UTC, leap seconds, and the BIPM, IAU, ITU et.al.

From: Neal McBurnett <neal_at_BCN.BOULDER.CO.US>
Date: Thu, 30 Jan 2003 18:08:08 -0700

Thanks to Steve for the reference:


I reproduce below a resolution of more specific relevance to this
discussion that was made at that meeting of the International
Astronomical Union. I'm glad the IAU is looking at a wider range of
options than the International Telecommunication Union
Radiocommunication Study Group is.

The IAU working group is due to report in mid-2003. Who knows more
about this IAU working group and their discussions?

This brings up the broader question of who is involved in this
decision making process.

ITU CCIR Recommendation 460-4. (188) is available at

EMISSIONS" and contains this language:

   UTC is the time-scale maintained by the BIPM, with assistance from
   the International Earth Rotation Service (IERS), which forms the
   basis of a coordinated dissemination of standard frequencies and
   time signals.

That leads me to believe that while the ITU wrote the recommendation
on how to *disseminate* UTC, the actual legal basis for determining UTC
rests with the BIPM, which is part of the General Conference on
Weights and Measures, which also handles the International System of
Units (SI).


Neal McBurnett http://bcn.boulder.co.us/~neal/
GPG/PGP signed and/or sealed mail encouraged. Keyid: 2C9EBA60

IAU Resolutions Adopted at the 24th General Assembly (Manchester, August 2000)

 Resolution B2 Coordinated Universal Time

 The XXIVth International Astronomical Union General Assembly,


   1. that the definition of Coordinated Universal Time (UTC) relies
   on the astronomical observation of the UT1 time scale in order to
   introduce leap seconds,
   2. that the unpredictability of leap seconds affects modern
   communication and navigation systems,
   3. that astronomical observations provide an accurate estimate of
   the secular deceleration of the Earth?s rate of rotation,


   1. that the IAU establish a working group reporting to Division I
   at the General Assembly in 2003 to consider the redefinition of
   2. that this study discuss whether there is a requirement for leap
   seconds, the possibility of inserting leap seconds at
   pre-determined intervals, and the tolerance limits for UT1-UTC, and
   3. that this study be undertaken in cooperation with the
   appropriate groups of the International Union of Radio Science
   (URSI), the International Telecommunications Union (ITU-R), the
   International Bureau for Weights and Measures (BIPM), the
   International Earth Rotation Service (IERS), and relevant
   navigational agencies.

On Thu, Jan 30, 2003 at 04:25:22PM -0800, Steve Allen wrote:
> The resolutions that have established the change have happened over
> the past four meetings of IAU General Assembly.
> The most recent set of resolutions which switched things from the old,
> non-inertial definitions to the new ones is visible at
> http://danof.obspm.fr/IAU_resolutions/Resol-UAI.htm
Received on Thu Jan 30 2003 - 17:18:38 PST

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