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T. Temma, N. Chanover (New Mexico State University), A. Simon-Miller, D. A. Glenar (NASA/Goddard Space Flight Center), J. Hillman (University of Maryland), D. Kuehn (Pittsburg State University)
A series of narrow-band images of Saturn was taken with the Acousto-optic Imaging Spectrometer (AImS) over a large number of wavelengths between 500 and 950 nm to perform a detailed study of Saturn's vertical cloud structure. The Air Force Research Laboratory's 3.67-meter Advanced Electro-Optical System telescope at the Maui Space Surveillance Complex was used for our observations on 6-11 February 2002. We photometrically calibrated the images with standard star data to obtain two sets of image cubes of Saturn. The high wavelength resolution and wide spectral coverage of AImS enabled us to sample different altitudes of the Saturnian equatorial region with higher vertical resolution than conventional narrow-band filter observations and to derive the wavelength dependence of aerosol optical properties. The center-limb profiles in the Saturnian equatorial region (-10\circ latitude) were fit with theoretical profiles generated from radiative transfer computations. We simultaneously fit 5 different profiles around the 890 nm methane band and 4 profiles around the 727 nm methane band to determine the vertical cloud structure and the aerosol property variation as a function of wavelength. Adopting 4 different cloud structure models with three different aerosol scattering phase functions, we varied at most nine free parameters and tried a total of 5800 initial conditions for optimization to seek the best solution in the vast multi-dimensional parameter space. In the Saturnian equatorial region, we draw the following main conclusions: 1) the tropospheric cloud extends up to the stratosphere (above 100 mb), 2) the wavelength dependence of the aerosol opacity suggests a lower limit of the average aerosol size of roughly 0.7-0.8 \mum for the upper tropospheric cloud. The US Air Force provided the telescope time, on-site support and 80% of research funds for this AFOSR and NSF jointly sponsored research under grant number NSF AST-0123443.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.