The International Space Station (ISS) is an internationally developed research facility currently being assembled in Low Earth Orbit. On-orbit construction of the station began in 1998 and is scheduled to be completed by 2011, with operations continuing until at least 2015. The station can be seen from the Earth with the naked eye, and, as of 2009, is the largest artificial satellite in Earth orbit, with a mass larger than that of any previous space station. The ISS serves as a long-term research laboratory in space, with experiments in fields including biology, human biology, physics, astronomy and meteorology being carried out daily in the station's microgravity environment. The station also provides a safe testing location for efficient, reliable spacecraft systems that will be required for long-duration missions to the Moon and Mars. The ISS and its experiments are operated by long-duration Expedition crews, with the station being continuously staffed since the first resident crew, Expedition 1, arrived on 2 November 2000. This has provided an uninterrupted human presence in space for the last 9 years and 53 days. As of 1 December 2009), the crew of Expedition 22 is aboard.

The ISS represents a synthesis of several space station projects including the American Freedom, the Soviet/Russian Mir-2, the European Columbus and the Japanese Kibō. Budget issues led to the separate projects being merged into a single multi-national space station. The ISS project began in 1994 with the Shuttle-Mir programme, and the first module of the station, Zarya, was launched in 1998 by Russia. Assembly has been ongoing, with a complex of pressurised modules, external trusses and other components being launched by American Space Shuttles, Russian Proton rockets and Russian Soyuz rockets. As of November 2009, the station consists of eleven pressurised modules and an extensive Integrated Truss Structure (ITS). Power is provided by sixteen large solar arrays mounted on the external truss, in addition to four smaller arrays on Russian modules. The station is maintained at an orbit between 278 km (173 mi) and 460 km (286 mi) altitude, and travels at an average speed of 27,724 kilometres (17,227 mi) per hour, completing 15.7 orbits per day.

The ISS is operated as a joint project between the American National Aeronautics and Space Administration (NASA), the Russian Federal Space Agency (RKA), the Japan Aerospace Exploration Agency (JAXA), the Canadian Space Agency (CSA), and the European Space Agency (ESA). Ownership and utilisation of the space station is set out via several intergovernmental treaties and agreements, with the Russian Federation retaining full ownership of its own modules, and the rest of the station being allocated between the other international partners. The cost of the station project has been estimated by ESA as €100 billion over a course of 30 years, although cost estimates vary between 35 billion dollars and 160 billion dollars, making the ISS the most expensive object ever constructed. This large cost has meant that the ISS programme has been the target of various criticisms over its financing, research capabilities and technical design.

The various sections of the station are controlled by several mission control centres on the ground, including MCC-H, TsUP, Col-CC, ATV-CC, JEM-CC, HTV-CC and MSS-CC. The station is serviced by a wide variety of manned and unmanned spacecraft, including the Soyuz spacecraft, Progress spacecraft, Space Shuttle, Automated Transfer Vehicle, and H-II Transfer Vehicle, and has been visited by astronauts and cosmonauts from 15 different nations.

See also:

• Science: Technology: Space: Missions: Manned: Russian: Mir Space Station (30)

• The European Robotic Arm
  esa.int
  Provides project overview and data on the walking robot planned to service the Russian segment.
• Cupola
  esa.int
  Provides design and project overview of the main observation post on the station.
• Human Spaceflight
  human-spaceflight.co.uk
  Dedicated to humans in space and the continuing construction of the International Space Station. Includes information on space shuttle missions.