Hubble is the only telescope designed to be maintained in space by astronauts. Five Space Shuttle missions have repaired, upgraded, and replaced systems on the telescope, including all five of the main instruments. The fifth mission was canceled on safety grounds following the Columbia disaster (2003), but NASA administrator Michael D. Griffin approved the fifth servicing mission which was completed in 2009. The telescope is operating as of 2019[update], and could last until 2030–2040. Its successor is the James Webb Space Telescope (JWST) which is scheduled to be launched in March 2021.