The Journées 2007 "Systèmes de référence spatio-temporels", with the sub-title "The Celestial Reference Frame for the Future", will be held from 17 to 19 September 2007 at Paris Observatory, Meudon section, Meudon, France.

These Journées will be focused on the issues related to the recent developments, perspectives of future realizations and scientific applications of the celestial reference frame.

There will be presentations and discussions related to the new Division 1 Commission 52 "Relativity in Fundamental astronomy", IAU Working Groups on "Numerical standards in Fundamental astronomy" and "The second realization of the ICRF" that have been established at the 26th IAU GA, and the IERS Working Groups on "The second realization of the ICRF" (joint IERS/IVS WG) and "Prediction".

The recent evolution in the concepts, terminology, models and results in fundamental astronomy will be discussed, as well as topics related to the geophysical excitation of Earth rotation.

There will be a special session dedicated to nutation in relation both with the "Descartes nutation" project and the 30-year anniversary of the IAU Colloquium No 78 on "Nutation and the Earth's rotation" that was organized in Kiev in 1977.

In addition, a session will be devoted to various aspects relative to prediction of the Earth Orientation