IERS Message No. 191: Colloquium on redefinition of UTC - Announcement

central_bureau at central_bureau at
Tue Jun 28 12:58:59 UTC 2011

IERS Message No. 191                                       June 28, 2011

Colloquium on redefinition of UTC - Announcement

Decoupling Civil Timekeeping from Earth Rotation

A Colloquium Exploring Implications of Redefining UTC
in Astrodynamics, Astronomy, Geodesy, Navigation,
Remote Sensing and Related Fields

October 5-6, 2011

Headquarters of Analytical Graphics, Inc.
220 Valley Creek Blvd, Exton PA, 19341-2380
(near Philadelphia)

Registration is now open at

Universal Time - the conventional measure of Earth rotation and
astronomical time-of-day - is the traditional basis for civil
timekeeping. Clocks worldwide are synchronized via Coordinated Universal
Time (UTC), an atomic time scale recommended by the Radiocommunications
Sector of the International Telecommunications Union (ITU-R).

A proposal to fundamentally redefine UTC will come to a conclusive vote
in January 2012 at the Radiocommunications Assembly of the ITU-R in
Geneva. It would halt the intercalary adjustments known as leap seconds
that maintain UTC as a form of Universal Time, and eliminate the
requirement that time services transmit the varying residuals (DUT1)
between Coordinated Universal Time and Universal Time of day. If the
proposal is approved, UTC would not keep pace with Earth rotation and
the value of DUT1 would become unconstrained.

Adverse impacts from redefining UTC have not been extensively researched
and documented. The implications extend from technical infrastructure to
legal, historical, logistical, sociological and economic domains.
Affected technologies may include (but are not limited to) applications
in astronomy, astrodynamics and celestial mechanics, geodesy,
ground-to-space satellite communications, navigation, remote sensing and
space surveillance.

This meeting will provide a venue for discussing and documenting the
repercussions of changing UTC along with possible mitigation strategies.

  Rob Seaman, National Optical Astronomy Observatory
  John Seago, Analytical Graphics, Inc.
  Steve Allen, University of California Observatories / Lick Observatory

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