WB-50 collected one 1,000-foor sample at H+6 hours on a bearing of 20° at 42 miles from ground zero. It is thought that this material came from about 45,000 feet. A third WB-50 mission was flown at 0700 the next day to 300 miles on a bearing of 58° based on an extrapolation of the previous contacts. From there, the aircraft was directed to 225 miles, bearing 55°, then to 200 miles, bearing 40°, and finally to 400-miles, bearing 60°, but no fallout was encountered. The aircraft was relaased after 6 hours for a weather mission. Shot Fir -was fired at Bikini on the day preceding Koa, On the day following Koa, there was a deposition of fallout in the Eniwetok area, and in the afternoon the gamma radiation background on Site Elmer rose to 25 to 30 mr/hr. The Fallout Prediction Unit (FOPU) was not able to establish definitely the origin of this material but felt that there was some rea- gon to think that it had come from Shot Fir. After arrival of the Koa samples at Los Alamos Sctentific Laboratory (LASL), a diapatch was received in the field ludicating that the cloud, and possibly the fallout samples, were heavily contaminated with Fir debris. The nature of the evidence was not known at the time Examination of the wind structures existing during the period of the Fir and Koa detonations indicated a possibility of some contamination of Koa fallout by Fir debrie, but no mechanism was apparent that could lead to heavy contamination. When the radiochemical data became available, it was found that all the Koa cloud samples contained some material from Fir but not enough to appreciably alter the significance of the results (Chapter 3). 2.3.3 Shot Walnut. It was planned to project a total of 10 rockets into the cloud, four each from Sites Mary and Sally and two from Site Wilma. The launchers on Mary were set for automatic positioning by blue-box signal, whereas on Sally and Wilma the quadrant elevations and azimuths were preset. After the shot, the firing circuits to Sally and Wilma wereintact, but the llne to Mary was open. A firing signal was sent at H+10 minutes, and the rockets on Sally and Wilma were launched, but the obscuring cloud cover prevented observation of their trajectories. The rockets on Mary did not launch, and later inspection showed that one launcher was inoperative, one elevated without rotating, and two elevated and rotated. Two nose sections from the Sally rockets were recovered by boat, but the others were lost. The closures on the nose sections recovered were intact, but water had leaked in. There was a smal! amountof activity in the water and on the filter, and the filter sample was returned to the NRDL for anal- ysis. It was identified by the name Whiskey 6 (Table B.3). Six samples were taken from the cloud at times between 1 ‘/, and 28 hours postshot time (Table B.3). Both the wing tank and the coincident samplers were operative on each flight. In preparing the height line flight program for this shot, it was intended that one WB-50 would collect 1,000-foot samples at 4, 6, 8, 10, and 12 hours with a second WB-50 standing by on the ground to take over the misgion, if necessary. No sampling flight was scheduled for D+1lday. The first aircraft encountered fallout at H+4 hours on a bearing of 320° at a distance of 42 miles from surface zero, and a sample was collected. Because of deposition of damp fallout material on the nose of the aircraft, a dose of 1.5 r (read on an electronic integrating dosimeter) was accumulated at the bombardier’s position during the sampling run. The dose was continuing to rise at the rate of 50 mr/min, and the radiological adviser aboard decided to diacontinue the mission and return to base. The standby aircraft took off and was flown to a point on a bearing of 330° at a distance of 120 miles from surface zero. At H+8 hours, the aircraft searched on a course of 225°, but no fallout was encountered. At H+10 hours, the active fallout area was reentered at bearing 282°, 140 miles from surface zero, and a sample taken. At H+13 hours, a third sample was collected at bearing 278°, 150 miles from surface zero. 2.3.4 Shot Oak. There was no rocket participation during Shot Oak. Circumstances leading to the discontinuation of the rocket sampling portion of the project are outlined in Section 2.3.5 and Appendix A. 25