Penumbra detection

I have a simple question about Rugged :
I wonder if we can use Rugged to check if a spacecraft on ground (basically a rover) is on penumbra because of the elevation.

Yes, you can do this with Rugged if you need to take into account shadows cast by mountains in the Digital Terrain Modelling. We already used that in a project a few years ago. Basically, you consider a single line of sight is from Sun to rover and computes its intersection with terrain. If this intersection not close to the rover (you can use a threshold of a few meters), it means a moutain is between the rover and the Sun and blocks the line of sight.

If you only consider a smooth ellipsoid without terrain modelling, then Orekit would be sufficient for the computation.