Delivered-To: igsmail@igscb.jpl.nasa.gov From: Jim Ray "(NGS" 301-713-2850 "x112)" Message-Id: <200507051525.LAA05604@ness.ngs.noaa.gov> Subject: [IGSMAIL-5172]: The Future of UTC Leap Seconds To: igsmail@igscb.jpl.nasa.gov Date: Tue, 5 Jul 2005 11:25:02 -0400 (EDT) Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-igsmail Precedence: bulk ****************************************************************************** IGS Electronic Mail 05 Jul 08:22:23 PDT 2005 Message Number 5172 ****************************************************************************** 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@obspm.fr), IERS EOP Center. Daniel Gambis Head Earth Orientation Center of the IERS Observatoire de Paris