[time-nuts] Using GPS for space-based instrument

[Strauss, Karl F]

I've been tasked (or was it I was volunteered?) to do some basic design & definition work on an ultra-stable master frequency system for a proposed instrument that is currently planned to be in an Earth-trailing orbit.   Given the first order accuracy requirement of 1 part in 1E-10, my first thought was to grab the GPS timing signal.

Sorry for the newbie questions here:    a) Do all satellites in the constellation broadcast a signal into space  (as opposed to, say,  bouncing off some ionospheric boundary layer); and b) is there some website/technical paper describing expected signal strength for these space-radiated signals?

Again, apologies to all for the Newbie Q's.  Hopefully this will be a fun topic of discussion

Thanks

Karl