  The inverse source problem for the radiative transfer equation is considered,
with partial data. Here we demonstrate numerical computation of the normal
operator $X_{V}^{*}X_{V}$ where $X_{V}$ is the partial data solution operator
to the radiative transfer equation. The numerical scheme is based in part on a
forward solver designed by F. Monard and G. Bal. We will see that one can
detect quite well the visible singularities of an internal optical source $f$
for generic anisotropic $k$ and $\sigma$, with or without noise added to the
accessible data $X_{V}f$. In particular, we use a truncated Neumann series to
estimate $X_{V}$ and $X_{V}^{*}$, which provides a good approximation of
$X_{V}^{*}X_{V}$ with an error of higher Sobolev regularity. This paper
provides a visual demonstration of the authors' previous work in recovering the
microlocally visible singularities of an unknown source from partial data. We
also give the theoretical analysis necessary to justify the smoothness of the
remainder when approximating the normal operator.
