http://www.washingtonpost.com/wp-dyn/content/article/2009/05/10/AR2009051001513.htmlAstronauts Ready For Repair Trip to Battered Hubble
... This will be the fifth and final servicing mission to the telescope and, unquestionably, the trickiest. The servicing had originally been scheduled for 2004, but NASA canceled the mission after the Columbia disaster heightened concerns about shuttle astronauts' safety. With the Hubble doomed to expire in orbit as its gyros failed, schoolchildren across the country donated their lunch money to prod NASA to reconsider. In 2006, NASA decided to reinstate the mission.