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

[Warner Losh]

On Mon, Mar 20, 2023 at 2:46 PM Richard B Langley <lang at unb.ca> wrote:

> "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.
>

ah, yes. I lisned to too many Gorby speeches back in the day, eh?

Thanks for the amusing correction...

Warner


> Sorry for being a bit off topic.
>
> -- Richard Langley
>
>
> -----------------------------------------------------------------------------
> | 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
>   |
> |        Fredericton?  Where's that?  See: http://www.fredericton.ca/
>    |
>
> -----------------------------------------------------------------------------
>
> ________________________________________
> 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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