Abstract

The interpretation of radiation emerging from planetary atmospheres relies on solutions to the radiative transfer equation (RTE). Monte Carlo integration of the RTE is a valuable approach for its flexible treatment of complex viewing and illumination geometries, and because it can intuitively incorporate polarization and other elaborate physics. I will present a novel Pre-conditioned Backward Monte Carlo (PBMC) algorithm for solving the vector RTE . As classical BMC methods, the PBMC algorithm builds the solution by simulating the photon trajectories from the detector towards the radiation source, i.e. in the reverse order of the actual photon displacements. Pre-conditioning of the scattering matrices introduces a sense of history in the photon polarization states through the simulated trajectories that prevents the numerical instabilities that potentially arise in strongly polarizing media. Since the convergence rate for MC integration is largely independent of the integral’s dimension, the algorithm is a valuable option for estimating the disk-integrated signal of thermal emission and reflected starlight from planets. Such a tool is relevant in the investigation of both exo- and solar system planet phase curves. Examples of ongoing work on the investigation of planet phase curves will be presented.