A space station is a manned artificial satellite designed to stay in low Earth orbit for a long time. In general, space stations can dock with other spacecraft. This allows transferring cargo and people. Today, the International Space Station is the only manned space station in orbit. Salyut, Skylab, Mir and Tiangong were the previous space stations.
Space stations are used to study the effects of long-term space flight on the human body. They also serve as a platform for extended scientific studies. All space stations have been designed with the intention of rotating multiple crews, with each crew member staying aboard the station for weeks or months, but rarely more than a year. As of today, Vladimir Titov, Musa Manarov, Sergei Avdeyev and Valeriy Polyakov have completed single missions of over a year, all aboard Mir.