Re: [LEAPSECS] future access to solar time?
The Astronomical Almanac (2019) says ∆UT = UT1 - UTC DUT1 = predicted value of ∆UT, rounded to 0.1 s, given in some radio time signals (Unfortunately, this scan cuts off part of the leftmost characters. But you can deduce them, except perhaps Ee and Eo: equation of the equinoxes and equation of the origins.) https://archive.org/details/binder1_202003/page/n121/mode/2up?view=theater IERS Bulletins A and B say "UT1-UTC" instead of ∆UT. I think that's a good idea. It prevents confusion about the sign. The current version of Bulletin A estimates UT1 will lose about 0.1 s with respect to atomic time during the next year. https://www.iers.org/IERS/EN/Publications/Bulletins/bulletins.html ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] future access to solar time?
Interesting!
Another example of “polysemy”
(http://hanksville.org/futureofutc/aas223/presentations/2-1-ISOterminologyAAS.pdf)
in timekeeping.
In addition to changes in funding (be careful what you ask for, precision time
community), best practices (and worse practices) should get a good workout as
this foundational standard is redefined.
Rob
On 11/21/22, 8:30 AM, "LEAPSECS" wrote:
On 2022-11-21 14:19, Seaman, Robert Lewis - (rseaman) wrote:
> In a post-leap-second world, precision values for dUT1 either become more
> critical or less. Or rather, they become no-less important scientifically but
> perhaps negligible politically. For
> example,https://www.sciencedirect.com/science/article/pii/S0273117719302388
> says “Global Navigation Satellite Systems (GNSS) are dependent on VLBI as
> they need dUT1 to maintain its operability”.
I am not sure if we mean the same thing by "dUT1". I used
it in the sense:
dUT1 is an additonal correction to UTC so that
UTC + DUT1 + dUT1
is a better approximation of UT1 than just
UTC + DUT1
and takes its values in the set {0, ±20, ±40, ±60, ±80} ms.
dUT1 in this sense is used only by some Russian time signals,
and its value is not defined by the IERS. Moreover, since the
amplitude of UT1 - UT2 is about 34 ms, dUT1 must be adjusted
for annual variations of UT1 - UTC.
I have seen the term "dUT1" to be used for ΔUT1 = UT1 - UTC
(and that is how I read it in the paper you quoted), and
also for the rate d(UT1) -- but these are different beasts.
Michael Deckers.
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Re: [LEAPSECS] future access to solar time?
On 2022-11-21 14:19, Seaman, Robert Lewis - (rseaman) wrote:
In a post-leap-second world, precision values for dUT1 either become more
critical or less. Or rather, they become no-less important scientifically but
perhaps negligible politically. For
example,https://www.sciencedirect.com/science/article/pii/S0273117719302388
says “Global Navigation Satellite Systems (GNSS) are dependent on VLBI as they
need dUT1 to maintain its operability”.
I am not sure if we mean the same thing by "dUT1". I used
it in the sense:
dUT1 is an additonal correction to UTC so that
UTC + DUT1 + dUT1
is a better approximation of UT1 than just
UTC + DUT1
and takes its values in the set {0, ±20, ±40, ±60, ±80} ms.
dUT1 in this sense is used only by some Russian time signals,
and its value is not defined by the IERS. Moreover, since the
amplitude of UT1 - UT2 is about 34 ms, dUT1 must be adjusted
for annual variations of UT1 - UTC.
I have seen the term "dUT1" to be used for ΔUT1 = UT1 - UTC
(and that is how I read it in the paper you quoted), and
also for the rate d(UT1) -- but these are different beasts.
Michael Deckers.
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Re: [LEAPSECS] future access to solar time?
Interesting. In a post-leap-second world, precision values for dUT1 either become more critical or less. Or rather, they become no-less important scientifically but perhaps negligible politically. For example, https://www.sciencedirect.com/science/article/pii/S0273117719302388 says “Global Navigation Satellite Systems (GNSS) are dependent on VLBI as they need dUT1 to maintain its operability”. To the UTC decision-makers does “operability” mean legal constraints or does it mean physical reality / technical infrastructure? (“UTC no longer depends on UT1, so why should we pay for it?”) For UTC/GPS context, Stephen Malys had a talk at the Exton meeting in 2011: http://hanksville.org/futureofutc/2011/preprints/32_AAS_11-675_Malys.pdf, but I don’t see the question of high precision requirements addressed directly (and much may have changed in 11 years). Which is to ask, I suppose, will redefining UTC imply that activities like VLBI will need to seek different funding streams? Rob Seaman Lunar and Planetary Laboratory University of Arizona On 11/21/22, 6:37 AM, "LEAPSECS" wrote: On 2022-11-20 15:15, Tony Finch asked: > (Do any of > the national broadcast signals actually follow the ITU spec?) Lists of UTC time signals with details about the coding are in the Annual reports of the BIPM time department, at [https://www.bipm.org/en/time-ftp/annual-reports]. A few of them transmit DUT1 (and even dUT1). Michael Deckers. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] future access to solar time?
On 2022-11-20 15:15, Tony Finch asked: (Do any of the national broadcast signals actually follow the ITU spec?) Lists of UTC time signals with details about the coding are in the Annual reports of the BIPM time department, at [https://www.bipm.org/en/time-ftp/annual-reports]. A few of them transmit DUT1 (and even dUT1). Michael Deckers. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
