The densification of the Celestial Reference System : present status and perspectives with respect to the CFHT database and GAIA.
Jean Souchay, Sebastien Bouquillon,Francois Taris, Christophe Barache , (SYRTE, observatoire de Paris)

Abstract: The ICRF (International Celestial Reference Frame) which is the current realization of the ICRS (International Celestial Reference System) is based on the celestial coordinates of a set of quasars, considered as quasi-inertial objects. We show how the observational dataset from the CFHT through its three main survey programms could bring substantial high quality astrometric measurements in the aim of the densification of the ICRS, insisting on specific by-products as the link with the dynamical system, the detrmination of proper motions, the choice of extragalactic objects as quasi-inertial astrometric standards etc...