from any particular detonation, taking into account weather conditions (particularly wind speeds and directions at all altitudes) forecast for shot time, In past test operations the Test Manager's decision to shoot or postpone a test has been based on similar computations worked out by the Nevada Test Organization's Fallout Prediction Unit. But since human computation is necessarily somewhat slower than that performed by the electronic devices, the time lag has required utilization of weather forecasts made earlier before scheduled shot time, This sometimes resulted in missed opportunities to fire a test when last-minute improvements in the weather outlook did not permit fallout computa- tion in time to confirm public safety before shot time. One of the computers produces almost instantaneous solutions, giving the Test Manager and his Advisory Panel the benefit of revised fallout predictions right up to shot time. This makes it possible to take advantage of improving weather, and would also help assure cancellation of a shot if a weather change for the worse was indicated in the immediate pre-shot weather forecast. Both computers are used in addition to continuing human computation by personnel of the Fallout Prediction Unit. The human computation, although slower, serves to check the accuracy of the electronic computations. Each of the computers is about the size of a large console-type home television set, and readily portable. One unit, developed by the National Bureau of Standards, actually contains a display device closely resembling a TV screen. This picture screen, which is lined similar to graph paper, provides a visual, quickly-interpreted pattern of fallout areas and their intensity. A map transparency of the Test Site area can be superimposed on the screen in order to pin-point the precise location of predicted fallout. The other computer, developed by AEC Sandia Laboratory, differs from the NBS model largely in the fact that it provides results in the form of a graph or chart. The Sandia-developed computer can be operated by technicians with little knowledge of higher mathematics. The NBS machine requires no mathematical experience at all. Data fed into the computers includes speed and direction of winds at various heights, size and shape of the atomic cloud, and chaf&cteristics of the various radioactive elements in the atomic cloud, 12, MILITARY PARTICIPATION Personnel and equipment of the Army, Navy, Air Force and Marine Corps are participating extensively in Operation Plumbbob. t Of primary importance to the Department of Defense and the Armed - 60 -