Surface Clutter and Echo Location Analysis for the Interpretation of SHARAD Data from Mars

This letter presents a suite of analysis techniques designed to support the interpretation of data from the Shallow Radar on Mars Reconnaissance Orbiter. Cross-track surface echoes ('clutter') with a time delay similar to potential subsurface echoes are known to present a major challenge to orbital radar sounding; furthermore, we demonstrate that the broad beam pattern of orbital sounders combined with cross-track long-wavelength surface slopes can result in first-received echoes arising from locations significantly distant from the nadir point, further hindering interpretation. Combining known surface topography (of lower resolution than the radar wavelength) with an appropriate radar model and orbital parameters, we can simultaneously address both of these challenges. Our technique has been applied to a variety of scientific targets on Mars with success and is recommended as a standard practice.