An advisory panel of the Test Organization has the responsibility of weighing carefully all factors related to the safety of the public. A series of meetings is held before the firing of each shot, with the principal function to evaluate off-site fallout. To assist in these deliberations, a complete weather unit is in operation at the Nevada Test Site, drawing upon all the data available from the U. S. Weather Bureau and the Air Weather Service, plus six additional weather stations ringing the test site. These data are evaluated for the current and predicted trends up to one hour before shot time. A shot can be cancelled at any time up to a few seconds before the scheduled detonation, Reduction of Fallout Controls and procedures for the test series were designed to assure that exposure of the public in the Test Site region for the entire series will be below the Commission's basic guide of 3.9 roentgens of whole-body exposure to gamma rays. In its day-to-day operations, the Test Organization tries to hold public exposure to fallout as near zero as possible. ing: Procedures for keeping fallout at a minimum include the follow(1) The Test Organization has established criteria defining the maximum permissible yield for devices exploded at specified altitudes. If the fireball produced by any detonation is expected to reach the surface of the Test Site, drawing up dust and debris into the atomic cloud and thereby increasing local fallout, there are severe restrictions on the weather conditions considered acceptable for the test. Such tests are conducted only when predicted weather conditions will not produce significant fallout on any inhabited locality. Improved weather forecasting techniques and highspeed electronic methods of predicting fallout paths and intensity are utilized, (2) There has been a continuing effort in the weapons laboratories to design devices of the lowest possible yield which will provide the desired scientific data. Decreasing the yield of a device has the effect of decreasing the amount of radioactive fission products which can descend as fallout. (3) Improved techniques such as balloons are being ~~, utilized to keep the fireballs of the detonations away from the surface of the testing area. Relatively little local fallout results from detonations in which the fireball does not approach close to the surface. - 47 - or