AIRBORNE INFRARED THERMAL DETECTION OF CAVES AND CREVASSES

Airborne infrared thermal scanners can be used to detect crevasses and cave openings, but only under certain conditions. First, the temperature inside the void must be significantly different from external conditions; and second, some mechanism must exist to bring this thermal difference to the surface where it can be detected by a scanner. Furthermore, it must be determined if other events influence this mechanism. In the case of crevasses, conduction and convection both play a role in altering the surface temperature of the snow bridge over a crevasse. For caves, convection is the mechanism that brings about the temperature alteration. Convection is linked to the breathing cycle which, in turn, is caused by changes in atmospheric pressure. From ground measurements of internal temperature, extgeranl temperature, and atmospheric pressure a flight time can be picked that will provide the most favorable circumstances. The cave signal is more of a problem because it is frequently surrounded by similar looking signals caused by other events. Results are given for a crevasse field in Greenland and for a cave system in Puerto Rico. /AUTHOR/