I decided to look up WATCH acronyms and came across this:

Wide Angle Telescope for Cosmic Hard (WATCH) x-rays instrument. It was used for experiments on a satellite called the European Retrievable Carrier (EURECA mission) from 1992-1993 that was launched by the Space Shuttle Atlantis and returned on SS Endeavor. The telescope had an extremely wide field of view, capable of observing ¼ of the sky. It was supposedly used to monitor x-ray sources, and was also flown a 2nd time on a Russian Granat mission. Pics are screenshots of the links included.

I don't know if this has already been dug, but I felt this might be relevant given an anon’s recent speculation that nukes were somehow hidden on satellites.

https://heasarc.gsfc.nasa.gov/docs/heasarc/missions/eureca.html

https://imagine.gsfc.nasa.gov/science/toolbox/missions/eureca.html