The International Space Station (ISS) is a habitable artificial satellite in low Earth orbit. It follows the Salyut, Almaz, Skylab and Mir stations as the ninth space station to be inhabited. The ISS is a modular structure whose first component was launched in 1998. Like many artificial satellites, the station can be seen from Earth without any equipment (referred to as naked eye). 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. Budget constraints led to the merger of three space station projects with the Japanese Kibō module and Canadian robotics. In 1993 the partially built Soviet/Russian Mir-2, the proposed American Freedom, and the proposed European Columbus merged into a single multinational programme. The Russian Federal Space Agency (RSA/RKA) is using the ISS as a work site to assemble their next space station, called OPSEK. Modules and components for the new station began arriving on orbit in 2010, and the RSA plans to commision the new station before the remainder of the ISS is de-orbited.