Three Almaz OPS space stations were flown from 1973 to 1976 in the Salyut programme: Salyut 2 (OPS-1), Salyut 3 (OPS-2) and Salyut 5 (OPS-3).
The first Almaz station (OPS-1 or Almaz 101.1), announced as Salyut 2, it was launched on April 3, 1973.