From owner-leapsecs@ROM.USNO.NAVY.MIL Sat May 10 03:14:54 2003 Received: from [192.5.41.253] (juno.usno.navy.mil [192.5.41.253]) by santo.ucolick.org (8.11.7+Sun/8.11.7) with SMTP id h4AAEmw08540 for ; Sat, 10 May 2003 03:14:48 -0700 (PDT) Received: from rom.usno.navy.mil by [192.5.41.253] via smtpd (for santo.ucolick.org [128.114.23.204]) with SMTP; 10 May 2003 10:25:56 UT Received: from ROM.USNO.NAVY.MIL (rom.usno.navy.mil [10.1.4.27]) by rom.usno.navy.mil (8.12.8/8.12.5) with ESMTP id h4AAElTA018977; Sat, 10 May 2003 10:14:47 GMT Received: from ROM.USNO.NAVY.MIL by ROM.USNO.NAVY.MIL (LISTSERV-TCP/IP release 1.8e) with spool id 15192 for LEAPSECS@ROM.USNO.NAVY.MIL; Sat, 10 May 2003 10:14:47 +0000 Received: from TS-FW.usno.navy.mil (TS-FW.usno.navy.mil [10.1.1.3]) by rom.usno.navy.mil (8.12.8/8.12.5) with SMTP id h4AAEkT8018970 for ; Sat, 10 May 2003 10:14:46 GMT Received: from geneva.ucolick.org ([128.114.23.183]) by TS-FW.usno.navy.mil via smtpd (for rom.usno.navy.mil [10.1.4.27]) with SMTP; 10 May 2003 10:25:54 UT Received: (from sla@localhost) by geneva.ucolick.org (8.11.6/8.11.2) id h4AAEjg18509 for LEAPSECS@ROM.USNO.NAVY.MIL; Sat, 10 May 2003 03:14:45 -0700 Date: Sat, 10 May 2003 03:14:45 -0700 From: Steve Allen To: Leap Second Discussion List Subject: will history repeat itself? Message-ID: <20030510101445.GB17917@ucolick.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.1i Sender: owner-leapsecs@ROM.USNO.NAVY.MIL Precedence: list X-Virus: Clean Status: RO Content-Length: 3769 Lines: 70 The existence of the ITU-R working group to study UTC strongly resembles the situation 33 years ago when leap seconds were first being proposed. At that time CCIR working group VII-1 was studying how radio broadcast time signals could provide standard time interval and frequency (both using atomic seconds) and also provide time-of-day. The complete history is probably not available even by reading the transactions of all of the international scientific and treaty organizations. The IAU proceedings and transactions from 1970 and 1973 shed some light on what happened. In 1968 the CCIR (predecessor to the ITU-R) formed the working group. Then, as now, the membership of the working group overlapped significantly with the membership of the commissions of several international scientific and treaty organizations. The 1970 report of IAU Commission 31 (Time) indicates that in autumn of 1969 there was a proposal that indicated "the urgent need that a Consultative Committee for Time Scales be created by the CIPM, being charged with the preparation of the time scale definition work and giving outlines to a laboratory working under these auspices, at best the BIH". The proposal was supported at meetings of URSI, CCIR, and CIPM, was recommended in a resolution of URSI, and explicitly stated "that the definition of astronomical time scales does pertain to the IAU". But in October 1969 the CCIR working party rediscussed the question, and submitted their documents to the January 1970 Plenary Assembly of the CCIR for a final decision. They did ask the opinion of the Scientific Unions concerned. The results of this activity show up in the 1970 proceedings of IAU commissions 31 and 4 (Ephemerides), who held joint meetings to discuss some aspects. The publications of the IAU are normally quite restrained, but in this instance there are indications that the meetings were sufficiently disturbed that some issues did not get resolved until the 1973 IAU General Assembly. The recommendations from the CCIR were effectively the system of UTC with leap seconds that we have now, and it was reported that the CCIR resolved that the IAU should be informed of them. Not all of the astronomers were happy with the system, but they were even less happy that the IAU had never received official communication from the CCIR about those recommendations. In the end commission 31 adopted a resolution consisting of supplementary recommendations about the new form of UTC, and noted that they considered the scheme to be the optimum solution in the presence of the conflicting requirements of UTC users. In 1973 IAU commissions 31 and 4 held a joint session which produced two resolutions regarding UTC. The first recognized that UTC "provides mean solar time directly to a precision that is needed for navigation and surveying" and recommended that UTC be the basis for standard time. The second refined the rules regarding when leap seconds might be inserted into UTC (and these rules were adopted). They also made several recommendations, the last one of which might relate to the incidents in 1970: Close cooperation between the scientific and treaty organizations, CIPM, CCIR, IUGG, URSI and IAU, must assure that the present evolution in worldwide standardization in the provision and use of precise time can continue in an orderly way. It will be interesting to see whether this recommendation produces more civil contents in the proceedings for the next few trienniums of the international scientific unions. -- Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064 sla@ucolick.org Voice: +1 831 459 3046 http://www.ucolick.org/~sla PGP: 1024/E46978C5 F6 78 D1 10 62 94 8F 2E 49 89 0E FE 26 B4 14 93