Tereral Taeceipt ion. Pann Arr‘. Reasitements were “ate oyer sicreys wer 8 planes oaqcdp ed woth SOU TAS ESe, gearitive, wife ranve gare selatiliation Snstrivertes capable of ~eae ries getuot | ofan lit saa “OH omrtse from aliitades Siryey Slight res Of FON, or ereater, 7 were wate cover creedeteocmiran pattern) tanta adits achiave axiom coverage im salacted acreage tre Marshall, Gar ine, “arinnay ard Yawaidar triramithadd te the wick tears Inccudes ands. Tata sac Soree reorsiorally from ervey abreraft Ete byt more penera® Ly from the wpiadror hase at the cracls in af each Miipht. “paritione The scintareters were onerated in Slight oy alrerafe crey rembers triined in the¢dr uae. Usually two instrumerts were carried, one reserved as a arare. “he secintameter crerater reno rlad beckrprrund reating, pomition, alvitute amd radiation tatmenrity fo each island in the survey cat ern. Jarksrouad san measured during the adpreach to each istard at a distance of several niles. “hese data were traramitted ti Trask Force “ewlquarters were ‘le intensity at the atated altitude aver each istand was comynrtes to ground in- tera'ty bv Treant of a calloration curve. . Measurenents were zenarally made from an altitude of -'. feat. Were the upper range cf the instrument (160 mrf/ne’ wag exceelad at ore fhes the neasurement would be rescated at signer altitudes until a vaiue within the range 7f the {natminent wast cbtainal. Altitude wag reasured with a radio altimeter. The ratic of ground intensity ‘o the intensity at tne operators position within the aimratt at 77°C tM. ig appreximately 1. (Scintameter calibration is described in Section VI}. The low and of the scintameter range 1s 0.002 me/or sot at theoretically the minimal detectable armind intensity fs O.017 arftr. In reality, the minimal detectable value is controlled primarily ov the gama backgrvind. This backrround can be caused by cosmic rays, nay cational instruments, fe reraft contamination, and possibly resi~ Seal bor> debris an tee wire “he oractical lower limit during CASTLE was in the order of C28 mr/ir. Following SPAT", sur sey narties, out ashore ab se~oral atolls in tre area of fea yiest fallout, recomied large radiation intensity eradients in darsct ons accreximately normal to the fallout patr. At Rongelap, aoproxirately ainety miles from ground zero, a difference of an order of magnitude in pamna radiation was noted Latween two opvagite ends of the atori, a distarce of about “C miles. Tris evidence was substantiated hy #SLE CLizhts repeated on B 4 3 and 3 ¢ 19 during whirh Cc ‘Iustre: ats are described in Secti on Vi. anfelt illferences betyees Ronpeals ard foumfola dis‘. These large gradfents were meter operators tad not Sstards Lo rveved within @ stantardize subgaqient acrin ? MtOll waa selected foe reicere- with FOMEC are in referensa ts 2 a 8 2 Pe “ear red acetis, SEANT meas Aayt ~ at stray at ee int ge i each on mer ints begter ey The plarned method -¢ valootir. fis based sp penopte cram monitcring statiors was tracp lic 4to after TAY Ine the eyacuttion -¢ : Roncer a, the enly ereverl “fe a nay yreund statio ’ n tn ¢ v orbit, Wu. abner lew) Winds rererally fren ts wes . a soth t Lo nethw es , uest vatterr ARTE A nraved to he the restouseN:l anid ~ at ome -f 4°) cat— terns. [t was disnatchad routin ely on yoon 38 1 . efore this was dore 4 air particle tratectery forecast, S % were reviewed for the pnosai btt ity of the cloud being over the northers Varshails on 2 & 1, The fopns Caz’ s were reasonatsty relia ble fora tr b thoes ta hourse Usually, & forecasts stace d ¢ heyonn the YUperet ais by (ff # 2h hours. Sirveys on D i AY were avoided because of the v isk of contaminating survey aircr aft The very least resutt, of flyin g thra the cloud detels youle -robal ly have be en the elimi nation -F tre afreraft from furtser low inten sit: measy fements. Fallout was ,enerally not forecast to he coor rete, ia the norttern Marshall's until late on D day or early oD & le