MARSIS Data Inversion Approach

In this paper we describe an inversion approach in order to analyze data from the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument on Mars Express. The inversion process allows the dielectric constant of the subsurface material to be estimated provided the dielectric constant of the surface is known. In addition, if impurity are present, it is possible to estimate the dielectric constant of any inclusions as well as the percentage amount of material in the inclusions relative to the host material provided knowledge of the host material up to the depth where the interface has been detected is available. The data inversion method is based on the analysis of the surface to subsurface power ratio and the relative time delay as measured by MARSIS. The data inversion has been performed at several frequencies in order to estimate the frequency dependent parameters affecting the behavior of the radar echoes. It is necessary that the surface and subsurface interfaces have the same roughness in order to estimate the Subsurface Fresnel reflectivity. As a preliminary approach, only flat surface have been selected. MOLA (Mars Orbiter Laser Altimeter) has already provided detailed data on the visible Martian surface and a simulator, with a facet model, has been utilized to use MOLA data in order to verify the correct selection of the frames that will be used for the data inversion (absence of clutter echoes).