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Title: Infrared detection of heat sources obscured by tropical rain forest vegetation
Authors: United States. Advanced Research Projects Agency
University of Michigan. Institute of Science and Technology
Rinker, J. N.
Johnson, Philip L., 1931-
Vogel, Theodore C.
Morgan, J. O.
Fisher, D. S.
Parker, D. C.
Keywords: Remote sensing
Aerial reconnaissance
Military operations
Puerto Rico
Vietnam War
Publisher: Cold Regions Research and Engineering Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Research report (Cold Regions Research and Engineering Laboratory (U.S.)) ; 149.
Description: Research Report
Summary: This study was conducted in Puerto Rico during November 1962 to determine the detectability of heat sources of the type associated with guerilla activity in Vietnam. USA CRREL was assisted by the University of Michigan (under USA CRREL Contract DA 27-021-ENG-9). Previous experience indicated that while many targets such as personnel, shelters, weapons caches, vehicles, etc., would have an extremely low probability of detection in a tropical rain forest, intense heat sources such as cooking and warming fires might be more readily detected. Implementation of the heat source detection program was based as closely as possible on the description of guerilla activities and environmental factors relayed by ARPA personnel. Two infrared scanners, one airborne radiometer, and a K-17 camera were used to obtain aerial imagery. All were carried in a Navy EC-47J (R4D) aircraft operated by the Infrared Laboratory, Institute of Science and Technology, University of Michigan. The infrared scanners used were the University of Michigan M-l scanner and a modified AN/AAD- 2 scanner. The detectors used with the scanners were an indium antimonide detector, filtered and unfiltered, and a copper doped germanium detector filtered for acceptance of wavelengths between 8 and 14 μ. The spectral band choice was based on a study of blackbody radiation curves which indicated the optimum spectral region for detection to be between 4.5 and 5.5 μ. The targets were charcoal fires in galvanized pails (14-in. diam. and 8.5-in. high); the pails were placed on the ground at selected sites under a variety of canopy cover. The targets in flight line 1 were located under a high, dense canopy, and the targets on flight line 2 were under a low-lying, dense canopy. A variety of methods were used in an effort to conceal some of the fires. These were not all successful. In order for the charcoal fires to be detected with the system used, an unobstructed line of sight must exist between the fire and the detecting cell. If holes in the canopy are not available, the fires will not be detected. The problem of detection is not concerned as much with the total amount of openness in the canopy as it is with the distribution of this openness over the fire. For equal densities of cover, a high canopy will decrease the chances of detection compared to a low-lying cover. The use of an infrared thermal scanner to detect small ground fires obscured by a vegetative canopy has been demonstrated to be feasible. The filtered indium antimonide cell (4.5 to 5.5 μ band pass) proved to be the best choice in flying over dense canopy as this cell detected 41.5% of all fires and 30.6% of the obscured fires. The signal intensity from many of the fires was so great that detection could be successful at much higher altitudes than the 1000 to 2500 ft used during this study. It is recognized that one of the problems to be encountered in field operations is the exact location of a detected signal and the speed with which it can be relocated.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Research Report

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