Airborne Surveys of Terrestrial Gamma Radiation in Environmental Research

Aerial surveys of terrestrial gamma radiation have many applications. These include (1) mineral exploration, (2) nuclear facilities environmental monitoring, (3) water equivalent of snow cover determinations, and (4) soil moisture estimates. The latter two applications are not yet operational in the United States, although snow surveys have been conducted in the USSR for many years. The primary detectors for all applications is the NaI(Tl) crystal. Single and multiple arrays are flown in a variety of aircraft (including helicopters) at altitudes varying from 25 to 150 m. Accuracy of results appear adequate for most applications. Accuracies can be improved by better accounting for the background components, particularly airborne radioactivity.