Completing Dextre assembly by installing a tool platform and tool holster assembly.

Evaluating the Shuttle Tile Ablator-54, or STA-54, material and a tile repair ablator dispenser for use as a shuttle thermal protection system repair technique. The Tile Repair Ablator Dispenser, or T-RAD, is similar to a caulk gun. They used TRAD to mix and squirt out the STA-54 material into holes in several demonstration tiles. The repaired samples will be returned to Earth for extensive testing.

Moving the Orbiter Boom Sensor System, the 50 ft. extension of the shuttle's robotic arm, to a temporary location on the station's main truss or backbone. The OBSS was left on the station because shuttle Discovery doesn't have enough room in its cargo bay to carry both the boom and the large Japanese pressurized module on the STS-124 mission. The spacewalkers also installed a new trundle bearing assembly in the starboard Solar Alpha Rotary Joint to allow the joint to rotate a little bit more if necessary. That SARJ has had limited ability for several months, and metallic debris has been found inside it. Additional spacewalk tasks included inspecting the SARJ and collecting debris samples.

Removing a cover that has been in place to protect a port on the Unity node, the location where Tranquility was attached robotically halfway through the spacewalk. Next, the spacewalkers removed and stored a spare parts platform from the Special Purpose Dexterous Manipulator, or Dextre, a two-armed space station robot capable of handling delicate assembly tasks currently performed by spacewalkers. Finally, they installed four electronics systems cables between Unity and Tranquility to bring the new node to life.

Installing ammonia plumbing connectors between Unity and Tranquility and covered them with thermal insulation. When turned on, the ammonia will provide cooling to Tranquility. Then they prepared a port on the Earth-facing side of Tranquility for the flight day 8 relocation and attachment of the Cupola.

Turning on the ammonia cooling lines between Unity and Tranquility, installing heater and data cables on Tranquility, removing insulation and launching locks from the newly installed Cupola, and installed handrails on the outside of Tranquility.