... HST . ... Because of HST's location above the Earth's atmosphere, these science instruments can produce high-resolution images of astronomical objects. ... HST servicing missions in December 1993, February 1997, December 1999, March 2002 and May 2009 were enormous successes and validated the concept of on-orbit servicing of Hubble. ... The Cosmic Origins Spectrograph ( COS ) is a fourth-generation instrument that was installed on the Hubble Space Telescope (HST) during the 2009 servicing mission. ...