  We discuss the feasibility to realize a space cold atom clock with
counter-propagating cold atoms in microgravity. The design of the space clock
is based on atomic beam clock with a Ramsey cavity, except a magneto-optical
trap (MOT) is placed at each side. Cold atoms are launched from MOTs at both
side of the clock simultaneously and move at counter-direction towards each
other. The velocity of launched atoms is precisely controlled to the
Ramsauer-Townsend resonance so that no additional collision frequency shift is
taken place. Such a configuration can efficiently cancel the frequency shift
led from cavity phase shift and increase the signal to noise.
