The complete set of LLR observations now covers a time interval longer than 30 years. During the last ten years the precision in the measurements has been improved noticeably. Presently an individual measurement shows at CERGA an error around 30-60 ps in time, which corresponds to 5 to 10 mm in the one-way distance (Chapront & Mignard 2000). Hence the quality in the determination of several parameters of the Earth-Moon system has been improved correspondingly. This is the case in particular for the precession constant and the secular acceleration in the Moon's longitude. Increasing the precision and the length of the observing time, the models have to be refined. As mentioned above, small trends in the obliquity and bias in the mean motions of the Sun and Moon have not been completely eliminated from our analysis and that should be improved in the near future.
Acknowledgements
The authors are grateful to the LLR staff at CERGA and McDONALD for providing the observations used. They thank D. D. McCarthy for helpful comments on the manuscript.
Copyright ESO 2002