aircraft was at a 32,000-foot (9.8-km) feet (27.8 km). altitude and a slant range of 91,000 A second B-50 IBDA aircraft was at a 30,000~foot (9.1-km) altitude and a slant range of 182,000 feet aborted. (55.5 km). The third IBDA B-50 A maximum radioactivity reading of 0.020 R/hr was recorded for 10 to 15 seconds onboard the B-36 effects aircraft; this was the only ra- diation noted by the effects aircraft during the CASTLE series. The Test The early cloud dimensions following the 0610 detonation are shown in Figure 88. The lowest level of the stem (surface to 15,000 feet [4.6 km]) was influenced by 17.3-mi/hr (27.8-km/hr) winds from the east. This move- ment was confirmed by a cloud-tracking aircraft reporting a maximum inten- sity of 0.063 R/hr at H+4, 60 nmi (111 km) west-southwest of ground zero at 10,000 feet (3.05 km). CONTAMINATION. Based on the position of cloud tracker contact and the forecast air trajectories, this contamination is believed to have passed to the south of Enewetak Atoll. was 0.002 R/hr. The peak activity reported at Enewetak Remnants of this portion ,of the cloud probably account for the 0.005 R/hr radiation level reported 460 nmi (852 km) ground zero during a weather reconnaissance mission on D+l. southwest of The middle level of the cloud (16,000 to 60,000 feet [5 to 18 km}]) moved to the eastnortheast at 17.3 mi/hr (27.8 km/hr). made with fallout from this segment. Several contacts were subsequently Between H+5 and H+7, the trailing edge of thecloud was clearly defined by one of the cloud~-tracking air- craft; maximum intensities of 2 R/hr were reported 300 nmi (556 km) eastnortheast of Bikini. The cloud top moved initially to the north and west. In the fallout process, however, this debris was carried back toward the east and intercepted several times. The first was at H+15, when a tracker aircraft was able to completely delineate a fallout area that was centered 340 nmi (630 km) to the east-northeast of ground zero (92 nmi [170 km] north of Bikar Atoll); the maximum reading inside this area was about 0.5 R/hr. At the same time, another cloud-tracking aircraft located radio- activity of 6 R/hr in this same general area, but at an altitude of 1,500 304