Mir was a space station that operated in low Earth orbit from 1986 to 2001, owned at first by the Soviet Union and then by Russia. Mir was the first modular space station and was assembled in orbit from 1986 to 1996. It had a greater mass than that of any previous spacecraft. It held the record for the largest artificial satellite orbiting the Earth until that record was surpassed by the International Space Station after Mir's deorbit on 21 March 2001. Mir served as a microgravity research laboratory in which crews conducted experiments in biology, human biology, physics, astronomy, meteorology and spacecraft systems in order to develop technologies required for the permanent occupation of space.