US-A

Launched between 1967 and 1988 to monitor NATO and merchant vessels using radar, the satellites were powered by nuclear reactors.

Had they used large solar panels for power, the orbit would have rapidly decayed due to drag through the upper atmosphere.

The US-A programme was responsible for orbiting a total of 33 nuclear reactors, 31 of them BES-5 types with a capacity of providing about two kilowatts of power for the radar unit.

US-A satellites were a major source of space debris in low Earth orbit.

The debris is created two ways: There were 38 Rorsat satellite launches from Baikonur, all with reported mass of 3,800 kg.