The Unified Clear-Sky Solar output Prediction Model is an open-source clear-sky prediction model, incorporating math algorithms based on latest research by the Environmental and Water Resources Institute of the American Society of Civil Engineers and a few veteran but still valid and publicly available NOAA/NASA computations. It has been around for a while but received a major revision, code refactoring and got bumped to primary project status, since it's becoming an essential tool in predicting Apollo-NG deployment location feasibility.
A long-term test setup collecting simulation and reference measurement data for the Odyssey (Command-Module) and Aquarius (Landing-Module) has been set up and will be published soon as well. The first results look quite promising - it's definitely on the right track to become a unified, reliable and open clear-sky global solar radiation prediction model. We are looking forward for you, to use, review, verify and enhance it as well.