Working from inside Friday night, the astronauts used the space station's mechanical arm to grab onto the robot named Dextre and energize the sleeping giant, which had been lying dormant outside the orbiting complex for nearly two days. Electricity quickly began streaming to the machine's various joints and electronics, to everyone's relief.
"Good news from the flight control room," announced Mission Control. "Dextre has power."
A cable design flaw had prevented power from reaching Dextre, once the robot was hoisted onto the space station Thursday. Engineers on the ground put in the wrong circuitry before Endeavour's flight; that was enough to create a roadblock in power and data to Dextre.
The robot had its hands attached to its arms during a spacewalk that ended well before dawn Friday. With the night's successful power bypass, NASA kept on track Saturday's spacewalk to hook the robot's 11-foot arms to its torso.
Dextre could not be completely assembled or tested without power to heat its joints and electronics.
The problem cable is in Dextre's transport bed, or pallet, which the astronauts are using as a staging area to put the robot together. Supplying power directly to Dextre, via the space station's robot arm, circumvented the cable and transport bed.
The Canadian-built robot - which cost more than $200 million - is intended to be a helper for spacewalking astronauts. It ultimately could take over some spacewalking jobs, saving time for space station crews while reducing their risk.
Engineers initially suspected the problem might be with a timer and require a simple computer software patch, but ruled that out. They tried the patch anyway, and it did not work.
Mission Control knew within minutes that the temporary robot-arm solution had succeeded.
Once it is completely assembled early next week, the robot will be removed from its transport bed. From that point on, it will be powered from its various attachment points directly on the space station.
Endeavour and its seven-man crew delivered Dextre - lying in pieces on its transport bed - to the space station. On Thursday, it was attached to the exterior of the orbiting outpost.
LeRoy Cain, chairman of the mission management team, said he did not know whether the Canadian Space Agency or NASA was at fault for the cable design flaw - or both. Preflight testing did not catch the problem because the circuitry between the ground equipment and cable was a proper match; in space, it is not.
He promised a full investigation "to run this to ground and understand exactly what happened and how and why."
Toward the end of the seven-hour spacewalk that began Thursday night, astronauts attached the first segment of Japan's Kibo lab, a storage compartment that is 14 feet long. The $1 billion lab itself will fly to the space station in May, aboard shuttle Discovery.
Late Friday, Japanese astronaut Takao Doi made a grand entrance into the new compartment.
"This is a small step for one Japanese astronaut, but a giant entrance for Japan to a greater and newer space program," Doi said.
Five spacewalks are planned for Endeavour's nearly two-week visit, the longest ever by a shuttle.
On Friday, mission managers concluded that Endeavour's heat shield made it through Tuesday's liftoff in good shape and formally cleared the shuttle for re-entry on March 26.
Visit NASA's Web Page for the STS-123 Mission for the latest developments, background on mission elements, crewmembers and multimedia.