Salyut 6

Salyut 6 (Russian: Салют-6; lit. Salute 6), DOS-5, was a Soviet orbital space station, the eighth flown as part of the Salyut programme. Launched on 29 September 1977 by a Proton rocket, the station was the first of the “second-generation” type of space station. Salyut 6 possessed several revolutionary advances over the earlier Soviet space stations, which it nevertheless resembled in overall design. These included the addition of a second docking port, a new main propulsion system and the station’s primary scientific instrument, the BST-1M multispectral telescope. The addition of the second docking port made crew handovers and station resupply by unmanned Progress freighters possible for the first time. The early Salyut stations had no means of resupply or removing accumulated garbage (aside from the limited amount that cosmonauts could carry in their Soyuz spacecraft), nor could the propulsion system be refueled once it exhausted its propellant supply. Consequently, once the consumables launched with the station were used up, its mission had to be concluded, and as a result, manned missions had a maximal duration of three months. Progress spacecraft could now bring fresh supplies and propellant and also be used to dispose of waste, which was then destroyed once the spacecraft was deorbited.

Five crew residencies took place over the station’s lifespan, in late 1977–early 1978, late 1978, mid-1979, mid-1980, and early 1981, including cosmonauts from Warsaw Pact countries as part of the Intercosmos programme. These crews were responsible for carrying out the primary missions of Salyut 6, including astronomy, Earth-resources observations and the study of the effect of spaceflight on the human body. Following the completion of these missions and the launch of its successor, Salyut 7, Salyut 6 was deorbited on 29 July 1982, almost five years after its launch.

~wikipedia