  We present a self-contained analysis of the stationary radiative transfer
equation in weighted $L^p$ spaces. The use of weighted spaces allows us to
derive uniform a-priori estimates for $1 \le p \le \infty$ under minimal
assumptions on the parameters. By constructing an explicit example, we show
that our estimates are sharp and cannot be improved in general. Better
estimates are however derived under additional assumptions on the parameters.
We also present estimates for derivatives and traces of the solution and
formulate a natural energy space, for which the data-to-solution map becomes an
isomorphism. As a side result, we are able to prove uniform convergence of the
source iteration for all $1 \le p \le \infty$ without the assumption of
positive absorption that is frequently used in the literature.
