Abstract: Both active and passive atmospheric modulation transfer function (MTF) measurements carried out simultaneously in both thermal imaging atmospheric windows are presented. Results indicate rather significant angular spatial frequency dependence of the MTF, in contradiction to the conventional approach which assumes contrast transfer is atmospheric transmission only. A theoretical explanation is discussed based upon aerosol forward scattering and absorption effects which are shown to be angular spatial frequency dependent and yield MTF results similar to those measured. This means that small targets are blurred much more than large targets by the atmosphere, thus also affecting target acquisition probabilities. !10
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