Monostatic and bistatic radar techniques for planetary surface exploration across the solar system

This doctoral thesis investigates the potential of centimeter-wavelength bistatic radar and meter-scale monostatic radar sounding techniques for planetary exploration, leveraging data from two sophisticated missions: the Cassini mission to Saturn and the Mars Reconnaissance Orbiter. The first part of this thesis examines radio science bistatic radar experiments conducted by the Cassini orbiter on Titan, Saturn’s largest moon, known to host stable liquid hydrocarbon seas and lakes at its poles. Reflections from solid terrain were generally weaker and intermittent, while strong, narrow reflections from Titan’s liquid bodies under oblique observation configurations enabled accurate retrieval of surface dielectric constants (connected to liquid composition) and surface roughness. Statistical differences in dielectric constants across the seas were found, though even the highest measured relative permittivity values indicate that ethane is a minor constituent of surface liquids on Titan. Lakes in the Northern Lake District appear uniform in both roughness and composition. The second part of this work focuses on SHARAD observations of Mars’ water ice-rich South Polar cap, where radargrams reveal a pervasive elevated radar background, commonly termed “fog”, that either underlies or obscures radar-bright parallel reflectors. These reflectors have been correlated with dust-rich layers formed by Mars’ orbital variations, but the fog lacks attribution and is generally associated with surface roughness and/or volume scattering. However, our quantitative analysis shows that this background pattern could also stem from densely packed, thin, fragmented, or low-dust-content layers generating specular reflections. This finding suggests that two contrasting radar patterns—bright continuous reflectors and dimmer pervasive backgrounds—might arise from similar dustrich geological structures. These insights may facilitate the interpretation of radargrams of icy moons, where complex subsurface features such as fractures, volume scattering, and slushy or impurity-rich layers are anticipated, especially for Europa.