International Space Station

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 international space station, the longest continous presence of humans in space and the largest spacecraft ever constructed, an accomplishment in international cooperation, human spaceflight and spaceflight technology. Its design is that of an orbital research station, where scientific experiments in microgravity are conducted and the space environment is studied.

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. A striking feature of the ISS is the Integrated Truss Structure, which connect the station's vast system of solar panels and radiators to its pressurized modules. These modules support diverse functions, including scientific research, crew habitation, storage, spacecraft control, and airlock operations. The ISS has eight docking and berthing ports for visiting spacecraft. The station orbits the Earth at an average altitude of 400 kilometres (250 miles) and circles the Earth in roughly 93 minutes, completing 15.5 orbits per day.

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 and Soyuz rockets and the Space Shuttle. Long-term occupancy began on 2 November 2000, with the arrival of the Expedition 1 crew. Since then, the ISS has remained continuously inhabited for 25 years and 135 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, Axiom Space's Payload Power Thermal Module. The station is expected to remain operational until the end of 2030, after which it is planned to be de-orbited using the US Deorbit Vehicle. Critique of this plan and the proposal of parking the station at a more stable orbit has gained support by 2026.