If you are thinking of a telecommunications satellite and think that it is some sort of non active radio mirror then you would be incorrect. A telecommunications satellite is a repeater that receives may even process and re-broadcasts the signal through a parabolic dish antenna.
If you did want to build some sort of "radio mirror" I don't think you would need any exotic material. All you would need are two high gain antennas on the right frequency which could be made out of anything conductive. The problem with this approach is that the signals would be extremely weak, and you would be missing the opportunity to amplify them.
Telecommunications Mirror for Outer Space
Re: Outer space mirror
