Chopter | INTRODUCTION 1.1 ; OBJECTIVES The general objective was to collect and correlate the data needed to characterize the fallout, interpret the observed surface-radiation contours, and check the models used to make predic-~ tions, for Shots Cherokee, Zuni, Flathead, Navajo, and Tewa during Operation Redwing. The specific objectives of the project were: (1) to determine the time of arrival, rate of arrival, and cessation of fallout, as well as the variation in particle-size distribution and gammaradiation field intensity with time, at several points close to and distant from ground zero; (2) . to collect undisturbed samples of fallout from appropriate land- and water-surface detonations for the purpose of describing certain physical properties of the particles and droplets, including their shape, size, density and associated radioactivity; measuring the activity and mass deposited per unit area; establishing the chemical and radiochemical composition of the fallout material; and determining the sizes of particles and droplets arriving at given times at several important points in the fallout area; (3) to make early-time studies of selected particles and samples in order to establish their radioactive-decay rates and gamma-~energy spectra; (4) to measure the rate of penetration of activity in the ocean during fallout, the variation of activity with depth during and after fallout, and the variation of the gamma-radiation field with time a short distance above the water surface; and (5) to obtain supplementary radiation-contour data at short and intermediate distances from ground zero by total-fallout collections and time-ofarrival measurements. It was not an objective of the project to obtain data sufficient for the determination of complete fallout contours. Instead, emphasis was placed on: (1) complete and controlled documentation of the fallout event at certain key points throughout the pattern, also intended to serve as Correlation points with the surveys of other projects; (2) precise measurements of timedependent phenomena, which could be utilized to establish which of the conflicting assumptions of various fallout prediction theories were correct; (3) analysis of the fallout material for the Primary purpose of obtaining a better understanding of the contaminant produced by water-surface operations; and (4) gross documentation of the fallout at a large number of points in and near the on. 1.2) BACKGROUND A few collections of fallout from tower shots were made in open pans during Operation Green- house (Reference 1). More extensive measurements were made for the surface and underground Shots of Operation Jangle (Reference 2). Specialized collectors were designed to sample increMentally with time and to exclude extraneous material by sampling only during the fallout period. The studies during Operation Jangle indicated that fallout could be of military importance in a- reas beyond the zones of severe blast and thermal damage (Reference 3). During Operation Ivy, a limited effort was made to determine the important fallout areas for a device of megaton yield (Reference 4). Because of operational difficulties, no information on