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J.L. Bandfield, M.D. Smith (NASA Goddard Space Flight Center)
Multiple emission angle observations allow for mathematical separation of radiative contributions from the Martian surface and atmosphere. This technique is applied to MGS TES data to retrieve surface emissivity and atmospheric opacity spectral shapes as well as refined surface temperatures. Atmospheric water vapor and minor carbon dioxide absorptions are initially removed using calculated synthetic radiances of previously determined abundances. Initial guesses for atmospheric opacity and surface emissivity and temperature are used to calculate radiance spectra using a plane parallel, non-scattering atmospheric model and the temperature profile retrieved from the 15 µm carbon dioxide fundamental absorption. The atmosphere and surface parameters are adjusted iteratively in a non-linear least squares fitting routine until the modeled radiances match measured observations. Results are typically limited to southern equatorial regions because of various natural and artificial constraints, including high surface temperatures, low dust opacity, and timing and locations of targeting. Two categories of surface spectral shapes are retrieved: high albedo surfaces and low albedo surfaces. Low albedo surfaces have significant dust contribution and may be closely modeled by a ~50-50