Changing out three boxes, each containing two of the telescope's six gyroscopes, and three batteries.

Repairing and upgrade the Space Telescope Imaging Spectrograph and install a stainless steel blanket on Hubble's exterior. The blankets provide additional thermal protection for some equipment bays, replacing the existing multi-layer insulation that has degraded over time.

Removing and replacing four of the six batteries on the port truss to store electricity from the solar arrays on that truss. The used batteries were installed on the cargo carrier for return to Earth on Atlantis.

Installing the final two new batteries on the truss and put the old batteries on the carrier. Next, they retrieved a grapple fixture from Atlantis' payload bay and brought it inside the station for use as a spare.