Re: Question
I'm actually involved with this project (on the science rather than hardware side). It's actually quite hard to keep cool in space due to the lack of air and convection. One side of the telescope will always be heated by the sun and the detector electronics produce heat. One of the big efforts of design for eROSITA was the heat pipe system which cools the cameras passively (search for a PhD thesis if you're interested). There are radiators on the side of the telescope away from the sun to radiate the heat into space. The CCD cameras are kept cool to prevent degradation by high energy particles.