Almaz

The Almaz (Russian: Алмаз, "Diamond") program was a highly secretive Soviet military space station program, begun in the early 1960s.

Three crewed military reconnaissance stations were launched between 1973 and 1976: Salyut 2, Salyut 3 and Salyut 5. To cover the military nature of the program the three launched Almaz stations were designated as civilian Salyut space stations. Salyut 2 failed shortly after achieving orbit, but Salyut 3 and Salyut 5 both conducted successful manned testing. Following Salyut 5, the Soviet Ministry of Defence judged in 1978 that the time consumed by station maintenance outweighed the benefits relative to automatic reconnaissance satellites.

The space stations cores were known internally as OPS (Russian: ОПС, GRAU index 11F71 and 11F71B), from "Orbital Piloted Station" (Russian: Орбитальная Пилотируемая Станция). As part of the Almaz program several spacecraft for supportive roles were developed: The VA spacecraft, the Functional Cargo Block and the TKS spacecraft, which were to be used in several combinations. The heritage of the Almaz program continues to this day with the ISS module Zarya being one example.

https://en.wikipedia.org/wiki/Almaz