  Observations of clusters in the 30 to 350 GHz range can in principle be used
to determine a galaxy cluster's Comptonization parameter, y, peculiar velocity,
v and gas temperature, T_e via the dependence of the kinetic and thermal
Sunyaev-Zeldovich (SZ) effects on these parameters. Despite the significant
contamination expected from thermal emission by dust in high-redshift galaxies,
we find that the simultaneous determination of optical depth (tau), v and T_e
is possible from observations with sensitivity of a few uK in three or more
bands with arc minute resolution. After allowing for realistic levels of
contamination by dusty galaxies and primary CMB anisotropy, we find that
simultaneous determinations of velocities to an accuracy of better than 200
km/s and temperatures to roughly keV accuracy should be possible in the near
future. We study how errors change as a function of cluster properties (angular
core radius and gas temperature) and experimental parameters (observing time,
angular resolution and observing frequencies). Contaminating synchrotron
emission from cluster galaxies will probably not be a major contaminant of
peculiar velocity measurements.
