The International Space Station (ISS) is a habitable artificial satellite in low Earth orbit. It follows the Salyut, Almaz, Skylab and Mir stations as the ninthspace station to be inhabited. The ISS is a modular structure whose first component was launched in 1998. Like many artificial satellites, the station can be seen with the naked eye from Earth without any special equipment. The ISS consists of pressurised modules, external trusses, solar arrays and other components. ISS components have been launched by American Space Shuttles as well as Russian Proton and Soyuz rockets. Budget constraints led to the merger of three space station projects with the Japanese Kibōmodule and Canadian robotics. In 1993 the partially built Soviet/Russian Mir-2, the proposed American Freedom, and the proposed European Columbusmerged into a single multinational programme. The Russian Federal Space Agency (RSA/RKA) is using the ISS as a work site to assemble their next space station, called OPSEK. Modules and components for the new station began arriving on orbit in 2010, and the RSA plans to commission the new station before the remainder of the ISS is de-orbited.
The ISS serves as a microgravity and space environment research laboratory in which crew members conduct experiments in biology, human biology, physics,astronomy, meteorology and other fields. The station is suited for the testing of spacecraft systems and equipment required for missions to the Moon and Mars.
The station has been continuously occupied for 11 years and 313 days, having exceeded the previous record of almost 10 years (or 3,644 days) held by Mir, in 2010. The station is serviced by Soyuz spacecraft, Progress spacecraft, theAutomated Transfer Vehicle, the H-II Transfer Vehicle, and formerly theSpace Shuttle. It has been visited by astronauts and cosmonauts from 15 different nations. On 25 May 2012, Space Exploration Technologies Corporation (or SpaceX) became the world's first privately held company to send a cargo load, the Dragon spacecraft, to the International Space Station.
The ISS programme is a joint project between five participating space agencies, the American NASA, the Russian Federal Space Agency, the Japanese JAXA, the European ESA, and the Canadian CSA. The ownership and use of the space station is established by intergovernmental treaties and agreements. The station is divided into two sections, the Russian orbital segment (ROS) and the United States orbital segment (USOS), which is shared by many nations. The ISS is maintained at an orbital altitude of between 330 km (205 mi) and 410 km (255 mi). It completes 15.7 orbits per day. The ISS is funded until 2020, and may operate until 2028.