  The launching of up to four astrometric missions in the next decade will
enable us to make measurements of stars in tidal streamers from Galactic
satellites of sufficient accuracy to place strong constraints on the mass
distribution in the Milky Way. In this paper we simulate observations of debris
populations in order to assess the required properties of any data set chosen
to implement this experiment. We apply our results to find the desired target
properties of stars (e.g., accuracy of velocity and proper motion measurements)
associated with the dwarf spheroidal satellites of the Milky Way.
