“…While orbital radar sounding investigations, like MARSIS, can conduct a global survey of Mars, at moderate spatial resolution, on a timescale of several years, their sensitivity is necessarily limited by their altitude, relative motion with respect to the planet's surface, and the necessity of having to sound through the Martian ionosphere. In contrast, a radar sounder, operating from a fixed lander, at the same frequency as MARSIS, can achieve a 90 dB improvement in sensitivity by its ability to perform many coherent additions of the reflected signal, which can dramatically improve signal to noise [ Ciarletti et al , 2003; LeGall et al , 2006, 2008]. The trade‐off for this improvement in sensitivity is that areal coverage provided by a sounder on a fixed lander is limited to a single point on the planet's surface (or up to several points, if the sounder is included as part of the payload of a multistation geophysical network [ Berthelier et al , 2003]).…”