Fwd: Bulletin C number 58
NIST's leap-seconds.list was finally updated today. Patch attached. I'd reached out to Christian Bizouard of IERS a bit ahead of the announcement in the hopes that we could settle the outstanding issues from 2017 with adding a public domain copyright notice to the IERS version of the file, but no luck this time around. -- Tim Parenti On Thu, 4 Jul 2019 at 12:11, Kurt Roeckx <kurt@roeckx.be> wrote:
---------- Forwarded message ---------- From: IERS EOP Product Center <iers.eoppc@obspm.fr> To: bulc.iers@obspm.fr Cc: Bcc: Date: Thu, 04 Jul 2019 15:06:25 +0200 Subject: Bulletin C number 58
INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS)
SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE
SERVICE DE LA ROTATION TERRESTRE DE L'IERS OBSERVATOIRE DE PARIS 61, Av. de l'Observatoire 75014 PARIS (France) Tel. : +33 1 40 51 23 35 e-mail : services.iers@obspm.fr http://hpiers.obspm.fr/eop-pc
Paris, 04 July 2019
Bulletin C 58
To authorities responsible for the measurement and distribution of time
INFORMATION ON UTC - TAI
NO leap second will be introduced at the end of December 2019. The difference between Coordinated Universal Time UTC and the International Atomic Time TAI is :
from 2017 January 1, 0h UTC, until further notice : UTC-TAI = -37 s
Leap seconds can be introduced in UTC at the end of the months of December or June, depending on the evolution of UT1-TAI. Bulletin C is mailed every six months, either to announce a time step in UTC, or to confirm that there will be no time step at the next possible date.
Christian BIZOUARD Director Earth Orientation Center of IERS Observatoire de Paris, France
For my products I use an algorithm (Meeus; Astronomical Algorithms 1998) to 'predict' deltaT into the future. Does anyone have a good source for a more recent algorithm that takes into account IERS values since 1998? On 2019-07-26 21:27, Tim Parenti wrote:
NIST's leap-seconds.list was finally updated today. Patch attached.
I'd reached out to Christian Bizouard of IERS a bit ahead of the announcement in the hopes that we could settle the outstanding issues from 2017 with adding a public domain copyright notice to the IERS version of the file, but no luck this time around.
-- Tim Parenti
On Thu, 4 Jul 2019 at 12:11, Kurt Roeckx <kurt@roeckx.be <mailto:kurt@roeckx.be>> wrote:
---------- Forwarded message ---------- From: IERS EOP Product Center <iers.eoppc@obspm.fr <mailto:iers.eoppc@obspm.fr>> To: bulc.iers@obspm.fr <mailto:bulc.iers@obspm.fr> Cc: Bcc: Date: Thu, 04 Jul 2019 15:06:25 +0200 Subject: Bulletin C number 58
INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS)
SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE
SERVICE DE LA ROTATION TERRESTRE DE L'IERS OBSERVATOIRE DE PARIS 61, Av. de l'Observatoire 75014 PARIS (France) Tel. : +33 1 40 51 23 35 e-mail : services.iers@obspm.fr <mailto:services.iers@obspm.fr> http://hpiers.obspm.fr/eop-pc
Paris, 04 July 2019
Bulletin C 58
To authorities responsible for the measurement and distribution of time
INFORMATION ON UTC - TAI
NO leap second will be introduced at the end of December 2019. The difference between Coordinated Universal Time UTC and the International Atomic Time TAI is :
from 2017 January 1, 0h UTC, until further notice : UTC-TAI = -37 s
Leap seconds can be introduced in UTC at the end of the months of December or June, depending on the evolution of UT1-TAI. Bulletin C is mailed every six months, either to announce a time step in UTC, or to confirm that there will be no time step at the next possible date.
Christian BIZOUARD Director Earth Orientation Center of IERS Observatoire de Paris, France
On Fri 2019-07-26T23:16:08-0400 David Patte hath writ:
For my products I use an algorithm (Meeus; Astronomical Algorithms 1998) to 'predict' deltaT into the future. Does anyone have a good source for a more recent algorithm that takes into account IERS values since 1998?
at the moment we seem to be pretty close to "Matsakis parabolic" https://www.ucolick.org/~sla/leapsecs/year2100.html but there are no guarantees -- Steve Allen <sla@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 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m
On 2019-07-26 22:49, Steve Allen wrote:
On Fri 2019-07-26T23:16:08-0400 David Patte hath writ:
For my products I use an algorithm (Meeus; Astronomical Algorithms 1998) to 'predict' deltaT into the future. Does anyone have a good source for a more recent algorithm that takes into account IERS values since 1998? at the moment we seem to be pretty close to "Matsakis parabolic" https://www.ucolick.org/~sla/leapsecs/year2100.html but there are no guarantees
We all know what a shock there was after the last break in regular leap second additions, and given short memories in popular development circles, expect similar reactions next year or whenever the next addition happens. Are there any sources providing pointers to explanations of recent changes in EOP parameters and their likely cause, or info about likely reasons for (rather than factors affecting) the current (and earlier) period(s) of reductions in dUT1 change? https://en.wikipedia.org/wiki/ΔT#References has an interesting comment: Stephenson, F. R. & Morrison, L.V. "Long-term fluctuations in the Earth's rotation: 700 BC to AD 1990". Philosophical Transactions of the Royal Society of London, Series A 351 (1995) 165-202. https://www.jstor.org/stable/54464. "Includes evidence that the 'growth' in Delta-T is being modified by an oscillation with a wavelength around 1500 years; if that is true, then during the next few centuries Delta-T values will increase more slowly than is envisaged." -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada This email may be disturbing to some readers as it contains too much technical detail. Reader discretion is advised.
