The International Space Station (ISS) is a space station in low Earth orbit (LEO). It is the product of the International Space Station program and is operated by five partner space agencies: NASA (United States), Roscosmos (Russia), ESA (Europe), JAXA (Japan), and CSA (Canada). It is the first space station built, maintained and crewed through international cooperation and the largest human spacecraft ever constructed. It is an orbital research station, where scientific experiments in microgravity are conducted and the space environment is studied. Since 2 November 2000, it has hosted the longest continuous human presence in space. Alongside China's Tiangong, it is one of two operational space stations. The station orbits between 51.64° north and south, at about 400 kilometres (250 miles) above Earth, below the Van Allen radiation belts and most space debris. Its orbit takes it at 7.67 km/s (27,600 km/h; 17,200 mph) roughly every 93 minutes around Earth, 15.5 times a day. Measuring 109 m (358 ft) (with solar arrays) by 73 m (239 ft), it is as large as a full-sized football or soccer field, and has a pressurised internal volume of 1,005 m3 (35,491 ft3), comparable to a Boeing 747 airliner. The station is a modular space station divided into two main sections: the Russian Orbital Segment (ROS), developed by Roscosmos, and the US Orbital Segment (USOS), built by NASA, ESA, JAXA, and CSA. The Integrated Truss Structure connects the station's vast system of solar panels and radiators to its 16 major pressurized modules. These modules support scientific research, crew habitation, storage, spacecraft control, and airlock operations. The ISS has eight docking and berthing ports for visiting spacecraft. In total, the station consists of 43 different modules and elements. Crews visit via the Soyuz and Crew Dragon spacecraft, and previously the Space Shuttle. Cargo supply craft include Progress, Cargo Dragon, Cygnus, Automated Transfer Vehicle, and HTV-X. The ISS is the political product of the development of international cooperation in space throughout the space age. The station combines two previously planned crewed Earth-orbiting stations: the United States' Space Station Freedom and the Soviet Union's Mir-2. The first ISS module was launched in 1998, with major components delivered by Proton, Soyuz and Space Shuttle launch vehicles. Long-term occupancy began with the arrival of the Expedition 1 crew on 2 November 2000. Since then, the ISS has remained continuously inhabited for 25 years and 297 days, the longest continuous human presence in space. As of August 2025, 290 individuals from 26 countries had visited the station. Future plans for the ISS include the addition of at least one module, the Payload Power Thermal Module by Axiom Space, forming the commercial segment of the station. The station is expected to remain operational until the end of 2030, by which parts of it are to be used for Axiom Station and the Russian Orbital Service Station. After this the ISS is planned to be de-orbited using the US Deorbit Vehicle, but critique of this plan and the proposal of parking the station at a more stable higher orbit has gathered congressional support as of 2026.
Conception
Purpose The ISS was originally intended to be a laboratory, observatory, and factory while providing transportation, maintenance, and a low Earth orbit staging base for possible future missions to the Moon, Mars, and asteroids. However, not all of the uses envisioned in the initial memorandum of understanding between NASA and Roscosmos have been realised. In the 2010 United States National Space Policy, the ISS was given additional roles of serving commercial, diplomatic, and educational purposes.
Scientific research
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