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D. R. Klassen (Rowan University), J. F. Bell, III (Cornell University)
Over the past several oppositions we have been collecting near-infrared spectral image sets of Mars in the wavelength ranges 1.5--2.5\micron and 2.9--4.1\micron. Several of these image sets have been radiometrically calibrated to radiance factor (rF) and/or intensity (I). This calibration allows us to model the atmosphere of Mars through radiative transfer methods, based upon the DISORT subroutine, in order to calculate the optical depth of water ice clouds which we have previously reported seeing though the techniques of band-depth mapping and principle componets analysis[2, 3].
We present here a comparison study of the growth of ice cloud optical depth within the aphelion cloud belt. Our images span several points in the late northern spring through mid northern summer seasons (LS\approx45\degr--130\degr). The results will be compared with the thermal infrared optical depths results from the Mars Global Surveyor Thermal Emission Spectrometer. Preliminary results show ice cloud optical depths on the order of 0.23 at 3.33\micron\ over the bright region Moab at LS=129\degr compared to the MGS-TES zonally averaged value of \approx0.12 at 12\micron\ at the same season.
This work was supported by grants from the NASA Planetary Astronomy Program (NAG5-6776), the NASA Mars Global Surveyor Data Analysis Program (NAG5-11076) and the NASA-ASEE Summer Faculty Fellowship program at NASA Goddard Space Flight Center.
References  Stamnes et al. 1988, Appl. Opt. 27, 2502.  Klassen et al. 1999, Icarus 138, 36.  Klassen & Bell 2001, B.A.A.S 33, 1910.  Pearl et al. 2001, JGR 106, 12325.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.