STS-125, or HST-SM4 (Hubble Space Telescope Servicing Mission 4), was the fifth and final space shuttle mission to the Hubble Space Telescope (HST). The launch of the Space Shuttle Atlantis occurred on 11 May 2009 at 2:01 pm EDT. Landing occurred on 24 May at 11:39 am EDT, with the mission lasting a total of just under 13 days.
Space Shuttle Atlantis carried two new instruments to the Hubble Space Telescope, the Cosmic Origins Spectrograph and the Wide Field Camera 3. The mission also replaced a Fine Guidance Sensor, six gyroscopes, and two battery unit modules to allow the telescope to continue to function at least through 2014. The crew also installed new thermal blanket insulating panels to provide improved thermal protection, and a soft-capture mechanism that would aid in the safe de-orbiting of the telescope by an unmanned spacecraft at the end of its operational lifespan. The mission also carried an IMAX camera with which the crew documented the progress of the mission for the Hubble IMAX movie.
The crew of STS-125 included three astronauts who had previous experience servicing Hubble. Scott Altman visited Hubble in 2002 as commander of STS-109, the fourth Hubble servicing mission. John Grunsfeld, an astronomer, has serviced Hubble twice, performing a total of five spacewalks on STS-103 in 1999 and STS-109. Michael Massimino served with both Altman and Grunsfeld on STS-109, and performed two spacewalks to service the telescope.
NASA managers and engineers declared the mission a complete success. The completion of all the major objectives, as well as some that were not considered vital, upgraded the Hubble telescope to its most technologically advanced state since its launch nineteen years before and made it more powerful. The upgrades helped Hubble to see deeper into the universe and farther into the past, closer to the time of the Big Bang.
STS-125 was the only visit to the Hubble Space Telescope for Atlantis; the telescope had been previously serviced twice by Discovery and once each by Columbia and Endeavour. The mission was the 30th flight of Space Shuttle Atlantis and also the first by Atlantis in over 14 years not to visit a space station, the last one being STS-66.