Simulation-based Assessment of Polarimetric L -band Synthetic Aperture Radar for Shallow Ice Detection on Mars

Polarimetric L -band synthetic aperture radar (SAR) has been proposed as a tool to detect and map shallow (<10 m) subsurface water-ice in the midlatitudes of Mars, a major science target and critical resource for future human exploration. In this study, we implement a radar backscatter forward model to assess the geophysical conditions under which such a system can identify and characterize shallow ice. The model combines shooting-and-bouncing ray physics, electric-field Monte Carlo integration, and the coherent backscatter opposition effect via time-reversed ray pairs to simulate backscattering from complex, diffusive, multilayer substrates. We produce polarimetric responses in both sounder and side-looking orientations, from which the Stokes parameters ( S 1–4 ) are used to derive the circular polarization ratio (CPR) and degree of polarization ( m ), forming a consistent set of observables. Results show ice-rich media exhibit high volumetric scattering, an enhancement of CPR, and a slow decay in radar echo power with round-trip delay, defining an “ice-like signature” that is useful for detecting shallow ice. We present a catalogue of 15 scenarios, with a variety of regolith and ice layer thicknesses, and two different scatterer inclusion fractions. We further explore two additional radar frequencies (very high frequency and the P band) in sounder mode and discuss what combination of sensors can offer the most comprehensive characterization of the subsurface. The chosen scenarios act as a reference for understanding scattering physics within a varied, ice-bearing subsurface. This work demonstrates the capability of identifying and differentiating subsurface ice with an L -band compact polarimetric SAR payload.