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Abolishing Leap Seconds



Dear All,

The Proposal to Discontinue Leap Seconds
----------------------------------------
Precise time, and the nature of time, is a subject of particular interest to
the satellite community.  A few of you may be aware of a proposal on the
table at the ITU WP-7A (*) to abandon leap seconds.  That is, to decouple
what we all think of as "time" from "sundial" time.  For thousands of years
solar time has been the basis of civil time with clocks adjusted to make it
so.  And for the last 30 years it's been maintained that way by the insertion
of occasional leap seconds into civil time.

The proposal has profound implications, and I cannot possibly do the subject
justice in this forum.  You will have to do your own research.

A symposium on the future of UTC was held in May 2003, and is recorded here:
  http://www.ien.it/luc/cesio/itu/ITU.shtml

Much detail can be gleaned from here:
  http://www.ucolick.org/~sla/leapsecs/

And below is the text of a recent "wake-up" call from the precise timing
community, a statement of concern that is about as clear as it gets.

Kindly note that I am only the messenger.  Please do not shoot me.

73 de James G3RUH

 * ITU WP-7A = International Telecommunications Union, Working Party 7A.
   Its area is "Time signals and frequency standard emissions"

______________________________________________________________________________

Date: Tue, 5 Jul 2005 13:50:31 +0200
From: "services.iers {at} obspm.fr" <services.iers {at} obspm.fr>
To: adresd1 {at} callisto.obspm.fr
Subject: Note to IERS Users

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
______________________________________________________________________________


-- 
==========================================================================
    James R Miller      WWW/PGP:     http://www.jrmiller.demon.co.uk/
  Cambridge, England   Stardate:        2005 Jul 08 [Fri] 2039 utc
==========================================================================
----
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