HASL AERIAL SURVEY SYSTEM by M.-E..Cassidy, R. T. Graveson, H. D. LeVine ABSTRACT Radioactive debris from nuclear detonations may fall out over an extensive area, A rapid evaluation of the distribution of such surface contamination can be obtained by an aircraft mounted detec= tor. The gamma field measured in the aircraft can be related to the intensity on the ground. The HASL "Top Hat" system measures the radiation intensity, in an aircraft, at any altitude up to 1500 feet. The data is contin- uously compensated to the reading that would be obtained if the measurements were taken at three feet from the ground surface. It will record the ground radiation field intensities from 0,01 mr/hr to 1000 r/hr. The Telepulse Coding Unit converts this information to a signal suitable for transmission to a plotting center via a standard voice radio transmitter. The transmitted signal is decoded by a Telepulse Receiving Unit and is automatically recorded on a strip chart. The radiation data must be correlated with the air- craft position to determine the location and intensity distribution of the contaminated area. iii