Data Analysis of Cassini Bistatic Radar Experiments

The purpose of this work is to analyse bistatic radar data collected by the Cassini spacecraft about Titan's surface, providing profiles of dielectric constant and rms surface slope with horizontal scales of centimeters to meters. These properties are plotted against longitudes and latitudes of Titan, supported by discussions about the consistency between computed values and present knowledge of general features of Titan geomorphology. The entire work is carried out on Python, with the help of the spiceypy package from NASA NAIF, as well as other useful packages like cartopy, scipy and numpy. General algorithms for signal processing of the bistatic radar data are developed, aimed at obtaining the spectra of the echoes scattered by Titan's surface. Once the reflections' spectra are available, the rms slope and the dielectric constant can be computed. The assessment of the rms slope, proportional to the spectral broadening of the echoes, consists on fitting echoes' spectra by means of a Gaussian template, to later evaluate the full-width half-power of the fitting curve. The dielectric constant is computed from the power ratio between orthogonally polarized components of signal reflections from Titan, and from the knowledge of the incidence angle of reflection. Five flybys, of the thirteen available ones, have been chosen to carry out the following study, trying to analyse bistatic observations spanning over regions of Titan expected to be morphologically different. As a general trend, the dielectric constant estimates are consistent with the expected materials covering the surface of the planet, while the rms slope results are more valuable if read in a comparative way instead of looking at them from an absolute point of view. The main issues with data analysis of bistatic radar experiments are also mentioned, from the inapplicability of the quasi-specular model to beam-limitation of computed results, and sometimes tackled in a qualitative manner.