009516 a 1 SHIP LCCATION CHARTS_ 1.1 The forecasts of the radiation fields expected from fall-out at Cperation CASTLE and the requirement that the participating radiocontrolled vessels experience high levels of contamination were the determining factors in establishing the basic decisions governing the ship's course. It became evident that the operation area would haveto be as close to bomb zero as possible; such factors as bomb blast over- pressure and the geographical configuration of the atoll limited to some extent the number of possibilities. It was further decided to steam the vessels upwind, thus eliminating failure of the washdown system due to undesirable wind speeds and directions relative to the vessel equipped with the countermeasure system. 1,2 Having established the above basic concepts for the operation, it was necessary to make further decisions in order to arrive at the best solution to the problem. Of the added variables to consider, some were fixed at the expense of others, while some were dependent upon | the forecast of the downwind direction of the fall-out and theeffective wind apeed in this direction; these meteorological variables cannot be determined until shortly before shot time. 1.3 The final decisions used to establish the ship's course are as follows: 1. Ship's direction, The ships will follow a straight line courseupwind toward ground zero, 2. Proximity to atoll reef, The nearest approach to the reef in allcaseswill benoless than 2 miles. 3, Blast pressure on ships. At the time of the detonation, the neships will sopositioned that the maximum overpressure experienced will be no greater than 1 psi. ST, LGuUiS FRC Ships' speed, Throughout the run, the ships will steam 4. ataconstant speed of either 7 or 10 knots depending on the effective wind speed.