  We have undertaken a Near-IR Weak Lensing (NIRWL) analysis of the wide-field
CANDELS HST/WFC3-IR F160W observations. With the Gaia proper-motion-corrected
catalog as an astrometric reference, we updated the astrometry of the five
CANDELS mosaics and achieved an absolute alignment within $0.02\pm0.02$ arcsec
on average, which is a factor of several superior to existing mosaics. These
mosaics are available to download. We investigated the systematic effects that
need to be corrected for weak-lensing measurements. We find the largest
contributing systematic effect is caused by undersampling. Using stars as a
probe of the point-spread function (PSF), we find a sub-pixel centroid
dependence on the PSF shape that induces a change in the PSF ellipticity and
size by up to 0.02 and $3\%$, respectively. We find that the brighter-fatter
effect causes a $2\%$ increase in the size of the PSF and discover a
brighter-rounder effect that changes the ellipticity by 0.006. Based on the
narrow bandpasses of the WFC3-IR filters and the small range of slopes in a
galaxy's spectral energy distribution (SED) within the bandpasses, we suggest
that the impact of galaxy SED on PSF is minor in the NIR. Finally, we modeled
the PSF of WFC3-IR F160W for weak lensing using a principal component analysis.
The PSF models account for temporal and spatial variations of the PSF. The PSF
corrections result in residual ellipticities and sizes, $|de_1| <
0.0005\pm0.0003$, $|de_2| < 0.0005\pm0.0003$, and $|dR| < 0.0005\pm0.0001$,
that are sufficient for the upcoming NIRWL search for massive overdensities in
the five CANDELS fields. NIRWL Mosaics:
https://archive.stsci.edu/hlsp/candelsnirwl
