I'm looking for a solar geometry library built for a cubesat in LEO. In my research so far, I've discovered the MINES Paris-Tech Solar Geometry 2 library (http://www.oie.mines-paristech.fr/Valorisation/Outils/Solar-Geometry/) which is a does something like what I need, but it only applies to earth-based observatories.
Instead, I'm looking to provide coordinates (ECI, Geodetic, or something similar) and time stamp as the input. For output, I'm looking to generate a vector that describes the orientation of the satellite relative to the sun given that position, and will calculate if we are in an eclipse or not using that data.
Does something similar exist for LEO (roughly 450km)? Ideally it would be in C but anything similar is certainly usable.