I have not followed this closely. Why not use the data itself? The
theoretical pattern for the telescope pair can be calculated. Even
though the signals are not i.i.d, from phototubes, the data can be slid
along and the delay pattern established and compared to the theoretical
pattern? Timing is then important for "pointing". Certainly the
compared signals can be used in any case to correct timestamps.
Sorry if this has been mentioned before, in that case, great minds run
in the same track :-) :-)
Don
On 2016-04-11 00:58, Ilia Platone wrote:
As alternative to independent clocks and single photon tagging, we
considered to use TDCs: a possible solution would be radio cross links
between the telescopes that drive the start/stop signals of the TDCs,
then we'd tag only the lapses between photon detection from each
telescope. In this way a single clock would be used on a receiving and
recording station.
Is this a good solution?
Regards,
Ilia.
Il 11/04/2016 07:00, Bruce Griffiths ha scritto:
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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