Any landed mission could benefit from having an orbiting radio relay satellite to help enhance its data rate to Earth. For polar landers on for example the Moon or Mercury it would be a necessity. For a lander on a distant object such as Europa, Uranus or a comet it would be especially helpful, easing the mass, electric power consumption and complexity of the lander somewhat.
What is required to complement such a radio relay orbiter so that it can second also as a powerful radar to study the object it is orbiting? Would the communication frequency be useful also as a science radar, for surface reflection or ground penetration? What are the synergies and problems with combining high data rate interplanetary radio communication with a capable multi frequency science radar? Could every orbiter with a radio dish be used as a science radar instrument too?
EDIT: Oops, I happened to log myself in with an old little used user name. I'm actually LocalFluff.