3. Maximm altitude capability (60,000) to obtain quality samples. 4, | Minimum endurance of five hours to allow sufficient time in the cloud area to collect a full sample. WA, Speed of .84 Mach to prevent overexposure of crew to radioactivity. 6. Be structurally clean to facilitate decontamination. 7. Capable of obtaining a full sample per aircraft to assure accuracy of sample. ‘The Air Force position with regard to this matter was that aircraft which would more adequately meet sampling requirements were under development, At the time, several fighter type aircraft were available which would meet the altitude and speed requirements only. Also the B-47A aircraft could be used as well as the reliable B-36, which was considered to be the most desirable for obtaining the samples at 50,000 feet. Unmanned aircraft in drone configura- tion were not considered suitable in view of the LASL criteria. Guid- ed missiles were available and, although not utilized for CASTLE for various operational: reasons, were given consideration. One B-57 (British-built Canberra) was at the Glenn L, Martin plant at that time but spare parts were not available. Because of the increasing complexity of cloud sampling, AEC had recommended to DOD after IVY that a permanemt cloud sampling unit be established. Advantages of such a unit were numerous. Ex- perienced personnel would be available at all times; more reliable samples could thus be assured; the same aircraft could be used for 56