Dextre, the International Space Station's robotic handyman, replaced an electrical switchboard outside the complex this week, the first time the Canadian space robot has performed a maintenance task.

File photo of the Dextre robot aboard the International Space Station. Credit: NASA
 
The two-armed robot completed the replacement job Sunday and Monday in a choreographed sequence of movements and commands. Engineers in Houston controlled the procedures from the ground, while support teams in Canada were available to help out.

Dextre retrieved a fresh Remote Power Control Module, or RPCM, from a cargo container Sunday with one arm. Then Dextre's other arm captured and extracted a bad circuit breaker from the port side of the space station's truss backbone.

The robot inserted the new switchbox into the same location on the P1 truss segment. NASA says the fresh RPCM was successfully powered up and is functioning well, while the old unit was put back in the cargo container by Dextre.

The changeout was ordered to overcome a problem with one of the module's power ports and restore the system to full functionality. It was delayed from last year after a rehearsal of the replacement procedure ran into problems, then the task was deferred until this week in favor of more critical space station assembly work.

RPCM units contain electrical switches and circuit breakers controlling the distribution of power across the orbiting complex. There are 72 such power controllers aboard the station, and each RPCM is about the size of a large dictionary and weighs more than 9 pounds.

Outfitted with two 11-foot-long arms and a toolkit, Dextre was launched in 2008 to reduce the workload for spacewalking astronauts. The robot was conceived to accomplish simple maintenance tasks outside the space station, so astronauts would only have to go outside for major work.

Diagram of the Dextre robot, also named the Special Purpose Dexterous Manipulator. Credit: CSA/MDA
 
Before Dextre, the RPCM replacement task would have been added to a spacewalk, which is always a risky endeavor.

Each of Dextre's arms is 11 feet long. It also includes a toolkit and a storage platform. The tips of Dextre's appendages include grippers with force moment sensors, giving the robot a sense of touch by determining how much pressure and torque to apply during maintenance jobs, much like a human.

Developed by MacDonald Dettwiler and Associates Ltd. for the Canadian Space Agency, Dextre helped unload supplies from a Japanese cargo freighter earlier this year.

Dextre was supposed to relocate the cargo container and the Robotic Refueling Mission module later this week from its workbench to a permanent storage position on an external logistics platform.

One of Dextre's next jobs will be working with the Robotic Refueling Mission, or RRM, which is designed to demonstrate technologies and techniques for robotically servicing satellites.

After verifying the RRM has good vision during testing this fall, refueling demonstrations should begin in January. Acting as a servicing spacecraft, Dextre will cut and peel back protective thermal blankets, unscrew caps, access valves, and transfer fluid to the module, which fills the role of a customer satellite.