  We investigate the performance of the upcoming ACES (Atomic Clock Ensemble in
Space) space mission in terms of its primary scientific objective, the test of
the gravitational redshift. Whilst the ultimate performance of that test is
determined by the systematic uncertainty of the on-board clock at 2-3 ppm, we
determine whether, and under which conditions, that limit can be reached in the
presence of colored realistic noise, data gaps and orbit determination
uncertainties. To do so we have developed several methods and software tools to
simulate and analyse ACES data. Using those we find that the target uncertainty
of 2-3 ppm can be reached after only a few measurement sessions of 10-20 days
each, with a relatively modest requirement on orbit determination of around 300
m.
