Hi
> On Nov 18, 2017, at 5:38 AM, Magnus Danielson <mag...@rubidium.dyndns.org> > wrote: > > Hi, > > On 11/18/2017 02:16 AM, Hal Murray wrote: >> kb...@n1k.org said: >>> Ok, 1 Hz at 437.5 MHZ is roughly 2 ppb. That is pretty much “slam dunkâ€� >>> accuracy with a GPSDO. Much easier to obtain and set up in a school >>> environment. The key will be orbit estimation for the +/- doppler part of >>> it. Orbit estimation is not quite a slam dunk sort of thing. The GPSDO >>> would also give accurate location. Even with good orbit data, the solution >>> still requires a good location estimate. >> What is the orbital period? It would be fun to plot the Doppler over time >> and see if you can get something that looks like a big chunk of an orbit. >> Ugh. What is the Doppler due to the Earth's rotation? > > You need to compensate for your position, because it would lower due to > longitude naturally. > > Yeah, and then the moon isn't in perfect circular orbit either. Effectively you have multiple things spinning around in various ways. The “orbit” isn’t a single thing in this case. Earth gravity “lumps and bumps” impact GPS orbits. There are a lot of things to have lumps and bumps in this caae. Depending on the orbit relative to this and that, you may have a fairly limited observation time on each pass. This and that accumulate on the “dark” part of the orbit, but you can’t observe it as it happens. You simply see a jump (versus prediction) at the start of the next pass. Bob > > The sat is also in a not so perfect orbit, so it would also needed to be > measured and characterized. > > Fun problem. > > I realized that my on the fly least square algorithms would be nice to adapt > to this problem. > > Cheers, > Magnus > _______________________________________________ > 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. _______________________________________________ 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.