Grunsfeld and Feustel will finish the mission’s battery replacement work. They will be working in the telescope’s Bay 3 to replace the second of two battery modules. Each module weighs 460 pounds and contains three batteries, providing electrical power to support Hubble operations during the night portion of its orbit. The first battery module was installed during the second spacewalk.
They also will be replacing one of the telescope’s fine guidance sensors. The sensors are used to provide pointing information and also serve as a scientific instrument for determining precise position and motion of stars.
After these two tasks are accomplished, Feustel and Grunsfeld will turn their attention to the New Outer Blanket Layer (NOBL) on the outside of the telescope’s Bay 5. The NOBL on Bay 8 was due to be installed during yesterday’s spacewalk, but the crew was unable to accomplish it during the spacewalk. If time permits, Feustel and Grunsfeld may be asked to install a partial or full set of NOBLs on Bay 8. The team in Mission Control will make the decision in real time based on the progress of the spacewalk.
Today’s spacewalk is scheduled to last 5 hours and 45 minutes.