A space station (or orbital station) is a spacecraft which remains in orbit and hosts humans for extended periods of time. It is therefore an artificial satellite featuring habitation facilities. The purpose of maintaining a space station varies depending on the program. Most often space stations have been research stations, but they have also served military or commercial uses, such as hosting space tourists.
Space stations have been hosting the only continuous presence of humans in space. The first space station was Salyut 1 (1971), hosting the first crew, of the ill-fated Soyuz 11. Consecutively space stations have been operated since Skylab (1973) and occupied since 1987 with the Salyut successor Mir. Uninterrupted human presence in orbital space through space stations has been sustained since the operational transition from the Mir to the International Space Station (ISS), with the latter's first occupation in 2000.