[fitsbits] Re: leap second alert

[Peter Bunclark]

Rob Seaman wrote:

> We had an interesting inquiry that deserves a wider distribution.
> An astronomer with a friend at the NIST forwarded this to an NOAO
> staff member who forwarded it to me.  Now it's in your lap, too.
>
>     > As you know, Coordinated Universal Time (UTC) is derived from cesium
>     > clocks with the occasional addition of leap seconds. These leap seconds
>     > guarantee that the magnitude of UTC-UT1 does not exceed 1 s.
>     >
>     > Managing leap seconds is an administrative headache, and there have
>     > been proposals for some time to abandon using them. If this were done,
>     > the difference between UTC and UT1 would grow without bound. Currently,
>     > the rate of divergence is about 1 minute per century, and this rate is
>     > projected to increase as the Earth continues to slow down.
>     >
>     > Assuming this were done, would the lives of astronomers be made more
>     > difficult?  If astronomers have to incorporate a UT1 correction in any
>     > case, does it matter how big it is? If they currently use this
>     > correction, how accurately do they need to know it?
>     >
>     > Thanks for your assistance.
>     >
>     > Judah Levine
>
> Our reply was basically that most ground-based astronomers and most
> ground-based observatories' "utility" chores (like pointing the telescopes)
> have no real need for high precision timing information - but that the
> small fraction that do may have very stringent needs indeed.  We also
> suggested that they should talk to the nice folks at the USNO and that
> this obviously rises to the level of requiring an IAU decision.
>
> The question is also phrased in a vague enough fashion that it isn't clear
> precisely what they are suggesting.  Clearly, astronomers can't be the only
> ones with a requirement for an "inertial" time system.  (One might imagine
> that a large number of inobvious terrestrial applications rely on leap
> seconds implicitly or explicitly.)
>
> Whatever they are suggesting we still will require continuing support for
> a time system that doesn't drift monotonically with respect to the sky.
>
> The explicit question in the reply was:
>
> >> What is the point of this inquiry?  Is this some time keeping authority
> >> wondering the equivalent of Kodak's request every couple of years about
> >> what emulsions astronomers may actually be using?
>
> And here is what I suggest you all ponder:
>
>     > From jlevine at india.colorado.edu Mon Nov 22 14:56:10 1999
>     > Subject: leap seconds
>     >
>     > Hello,
>     >
>     >> What is the point of this inquiry?  Is this some time keeping
>     >> authority wondering ...
>     >
>     > Thank you for your comments. The Time and Frequency community
>     > regards leap seconds as a nuisance and a bother, and there is an
>     > increasingly strong push to abolish them. This would cause UT1-UTC
>     > to grow without bound. Time and frequency folks generally don't
>     > care about UT1, but I thought that this might bother astronomers.
>     > If it does not, then so much the better. On the other hand, if there
>     > is some application that would be seriously affected by this change
>     > then it would be useful to know about it now before the move to
>     > abolish leap seconds gains something approaching ustoppable momentum.
>     >
>     > Judah Levine
>     > Time and Frequency Division
>     > NIST Boulder
>
> So - any comments on specific FITS leap second requirements?
>
> Any more general astronomical concerns should be directed toward raising
> an immovable object in the path of that unstoppable momentum.  I'm a bit
> concerned at the rather unofficial channels that this official of the
> "Time and Frequency community" decided were sufficient to consult.
> (After all, we were the original time and frequency community...)
>
> Rob
>
> --
> seaman at noao.edu, http://iraf.noao.edu/~seaman
> NOAO, 950 N Cherry Ave, Tucson AZ 85719, 520-318-8248

There's some discussion of this on comp.protocols.time.ntp;
not all of it serious.
    Demetrios N. Matsakis <dnm at orion.usno.navy.mil> seems to be collecting
votes,
please cast yours.

Pete.

PS, my feeling is, they can go ahead if they pay for the audit and
subsequent re-engineering of all timekeeping-related software and
firmware, everywhere.  Shouldn't cost much more than the
Y2K fixes.