Optical EngineeringContrast transmission predictions versus far-infrared imager measurements for low-altitude horizontal paths
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The Mobile Imaging Spectroscopy Laboratory of the U.S. Army Research Laboratory was used to measure horizontal-path contrast transmission with 8- to 12-μm imagers in 1988. The values obtained were only about one-half of what was predicted by LOWTRAN7. In 1990 a large-area target board, 1.8 x 1.8 m, was used and resulted in resolvable temperatures that could be consistently measured over a 1.6-km path, even during times of strong optical turbulence, and were compared to 0.1-km reference temperatures to obtain values of contrast transmission. These new measurements compare very well with LOWTRAN7 calculations except for cases when aerosol attenuations from patches of ground fog and vehicular dust were present but not included in the calculations.