Comparison of Atmospheric Transmittance Measurements in the 0.4-0.7micro-m, 1.3-5.5micro-m and 8-12micro-m Spectral Regions with MODTRAN: Considerations for Long Path Geometries Applicable for Theatre Defense

This report results from a contract tasking IARD Institute for Advanced Research and Development as follows: The contractor will investigate atmospheric transmission modelling techniques. During the research, the contractor will take observations by infrared sensors deployed during tropospheric operations to detect objects on the Earth's surface from a manned aircraft or from an unmanned airborne vehicle (UAV) using long, near-horizontal viewing geometries. The contractor will begin by repeating measurements collected during a previous EOARD contract under desert conditions with additional instruments that will enable us to test the predictions of MODTRAN code in the 0.4-0.7 micro-m (the photopic region), and in the 1.3-5.5 micro-m and 8-12 micro-m spectral regions. The measurements proposed would be performed in Israel in the winter, summer and autumn 2000 with an infrared spectroradiometer having both high signal-to-noise ratio and high spectral resolution. The wide range of absolute humidities and air temperatures will help in the validation of the MODTRAN code with special attention to the negative temperature dependence of the water continuum in the 8-12 micro-m spectral region. The spectroradiometer will be adapted to make the measurements in 1.3-3.0 micro-m spectral region without saturation of its detector. An additional spectroradiometer will measure the slant path visibility in the 0.4-0.7 micro-m photopic spectral region. The autumn measurements will be synchronized with slant path visibility measurements that will be done in the framework of MEIDEX experiment on NASA STS-107 (November 2000).