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5 September 2003 Factors affecting signature propagation through intense forward-scattering atmospheres
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Methods are examined for modeling signature propagation through optically dense atmospheres accounting for both direct signal attenuation, isotropic scattering, and strong forward (multiple) scattering considering both existing analytical approaches and numerical Monte Carlo photon transport simulations. Examples are given for the case of upward propagation through plane layers in the form of angular distribution functions, based on a point source of light, from which one can determine an atmospheric modulation transfer function (MTF) widely used in simulating the effects of obscurants in imaging systems performance models. Methods can also be used to estimate correction factors for compensating errors in transmission measurements due to multiple forward scattering into the sensor field of view. Results suggest that even at large optical thicknesses where the directly transmitted signal is minimal, there is enough spatial contrast in the diffuse signal to make point sources detectable. However the major effect is on the broadening of the received signal which for the case of isotropic scattering yielded values on the order of 5-10 m for the width of the point spread function (PSF) for a sensor field of view of 100 milliradians. For more intense forward scattering the relative signal strength is increased and the PSF widths are decreased.
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Robert A. Sutherland, Joseph R. Montoya, and Bryan R. Usevitch "Factors affecting signature propagation through intense forward-scattering atmospheres", Proc. SPIE 5075, Targets and Backgrounds IX: Characterization and Representation, (5 September 2003);

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