Sorry if this was asked before. I was unable to find such a question elsewhere in SE.
Why does space-wave communication (ie/ satellites) utilize different ground-station (GS1) broadcast and satellite (S)(re)broadcast frequencies? If "interference" is the answer, from where is it originating? Would it be GS1/receiving GS interference (sans S)? This would seem to imply that the broadcast signals are not ~straight-line. It would also seem to imply that the receiving GS would suffer the same problem from other (unmatched?) GS1s.
I was thinking that any slight ionospheric reflection (if any at these higher frequencies) of the GS1 signal received at GS, would be interfered with the S (re)broadcast.
Now, if the frequencies really must be different, then why is it usually written that f(GS1)>F(S). If rain attenuation is the answer, then how would this not affect (a) the GS1 signal, and (b) transmissions using higher frequencies (maybe none lower are available), then both GS1 and S signals will suffer.