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    UTC redefinition: opinion survey
    From: Paul Hirose
    Date: 2011 Aug 19, 14:18 -0700

    The IERS (International Earth Rotation and Reference Systems Service) is 
    soliciting opinions regarding a possible redefinition of the UTC time 
    scale. They have a Web questionnaire:
    http://hpiers.obspm.fr/eop-pc/index.php?index=questionnaire
    
    
    [QUOTE]
    
    After years of discussions within the scientific community, a proposal 
    to fundamentally redefine UTC will come to a conclusive vote in January 
    2012 at the ITU-R in Geneva. If this proposal is approved, it would be 
    effective five years later. It would halt the intercalary adjustments 
    known as leap seconds that maintain UTC as a form of Universal Time.
    
    Then, UTC would not keep pace with Earth rotation and the value of DUT1 
    would become unconstrained.Therefore UTC would no longer be directly 
    useful for various technical applications which rely on it being less 
    than 1 second from UT1. Such applications would require a separate 
    access to UT1, such as through the publication of DUT1 by other means.
    
    The objective of the survey is to find out the strength of opinion for 
    maintaining or changing the present system.
    
    Your response is appreciated before 31 August 2011.
    
    Two references:
    
    1 - Nelson, R.A., McCarthy, D.D., Malys, S., Levine, J., Guinot, B., 
    Fliegel, H.F., Beard, R.L., and Bartholomew, T.R., The leap second: its 
    history and possible future. Metrologia, Vol. 38, 2001, pp. 509-529
    http://www.cl.cam.ac.uk/~mgk25/time/metrologia-leapsecond.pdf
    
    2 - Finkleman, D., Seago, J.H., and Seidelmann, P. K. The Debate over 
    UTC and Leap Seconds. Proceedings of the AIAA/AAS Astrodynamics 
    Specialist Conference,Toronto, Canada, 2010.
    
    http://www.agi.com/downloads/resources/user-resources/downloads/whitepapers/DebateOverUTCandLeapSeconds.pdf
    
    [QUOTE]
    
    
    Both documents note that any change will affect celestial navigators.
    
    "While reliance on celestial navigation has greatly diminished with the 
    advent of GNSS, the generalization that celestial navigation is no 
    longer actively practiced is unfounded. Electronic navigation aids are 
    subject breakdown and jamming, such that the US armed forces still teach 
    navigation without GNSS and other electronic aids. Because LORAN is 
    being phased out in the USA, celestial navigation is still used as a 
    backup to GNSS, especially where military requirements mandate some kind 
    of navigational backup at sea. Many professional sailors and civilian 
    merchant marines also rely on celestial navigation as a back-up to GNSS, 
    evidenced by the availability of private instruction on celestial 
    navigation and the continuing production of sextants, nautical almanacs, 
    and celestial navigation textbooks. Also, the concept of the leap second 
    was not introduced “to meet the requirement of celestial navigation” 
    since that requirement was being met previously by timing-signal 
    broadcasts without leap seconds. Rather, the UTC system with leap 
    seconds was motivated to convenience the calibration of frequency while 
    still satisfying legislative and regulatory obligations to keep timing 
    signals synchronized with astronomical time of day." (Finkleman et al)
    
    The latter paper makes a case against a UTC redefinition.
    
    I can go either way. This possibility has been in the air for years. By 
    now, anyone who writes software which is sensitive to the precise 
    definiton of UTC should be ready for the end of leap seconds. But as a 
    mere hobbyist I'm staying out of the IERS poll.
    
    -- 
    I filter out messages with attachments or HTML.
    
    
    
    

       
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