re: Need a radio relay satellite
But simply to relay the signal and possibly boost it a bit certainly wouldn't require the size dishes they have on Earth I would think. Of course my thoughts are based only on a hunch and not on any studies of radio signal technology.
I have the feeling that as more and more missions go out to the outer planets and beyond that NASA is going to have to think in terms of signal relay devices. Unless we find other communications media beyond radio signals we're going to be pushing the envelope of the technology.