Overview and stellar statistics of the expected Gaia Catalogue using the Gaia Object Generator

International audienceAims. An effort has been made to simulate the expected Gaia Catalogue, including the effect of observational errors. We statistically analyse this simulated Gaia data to better understand what can be obtained from the Gaia astrometric mission. This catalogue is used to investigate the potential yield in astrometric, photometric, and spectroscopic information and the extent and effect of observational errors on the true Gaia Catalogue. This article is a follow-up to previous work, where the expected Gaia Catalogue content was reviewed but without the simulation of observational errors. Methods. We analysed the Gaia Object Generator (GOG) catalogue using the Gaia Analysis Tool (GAT), thereby producing a number of statistics about the catalogue.Results. A simulated catalogue of one billion objects is presented, with detailed information on the 523 million individual single stars it contains. Detailed information is provided for the expected errors in parallax, position, proper motion, radial velocity, and the photometry in the four Gaia bands. Information is also given on the expected performance of physical parameter determination, including temperature, metallicity, and line-of-sight extinction