  There are a handful of spectral windows in the near-IR through which we can
see down to Venus' surface on the night side of the planet. The surface of our
sister planet has thus been imaged by sensors on Venus-orbiting platforms
(Venus Express, Akatsuki) and during fly-by with missions to other planets
(Galileo, Cassini). The most tantalizing finding, so far, is the hint of
possible active volcanism. However, the thermal radiation emitted by the
searing (c. 475 degrees C) surface of Venus has to get through the opaque
clouds between 50 and 70 km altitude, as well as the sub-cloud atmosphere. In
the clouds, the light is not absorbed but scattered, many times. This results
in blurring the surface imagery to the point where the smallest discernible
feature is roughly 100 km in size, full-width half-max (FWHM), and this has
been explained using numerical models. We describe a new analytical modeling
framework for predicting the width of the atmospheric point-spread function
(APSF), which is what determines the effective resolution of surface imaging
from space. Our best estimates of the APSF width for the 1-to-1.2 micron
spectral range are clustered around 130 km FWHM. Interestingly, this is
somewhat larger than the accepted value of about 100 km, which is based on
visual image inspection and numerical simulations.
