Deciphering the (Near-)Surface of Planets with Nadir-pointing Radar Statistics

The production of knowledge on how planetary worlds work is still mainly driven by remote observations that offer fragmented insights at the surface processes at meters scales and a hollowed vision on the near-surface structure down to few decameters deep. The latter statement also holds for remote polar environments on Earth where in-situ investigations do not necessarily sample exhaustively the vast extents of the cryosphere.

Yet, those superficial portions of planetary bodies hold signatures of outstanding processes related to the regional depositional and erosional history. They also host structures relevant to future in-situ exploration such as surface roughness and porosity for landing site reconnaissance, snow deposits, buried ice lenses and putative accessible aquifers.

Because of its meter-scale wavelengths, the surface echo strength recorded by air- and space-born radar sounders convolves many information on the (near-)surface structure and composition. The Radar Statistical Reconnaissance (RSR) is a technique developed over the last decade to disentangle those signatures, essentially extending the capability of a nadir radar sounder to be used as both a surface reflectometer and scatterometer. We review some recent application strategies of the RSR in the Terrestrial cryosphere and in the solar system. Future advancements and targets will also be presented to highlight the interplanetary development and challenges of this technique.