Yves Viala is a member of the scientific team at Observatoire de Paris (Department GEPI) involved in preparations for Gaia. Prior to joining the team in 2002 he was primarily concerned with studying aspects of the interstellar medium, in particular modelling the chemistry, thermodynamics and radiative transfer of molecular clouds.
As a core member of the Gaia Radial Velocity Spectrometer (RVS) Working Group Yves has developed a model to predict the telemetry budget expected for the Radial Velocity Spectrometer instrument. This model combines the Gaia Nominal Scanning Law and star counts from the GSC-II (v 2.2) catalogue, implemented at the CDS in Strasbourg, to predict the telemetric flow from the RVS and its variation with time all along the Gaia mission. The model was used to assess the impact of various parameters of the RVS instrument (resolution, CCD size and number, spectrum size, magnitude limit of observations, telemetry rate transmission, data storage capacity on board, etc.) on the RVS telemetry budget and the amount of scientific data that can be recovered.
Other topics of interest for Yves include the analysis of large star catalogues (for example, GSC-II v3, USNO, DENIS) and determination of star densities versus magnitude, coordinates, colour, etc. These can serve to refine telemetry budget predictions or to address other specific problems related to Gaia observations.
Yves is Chair of the Local Organising Committee for the Gaia Symposium "The Three-Dimensional Universe with Gaia".