During the spacewalk which lasted 7-hour, 8-minute Mission Specialists Richard Linnehan and Mike Foreman assembled the stick-figure-shaped Dextre, also known as the Special Purpose Dextrous Manipulator (SPDM), a task that included attaching its two arms.
Dextre is the third and final component of the Mobile Servicing System developed by Canada for the ISS. With advanced stabilization and handling capabilities, Dextre can perform delicate human-scale tasks such as removing and replacing small exterior components. Operated by crew members inside the station or by flight controllers on the ground, it also is equipped with lights, video equipment, a stowage platform, and three robotic tools.

The technology behind Dextre evolved from its famous predecessor Canadarm2. Dextre is the world’s first on-orbit servicing robot with an operational mission, and it lays the foundation for future satellite servicing and space exploration capabilities.

While one arm is used to anchor and stabilize the system, the other can perform fine manipulation tasks such as removing and replacing station components, opening and closing covers, and deploying or retracting mechanisms. To grab objects, Dextre has special grippers with built‐in socket wrench, camera, and lights.

The two pan/tilt cameras below its rotating torso provide operators with additional views of the work area. Currently, astronauts execute many tasks that can only be performed during long, arduous, and potentially dangerous spacewalks. Delivery of this element increases crew safety and reduces the amount of time that astronauts must spend outside the station or routine maintenance. Some of the many tasks Dextre will perform include: installing and removing small payloads such as batteries, power switching units, and computers, providing power to payloads, manipulating, installing, and removing scientific payloads.

Designed for station maintenance and service, Dextre is capable of sensing forces and movement of objects it is manipulating. It can automatically compensate for those forces and movements to ensure an object is moved smoothly.

According to the STS-123’s schedule, the assembly of the Candian robot, will be completed during the third spacewalk, that is set to begin late on Monday.

"Dextre looks quite a bit different today," observed NASA flight director Dana Weigel. "It's almost fully assembled: It has two hands, two arms and the main body is pivoted up."

Dextre encountered a technical glitch before its assembly, but the astronauts have used Canadarm2 to successfully power up Dextre and to bypass a faulty cable that wasn't able to transmit power to the robot.
In the meantime, the station and shuttle crew members continued outfitting the Japanese Logistics Module - Pressurized Section (JLP).

Besides Monday’s spacewalk, the STS-123’s astronauts will have to complete two more. 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.

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.

On the fifth spacewalk, mission specialists Robert L. Behnken 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.