Résumé
The Gaia-RVS will measure some 10^8 stellar radial velocities using the correlation method with well-adapted template spectra for each individual case. Ground-based RV standards will be used to fix the zero-point. Gaia instruments are ``self-calibrating'' and no calibration device is available on board. But for the beginning of the mission, until the needed calibration parameters become available, the calibrations have to come from external sources, i.e. existing ground-based observations of already very well-known objects. Therefore beside the basic list of 1400 very stable and well-measured primary standards, several secondary RV lists have been built recently. The basic list itself will be extended with around 500 new "primary standard". The libraries of existing spectra have been carefully investigated: a lot of high-quality material is available for the start of the reductions and for the validation of the pipeline results. In addition, as the data expected from the photometric instrument are not available at the beginning, very large lists with atmospheric parameters (Teff, log g, metallicity) have been produced from the literature. Grids of 3D atmospheric models have been calculated, in order to select the best template for the correlation; they will be used in the future and will automatically take into account the stellar convective shift across the HR diagram.