Most manned missions to a space telescope

The Hubble Space Telescope is the only space observatory designed to be visited and serviced by astronauts. The discovery of spherical aberration in its primary mirror shortly after its launch on 24 April 1990, would have caused HST’s mission to be a complete failure had it not been able to be fixed in orbit. The first mission to HST was STS-61 in December 1993, during which astronauts installed corrective optics, fixing the spherical aberration. Four further space shuttle missions to Hubble occurred in February 1997, December 1999, March 2002 and May 2009. The five Hubble servicing missions are regarded by many as highlights of NASA’s space shuttle programme.