SALYUT 4

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 uncrewed 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.