Radiative transfer through spherically-symmetric atmospheres and shells

The application of an integral equation method to problems of radiative transfer through extended atmospheres and shells of spherical symmetry is discussed under the assumption that the opacities are known functions of radius. Expressions for the integral operators, obtained through the use of spline representations for the source function, are given for linearized non-grey LTE models, for multi-temperature dust shells, for picket fence-models, and for anisotropic scattering. Some results are described for a grey shell model and for a two-step picket-fence atmosphere. (orig.)