[IGSMAIL-5172]: The Future of UTC Leap Seconds

Tue Jul 5 08:25:02 PDT 2005

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IGS Electronic Mail      05 Jul 08:22:23 PDT 2005      Message Number 5172
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Author: Daniel Gambis (forward by Jim Ray)

[Note also that the latest IERS Bulletin C just announced a leap second
to be added on 31 December 2005, after which time TAI-UTC will be +33 s
and GPS Time-UTC will be +14 s.  --J. Ray]

July 2005
Letter to IERS Bulletins C and D users

Dear colleague,

As you are probably aware, international discussions are in progress on a
redefinition of UTC, including a possible suppression of the leap seconds
procedure.

To reply to the request of several international organizations on a possible
evolution of UTC the International Telecommunication Union, ITU decided in
October 2000 the creation of a Working Group called "Special Rapporteur
Group", SRG chaired by Mr Ron Beard of the Naval Research Laboratory (NRL-
USA), in charge of studying by a large consultation the different possible
solutions. The SRG reports its conclusions to the ITU working party WP-7A.

The Special Rapporteur Group (SRG) organized a colloquium in Torino, Italy in
May 2003. No general agreement emerged from this colloquium.

In parallel, the US delegation to the WP-7A submitted, at the last meeting in
Geneva in October 2004, a proposal which contained the following items:

1 - Maintenance of a time scale called UTC.

2 - Suppression of the leap seconds adjustments which maintains UTC close to
UT1, a time scale based on the Earth's rotation (currently UT1-UTC < .9 s)

3 - The difference of UT1 from UTC should not exceed 1 hour.

4 - The change should take effect at 21 December 2007, 00:00 UTC

If your activity is affected by the content of the US proposal which will be
discussed in November 2005 at the WP-7A, you are urged to react. This could be
the last opportunity before a recommendation is issued by the WP-7A.

If you wish you can express your opinion to your representative(s) at the
WP-7A of ITU (for the list see the ITU website, http://www.itu.int/home/
index.html) with a copy to Daniel Gambis (daniel.gambis at obspm.fr), IERS EOP
Center.

Daniel Gambis
Head
Earth Orientation Center of the IERS
Observatoire de Paris