The International Space Station (ISS) is a space station, or a habitable artificial satellite in low Earth orbit. It is a modular structure whose first component was launched in 1998. Now the largest artificial body in orbit, it can often be seen at the appropriate time with the naked eye from Earth.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. In 1984 the ESA was invited to participate in Space Station Freedom. In 1993, after the USSR ended, the United States and Russia merged Mir-2 and Freedom together.
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.
Since the arrival of Expedition 1 on 2 November 2000, the station has been continuously occupied for 13 years and 155 days, the longest continuous human presence in space.
The station crew currently consists of three Russians — Mikhail Tyurin, Alexander Skvortsov and Oleg Artemyev — two NASA astronauts — Rick Mastracchio and Steven Swanson — and Expedition 39 commander Koichi Wakata, the first Japanese astronaut to command the outpost. Skvortsov, Artemyev and Swanson were launched to the station March 25.
The station is now virtually complete, at a cost to U.S. taxpayers of some $100 billion over the past three decades, and the Obama administration recently approved long-range plans to operate the outpost at least through 2024.
The ISS maintains an orbit with an altitude of between 330 km (205 mi) and 435 km (270 mi) by means of reboost manoeuvres using the engines of the Zvezda module or visiting spacecraft. It completes 15.50 orbits per day.