Binary asteroids are key objects to understanding the intimate internal nature of asteroids as for them, it is possible to compute the total mass and the bulk density. The formation itself of asteroid satellites can be the result of collisions, fission and rotational spin up, whose issue depends on the internal structure. However, the currently known sample of binaries is heavily biased by the currently available techniques, ad a whole range of possible separation / sizes has remained inaccessible up to now. In GaiaMoons we will exploit the ultra-accurate astrometry of forthcoming data releases by the Gaia mission, to discover a large number of Main Belt binaries belonging to this unknown population, and to better characterise the known ones. The new approach consists in measuring the astrometric perturbation induced by the presence of a satellite. With the additional information provided by photometry and Gaia spectroscopy, we will determine their physical properties (mass, density), the orbital parameters of the companion, and the composition. In turn, composition and density will allow us to constraint the asteroid internal porosity, thus discriminating between the compact or fragmented internal structure inherited from the evolution history. We also exploit data obtained so far by stellar occultations, and observe new events to obtain an independent validation of our discoveries. Our project is based on a collaboration between experts of Gaia at the Observatoire de la Côte d'Azur, specialists in occultation techniques at Observatoire de Paris and in photometry at the University of Poznan.