[time-nuts] Precise Time transfer and relative position over a short baseline

Björn bg at lysator.liu.se
Mon Apr 11 08:40:22 UTC 2016


Hi Bruce,

For such short baselines single frequency GNSS should be able to keep fixed integer solutions. Not sure how much money thas is going to save, since you might need timing specific geodetic receivers to get external 10MHz input.

Did you consider implementing time transfer using time reversal using say a sdr tranciever (usrp or other) where your clock is driving the radio. As done on HF by Yen & Sengupta at last PTTI.

https://www.ion.org/ptti/abstracts.cfm?paperID=3373

--

      Björn




<div>-------- Originalmeddelande --------</div><div>Från: Bruce Griffiths <bruce.griffiths at xtra.co.nz> </div><div>Datum:2016-04-11  12:00  (GMT+07:00) </div><div>Till: Discussion of Precise Time and Frequency Measurement <time-nuts at febo.com> </div><div>Rubrik: [time-nuts] Precise Time transfer and relative position over a
 	short baseline </div><div>
</div>There is a proposal to use multiple light bucket style optical telescopes to do Intensity stellar Interferometry over short baselines (up to perhaps 1km  or so) by using independent clocks to time tag photon  arrivals. store the time tags and process the data off line. Depending on the time tag resolution there is a need to measure the time differences between the independent clocks to an accuracy in the 1ns to 100ps range. Is there a better way of doing this other than using geodetic grade GPS receivers capable of GPS carrier phase measurements?Since the local clock flywheel oscillators will need to not deviate by more than 100ps or so over the several minutes required to perform the carrier phase averaging what sort of clock will be suitable apart from a good rubidium standard with a cleanup oscillator?
NB Running fibres or coax between the telescopes isnt an option.

The relative positions of the telescopes has to be known to within a cm or so for this to work.
Bruce

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