  We describe a new image co-addition tool, AWAIC, to support the creation of a
digital Image Atlas from the multiple frame exposures acquired with the
Wide-field Infrared Survey Explorer (WISE). AWAIC includes preparatory steps
such as frame background matching and outlier detection using robust
frame-stack statistics. Frame co-addition is based on using the detector's
Point Response Function (PRF) as an interpolation kernel. This kernel reduces
the impact of prior-masked pixels; enables the creation of an optimal matched
filtered product for point source detection; and most important, it allows for
resolution enhancement (HiRes) to yield a model of the sky that is consistent
with the observations to within measurement error. The HiRes functionality
allows for non-isoplanatic PRFs, prior noise-variance weighting, uncertainty
estimation, and includes a ringing-suppression algorithm. AWAIC also supports
the popular overlap-area weighted interpolation method, and is generic enough
for use on any astronomical image data that supports the FITS and WCS
standards.
