large enough to alter the free-field measurements significantly. Such heavy deposition contrib- uting up to 50 percent of the recorded dose rate had, for instance, been experienced on Operations Castle and Redwing (References 32 and 33). During Operation Hardtack, the proximity of some proposed stations to surface zero placed the gamma-intensity-time recorders (GITR)— developed by the Naval Radiological Defense Laboratory (NRDL)—in areas where large amounts of erupted water with presumably high scavenging efficiency could be expected. The radioactive material remaining on coracle and detector surfaces might therefore be sufficient to represent a significant contribution to the gross gamma record; thus, some approximate meansof correcting for such deposition appeared necessary. Consequently, the GITR’s were used in conjunction with an incremental collector (IC) capable of collecting radioactive material deposited at the detector for short increments of time during transit of the radiating cloud. These collections were to be counted after coracle recovery, corrected for decay, and applied to the gross gamma record, using conversion factors for detector response to known concentrations of deposited activity (Section C.5). Other possible sources of radiation such as deposited radioactive material suspended in the water surrounding the coracle or the upwelling of water directly contaminated by the detonation were also examined and considered to be of secondary importance in comparison to deposits on coracle surfaces (Section 1.3.1). Although later experience in the field demonstrated that such corrections were unnecessary, the relative insignificance of deposited activity is in itself of particular importance. An alternative method of deducing the free-field gamma intensity I, was also available. This method was first employed on Operation Redwing data (Reference 34) and is based on the assumption that the rate of deposition is a function of the concentration of fallout in the air immediately over the point of deposition. Thus, In = K, S(t) t7'? . where S(t) is the concentration of fallout per unit volume of air, K, is a constant of proportionality for instrument response to a radiating cloud, and t represents time. The rate of deposition dD/dt is therefore defined by d = ksi & where K, is a constant of proportionality describing deposition from the cloud. The response Ip due to the deposited material is necessarily some function of the amount of deposited material D(t). Thus, Ip = Ks Dit) t7'? where K; is a constant of proportionality for instrument response to a deposited field. gross radiation intensity Ig is therefore The Ig = Ky, Xt) tT? + Ky Dit) t7 1? This equation is solved for S(t) in terms of I,, yielding the expression t S(t) = Kt f F(t) eX at ty where K K; K, = K, and Ga 30