International Space Station Russian space station called OPSEK. The ISS is the ninth space station to be inhabited by crews, following the Soviet and later Russian "Salyut", "Almaz", and "Mir" stations as well as "Skylab" from the US. The station has been continuously occupied for since the arrival of Expedition 1 on 2 November 2000. This is the longest continuous human presence in low Earth orbit, having surpassed the previous record of held by "Mir". It has been visited by astronauts, cosmonauts and space tourists from 17 different nations. After the American Space Shuttle programme ended in 2011, Soyuz rockets became the only
Orbit of the Moon frequencies. See also tidal acceleration for a more detailed description. The Moon is gradually receding from Earth into a higher orbit, and calculations suggest that this would continue for about 50 billion years. By that time, Earth and the Moon would be in a mutual spin–orbit resonance or tidal locking, in which the Moon will orbit Earth in about 47 days (currently 27 days), and both the Moon and Earth would rotate around their axes in the same time, always facing each other with the same side. This has already happened to the Moon—the same side always faces Earth—and is