of CYLDA while flying a@ he nortit end of the racetraci patterty sew Appersens: dix Le The maximum intensity cf 60 Mr/iv was reported a@ 2340 Zebra bum contacts continued to be nade in the same general. ares until C117 Zebran. I6. ia interesting.to note that alZ fallout was encountered at the northerm ends amexcellent verification of the path forecast by the aix of the patter, 1 -Q * va particle trajectorfee. Later during UNION day it became cbvicus that thd wind patterns were relatively unstable and that there was 4 alight possibin lity that fsliou® may have cacurred in the vicinity of the populsted atolls to the sgutheast of Ground Zerca To evaluate this possibility, WILSOM THRES | was dirgeted at 0200 Zebra to conduct arm area search slong a true bearing of 100 degrees from Ground Zero at an altitude of one thousand foet. In addie tion, a survey of sachr atoll in thia regtos was to be conducted at minimum © altitudes Enrouts to the designated sector V/ILSOMN THREE passed almos® iirect~ ly over Ground Zero. Gamma radiation or "shine” frou the crater is, without a doubt, the cause for the very hight readings reported at 0230 and (232 Zebra (1000 and 2000 Mr/He respectively). In this case the aircraft back— ground remained at 5 Mr/Hrs This is in direct contras® to the experience cf the WILSON TO flight. which encountered fallout measuring 2000 Mr/iir where the subsequent. aircraft backgrouni was 250 Mrfir; The msulte of the stoll survey are tabulated in Appendix I (atoll locations can be determined by comparing the time of survey with the positics plot). It cam be seen that RONGELAP, RONGERIK and T.A -TOLLS appeared to have received very slight fall- out, probably very few Mr/Hr. The readings at the other atolla were undcub— tedly aircraft background. dA more ccouprehensive survey conducted for the NYKOPO onUNION plus one day confirmed the validity of the ‘JILSONTHRES survey. The only other GILDA contact reported by this aircraft was at Odh Zebra, fifty miles west-southwest of Ground Zoro, This wag undoubtedly £ out from a level of the cloud that initially mowed east and then was carried back by the "sasterlies" prevailing at the lower altitudes. CG. ‘ILSON TWO, flying at ten thousand feet, made no contamination contacts in the racetrack patters betweerr plus two ani plus five hours which indicates. that the upper limit of the westwaremoving cloud was about ten to fifteen thousand feet. Later, while carrying out the area search (betweer 65 and 95 degrees from Groumt Zero, this aircraft made its first interceptions of GILD\, eighty-five niles sast-northeast of BIXINT ATOLL. The radiac instru= ments soon (2334 Zebra) indicated a maximum reading of 2 R/Hr; contamination which obviously mst hayes been fallcut from the wenty, thirty, and forty thousand foct levels (See Trajectories). This penetration left the aircralt with a background of approximately 250 Mrfir. Subsequent reports by this aircraft probably reflect. no new contacts but rather the decay of the resi- dual contamination.s de, “TLSON FOUR ceperted ENIETOK ISLIND at approximately UNION plus twelve hours with the mission of conducting an area search out to maximm range between 65 and 9§ degrees true from Ground Zero at an altitude of ten thousand feet. At plus fifteen hours this aircraft was directa to divert. for the purpose of making . a minimum altitude surwey of “OTHO .TOLL, the only populated atoll for which a potential hazard oxisted and which had not been surveyed by “ILSON THREE, This survey, as one would suspect, showed no con= tamination at that point. “TLSON FOUR resumed search in his previously N=34