On Sat 2019-07-27T01:59:14-0600 Brian Inglis hath writ:
https://en.wikipedia.org/wiki/ΔT#References has an interesting comment: Stephenson, F. R. & Morrison, L.V. "Long-term fluctuations in the Earth's rotation: 700 BC to AD 1990". Philosophical Transactions of the Royal Society of London, Series A 351 (1995) 165-202. https://www.jstor.org/stable/54464. "Includes evidence that the 'growth' in Delta-T is being modified by an oscillation with a wavelength around 1500 years; if that is true, then during the next few centuries Delta-T values will increase more slowly than is envisaged."
P.J. Huber, 2006, Journal of Geodesy, 80, 283-303 points out that the poor sampling of the ancient data and the magnitude of the stochastic terms means that the appearance of a 1500 year term could be due only to statistical fluctuation. -- Steve Allen <sla@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 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m
Another good paper on delta T from Stephenson, Morrison and Hohenkerk is "Measurement of the Earth's rotation: 720 BC to AD 2015". The paper's data, which includes projected values of delta T from the year -2000 to the year +2500, is at http://astro.ukho.gov.uk/nao/lvm/ Also, the IERS in their Bulletin A projects UT1-UTC a year in advance, and gives a formula for extending that projection. It is easy enough to convert UT1-UTC to delta T if you have a table of leap seconds. John Sauter (John_Sauter@systemeyescomputerstore.com) -- PGP fingerprint E24A D25B E5FE 4914 A603 49EC 7030 3EA1 9A0B 511E
On 2019-07-27 06:54, Alois Treindl wrote:
On 27.07.19 05:16, David Patte wrote:
For my products I use an algorithm (Meeus; Astronomical Algorithms 1998) to 'predict' deltaT into the future. Does anyone have a good source for a more recent algorithm that takes into account IERS values since 1998?
In Swiss Ephemeris, we have an implementation of delta T which tries to be state of the art.
See documentation here https://www.astro.com/swisseph/swephprg.htm#_Toc11319101
and source code here https://www.astro.com/ftp/swisseph/src/
The delta T source code is in file swephlib.c https://www.astro.com/ftp/swisseph/src/swephlib.c
The implementation is complicated by the fact that we try to be consistent with different versions of JPL ephemerides, which use different values for the Moon's tidal acceleration.
All the code of Swiss Ephemeris is published under GPL.
A commercial license is available for those who do keep their projects free of the obligations arising from Gnu public license,
Many developers who wish to promote using their code as a standard choose instead to license under the BSD or MIT licences as an option to or instead of the GPL, any mention of which deters most commercial licensees from even looking. Commercial licensees would rather deal with a few comprehensive sources than a bunch of little bits and pieces. As in all forms of commodity publishing, the issue is not really about buying, it is getting anyone interested in any of a particular author's works: the publishing businesses take a statistical shotgun approach, in the hopes that buyers will like a few works by some of their authors. -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada This email may be disturbing to some readers as it contains too much technical detail. Reader discretion is advised.
Thanks, I installed that into the development version on GitHub. I see that the updated file has a space at the end of the '#@ 3802291200' line that encodes the expiration (2020-06-28 00:00:00 UTC). I assume this was inadvertent. It doesn't break tzcode (which ignores that line), but the format of the line is not documented anywhere that I can see. I dropped Judah Levine a line about this.
On 2019-07-27 08:21, Paul Eggert wrote:
Thanks, I installed that into the development version on GitHub.
I see that the updated file has a space at the end of the '#@ 3802291200' line that encodes the expiration (2020-06-28 00:00:00 UTC). I assume this was inadvertent. It doesn't break tzcode (which ignores that line), but the format of the line is not documented anywhere that I can see. I dropped Judah Levine a line about this.
leap-seconds.list tail says: # the following special comment contains the # hash value of the data in this file computed # use the secure hash algorithm as specified # by FIPS 180-1. See the files in ~/pub/sha for # the details of how this hash value is # computed. Note that the hash computation # ignores comments and whitespace characters # in data lines. It includes the NTP values # of both the last modification time and the # expiration time of the file, but not the # white space on those lines. # the hash line is also ignored in the # computation. # #h f28827d2 f263b6c3 ec0f19eb a3e0dbf0 97f3fa30 so only the NTP values in the special comments lines and the data lines are significant: all non-special comments lines may be ignored, as can comments in data lines, only the digits in the data and special comments lines are significant for the hash; and only the hex digits in the hash line are significant for validation. Strictly speaking, the file should also follow the format and naming documented for NTP source crypto files, as it is part of and distributed using those mechanisms, but that is not enforced anywhere. -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada This email may be disturbing to some readers as it contains too much technical detail. Reader discretion is advised.
On 7/27/19 1:36 PM, Brian Inglis wrote:
Many developers who wish to promote using their code as a standard choose instead to license under ... Let's not get bogged down in advocacy for particular free-software licenses for 3rd-party software. Other mailing lists are a better place to discuss that.
participants (8)
-
Alois Treindl -
Brian Inglis -
David Patte -
John Sauter -
Kurt Roeckx -
Paul Eggert -
Steve Allen -
Tim Parenti