Shuttle Blasts Off To Repair Hubble
By Jefferson Morris
KENNEDY SPACE CENTER, Fla. - Shuttle Atlantis lifted off from Launch Pad 39A in picture-perfect weather at 2:01 p.m. EDT May 11, kicking off the fifth and final servicing mission to the Hubble Space Telescope.
Veteran astronaut Scott Altman commands STS-125, with retired Navy Capt. Gregory Johnson serving as pilot. Aboard as mission specialists are veteran astronauts John Grunsfeld - making his third trip to Hubble, and Mike Massimino, along with first-time astronauts Andrew Feustel, Michael Good and Megan McArthur.
Shuttle Endeavour, meanwhile, is poised at Launch Pad 39B, ready to lift off within a week of Atlantis to conduct a rescue mission if on-orbit inspections reveal any damage to Atlantis that make it unable to safely re-enter Earth's atmosphere. The rescue mission, designated STS-400, is necessary because Atlantis will be unable to reach the refuge of the International Space Station from Hubble's orbit.
Loading of Atlantis' external tank with 500,000 pounds of liquid hydrogen and liquid oxygen propellants began at 4:41 a.m.
The highest scientific priorities for the seven-person STS-125 crew during the 11-day Servicing Mission 4 (SM4) are the installation of the new Wide Field Camera 3, which will replace the Wide Field and Planetary Camera 2, and the Cosmic Origins Spectrograph, which replaces the Corrective Optics Space Telescope Axial Replacement (COSTAR). COSTAR was the original "contact lens" installed to correct Hubble's vision during the first servicing mission in 1993, but is no longer needed because all of Hubble's replacement instruments already compensate for the flawed optics.
The astronauts also will repair Hubble's Advanced Camera for Surveys (ACS), which was crippled by an electrical short in 2007, and the Space Telescope Imaging Spectrograph (STIS), which has been inoperative since a power failure in 2004.
A late addition to the schedule is the installation of a replacement Science Instrument Command & Data Handling (SI C&DH) unit - a crucial component that commands the telescope's instruments and directs its data before transmission to the ground. In September 2008, just two weeks before STS-125 was originally scheduled to lift off, a malfunction of one of Hubble's Control Unit/Science Data Formatters (CU/SDF) left the SI C&DH only one subsystem failure away from rendering the entire telescope useless. NASA made the decision to put off the mission while a backup SI C&DH was refurbished and tested so it could be installed as well.
The astronauts also will replace all six of Hubble's 125-pound batteries with new and improved versions, as well as all six of its stabilizing gyroscopes. Three of Hubble's current gyroscopes have failed, two are operating, and one is serving as a backup. Also slated for replacement is a worn-out Fine Guidance Sensor (FGS), which measures star positions to help the telescope point, as well as some of the insulation that protects Hubble's equipment bays.
Finally, the crew will install a new soft capture mechanism that will one day allow a deorbiting module to be autonomously attached to the telescope, permitting safe disposal at the end of its life.
After the mission and a few months of checkout tests run by telescope controllers at Goddard Space Flight Center in Greenbelt, Md., Hubble will be working at its peak, with five operational instruments. The servicing should keep the telescope operating at least through 2014.
Atlantis launch photo: NASA TV
