Any large structure designed for human occupation in space for extended periods of time. Space stations are used for carrying out astronomical observations and surveys of Earth, as well as for biological studies and the processing of materials in weightlessness. The first space station was the Soviet Salyut 1, launched in 1971. In 1973, NASA launched Skylab. The core of the Soviet space station Mir was launched in 1986. In 1998, the first component of the International Space Station, being constructed by the USA, Russia, and 14 other nations, was launched. The first crew arrived at ISS in November 2000. In September 2011, China launched its first space station, Tiangong 1, which was first crewed in June 2012 and is expected to re-enter Earth’s atmosphere in early 2018; China launched its second space station, Tiangong 2, in September 2016, and was crewed the next month.