Towards a new set of radial velocity standards for Gaia

The ESA GAIA mission (launch expected end 2011) will measure positions, proper motions, parallaxes and magnitudes in various spectral bands for about 10^9 objects, and produce radial velocities and spectra for about 10^8 objects. Although Gaia is usually labelled as a self-calibrating instrument, some external calibrations are mandatory, especially for radial velocities and photometry. A coordinated plan of ground-based observations is being organised in support of Gaia to obtain the necessary auxiliary data. In particular, the calibration of the wavelength scale and zero-point of the radial velocities will rely on asteroids and on a set of about one thousand reference stars. Such stars must be selected from larger existing lists with drastic criteria and qualified as radial velocity standards from ground based observations. This poster describes the selection of stars, the observing programme on various telescopes, and the first results obtained with the ELODIE and SOPHIE spectrographs