Radar Sounder Observation of Phobos

Since 2004, Mars Express has been orbiting around Mars. Due to its elliptical orbit, the Mars Express spacecraft provides MARSIS a unique opportunity to observe Phobos from a relatively close distance of a few hundred kilometres. The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) is a 1.3-5.5 MHz subsurface sounder that has been probing Mars to a depth 3.7 km from orbit. Although originally MARSIS was not designed to probe Phobos, we have been able to use this radar sounder to investigate it at decametre wavelengths for the first time.