[LEAPSECS] UT1 via NTP

[Rob Seaman]

Heading to the telescope to work on timekeeping for a new instrument, so
don't have time to write emails talking about timekeeping for the old
ones :-)

NTP, of course, can be used with local reference clocks. It would be
great if the NIST UT1 implementation were available for local
deployment, or perhaps the GNSS vendors could support same.

That said, there are use cases for Universal Time over NTP - indeed,
nearly all of them currently - and in addition to precision timekeeping
for scientists, I believe this will continue for many other communities
and the requirements will grow should UTC itself no longer serve this role.

And on the other hand, radio astronomers, solar system astronomers,
space situational awareness, precision navigation, etc, may well need
UT1 now and in the future to significantly more precision than a tenth
second. Indeed, UT1 itself is measured with respect to distant fixed
radio sources.

Jamming of GPS / GNSS is a different, if also important, thread. What
are the robust alternatives for widely distributed sources of TAI / UTC?

Rob

--


On 3/21/18 9:06 AM, Steve Allen wrote:
> On Wed 2018-03-21T08:51:37-0700 Steve Allen hath writ:
>> Our robotic telescope with small FOV on the guider does better if it
>> is given UT1 to 0.1 second.  That telescope grabs the USNO predictions
>> of EOP every week to update the pointing.
> I'll add that I do not see any place where I would want to use UT1 via
> NTP for astronomical observations.  The real-time operation of the
> telescopes does not want to be dependent on a very small number of
> external real-time sources over telecomm links that can fail.
>
> That is why we rely on the USNO predictions, for they give us several
> months of lookahead.  Thus also we have several months of warning if
> the USNO decides to stop publishing EOP, and that is enough time to
> engineer a replacement source of information.
>
> It was not happy when DoD was doing theater-level jamming near Hawaii
> and the Keck telescope GPS time servers had dates that were completely
> insane.  In that case the local system clocks retained sanity for the
> duration of the jamming.  In extension of all this I argue again that
> what is really wanted is a source of Atomic Time that is completely
> robust plus a widely disseminated source of tabular or polynomial
> predictions of Atomic Time minus Universal Time.
>
> --
> Steve Allen                    <sla at ucolick.org>              WGS-84 (GPS)
> UCO/Lick Observatory--ISB 260  Natural Sciences II, Room 165  Lat  +36.99855
> 1156 High Street               Voice: +1 831 459 3046         Lng -122.06015
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