  We describe the complete cohomology of the Berkovits BRST operator for the
superparticle. It is non-zero at eight ghost numbers, splitting into two
quartets, the members of each quartet being completely isomorphic. Based only
on considerations of the isomorphisms of the cohomology, and using only the
standard inner product, we derive the inner product appropriate for string
amplitudes. It is in agreement with Berkovits' conjectured prescription, which
is one element of an equivalence class. We discuss the Chern-Simons style
action for D=10 super Yang-Mills, which is now manifestly superspace covariant.
