Taking the opportunity of the Gaia reference star catalogue for observing the Solar system in the past D. Hestroffer , J.-E. Arlot , V. Lainey , V. Robert 1 1 1 1,2 1 - IMCCE ... Institut Polytechnique des Sciences AvancИes (IPSA), 7-9 rue Maurice Grandcoing, F-94200 Ivry-s/-Seine, France Abstract The Gaia astrometric catalogue of reference stars will provide proper motions of stars until mag 18 with an accuracy better than 6 mas over one century ...