Simulated RADAR Soundings of Models of the Martian Subsurface
Résumé
Interpreting and understanding ground penetrating RADAR (GPR) measurements of the Martian shallow subsurface is directly linked to the capability to correctly (and efficiently) simulate the electromagnetic wave propagation, taking into account all relevant effects at multiple scales. This is especially crucial for broadband RADAR instruments like WISDOM, a payload of the ExoMars “Rosalind Franklin” rover, scheduled for 2022. We present preliminary simulation results for models of the shallow Martian subsurface using a raytracing-based simulation tool in this contribution.
The raytracing tool developed explicitly for GPR applications, can be applied to heterogeneous and inhomogeneous media and includes the antenna characteristics of the WISDOM instrument and the rover structures. It simulates the wave propagation in complex media, taking into account polarization effects. The method is a hybrid between conventional raytracing (SBR), differential raytracing, and physical optics. The simulation complexity can be controlled and weighed against approximation necessary for the specific simulation case and the expected results. This tool can simulate electrically large domains with an acceptable accuracy yielding good predictions of the propagation properties in Martial soil while being significantly less computationally expensive than conventional full-wave solvers like FEM or the Finite-Differences in Time-Domain Method.
From hypothesized structural, geophysical, and material models of Oxia Planum’s subsurface, geoelectrical simulation models are derived as input for the simulation tool. Synthetic radargrams are generated for these models, giving insight into the capabilities and expected outcome of the WISDOM instrument and the simulation tool.