UWB processing applied to multifrequency radar sounders. The case of MARSIS and comparison with SHARAD

We readapt ultrawideband (UWB) processing toenhance the range resolution of the Mars Advanced Radar forSubsurface and Ionosphere Sounding (MARSIS) up to a factorof 6 (25 m). The technique provides for the estimation of radarsignature over a wider spectrum via the application of wellknown super-resolution (SR) techniques to adjoining subbands.The measured spectra are first interpolated and then extrapolatedoutside the original bands. The revised algorithm includes theestimation and removal of ionospheric effects impacting thetwo signals. Because the processing requires the realignment ofthe echoes at different frequencies, we derived the maximumtolerable retracking error to obtain reliable super-resolved rangeprofiles. This condition is fulfilled by low-roughness areas compared to MARSIS wavelength, which proves to be suitable for theapplication of our processing. Examples of super-resolved experimental products over different geological scenarios show thedetection of shallow dielectric interfaces not visible from originalMARSIS products. Our results are validated by comparison withthe Shallow Radar (SHARAD) data acquired at the crossovers,demonstrating the potential of the method to provide enhancedimaging capabilities.