This work was undertaken because of a mutual interest of the Department of Defense, Advanced Research Projects Agency (ARPA), and the USDA Forest Service in the problems of detecting hot targets against natural terrain backgrounds using airborne infrared (IR) line scanning instrumentation. The study objectives were broadly defined in ARPA Order No. 544, which contains three specific task assignments that were modified from time to time during the course of the study. The basic problem was to examine the target obscuring effects of timber foliage or canopies on small charcoal fires in the forest cover types of North America. A concurrent objective was to develop an optimum system for airborne forest fire detection including the development of the operational patrol procedures.