[LEAPSECS] Inside GNSS published an update of my CGSIC talk

[Richard B Langley]

"I'd also note that if GLASNOS can't be fixed by 2035 ..."

Interesting slip of the tongue.

Glasnos[t] was taken to mean increased openness and transparency in government institutions and activities in the Soviet Union (USSR). Glasnost reflected a commitment of the Gorbachev administration to allowing Soviet citizens to discuss publicly the problems of their system and potential solutions.

Of course, GLONASS was meant. But we are reminded that in today's Russia, openness and transparency, not to mention freedom of speech, is a thing of the past.

Sorry for being a bit off topic.

-- Richard Langley

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| Richard B. Langley                            E-mail: lang at unb.ca         |
| Geodetic Research Laboratory                  Web: http://gge.unb.ca      |
| Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506 453-5142   |
| University of New Brunswick                                               |
| Fredericton, N.B., Canada  E3B 5A3                                        |
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________________________________________
From: LEAPSECS <leapsecs-bounces at leapsecond.com> on behalf of Warner Losh <imp at bsdimp.com>
Sent: March 20, 2023 5:18 PM
To: Leap Second Discussion List
Subject: Re: [LEAPSECS] Inside GNSS published an update of my CGSIC talk

✉External message: Use caution.


On Mon, Mar 20, 2023 at 1:37 PM Michael Deckers via LEAPSECS <leapsecs at leapsecond.com<mailto:leapsecs at leapsecond.com>> wrote:

    On 2023-03-20 07:54, Jürgen Appel via LEAPSECS wrote:


> In your Conclusion, you say "the CGPM resolution also stipulates that no
> change to current practices can occur before 2035."
>
> This is not how I read read the CGPM document on the BIPM website:
> "The General Conference on Weights and Measures (CGPM), at its 27th meeting
> [...] decides that the maximum value for the difference (UT1-UTC) will be
> increased in, or before, 2035,"
>
> So in case the negative leap seconds become a real threat, according to my
> interpretation is is an option to increase the tolerance value earlier than
> 2035 to avoid trying out negative leap seconds a last and first time.
>
> Can someone confirm my view?



     You read correctly, the French (official) version has

        ..."décide que la valeur maximale pour la différence
            (UT1 - UTC) sera augmentée au plus tard en 2035,"....

     which means "in 2035 at the latest".

     Note also that the definition of UTC as approved by the
     CGPM never mentions _any_ explict bound for |UT1 - UTC|; it
     only says that (TAI - UTC) is an integral multiple of 1 s
     as determined by the IERS. It is the IERS who state that

        "Coordinated Universal Time (UTC) a measure of time
         that conforms, within approximately 1 s, to the mean
         diurnal motion of the Sun and serves as the basis of
         all civil timekeeping."

     quoting the IAU "Nomenclature for Fundamental Astronomy (NFA)"
     found at http://syrte.obspm.fr/iauWGnfa/NFA Glossary.html.

     This seems to be lenient enough to allow for not scheduling
     a negative leap second even in the case that the difference
     (UT1 - UTC) should go a bit below -1 s before 2035.

So is "approximately" here to be read in the "astronomer" sense that it's that, give or take an order of magnitude, or some more close reading :) For astronomy, often times things that are approximately the same can vary quite a bit, and that's fine.

More seriously even 2s is approximately 1s if there's some kind of effort to keep it from freewheeling to 10s, 100s, or 1000s of seconds.

For example, the Gregorian calendar approximates the year over the centuries, but any given year can deviate up to 2 days (worst case) from the idealized solstice dates.

I'd also note that if GLASNOS can't be fixed by 2035, then a fallback to a schedule of leap seconds to keep the answer approximately 1s in the long haul could also be on the table. Having it be scheduled, rather than observational, has advantages: everybody gets leap years right, and will for the next few hundred years (maybe with a glitch at 2100 and 2400). A much lower percentage get leap seconds right because leap second knowledge propagates imperfectly, even after all these years of trying (my first anti-leapsecond screeds date back maybe 20 years). So my first choice is always 'none, cope with shifting civil time on the scale of centuries' but my second choice is 'schedule for the long-term average and don't worry about going > 1s' .

Warner

     Michael Deckers.

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