US-PM (Upravlenniye Sputnik Passivny Modifikirovanny) (also reported as US-PU) was a solar powered improved EORSAT (Electronic Ocean Reconnaissance Satellite). It used an passive ELINT devices to track naval vessels from space by registering their electronic emmissions.
US-PM was a modified version of the US-P and replaced both the US-P and the nuclear US-A satellites.
It shared the same US bus with its precedessors, which provided maneuvering capabilities to the spacecraft.
The satellites were built by the KB Arsenal design bureau in Leningrad/St.-Petersburg, and the payloads by the Central Scientific Radiotechnical Research Institute or TsNIRTI in Moscow.
The US-PM were placed into a 420 km orbits inclined 65 degrees by the Tsiklon-2 booster. Systems aboard the 3300 kg satellite included the Radio-Technical Reconnaissance system and systems for electronic camouflage and self-protection. An engine unit maintained the orbital altitude and made a final deorbit of the satellite at the end of the mission.
It has been reported, that Kosmos 2421 failed to open one of its eight solar panel segments after launch.
[Important] controls: AG.1 is the solar panels, AG.2 is self explanitory, slider 2 is for ALL of the camera’s zoom, slider 3 & 4 extend the parabolic antennas i think.
https://www.russianspaceweb.com/us.html
https://space.skyrocket.de/doc_sdat/us-pm.htm