The Camera That Saved Hubble... Twice

The Camera That Saved Hubble... Twice: JPL's Wide Field and Planetary Camera 2
First motion is almost always a big event in the world of space exploration. Whether the first motion is of a wheel beginning to rotate or a rocket lifting off the pad, first motion means things are definitely changing. On day four of the upcoming shuttle servicing mission of the Hubble Space Telescope, there will be another such significant first motion. It will begin when a bolt that has been frozen in place for a decade and a half completes its 20th counterclockwise rotation. "When that happens, that will be the first time in 15-and-a-half years that our instrument will have moved over one one-millionth of an inch from its position aboard the Hubble Space Telescope," said John Trauger of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "That is when the mission of the camera that saved Hubble will come to an end."
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http://www.jpl.nasa.gov/news/features.cfm?feature=2144