ELUEH and URSULA witls negatiy loftenisatiom, NYKOPC Flight ABIES wae -~ : at RONGERIK and TAKAe scpeduted for Y plus 1 day and direated ta make preliafnsry in-flight reports. Cloud tracicing operations subsequent to noort on shot day were mostly routinerand in accordance with plan exept that no flights were performe®? after-H“plus 24 hourgee. (See inclosure reference YANKEE Air Radsafe Operat tionae} . Some unusual features were as followsr (ilson & (4 replacement. for “ilson 3, whic picked up s 2 r/hr aireraft background in the vicinity of BIKINI Fsland) conducted a low level survey of the northert Marshalls between. and 1740M on shot day at altitudes of 100 to 400 fect. This survey included "IOTHO, sILINGINAS, RONGELAP, RONGERIK, UTIRIC, alLUK and LIKIEP. No significant contamination wes detected. (It should be noted that the instruments available to the cloud trackers, although of the same kind, were not nearly as sensitive aa those used by the surveys made by the New York Operations Office. The negative results obtained were suffieiently ascurate to state only that significant contamination (more than about 10 or/hr) was not presente & further limitation lies in the fact that serious contamination could possibly occur later than the afternoon of shot day. For thig reason, the precision survey flights for the New York Operations Office were scheduled for shot day plus one at the earliest.) In an attempt to obtain maximum documentation of YANKEE, “lson 5 was directed to search 4 sector from true bearings 40° to 70° out to maxinum range at 10,000 feet from H plus 14 to H plus 21 hours. The informtion fran this flight was extremely useful in analyzing the long-range fall-cut pattern, Based om a cloud tracker contact with the cloud 50-70 NM north of BIKAR ats; 052030M (1.0 to 6,0 r/hr at 10,000 feet) all units were again alerted to : the possibility of light fall-out in the BIKINI area by approximately day~ break on 6 May, This fall-out did not materialise, nor did NYKOPO Flight ABLE record corresponding intensities at BIKAR on Y plus 1 day, thus furnish=ing further evidence of the serosol, fall-cut-reslatant characteristica of the clouds from water surface shota. (See ir Radsafe Operations inclosure for further details on the cloud tracking efforts.) In accordanse with plan, CINCPACFLT was advised at 200Qf on shot. day of the current radsafe situation. This advisory consisted of the followings No significant change in the forecast 72-hour air particle trajectories, no ‘known fall-out existing or forecast for surface and alr routes except 4s previously indicated relative to closing the K",JALEIN-GUAM air route. The advisory further stated that cloud tracking results on ¥ day indicated the main portion of the cloud passed to the east-snortheast and well to the north of a line through RONGELAP and UTIRIK, and that low level flights over the northern Marshalls on shot day indicated ecntamination less than 10 ar/hr from YANKEE. CINCPACFLT was also advised that NYKOPO Flight ABLE was schedule ed for Y plus 1 day. On 6 May informition was received relative to a contact with contaminae “© tion made by two LST's enroute in company from ENI'STOK to Pearl, The incident involved an area approximately 700 NI east-northeast of GZ from approxizately H plus 35 to H plus 4l hours. One of the ships, LST 762, waa equipped with stamiard task foree wash-down equipment. The other, LST On5