  Upcoming and current large astronomical survey experiments often seek to
constrain cosmological parameters via measurements of subtle effects such as
weak lensing, which can only be measured statistically. In these cases,
instrumental effects in the image plane CCDs need to be accounted and/or
corrected for in measurement algorithms. Otherwise, the systematic errors
induced in the measurements might overwhelm the size of the desired effects.
Lateral electric fields in the bulk of the CCDs caused by field shaping
potentials or space charge build up as the electrons in the image are acquired
can cause lateral deflections of the electrons drifting in the CCD bulk. Here,
I report on the LSST effort to model these effects on a photon-by-photon basis
by the use of a Monte Carlo technique. The eventual goal of this work is to
produce a CCD model validated by laboratory data which can then be used to
evaluate its effects on weak lensing science.
