Discovery was NASA's third space shuttle orbiter and is known as OV-103. It conducted its maiden flight in 1984 and its final mission in 2011, accumulating 365 days in space over 39 flights. Some key missions included launching the Hubble Space Telescope, the first flight of a Russian cosmonaut on a shuttle, and missions servicing the International Space Station. Discovery was retired in 2011 as the first space shuttle to leave NASA's fleet.