The SHAllow RADar (SHARAD) Experiment, a subsurface sounding radar for MRO

SHARAD (SHAllow RADar) is a radar for the study of the Martian subsurface provided by the Italian Space Agency (ASI) as a facility instrument on board NASA’s Mars Reconnaissance Orbiter 2005 spacecraft. The scientific objective of SHARAD is the detection of water, either liquid or solid, and the profiling of subsurface ice layers in the first hundreds of meters of the Martian subsurface. Although the Martian surface is not uniformly amenable to subsurface sounding, it will be possible to find favourable conditions for the achievement of scientific objectives. SHARAD is complementary to the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) experiment on board ESA’s Mars Express spacecraft, as it is capable of a better resolution (because of the wider transmitted bandwidth) at the cost of a reduced penetration (higher operating frequency). SHARAD benefits from MARSIS experience both for the modelling of the expected surface clutter, and for the inversion of echo data. Preliminary data acquired during the instrument commissioning period around Mars have demonstrated the correct working of the instrument. Seu et al.: SHARAD, a radar sounder for MRO 27 Fig. 1. Plot of an individual processed radar echo (or “frame”) from the MARSIS experiment. The horizontal axis is the time delay of the echo in μs, while the vertical axis is the echo power in dB. The main peak in the plot is the reflection produced by the Martian surface, while smaller subsequent peaks are subsurface reflections. Distant peaks (i.e. peaks reaching the radar 15 μs or more after the surface reflection) are lateral surface echoes, the so-called “clutter”.