  We have reprocessed over 100 terabytes of single-exposure WISE/NEOWISE images
to create the deepest ever full-sky maps at 3-5 microns. We incorporate all
publicly available W1 and W2 imaging - a total of ~8 million exposures in each
band - from ~37 months of observations spanning 2010 January to 2015 December.
Our coadds preserve the native WISE resolution and feature depth of coverage ~3
times greater than that of the AllWISE Atlas stacks. Our coadds are designed to
enable deep forced photometry, in particular for the Dark Energy Camera Legacy
Survey (DECaLS) and Mayall z-Band Legacy Survey (MzLS), both of which are being
used to select targets for the Dark Energy Spectroscopic Instrument (DESI). We
describe newly introduced processing steps aimed at leveraging added redundancy
to remove artifacts, with the intent of facilitating uniform target selection
and searches for rare/exotic objects (e.g. high-redshift quasars and distant
galaxy clusters). Forced photometry depths achieved with these coadds extend
0.56 (0.46) magnitudes deeper in W1 (W2) than is possible with only
pre-hibernation WISE imaging.
