AAS 204th Meeting, June 2004
Session 28 The Reference System Resolutions of the IAU
Special Session, Monday, May 31, 2004, 2:00-3:30pm, 706

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[28.01] The IAU 2000 Recommendations on Reference Systems and their Application

N. Capitaine (Observatoire de Paris), D. D. McCarthy (U. S. Naval Observatory)

Resolutions adopted by the International Astronomical Union (IAU) in 2000 recommend significant improvements in the definition of the International Celestial Reference System and the procedures to be used in its realization. These recommendations correspond with the unprecedented observational accuracy that is now achievable in accessing the reference system, and deal with relativistic considerations, an improved precession-nutation formulation, and more rigorous definitions of the pole and equatorial origin of the reference system. The International Earth Rotation Service (IERS) has implemented these recommendations and maintains the necessary software and data files to allow the astronomical and geodetic communities to use them. It also continues to provide the data necessary to implement the previous definitions.

These recommendations are not only addressed to the specialized astronomical community that deals with the realization or maintenance of reference systems, time scales, celestial mechanics and high accuracy astrometry. They have consequences for the whole astronomical community as they relate to the IAU precession-nutation model, the definition of Universal Time and its relationship to sidereal time and the abandonment of the intermediary reference to the ecliptic and equinox.

At its 2003 General Assembly the IAU established working groups to finalize the implementation of the 2000 resolutions, namely (1) to standardize the associated new nomenclature and (2) to formulate a dynamical expression for precession consistent with the IAU 2000 precession-nutation formulation. This talk explains the reasons for these resolutions, describes their consequences for astronomers and provides the current status of their implementation. It also reports on the latest international discussions on nomenclature and educational efforts.

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