A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Peter Monta
Date: 2016 Jan 30, 22:25 -0800
EPIRBs and COSPAS/SARSAT use this in reverse for the sat to find the EPERB.
I know this is not exactly celestial navigation but I was wondering how accuratly you could get a fix by observing the Doppler shift as a satellite goes by. Certainly with the amateur communication satellites one can observe a significant shif in the UHF or VHF frequency, and it should be easy to automate measuring this with a cheap software defined radio dongle (like a TV dongle). I wonder how accurate the frequency is on the oscillators and how accurately we know teh emphemeris data? My guess is provided the orbit is fairly well known it should be as accurate as an EPIRB (a couple of nautical miles).
A network of inexpensive receivers camped out on various ad-hoc satellite signals, and using GPS as a reference, would be just the thing, if orbits are not otherwise available. Do the commercial LEO constellations (Iridium, Globalstar, Orbcomm, etc.) publish meter-quality orbits as a public service? Surely they all have GPS on board. Anyway, once good orbits are available, what you propose is then similar to TRANSIT, as you mentioned (or perhaps "assisted TRANSIT", with ephemeris information from this external source).