  A new generation of instruments will reveal the microwave sky at high
resolution. We focus on one of these, the Atacama Cosmology Telescope, which
probes scales 1000<l<10000, where both primary and secondary anisotropies are
important. Including lensing, thermal and kinetic Sunyaev-Zeldovich (SZ)
effects, and extragalactic point sources, we simulate the telescope's
observations of the CMB in three channels, then extract the power spectra of
these components in a multifrequency analysis. We present results for various
cases, differing in assumed knowledge of the contaminating point sources. We
find that both radio and infrared point sources are important, but can be
effectively eliminated from the power spectrum given three (or more) channels
and a good understanding of their frequency dependence. However, improper
treatment of the scatter in the point source frequency dependence relation may
introduce a large systematic bias. Even if all thermal SZ and point source
effects are eliminated, the kinetic SZ effect remains and corrupts measurements
of the primordial slope and amplitude on small scales. We discuss the
non-Gaussianity of the one-point probability distribution function as a way to
constrain the kinetic SZ effect, and we develop a method for distinguishing
this effect from the CMB in a window where they overlap. This method provides
an independent constraint on the variance of the CMB in that window and is
complementary to the power spectrum analysis.
