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.[7] Now the largest artificial body in orbit, it can often be seen with the naked eye from Earth.[8] 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.[9] In 1984, the ESA was invited to participate in Space Station Freedom.[10] After the USSR dissolved, the United States and Russia merged Mir-2 and Freedom together in 1993 The ISS programme is a joint project among five participating space agencies: NASA, Roscosmos, JAXA, ESA, and CSA.[15][17] The ownership and use of the space station is established by intergovernmental treaties and agreements.[18] 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 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 15.53 orbits per day.[19] As of January 2014, the US-portion of the ISS was funded until 2024, and may operate until 2028.[20][21][22] The Russian Federal Space Agency, Roskosmos (RKA) 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." Purpose: According to the original Memorandum of Understanding between NASA and Rosaviakosmos, the International Space Station was intended to be a laboratory, observatory and factory in low Earth orbit. It was also planned to provide transportation, maintenance, and act as a staging base for possible future missions to the Moon, Mars and asteroids. In the 2010 United States National Space Policy, the ISS was given additional roles of serving commercial, diplomatic[25] and educational purposes. Scientific research: The ISS provides a platform to conduct scientific research. While small unmanned spacecraft can provide platforms for zero gravity and exposure to space, space stations offer a long term environment where studies can be performed potentially for decades, combined with ready access by human researchers over periods that exceed the capabilities of manned spacecraft. The Station simplifies individual experiments by eliminating the need for separate rocket launches and research staff. The wide variety of research fields include astrobiology, astronomy, human research including space medicine and life sciences, physical sciences, materials science, space weather, and weather on Earth (meteorology).Scientists on Earth have access to the crew's data and can modify experiments or launch new ones, which are benefits generally unavailable on unmanned spacecraft.Crews fly expeditions of several months duration, providing approximately 160-man-hours a week of labour with a crew of 6.