Sun heats, and the lunar sun is unrelenting. Electronics also heat, and the laws of thermodynamics are unrelenting. Radiators are essential to dump heat and regulate a moderate operating temperature. Early Astrobotic rovers had solar arrays on all sides, which gathered too much heat, but did not provide enough radiator surface for cooling. The current rover design is asymmetric. One end is solar, and the other is shade. Here is how thermal regulation and solar power work on the asymmetric rover.