EDP Sciences
Free Access
Volume 400, Number 3, March IV 2003
Page(s) 1145 - 1154
Section The solar system
DOI https://doi.org/10.1051/0004-6361:20030077

A&A 400, 1145-1154 (2003)
DOI: 10.1051/0004-6361:20030077

Expressions for the Celestial Intermediate Pole and Celestial Ephemeris Origin consistent with the IAU 2000A precession-nutation model

N. Capitaine1, J. Chapront1, S. Lambert1 and P. T. Wallace2

1  Observatoire de Paris, SYRTE/UMR8630-CNRS, 61 avenue de l'Observatoire, 75014 Paris, France
2  H.M. Nautical Almanac Office, Space Science and Technology Department, CLRC / Rutherford Appleton Laboratory, UK

(Received 18 July 2002 / Accepted 9 January 2003)

Expressions for the position of the Celestial Intermediate Pole (CIP) and the Celestial Ephemeris Origin (CEO) in the Geocentric Celestial Reference System (GCRS) have been computed using the IAU 2000A precession-nutation. These expressions are for use in the new transformation between the GCRS and the International Terrestrial Reference System (ITRS) which is recommended by IAU Resolution B1.8. Various comparisons and numerical checks have been performed between the classical and the new transformations based on the IAU 2000A precession-nutation. These comparisons revealed necessary improvements to be applied to the classical form of the transformation in order to achieve the required level of accuracy. Once these improvements are applied, the consistency between the positions of the CIP in the GCRS corresponding to the classical and the new transformations is at a level of a few microarcseconds after one century. This work has demonstrated that the new method, in addition to providing an explicit separation between precession-nutation of the equator from Earth rotation, is more simple, compact and direct than the classical one, achieving accuracies at the level of a few microarcseconds with greatly reduced scope for accidental misuse. The resulting expressions for X, Y and s have been included in the IERS Conventions 2000. References for the numerical expressions are provided in Appendix C.

Key words: astrometry -- reference systems -- ephemerides -- time

Offprint request: N. Capitaine, capitaine@syrte.obspm.fr

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