©Canadian Space Agency
After several delays Canada's robotic handyman named Dextre aboard the International Space Station (ISS) has passed its final exam and is now ready for full duties. Dextre, short for Special Purpose Dexterous Manipulator, was designed and built by MacDonald Dettwiler (MDA) for the Canadian Space Agency (CSA). Dextre along with Canadarm-2 on the ISS are known as the Mobile Servicing System (MSS).
Dextre arrived at the International Space Station on NASA's Space Shuttle Discovery (STS-123) after it was launched on March 11, 2008. Since it arrived on the station Dextre has completed a series of planned tasks to certify the robot for duty, culminating with this final exam.
The idea for Mobile Servicing System was conceived by Savi Sachdev who was an engineer at Spar Aerospace in the 1980's. He envisioned the concept of a relocatable arm for the International Space Station. The idea evolved and later became the Mobile Servicing System. Sachdev is now the Director General of Space Utilization for the Canadian Space Agency
In its final exam, which took two days, Dextre performed a series of steps to remove a 442-kg storage box known as a cargo transport carrier and relocate it to another work site a short distance away. The move was necessary to free up the work site for the Alpha Magnetic Spectrometer which is scheduled for delivery by the Space Shuttle Endeavour (STS-134) in early April, 2011.
Dexter's final exam would seem like a relatively simple exercise. However for a robot it takes a series of precise moves to accomplish the task. Working in weightlessness makes the task harder as everything not properly anchored down could float away and possibly even becoming a danger to the ISS.
To start the exam Dextre first unbolted the cargo transport carrier, lifted it up and then fastened it onto its workbench. The workbench acts as a temporary storage platform that allows the Dextre to carry equipment while keeping his manipulators free. According the CSA setting the cargo transport carrier down onto the workbench requires extreme precision and delicacy as Dextre's human operators on the ground need to align the carrier within one degree in order to lock down the interfaces properly, all while ensuring that the mechanical parts were not crushed in the process by applying too much force.
"When astronauts train to do this type of task during a spacewalk, they get to practice again and again until they are comfortable with the procedure," says Tim Braithwaite, the Canadian Space Agency's representative at NASA's Johnson Space Center in Houston, Texas. "We're operating a new robot via remote control, doing a task that has never been done robotically, with precision levels that have to be near-perfect. So this test is also about gaining experience for the ground team and learning how to operate Dextre's complicated systems."
Operations on the first day wrapped up when Dextre successfully locked the cargo transport carrier down onto his workbench, where it sat throughout the night. Day 2's tasks consisted of removing the carrier from the workbench, and latching it down to its new location on the ISS.
Dextre will perform routine tasks which otherwise astronauts would have to do thus allowing astronauts more time to perform science experiments on the space station.
Dextre's first official task will be to unload the External Pallet from Japan's HTV-2 cargo spacecraft which is set to bring supplies to the space station in early February 2011.
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