closed to the public. Aerial and surface surveys are made to insure that no persons or animals wander into the area. Each nuclear detonation is publicly announced ahead of time. 4 As a part of the Test Organization there is an advisory panel of experts in the fields of biology and medicine, blast, fallout pre- diction and meteorology. A series of meetings is held before the fir- ing of each shot to weigh carefully all factors related to the safety of the public. A complete weather unit is in operation at the Nevada Test Site, drawing upon all of the extensive 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 cur— rent 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. In the past, more than 80 postponements have been made due to unfavorable weather conditions. Several measures have been used to reduce the radioactive fallout off the test site. vices are tested at Nevada. First, of course, only small nuciear de~ Since the greater the height of the fire- ball above the surface the less is the fallout in nearby areas, the test towers have been extended to 500 feet, and during Operation Plumbbob (Spring 1957) there will be at least one 700-foot tower. a new technique of using captive balloons is being developed. Also, Exten- sive tests are being conducted to determine the feasibility of detonating nuclear devices so far undergound that all of the radioactive material —— - 27 - - | i