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 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.
After the USSR dissolved, the United States and Russia merged Mir-2 and Freedom
together in 1993.
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 348 days, the longest continuous human
presence in space. In 2010, the station surpassed the previous record of almost 10
years or 3,634 days held by Mir. The station is serviced by a variety of visiting
spacecraft: Soyuz, Progress, the Automated Transfer Vehicle, the H-II Transfer
Vehicle, Dragon, and Cygnus. It has been visited by astronauts and cosmonauts from
15 different nations.
After the U.S. Space Shuttle program ended in 2011, Soyuz rockets became the only
provider of transport for astronauts at the International Space Station, while
Dragon became the only provider of bulk cargo-return-to-Earth services - downmass
capability of Soyuz capsules is very limited.
The ISS programme is a joint project among five participating space agencies:
NASA, Roscosmos, JAXA, ESA, and 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 and the United States Orbital
Segment, which is shared by many nations. The ISS maintains an orbit with an
altitude of between 205 miles and 270 miles by means of reboost manoeuvres using
the engines of the Zvezda module or visiting spacecraft. It completes 15.51 orbits
per day. As of January 2014, the US-portion of the ISS was funded until 2024, and
may operate until 2028. The Russian Federal Space Agency, Roskosmos has proposed
using the ISS to commission modules for a new space station, called OPSEK, before
the remainder of the ISS is deorbited. The Russian ISS program head, Alexey B.
Krasnov, said in July 2014 that "the Ukraine crisis is why Roscosmos has received
no government approval to continue the station partnership beyond 2020."
ISS is the ninth space station to be inhabited by crews, following the Soviet and
later Russian Salyut, Almaz, and Mir stations, and Skylab from the US.
