Suitability. In early 1952 a decision was made to employ the F-84G sinple- place fighter-bomber. This aircraft had an ejection seat, anti-G suit Pro- visions, windshield defroster system, automatic fuel transfer system, an inflight refueling system. First accepted by the Air Force in June 1951, it was considered a first-line combat aircraft (Reference 29). teen of these aircraft were specially modified for IVY sampling operati under the supervision of the Air Materiel Command (Reference 29, p. 66) These aircraft received four new avionics systems, radiac instruments, dual cloud-sampling systems. A filter was also installed in the cabin pressurization system to prevent nuclear cloud particulates from enteri the cockpit. This con- Kad One of the two sampling systems was called a "Snap-bag." sisted of a plastic bag mounted in the gun deck of the aircraft nose. system was actuated by a trigger switch on the control stick enabling c lection of gaseous samples for 10 to 20 seconds (Reference 29, Chapter et seq). A second sampling system involved modifications to the wingti fuel tanks for the purpose of collecting particulate matter in the nucl clouds. A diagram of this wingtip system is shown in the inset of Fig- ure 23. The operation was fairly simple; the pilot could open the valv behind the air scoop to admit ram air through the scoop. This air pass through filter paper, where particulate matter was collected, and then vented. An ion chamber was mounted in the tiptank as a sensor to measu radioactivity of the filter paper and indicated the amount of sample co lected at any given time. Figure 23 also shows the major modifications made to these F-84G aixcraft to include the four avionics systems: the ARA-& homing device, p=3 VHF radio transceiver, the APX-6 IFF transponder, and the F-5 autopilot. Note also the sampling probe on the nose, which fed to the snap-bag. In January 1953, shortly after Operation IVY was concluded, AFSWC reb- resentatives met with LASL representatives to discuss CASTLE sampling r quirements (Reference 29, p. 94). The sampling project manager outline 134