On Wed, Jul 10, 2013 at 02:42:19PM -0700, J. Forster wrote: > David, > > While I can easily see how you can do closed loop correctioin for Dopplar > from the transmission point for a 'bent pipe' repeater, at any other > location that correction would not be valid, because the paths are not > parallel.
Sorry for my poor choice of words. That is precisely what I meant by "for an observer on the ground it is necessary to correct for the satellite orbit induced doppler". This is true for ANY observer, since it would seem certain that the closed loop correction actually is structured and calculated to cause the satellite to radiate a carrier (and timing modulation on it) equivalent to what an accurate local GPS satellite reference clock would generate if one was aboard the hosted payload rather than on the ground. Anything else would make no sense as it is not incumbent on users to try to figure out ground relative timing for some unknown uplink antenna somewhere. And offsetting radiated uplink time and frequency on the ground to make it right on the satellite at the output of the bent pipe repeater is very feasible and more or less a no brainer. But if the satellite radiates what a local GPS package would and transmits ephmerides defining its position and motion it could be included in a GPS solution and could be used for timing and frequency purposes the same as any other GPS satellite subject to whatever degree of relative accuracy the bent pipe clock obtains and the degree to which the ephemerides in the format transmitted allow an accurate position to be determined. And from what I have read it seems very likely the WAAS birds meet these criteria.. -- Dave Emery N1PRE/AE, d...@dieconsulting.com DIE Consulting, Weston, Mass 02493 "An empty zombie mind with a forlorn barely readable weatherbeaten 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in celebration of what could have been, but wasn't and is not to be now either." _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.