Mapping the substructure in the Galactic halo with the next generation of astrometric satellites

We run numerical simulations of the disruption of satellite galaxies in a G alactic potential to build up the entire stellar halo, in order to investig ate what the next generation of astrometric satellites will reveal by obser ving the halo of the Milky Way. We generate artificial DIVA, FAME and GAIA halo catalogues, in which we look for the signatures left by the accreted s atellites. We develop a method based on the standard Friends-of-Friends alg orithm applied to the space of integrals of motion. We find this simple met hod can recover about 50 per cent of the different accretion events, when t he observational uncertainties expected for GAIA are taken into account, ev en when the exact form of the Galactic potential is unknown. The recovery r ate for DIVA and FAME is much smaller, but these missions, like GAIA, shoul d be able to test the hierarchical formation paradigm on our Galaxy by meas uring the amount of halo substructure in the form of nearby kinematically c old streams with, for example, a two-point correlation function in velocity space.