  I present an exact and explicit solution to the scalar (Stokes flux
intensity) radio interferometer imaging equation on a spherical surface which
is valid also for non-coplanar interferometer configurations. This imaging
equation is comparable to $w$-term imaging algorithms, but by using a spherical
rather than a Cartesian formulation this term has no special significance. The
solution presented also allows direct identification of the scalar (spin 0
weighted) spherical harmonics on the sky. The method should be of interest for
future multi-spacecraft interferometers, wide-field imaging with non-coplanar
arrays, and CMB spherical harmonic measurements using interferometers.
