RF transmission characteristics in space (zero gravity)

[Nepaliman]

-What are the characteristics (RF propagation) of RF transmission in space? Like- Free space path loss, absorption, reflecftion...
-Can RF transmission in space be farther than Earth?
-Which frequency is useful for space to space or space to earth communication?

 

[WTP Pepper]

Anything around 2.45GHz on earth will be less than in space due to water absortion. I believe there is another issue with water at around 60GHz.
The classic equations of 32+20log D +20log F do not take into account absortion factors nor ground clutter caused by buildings or local reflections

 

[JMW]

Oxygen atoms also cause some problems. The main difference is velocity. Air at sea level "slows" light by approx 5%. Therefore in space the wavelength will be shorter than on earth.

 

[Sceadwian]

It's important to note we're not talking about true velocity here, light NEVER slows down, it just takes circuitous routes through some media. What JMW is talking about is phase velocity and has nothing whatsoever to do with the true velocity of the RF energy which is always the speed of light. I'm not sure where the 5% number comes from though as it's different depending on frequency.