Five samples were taken from the cloud by B-57D aircraft between 2 and 26 hours postshot time (Tables B.5 and B.6). Both the wing tank and coincident samplers were operative on all hts. me WB-50 aircraft collected samples from the northeastern edge of the fallout pattern at 4, 6, 8, 10, and 1f ‘, hours after the detonation. The fallout was encountered on a bearing of 300° to 310° at 65, 93, 125, 160, and 187 miles from surface zero. The operation progressed without incident, mainly because of the experience gained by the participating personnel on the first two shots. 2.3.5 Rocket Development. The project cloud sampling rocket (Section 2.2.1) was a new one of complex design. The main motor had been used previously on the ASP (atmospheric sounding projectile) and the sustainer motor on the RTV (reentry test vehicle), but the nose section and associated equipment had not been used as a componentof a rocket before. Devel- opment work on a similar sampling device had been done during Operation Plumbbob, and at the end of the operation a satisfactory unit for land recovery had evolved. After Plumbbob, Project 21.3 was set up for the purpose of developing a sea recovery version of the rocket for ‘Operation Hardtack. When Project 2.8 was established, the existing rocket contracts were extended to provide additional units for use on this program. Because of the experimental nature of the rocket, the sponsors of this work, UCRL, assessed the probability of obtaining any rocket data as being of the order of 50 percent. The development problems were the responsibility of Project 21.3, but a review of their work at EPG is of interest, because a large portion of Project 2.8 was directly dependent on the availability of a suitable rocketborne cloud sampler. This review will also serve to provide an explanation of the circumstances that led to the cancellation of the rocket experiment prior to Shot Oak. Notes on the developmental rocket firings and tests are outlined in Appendix A. Details -of the flrings on Koa and Walnut (Sections 2.3.2 and 2.3.3) are not repeated. 2.3.6 Aircraft Samples. The B-57D aircraft used for the cloud sampling work were under the control of a LASL representative. The person responsible for these collections communi- cated with the aircraft by normal voice radio from the Air Operation Center on Site Fred. fallout samples were taken by WB-50 aircraft controlled by an NRDL representative. The They were directed from the Air Weather Central on Site Elmer using CW radio communication. The transmitters used by the Air Weather Central operated on a long wavelength, thereby making it possible to maintain radio contact with the WB-50’s at long ranges and low altitudes. Estimated coordinates for each sampling position on the height line flights were furnished by the FOPU. Theinitial 4-hour position prediction was based solely on the wind data available at shot time, but contacts made by the sampling aircraft, plus additional wind data, assisted in preparing the later estimates. Interchange of information between FOPU and the Air Weather Central was maintained throughout the sampling flights. The FOPU predictions were generally quite accurate with respect to radial distance from ground zero, but the wind information was not always adequate to determine the angular position. For example, on Koa the estimated height line bearing was 0°, but the sampling aircraft encountered fallout at a potar angle of 50°. For Walnut the 4-hour sampling position given was quite accurate, but the later curving of the height line toward the west could not be predicted. Sam- pling position estimates were the best of all on Oak, and even the most distant points were pre- dicted within 2° in bearing and 3 miles in distance. Tables B.1 through B.6 give a summaryof all the samples collected by aircraft for the proj- ect. It will be noted that in addition to the cloud samples taken from the light and variable layer, there were several samples on each shot from lower altitudes. Analytical data for these samples are included, inasmuch as it gives information on the variation of cloud composition with altitude (Appendix D). 28