The International Space Station
 (ISS) is an internationally developed research facility, which is being
 assembled in low Earth orbit. On-orbit construction of the station 
began in 1998 and is scheduled for completion by 2011. The station will 
remain in operation until at least 2015. With a greater mass than that 
of any previous space station, the ISS can be seen from the Earth with 
the naked eye, and, as of 2010[update], is the largest artificial 
satellite orbiting the Earth. The ISS serves as a research laboratory 
that has a microgravity environment in which crews conduct experiments 
in biology, human biology, physics, astronomy and meteorology. The
 station has a unique environment for the testing of the spacecraft 
systems that will be required for missions to the Moon and Mars. The ISS
 is operated by Expedition crews, and has been continuously staffed 
since 2 November 2000—an uninterrupted human presence in space for the 
past 9 years and 75 days. As of 1 December 2009, the crew of Expedition 
22 is aboard.
The
 ISS is a synthesis of several space station projects that includes the 
American Freedom, the Soviet/Russian Mir-2, the European Columbus and 
the Japanese Kibō. Budget constraints led to the merger of these 
projects into a single multi-national programme. 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 continues, as 
pressurised modules, external trusses and other components are launched 
by American space shuttles, Russian Proton rockets and Russian Soyuz 
rockets. As of November 2009[update], the station consisted of 11 
pressurised modules and an extensive integrated truss structure (ITS). 
Power is provided by 16 solar arrays mounted on the external truss, in 
addition to four smaller arrays on the 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 km (17,227 mi) per 
hour, completing 15.7 orbits per day.
Operated
 as a joint project between the five participant space agencies, the 
station's sections are controlled by mission control centres on the 
ground operated by 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). The ownership and use of the space 
station is established in intergovernmental treaties and agreements that
 allow the Russian Federation to retain full ownership of its own 
modules, with the remainder of the station allocated between the other 
international partners. The station is serviced by Soyuz spacecraft, 
Progress spacecraft, space shuttles, the Automated Transfer Vehicle and 
the H-II Transfer Vehicle, and has been visited by astronauts and 
cosmonauts from 15 different nations. The cost of the station has been 
estimated by ESA as €100 billion over 30 years, and, although estimates 
range from 35 billion dollars to 160 billion dollars, the ISS is believed to be the most expensive object ever constructed. The financing, research capabilities and technical design of the ISS programme have been criticised because of the high cost.




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