (Reference 29, Chapter 8, et seq). The double-squeegee was designed for operation at altitudes of 36,000 to 50,000 feet (10.97 to 15.24 km). Two air-cooled, four-stage radial com- pressors, operated electrically, exhausted a portion of the jet engine intake air into a 500-in> (211 kg/cm?) . (8,193-cm?) collection vessel at 3,000 1b/in” Each compressor was rated at 1,728 in?/min (28,317 cm?/min) . Both compressors operated in parallel, pumping into a single collection vessel. There were two versions of the double-squeegee that differed only with respect to filtering the compressor input air. A “special" double- squeegee was used on three F~84Gs, which contained a special filter integral to the sampling system. The other seven F-84G systems used the filter in the cabin pressurization system (Reference 29, Chapter 8 et seq). (Air Passing through-the filter was not used for breathing during cloud sampling operations; TG 7.4 policy required sampler aircraft personnel to breathe 100-percent oxygen from the time of cloud entry to mission completion at Enewetak.) Table 12 summarizes the sampling systems installed on the F-84Gs. The RB-36 that served as the airborne sampler controller was No. 1386 (radio call sign Cassidy). The radio compartment contained two ART-13 HF transceivers: one operated in the range of 3.3 to 18.1 MHz, the other from 200 to 600 kHz. The TG 7.4 Technical Advisor rode in this compartment and had selection switches enabling monitoring or communication with sampler 136