We survey radiative Green function theory (1) in linear transport theory where numerical procedures are required to obtain
specific results and (2) in the photon diffusion limit (large optical depths) where it is analytically tractable, at least for
homogeneous plane-parallel media. We then describe two recent applications of Green function theory to passive cloud
remote sensing in the presence of strong three-dimensional transport effects. Finally, we describe recent instrumental
breakthroughs in “off-beam” cloud lidar which is based on direct measurements of radiative Green functions with special
attention to the data collected during the Shuttle-based Lidar In-space Technology Experiment (LITE) mission.