[time-nuts] Optical transfer of time and frequency

[Bruce Griffiths]

Not so, the common time base doesnt ,in this case , have to have hydrogen maser or better stability as long as the realisations of this timebase at each telescope track sufficiently closely within 100 ps or so is adequate for a 1ns arrival time stamp quantisation. 

Just as one can measure the PN contribution of an RF amplifier that is 30dB or so below the PN of the test source, one can achieve a relative ADEV between the telescope timebase realisation and the master timebase that is better than the absolute ADEV of either.
Bruce
  

    On Saturday, 30 April 2016 12:01 AM, Azelio Boriani <azelio.boriani at gmail.com> wrote:
 

 Yes, but I see that the allan deviation figures they cite aren't
achievable with common time-nuts gear now. Considering a VLBI project:
first premium stability then superb time transfer.

On Fri, Apr 29, 2016 at 5:18 AM, Bruce Griffiths
<bruce.griffiths at xtra.co.nz> wrote:
> Quoting Michael Wouters: "According to this,
>
> http://www.nist.gov/manuscript-publication-search.cfm?pub_id=912449
>
> there are many practical challenges  with a one way free-space optical link."
> That paper indicates that  one way transfer with noise of a few picosec should be feasible using an IR laser. Especially if only required at night for synchronisation of the timebases of the various telescope/detectors in a stellar intensity interferometer.
> Atmospheric scintillation should be lower as well as background noise from the sky, sun etc. The other factors like rain, hail, snow, fog etc aren't an issue  as these preclude observation of the stars of interest.
> Bruce
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