Jim is it possible you just gave a workable solution: Equip each site with a small radio telescope and watch pulsars.
Aren't pulsars a reliable accurate time source or do they not provide the 30nS over ten days accuracy? Regards, David Partridge -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of jimlux Sent: 10 September 2010 06:14 To: rich...@karlquist.com; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Timing Distribution in Mountainous Terrain Rick Karlquist wrote: > > I would like to point out that the environmental sensitivities of the > 5071A are unmeasureable, and the measurement threshold is far below > 5.8E-14. I would estimate that the 5071A (and ONLY the 5071A among > commercial clocks) could get the job done provided that you could > compare its frequency to GPS to the stated accuracy. This would be > using the 5071 as a secondary standard. You still need to deal with > the short term stability of the 5071A, depending on your system needs. > JPL uses H masers as flywheels. We also use the maser as a very low phase noise signal in the 10-1000 second tau range.. We multiply it up and send the (very clean) signal out to the spacecraft, it gets tracked by a loop with a few Hz BW, then sent back to earth where it's compared to the maser again to measure Doppler. Basically we measure doppler and doppler rate over a few minutes, assuming that the transmitted signal is constant during that time (which the maser is, for all practical purposes). Over a longer time span (e.g. the time between transmit and receive, which could be many hours, implying that we are transmitting from one station and receiving from another) I assume we use atomic standards and/or astronomical sources (pulsars). _______________________________________________ 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.