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	Gazette IERS Gazette IERS Gazette IERS Gazette IERS Gazette 
                                   ________________________________________
	No 51, 07 January 2000    /
_________________________________/        Contact: iers@obspm.fr
                                     ftp: hpiers.obspm.fr (145.238.100.28)
                                     WWW: http://hpiers.obspm.fr
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        Title  : IAU Colloquium 180 - Second announcement
        Authors: Kenneth J. Johnston  
                 George H. Kaplan 

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              International Astronomical Union
            International Earth Rotation Service
                   U.S. Naval Observatory

TOWARDS MODELS AND CONSTANTS FOR SUB-MICROARCSECOND ASTROMETRY
                     IAU Colloquium 180

                      27-31 March 2000
        U.S. Naval Observatory, Washington, DC, USA

             http://aa.usno.navy.mil/colloq180/
         or  http://mach.usno.navy.mil/colloq180/

           --> PAPER ABSTRACTS DUE BY 24 JAN <--

IAU Colloquium 180 has been organized to prepare a series of
important resolutions for consideration by a Joint Discussion at
the XXIV IAU General Assembly that will complete the
specification of the International Celestial Reference System
(ICRS).  These resolutions will, in effect, specify definitions,
standard algorithms, and parameters that link observable
quantities with reference coordinates within the ICRS.
Specifically to be recommended are definitions of the celestial
ephemeris pole and celestial ephemeris origin, an improved
precession/nutation theory, and a new set of standard values for
astronomical constants.  These resolutions will have far-reaching
effects on positional and dynamical astronomy.

The colloquium will also discuss future requirements of the
celestial reference system that are necessary to support present
and planned high-precision astrometric programs.

SCIENTIFIC ORGANIZING COMMITTEE:  Kenneth Johnston (chair),
Victor A. Brumberg, Nicole Capitaine, Veronique Dehant,
Toshio Fukushima, Wenjing Jin, Jean Kovalevsky, Dennis McCarthy,
Francois Mignard, Gerard Petit, P. Kenneth Seidelmann,
Michael Soffel, E. Myles Standish, Jan Vondrak.

LOCAL ORGANIZING COMMITTEE:  George Kaplan (chair),
F. Stephen Gauss, William E. Howard III, Brian Luzum, Chopo Ma,
Nancy Oliversen, Jane Russell, Lynn Treadway, Sean Urban.

PROCEEDINGS EDITORS:  Kenneth Johnston, Dennis McCarthy,
George Kaplan, Brian Luzum.

WEB SITE:  http://aa.usno.navy.mil/colloq180/     or
           http://mach.usno.navy.mil/colloq180/

The web sites (mirror sites - same content) contain details of
the scientific program, including invited and contributed papers,
accomodations, and local information.  On-line registration and
on-line submission of paper abstracts are provided.

IMPORTANT DEADLINES:

   24 Jan - Deadline for paper abstracts
   25 Feb - Deadline for reduced rate registration at $225
            ($275 after this date)
   11, 18, 26 Feb - Hotel room blocks released - rates and
            availability no longer guaranteed
   27 Mar - Colloquium begins
    1 May - Papers due for Proceedings

We look forward to seeing you at this important meeting.

                 Kenneth J. Johnston
                 Chair, IAU Colloquium 180
                 Scientific Organizing Committee
                 johnston.kenneth@usno.navy.mil

                 George H. Kaplan
                 Chair, IAU Colloquium 180
                 Local Organizing Committee
                 gkaplan@usno.navy.mil