GPR field-tests on Svalbard – WISDOM on ExoMars
Résumé
The WISDOM ground-penetrating (GPR) radar aboard the 2022 ESA-Roscosmos Rosalind-Franklin ExoMars Rover will probe the shallow subsurface of Oxia Planum using electromagnetic waves in a frequency range of 500MHz to 3GHz. A broadband antenna assembly transmits the dual polarized WISDOM signal into the Martian subsurface and receives the fully polarimetric echoes from the subsurface stratigraphy.
For the verification of the radar performance under permafrost conditions, the GPR has been tested on Svalbard on different sites e.g. on polygonal terrains, on alluvial fans, on pingos and on glaciers. A flight equivalent WISDOM unit was mounted on a remote controlled, simplified rover mockup to perform the field tests under most realistic conditions in terms of electromagnetic coupling and field of view with respect to the antenna to ground distance.
The interpretation of the measurement results has been compared with the well-known subsurface structures. Therefore, the performance has been estimated in terms of penetration depth and resolution for different types of soil. The radargrams show the composition of the shallow subsurface in different levels of resolution, depending on the relative permittivity of the ground and the applied post-processing. This provides a useful indication of the results that can be achieved on Mars.