Salyut 4 was a Salyut space station launched on December 26, 1974 into an orbit with an apogee of 355 km, a perigee of 343 km and an orbital inclination of 51.6 degrees. It was essentially a copy of the DOS 3, and unlike its ill-fated sibling it was a complete success. Three crews attempted to make stays aboard Salyut 4. The second stay was for 63 days duration, and an unmanned capsule, called Soyuz 20, remained docked to the station for three months, proving the system's long-term durability despite some deterioration of the environmental system during Soyuz 18's mission. Salyut 4 was deorbited February 2, 1977, and re-entered the Earth's atmosphere on February 3.

Soyuz 17 was the first of two long-duration missions to the Soviet Union's Salyut 4 space station in 1975. The flight by cosmonauts Aleksei Gubarev and Georgy Grechko set a Soviet mission-duration record of 29 days, surpassing the 23-day record set by the ill-fated Soyuz 11 crew aboard Salyut 1 in 1971.