  In its decade of operation the Cassini mission has allowed us to look deep
into Saturn's atmosphere and investigate the processes occurring below its
enshrouding haze. We use Visual and Infrared Mapping Spectrometer (VIMS)
4.6-5.2 micron data from early in the mission to investigate the location and
properties of Saturn's cloud structure between 0.6 and 5 bars. We average
nightside spectra from 2006 over latitude circles and model the spectral limb
darkening using the NEMESIS radiative transfer and retrieval tool. We present
our best-fit deep cloud model for latitudes between -40 and 50 degrees, along
with retrieved abundances for NH3, PH3 and AsH3. We find an increase in NH3
abundance at the equator, a cloud base at ~2.3 bar and no evidence for cloud
particles with strong absorption features in the 4.6-5.2 micron wavelength
range, all of which are consistent with previous work. Non-scattering cloud
models assuming a composition of either NH3 or NH4SH, with a scattering haze
overlying, fit limb darkening curves and spectra at all latitudes well; the
retrieved optical depth for the tropospheric haze is decreased in the northern
(winter) hemisphere, implying that the haze has a photochemical origin. Our
ability to test this hypothesis by examining spectra at different seasons is
restricted by the varying geometry of VIMS observations over the life of the
mission, and the appearance of the Saturn storm towards the end of 2010.
