CSA’s Dextre Robotic Arm Ready for Duty on ISS


December 24, 2010 – Dextre, the Canadian Space Agency’s robotic handyman aboard the International Space Station (ISS), successfully passed his final exam yesterday and is now officially certified for duty.

While riding on the end of Canadarm2, Dextre performed a series of steps to remove a 442-kg storage box known as a cargo transport carrier (a generic platform for ISS cargo and payloads) and relocate it to another worksite a short distance away. The move was necessary to free up the worksite for the Alpha Magnetic Spectrometer, scheduled for delivery on STS-134 (the final Space Shuttle flight) in 2011.

Extreme precision—with a delicate touch

For humans, the exam seems deceptively simple: it’s a no-brainer for us to pick up a box and move it a few metres away. Not so for a robot, though—especially one working in weightlessness, where everything not properly anchored down could risk floating away, and possibly even becoming a danger to the Station.

Instead, the move was broken down into a sequence of steps that took a total of two days to complete. First, Dextre unbolted the cargo transport carrier, lifted it up and then fastened it onto his workbench (a temporary storage platform that allows the robotic handyman to carry equipment while keeping his hands free). But setting the cargo transport carrier down onto the workbench requires extreme precision and delicacy: Dextre’s human operators on the ground needed 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.

What’s next for Dextre?

Dextre was developed by MDA for the Canadian Space Agency to reduce the need for astronauts to conduct spacewalks for routine maintenance on the Space Station’s exterior, and therefore free up the crew’s time for more important activities, like conducting science experiments. Since its launch in 2008, Dextre has been completing a series of planned tasks to certify the robot for duty. Designed to test its systems and performance, the certification process is essential because the robot could not be assembled and tested in Earth’s gravity. It also serves as a dress rehearsal for Dextre’s first official task when it will unload EP (External Pallet) from Japan’s HTV-2 spacecraft (a space “moving van” that carries supplies to the ISS) in early February 2011.

Dec. 30, 2010

NASA has awarded a sole source contract to Lockheed Martin Space Systems Company (LMSSC) of Greenbelt, Md., for Systems Engineering for In-Space Servicing (SEISS). This cost-plus-fixed-fee, 18-month contract has a value of $31.2 million.

LMSSC will provide systems and discipline engineering support to develop and execute two demonstrations to test and verify new robotic servicing capabilities using the Dextre robot aboard the International Space Station. The Canadian Space Agency’s Special Purpose Dexterous Manipulator, or Dextre, is a two-armed robotic system designed to perform intricate maintenance and servicing tasks, which previously would have required spacewalks.

The first demonstration will use a customized payload task box, Dextre and specialized tools to robotically demonstrate refueling and repair tasks in orbit. Tasks will include locating, accessing and uncapping valves and transferring simulated liquid fuel. During the second demonstration, Dextre will test and evaluate a variety of tools, sensors and instruments to support autonomous rendezvous and capture capabilities for orbiting spacecraft systems.

NASA’s Goddard Space Flight Center in Greenbelt, Md., is developing both demonstration payloads. These demonstrations are intended to increase NASA’s technical capability to conduct robotic in-space servicing. The contract encompasses requirements definition and verification, hardware design, support of flight and ground hardware/software development, and mission planning support.