International Space Station program ocean was found to be possible only with Russia's assistance. At the time ISS was launched, the Russian Space Agency had experience from de-orbiting the Salyut 4, 5, 6, and 7 space stations, while NASA's first intentional controlled de-orbit of a satellite (the Compton Gamma Ray Observatory) would not occur for another two years. NASA currently has no spacecraft capable of de-orbiting the ISS at the time of decommissioning. Skylab, the only space station built and launched entirely by the US, decayed from orbit slowly over 5 years, and no attempt was made to de-orbit the station using a deorbital
International Space Station leftover USOS hardware and '"Zvezda" 2' as a refuelling depot and service station located at one of the Earth-Moon Lagrange points, L1 or L2. The entire USOS cannot be reused and will be discarded, but some Russian modules are planned to be reused. "Nauka", the Uzlovoy Module, two science power platforms and "Rassvet", launched between 2010 and 2015 and joined to the ROS, may be separated to form OPSEK. "Nauka" will be used in the station, whose main goal is supporting manned deep space exploration. OPSEK will orbit at a higher inclination of 71 degrees, allowing observation to and from