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URSI Working Group on the Leap Second
Letter from Dr. Demetrios Matsakis, Chair, URSI Working Group on the Leap SecondDear URSI Colleague, The URSI Secretariat has received a letter from the Special Rapporteur Group of the International Telecommunication Union (ITU), whose charter is to study and make recommendations on the redefinition of Coordinated Universal Time (UTC), which differs from International Atomic Time (TAI) by the insertion of leap seconds to account for the variable rotation of the Earth. The letter invites URSI participation in their study, which has since been narrowed to consideration of whether the current practice of inserting leap seconds so as to keep |UT1-UTC| < .9 seconds should be replaced by a policy of inserting no leap seconds, so that UTC-TAI will remained at a fixed value indefinitely. This would affect systems that depend upon UT1 being close enough to UTC that the difference can be ignored or that the format for specifying the difference can have a fixed sized. An analysis of the motivation for a change was recent published in Metrologia, 2001, 38, pp. 509-529, a copy of which is attached. Previous to the formation of the ITU Special Rapporteur Group, an URSI Commission J Working Group was formed at the 1999 URSI General Assembly in Toronto, Canada and their report is attached. Subsequently, the 2002 URSI General Assembly in Maastricht, The Netherlands formed an URSI Working Group (WG) to study the effects of such a change upon systems relevant to URSI radioscientists, and to propose a response to the ITU. The resolution creating the WG is attached. The members of the WG are Demetrios Matsakis (chair), Wim Brouw, Sigfrido Leschiutta, and Inoue Makoto, and their contact information is also attached. An informal listserv on the technical, scientific, and political aspects of this matter can be accessed via http://rom.usno.navy.mil/archives/leapsecs.html , and a broader summary is being maintained by Markus Kuhn at http://www.cl.cam.ac.uk/~mgk25/time/leap/ . Both of these sites provide an excellent summary, by Markus Kuhn, of discussions and presentations at an ITU-sponsored symposium on this subject, held in May 2003 at Torino, Italy. In order to fulfill our charter, we have composed a questionnaire that we would appreciate your assistance in distributing to all official members of your commission. This questionnaire will help us better understand their needs. While we do ask that the form of the questionnaire be followed, the responders should feel free to use as much space to answer the questions as required. Please send the completed questionnaire to Matsakis.Demetrios@usno.navy.mil by January 1, 2004. Sincerely, Dr. Demetrios Matsakis Back to the top of this page
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