Mission specialists Mike Massimino and Mike Good completed the for this mission today. The spacewalk was a long one, lasting 8 hours and 2 minutes, making it the sixth longest in U.S. history.
NASA reported that Massimino and Good the orbiter's Space Telescope Imaging Spectrograph, or STIS, which is a critical tool for Hubble.
The Imaging Spectrograph is NASA's major black hole hunter. It acts as a sort of outer space prism, separating light from the universe into its component colors, giving scientists a "wavelength fingerprint" of any object. That data can offer clues to an object's temperature, chemical composition and motion.
The spectrograph is designed to pick up the light and color signature of black holes. It also helps astronomers map the motion of gas affected by a black hole's gravitational pull.
The spectrograph, which was installed on Hubble during a 1997 shuttle service mission, suffered a power supply failure in 2004 and has since been in safe mode, leaving it offline, but protected, NASA said.
The trouble arose in today's spacewalk when Massimino, in space, was unable to remove a bolt from the spectrograph's handrail. Eventually, the astronaut worked around the issue by simply yanking the handrail until the head of the bolt snapped off. After that, the two astronauts were able to finish the repair job.
However, because they spent so much effort on the handrail, they didn't have time to install a new stainless steel blanket on the outside of the telescope. The blanket, which should offer thermal protection for equipment bays, will replace multi-layer insulation that has started to fall apart.
Mission Control is trying to reconfigure a final Hubble spacewalk Monday to see if the astronauts can fit in the installation of the blanket .
Monday's spacewalk will focus on installing a battery module containing three batteries. On Tuesday, the seven-astronaut crew will deploy . They're scheduled to return to Earth on Friday.