Spectral Imaging of Titan's Tropospheric Methane and Lower Atmosphere Haze Profile

We report high spatial resolution images of Titan between 0.6 and 1 micron taken at Ls=240 in November 2000, acquired with the Space Telescope Imaging Spectrograph as part of program GO-8580. We utilize more than 100 wavelengths that traverse the 0.6 to 1 micron spectral region to address the methane abundance and degree of methane saturation in the troposphere, and Titan's vertical distribution of haze below 100 km. The 0.619 micron methane band is of particular interest because previous investigators have had difficulty matching Titan's modeled and observed albedo spectrum simultaneously at 0.619 and 0.888 micron. We employ a 1D radiative transfer fractal aerosol model with a Bayesian parameter estimation algorithm that computes Titan's geometric albedo per pixel by adjusting the haze vertical distribution below 100 km and the methane mixing ratio below 40 km. Results of this work will help to constrain Titan's lower atmospheric haze opacity in dynamical models, and examine the spatially varying degree of methane saturation in conjunction with areas of known cloud formation. The correlation of our results with the Huygens GCMS and DISR results will be discussed.