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International Space Station

The International Space Station (ISS) combines NASA's Space Station Freedom project with the Soviet/Russian Mir-2 station, the European Columbus station, and the Japanese Kibo laboratory module. NASA originally planned in the 1980s to develop Freedom alone, but US budget constraints led to the merger of these projects into a single multi-national program in 1993, managed by NASA, the Russian Federal Space Agency (RKA), the Japan Aerospace Exploration Agency (JAXA), the European Space Agency (ESA), and the Canadian Space Agency (CSA). The station consists of pressurized modules, external trusses, solar arrays and other components, which have been launched by Russian Proton and Soyuz rockets, and the US Space Shuttles. It is currently being assembled in Low Earth Orbit. The on-orbit assembly began in 1998, the completion of the US Orbital Segment occurred in 2011 and the completion of the Russian Orbital Segment is expected by 2016. The ownership and use of the space station is established in intergovernmental treaties and agreements which divide the station into two areas and allow Russia to retain full ownership of the Russian Orbital Segment (with the exception of Zarya), with the US Orbital Segment allocated between the other international partners.
Long duration missions to the ISS are referred to as ISS Expeditions. Expedition crew members typically spend approximately six months on the ISS. The initial expedition crew size was three, temporarily decreased to two following the Columbia disaster. Since May 2009, expedition crew size has been six crew members. Crew size is expected to be increased to seven, the number the ISS was designed for, once the Commercial Crew Program becomes operational. The ISS has been continuously occupied for the past 18 years and 131 days, having exceeded the previous record held by Mir; and has been visited by astronauts and cosmonauts from 15 different nations.
The station can be seen from the Earth with the naked eye and, as of 2019, is the largest artificial satellite in Earth orbit with a mass and volume greater than that of any previous space station. The Soyuz spacecraft delivers crew members, stays docked for their half-year-long missions and then returns them home. Several uncrewed cargo spacecraft service the ISS, they are the Russian Progress spacecraft which has done so since 2000, the European Automated Transfer Vehicle (ATV) since 2008, the Japanese H-II Transfer Vehicle (HTV) since 2009, the American Dragon spacecraft since 2012, and the American Cygnus spacecraft since 2013. The Space Shuttle, before its retirement, was also used for cargo transfer and would often switch out expedition crew members, although it did not have the capability to remain docked for the duration of their stay. Until another US manned spacecraft is ready, crew members will travel to and from the International Space Station exclusively aboard the Soyuz. The highest number of people occupying the ISS has been thirteen; this occurred three times during the late Shuttle ISS assembly missions.
The ISS program is expected to continue until at least 2020, and may be extended beyond 2028. On March 29, 2019 the ISS will have its first all-female spacewalk; Anne McClain and Christina Koch will take flight during Women's History Month.