Analysis and comparison of precise long-term nutation series, strictly determined with OCCAM 6.1 VLBI softwareReport as inadecuate

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1 L3AB - Laboratoire d-astrodynamique, d-astrophysique et d-aéronomie de bordeaux 2 OASU - Observatoire aquitain des sciences de l-univers 3 IGG - Institute of Geodesy and Geophysics 4 LAB - Laboratoire d-Astrophysique de Bordeaux Pessac 5 Université Sciences et Technologies - Bordeaux 1

Abstract : The IAU-IUGG Working Group on -Nutation for a non-rigid Earth-, led by Véronique Dehant, won the European Descartes Prize in 2003, for its work developing a new model for the precession and the nutations of the Earth. This model MHB2000, Mathews et al. 2002 was adopted by the IAU International Astronomical Union during the General Assembly in Manchester, in 2000. It is based i on some improvements for the precession model with respect to the previous one of Lieske et al. 1977 owing to the VLBI technique, and ii on a very accurate nutation model, close to the observations. With this prize, the Descartes nutation project could offer for international scientists some grants, to be used for further improvements of the precession-nutation Earth model. At the IGG Institute of Geodesy and Geophysics, with the OCCAM 6.1 VLBI analysis software and the best data and models available, we re-analyzed the whole VLBI sessions available from 1985 till 2005 solving for the Earth Orientation Parameters EOP. In this paper we present the results obtained for the EOP and more particularly for the nutation series. We compare them with the other IVS analysis centers results, as well as with the IVS combined EOP series from the analysis coordinator. The series are in good agreement, except for the polar motion coordinates that show a shift with respect to the other ones and that we discuss here. Finally, we analyse the nutation series in the framework of the free core nutation FCN study and modelisation.

Author: G. Bourda - J. Boehm - R. Heinkelmann - H. Schuh -



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