(FO;,) and the corresponding field radiction intensity, (Ry); (2) uetermining the fallout per unit area over water, (FQ;) and; (3) calcwlating the radiation field, (R,) which would have occurred had the water areas been land, from the assumed rel-tionship, FQ) —t = 2.1 This method of approach required the following neasurements: (a) Fallout per unit area on available islands of the test atolis (0) Gamma fields produced at sampling locations. in terms of wuantity of radioactivity. (c) Fallout per unit area in the lagoon and oer the surrounding ocean, It was also important to obtain inforwation concerning particle size and note times of crrival and cessation of the fallout as well as the variations in the radiation field with time. Zelel Predicted Camms Fields Estimates of the extent and level of gcomma fields expected from the fallout were sade for each of the originally planned shots, These predictions were based on scaled surface JANGL: data using the cube root relutionship with modifications in the crosswind and upwind ;atterns indicated by IVY data.7/ It was estimated that the fallout would curry dowmwind at the rate ot 15 miles per hour and that the durationof fallcut at any one point would be 2 hr for meguton yields, Value3 calculeted for 2 and 3 hr after detonation represent the levels the.t would exist haa the fallout deposited over extended land areas, Table 2.1 sum:arizes the predictions for three of the detonstions; the effect of decay and the delay in arrivas of fallout on the gumma fields can be noted. Giscussion of this scaling is presented in Cection 5.2.8, 2.1.2 ee oe A Sumpling Stetions On the basis of the predictions given in the prec. ding section, it appeared tht the minimum area of military interest would e>tend to a distance of 50 miles from tue chot point and vould have s maximum width of 20 miles. Since it was not possible to predict the sector in which the primary fallout would arrive cufficientiy in advance of shot time to permit proper placement and activetion of sumpling ststions, an array completely surrcunding the chet point was needed. Experience at IVY showed that, it would not be feasible to document the fallout more than 50 miles from greund zero vith available losistic support. ‘he radial array of campling staticns chown im Fig. 4,1 was evolved from these criteria, This vlan was modified within the atolls to take adventage of availceble islands and to permit the plucement of simple rectangular grid arrays in the lagoons. In addition, limited samling stations were arranged at a number of outlying; islends, Operationally, Project 2.5a was divided into two phases - one requiring the collection of data from lund and layvoon stations, and the other from sea stetions, Logistic support for the land and lagoon phase involved the use of smi]] pouts and helicopters while mounting of the 22