The International Space Station completed

 
 
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.[6] The station can be seen from the Earth with the naked eye,[7] and, as of 2009[update], is the largest artificial satellite in Earth orbit, with a mass larger than that of any previous space station.[8] 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.[9][10][11] 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.[12] 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 &0000000000000009.0000009 years and &0000000000000035.00000035 days.[13] As of 1 December 2009 (2009 -12-01)[update], the crew of Expedition 22 is aboard.[14]
The station represents a union of several space station projects including the American Space Station Freedom, the Soviet/Russian Mir-2, the European Columbus and the Japanese Kibō.[15][16] Budget issues with each station, however, led to the separate projects being merged into a single multi-national space station.[15] The ISS project began in 1994 with the Shuttle-Mir programme,[17] and the first module of the station, Zarya, was launched in 1998 by Russia.[15] Assembly has been ongoing ever since, with a complex of pressurised modules, external trusses and other components being launched by American Space Shuttles, Russian Proton rockets and Russian Soyuz rockets.[16] As of November 2009[update], 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.[18] 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.[19]
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).[20] Ownership and utilisation of the space station is set out via several intergovernmental treaties and agreements,[21] with the Russian Federation retaining full ownership of its own modules,[22] and the rest of the station being allocated between the other international partners.[21] The cost of the station project has been estimated by ESA as €100 billion over a course of 30 years,[23] although cost estimates vary between 35 billion dollars and 160 billion dollars, making the ISS the most expensive object ever constructed.[24] This large cost has meant that the ISS programme has been the target of various criticisms over its financing, research capabilities and technical design.[25]
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.[26] 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,[26] and has been visited by astronauts and cosmonauts from 15 different nations
 
 Purpose

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The International Space Station serves primarily as a research laboratory, offering an advantage over spacecraft such as NASA's Space Shuttle because it is a long-term platform in the space environment, allowing long-duration studies to be performed, both on specific experiments and on the human crews that operate them.[8][27] The presence of a permanent crew means that the station offers benefits over unmanned spacecraft as experiments can be monitored, replenished, repaired or replaced as required by the crew, as can other components of the spacecraft itself. Scientists on the ground have swift access to their data and can modify experiments or launch new ones as and when required; benefits generally unavailable on specialised unmanned spacecraft.[27]
Crews flying long-term expeditions lasting several months, conduct scientific experiments each day (approximately 160 man-hours a week)[28] across many fields, including human research (space medicine), life sciences, physical sciences and Earth observation.[9] As of the conclusion of Expedition 15, 138 major science investigations had been conducted on the ISS since the launch of Zarya in 1998.[29] Scientific findings, in fields ranging from basic science to exploration research, are being published every month.[12]
The ISS provides a testing location for efficient, reliable spacecraft systems that will be required for long-duration missions to the Moon and Mars, allowing for equipment to be evaluated in the relatively safe location of Low Earth Orbit. This provides experience in maintaining, repairing, and replacing systems on-orbit, which will be essential in operating spacecraft further from Earth. This aspect of ISS operations reduces mission risks, and advances the capabilities of interplanetary spacecraft.[12]
Part of the crew's mission is educational outreach and international cooperation. The crews of the ISS provide educational opportunities for students back home on Earth, including student-developed experiments, educational demonstrations, student participation in classroom versions of ISS experiments, NASA investigator experiments, and ISS engineering activities. The ISS programme itself, and the international cooperation that it represents, allows 14 nations to live and work together in space, providing important lessons that can be taken forward into future multi-national missions.[30]
 Scientific research

A comparison between fire on Earth (left) and fire in a microgravity environment (right), such as that found on the ISS.

