  Saturn was observed on 6-11 February 2002 using an Acousto-optic Imaging
Spectrometer (AImS) to study Saturn's vertical cloud structure. The 3.67-m
Advanced Electro-Optical System telescope at the Maui Space Surveillance
Complex was used. The high spectral resolution and wide spectral coverage of
AImS (500 - 1000 nm) enabled us to sample the Saturnian atmosphere with high
vertical resolution and to derive the wavelength dependence of aerosol
properties. The model center-limb profiles were fit to the observed profiles in
the equatorial region. Adopting four different cloud models with three aerosol
phase functions, we varied up to nine free parameters to seek the best
solution. The results of the simultaneous fits to nine different profiles
around the 890-nm and 727-nm methane bands suggest that : 1) a cloud model
having higher aerosol density in the lower troposphere (0.15 - 1.5 bar) is
favorable, 2) the tropospheric cloud extends into the stratosphere, 3) the
wavelength dependence of the upper cloud optical thickness indicates that the
average aerosol size is larger than 0.7 - 0.8 micron, 4) the average aerosol
size of the upper tropospheric cloud increases with depth from about 0.15
micron to between 0.7--0.8 and 1.5 micron, 5) the aerosol properties in
February 2002 are similar to those observed during the 1990 equatorial
disturbance.
