‘ have tended to minimize exposure to take a course that was probably nearly along the “hot line" of the BRAVO cloud. At 1900 a second cloud-track aircraft, Wilson 3, was sent east from Enewetak. The flight path was nearly straight east until beyond Rongerik, and then the aircraft headed generally northeast while making several zigzag swings across this northeast vector in search of the cloud. At the southern tip of one of these swings, after 2200, Wilson 3 got two readings that may have been the northern edge of the cloud, but these readings were not much above the background readings taken throughout the flight. Low readings were taken at 10,000 feet (3.05 km) over the Rongelap and Rongerik atolls shortly after 2000 hours. It is clear that at this time Hq JTF 7 did not know where the cloud was, nor where it had been. There was apparently no great concern about this, however, as the Wilson 4 cloud-track flight was cancelled at 1930 (Reference 26). The MIKE experience indicated that although less than 6 Percent of the detonation's radioactive debris had been accounted for, no problems had occurred. The controlling assumption was that the cloud had gone out on the 65° bearing and that the tracking aircraft were simply behind it. The morning's contamination of the fleet lying southeast of Bikini and the unquantified report of contamination by the vP-29 P2vV that aborted were not consistent, but this contamination was believed the result of a wind change at the 20,000-foot (6.1-km) level. This wind change was presumed to have resulted in a widespread east-west distribution of fine particles (Reference 16, p. K-5) and was apparently assumed to he a minor irritation, not a major problem, During the briefing of the task force commander on the Estes at 2000 a second message arrived from the Rongerik detachment. This message re- iterated that the pen had been off the chart since 1450 and requested an acknowledgment (Reference 83). At about the same time, messages were re- ceived from Wilson 3 indicating low readings above this area (Reference 16). At 2200 a reply was prepared explaining to the Rongerik detachment 220