At the time, it became the sixth longest spacewalk in history. It was the twenty-second spacewalk devoted to servicing the Hubble telescope, and Massimino's fourth spacewalk, bringing his total EVA time to thirty hours, forty-four minutes. During the mission status briefing, Jennifer Wiseman, Chief of Exoplanet and Stellar Astrophysics for Goddard Space Flight Center, noted that the repair of STIS was a major victory for both the mission and the science community, as that part of the telescope performed unique functions, helping scientists understand the materials planets are composed of, and looking at things like the motion of stars around black holes. After initial aliveness testing that showed no issues, STIS was taken into functional testing, and issues were seen when the telescope put itself into safe mode due to a low thermal limit sensor. Ground controllers at Goddard would restart the testing once the thermal limit sensor was back in normal sensor range, but it is believed the component is in good shape. Completing the fifth of the five planned spacewalks, Grunsfeld and Feustel successfully installed the second battery, removed and replaced the Fine Guidance Sensor number three, and worked so efficiently that they were over an hour ahead of the timeline, giving them time to remove degraded insulation panels from three bays of the telescope, and install three New Outer Blanket Layers (NOBLs). Beginning the spacewalk at 12:20 UTC, the pair first worked on removing an aging battery module, and replaced it with a new pack, which combined with the battery replacement performed during the second spacewalk, gave the telescope all new nickel-hydrogen batteries. They then moved on to the removal and replacement of the Fine Guidance Sensor unit number three, improving Hubble's focus and stability when imaging. NASA engineers liken the new FGS to being able to keep a laser beam focused on a U.S. dime coin that is away. Both the new batteries, and the FGS passed both aliveness and functional testing. The mission's final EVA concluded at 19:22 UTC, after seven hours and two minutes. The total time spent during the mission in extra-vehicular activity was thirty-six hours, fifty-six minutes. The twenty-third and final spacewalk to service Hubble brought the total time spent in EVA working on the telescope to one hundred and sixty-six hours, six minutes. Lead Flight Director Tony Ceccacci noted that the final EVA was also the last planned spacewalk from a shuttle airlock.