A main goal of the ISS is to provide a place to conduct experiments that require one or more of the unusual conditions present on the station. The primary fields of research include biology, physics, astronomy, and meteorology.[10][11] The 2005 NASA Authorization Act designated the American segment of the International Space Station as a national laboratory with a goal to increase the use of the ISS by other Federal entities and the private sector.[31]
One research goal is to improve the understanding of long-term space exposure on the human body. Subjects currently under study include muscle atrophy, bone loss, and fluid shift. The data will be used to determine whether space colonisation and lengthy human spaceflight are feasible. As of 2006, data on bone loss and muscular atrophy suggest that there would be a significant risk of fractures and movement problems if astronauts landed on a planet following a lengthy space cruise.[32]
A variety of large scale medical studies are being conducted aboard the ISS via the National Space and Biomedical Research Institute (NSBRI). Prominent among these is the Advanced Diagnostic Ultrasound in Microgravity study in which Astronauts (including former ISS Commanders Leroy Chiao and Gennady Padalka) perform ultrasound scans under the guidance of remote experts to diagnose and potentially treat hundreds of medical conditions in space. Usually, there is no physician onboard the International Space Station and diagnosis of medical conditions is challenging. This study's techniques are now being applied to cover professional and Olympic sports injuries as well as ultrasound scans performed by non-expert operators in populations such as medical and high school students. It is anticipated that remotely guided ultrasound scans will have application on Earth in emergency and rural care situations, where access to a trained physician is often rare.[33][34][35]
Researchers are investigating the effect of the station's near-weightless environment on the evolution, development and growth, and the internal processes of plants and animals. In response to some of this data, NASA wants to investigate microgravity's effects on the growth of three-dimensional, human-like tissues, and the unusual protein crystals that can be formed in space.[10]
The physics of fluids in microgravity is being investigated, enabling researchers to better model the behaviour of fluids in the future. Because of the ability to almost completely combine fluids in microgravity, physicists are interested in investigating the combinations of fluids that will not normally mix well on Earth. In addition, by examining reactions that are slowed down by low gravity and temperatures, scientists hope to gain new insight regarding superconductivity.[10]
Materials science is an important part of the research activity aboard the station, with the goal of reaping economic benefits by improving techniques used on the ground. Experiments are intended to provide a better understanding of the relationship between processing, structure, and properties so the conditions required on Earth to achieve desired materials properties can be reliably predicted.[36]
Other areas of interest include the effect of the low gravity environment on combustion, studying the efficiency of burning and control of emissions and pollutants. These findings may improve our understanding of energy production, and in turn have an economic and environmental impact. There are also plans to use the ISS to examine aerosols, ozone, water vapour, and oxides in Earth's atmosphere, as well as cosmic rays, cosmic dust, antimatter, and dark matter in the universe.[10]
 Origins

Space Shuttle Atlantis docked to Mir on STS-71, during the Shuttle-Mir Programme

Originating during the Cold War, the International Space Station represents a union of several space station projects from various nations. During the early 1980s, NASA had planned to launch a modular space station called Freedom as a counterpart to the Soviet Salyut and Mir space stations. Whilst the Soviets were planning to construct Mir-2 in the 1990s as a replacement for Mir.[15] Because of budget and design constraints, however, Freedom never progressed past mock-ups and minor component tests.
With the fall of the Soviet Union ending the Cold War and Space Race, Freedom was nearly cancelled by the United States House of Representatives. The post-Soviet economic chaos in Russia also led to the cancellation of Mir-2, though only after its base block, DOS-8, had been constructed.[15] Similar budgetary difficulties were being faced by other nations with space station projects, prompting American government officials to start negotiations with partners in Europe, Russia, Japan, and Canada in the early 1990s to begin a collaborative, multi-national, space station project.[15]
In June 1992, American President George H. W. Bush and Russian president Boris Yeltsin agreed to cooperate on space exploration by signing the Agreement between the United States of America and the Russian Federation Concerning Cooperation in the Exploration and Use of Outer Space for Peaceful Purposes. This agreement called for setting up a short, joint space programme, during which one American astronaut would board the Russian space station Mir and two Russian cosmonauts would board a Space Shuttle.[15]
In September 1993, American Vice-President Al Gore, Jr., and Russian Prime Minister Viktor Chernomyrdin announced plans for a new space station, which eventually became the International Space Station.[37] They also agreed, in preparation for this new project, that the United States would be heavily involved in the Mir programme in the years ahead, as part of an agreement that later included Space Shuttle orbiters docking with Mir.[17]
The ISS programme was planned to combine the proposed space stations of all participating space agencies, including Freedom, Mir-2 (with DOS-8 later becoming Zvezda), ESA's Columbus, and the Japanese Kibō laboratory. When the first module, Zarya, was launched in 1998, the station was expected to be completed by 2003. Because of delays, however, the estimated completion date has been put back to 2011.[38]
http://en.wikipedia.org/wiki/International_Space_Station