The astronauts form Endeavour and the ISS have moved the Canadian-built Dextre and attached it to a power and data grapple fixture located on the U.S. laboratory Destiny. The new robotic system is the final element of the International Space Station’s Mobile Servicing System.

The assembly of the robot was finished earlier this week by Mission Specialists Rick Linnehan and Mike Foreman during the third spacewalk from the five scheduled for t STS-123 mission.

Canadarm2, the International Space Station’s robot arm, grabbed the pallet that secured Dextre during its journey to the orbital outpost and returned the pallet to space shuttle Endeavour’s payload bay for the trip back to Earth.

The station and shuttle crews also prepared hardware to be used in a shuttle tile repair test on the next spacewalk, and they got some much needed off duty time.

The fourth spacewalk will be used to replace a remote power control module and test a shuttle tile repair material. The repair material test was originally scheduled for Discovery’s mission last October, but was rescheduled so that problems with the station’s solar arrays could be addressed. Foreman and Mission Specialist Robert Behnken are slated to begin the mission’s fourth spacewalk at 6:28 p.m. Thursday

The primary purpose of the detailed test objective is to evaluate the Shuttle Tile Ablator-54 (STA-54) material and a tile repair ablator dispenser in a microgravity and vacuum environment for their use as a space shuttle thermal protection system repair technique. Spacewalkers Robert Behnken and Mike Foreman will set up for the test on the outside of the Destiny lab.

The Tile Repair Ablator Dispenser (T-RAD) is similar to a caulk-gun.  Both spacewalkers will use the T-RAD to mix and extrude the STA-54 material into holes in several demonstration tiles.  The spacewalkers will watch for swelling of the material and work it in until it is smooth by tamping the material with foam-tipped tools. The repaired samples and tools will be stowed in Endeavour’s cargo bay for return to Earth.  The samples will undergo extensive testing on the ground.

The goal is to complete this test before space shuttle Atlantis flies to the Hubble Space Telescope in August. Unlike missions to the space station, Atlantis’ crew members wouldn’t be able to wait on the station for another shuttle to bring them home if Atlantis was damaged.

In addition during the fourth spacewalk the astronauts will replace a failed Remote Power Controller Module on the station’s truss.

Veteran Rick Linnehan is the mission’s lead spacewalker.  He conducted three spacewalks in March 2002 during STS-109, the fourth Hubble Space Telescope servicing mission. 

On the fifth and final spacewalk of STS-123, he and Mike Foreman will store on the station the boom that attaches to the shuttle’s robotic arm for heat shield inspections. The boom is being stored on orbit since the next shuttle will not have enough room to carry both the boom and the larger JAXA module in the cargo bay.

Also they will remove additional covers from the starboard SARJ and perform inspections, capture digital photography and perform debris collection.