INTERNATIONAL SPACE STATION — NASA astronauts Jessica Meir and Chris Williams completed a seven-hour and 20-minute spacewalk outside the International Space Station to replace a broken joint on the station's robotic arm, Canadarm2. The operation restored functionality after ground controllers at Johnson Space Center in Houston detected a fault on May 27.

On May 27, flight controllers observed that one of Canadarm2's seven joints was drawing more current than expected and not moving properly. NASA managers and experts with the Canadian Space Agency concluded the joint had failed and needed to be replaced. Meir and Williams began the spacewalk when they switched their spacesuits to battery power at 8:20 a.m. ET.

During the spacewalk, Williams and Meir detached the arm's latching end effector (LEE) and two other healthy joints. The 900-pound LEE assembly was temporarily mounted on a nearby shelf. They then removed joint No. 5, a 200-pound wrist joint that had failed. Flight director Fiona Antkowiak said, "We'll remove the failed joint five, replace it with the spare joint and then once that's back on the arm, our last major task will be to get that LEE cluster that we temporarily stowed and put it back onto the robotic arm so that we have a fully assembled arm at the end of the spacewalk."

The replacement joint, sourced from one of two spares stored on an external stowage platform, was successfully installed four and a half hours into the spacewalk. Williams and Meir reattached the LEE cluster five and a half hours after starting their extravehicular activity. Flight controllers subsequently powered up the arm and verified good electrical connections through the newly installed joint. NASA commentator Sandra Jones said, "Today we did hear good confirmation that ... Canadarm2 has two good strings of power and data to the arm. So today's wrist surgery was successful."

Williams brought the failed joint back into the airlock so it can eventually be returned to Earth for repairs. Once repairs are complete, the refurbished joint and one other will be relaunched to the space station for future use. Canadian astronaut Jenni Gibbons commented on the astronauts' efforts upon the successful installation, stating, "That is a good install, you guys. I know that was tough. Wonderful work." This spacewalk marked Meir's fifth spacewalk and Williams's second; it was also the third ISS spacewalk of the year and the 280th overall.

Why It Matters

The robot arm is used to capture Northrop Grumman's Cygnus cargo ships and move components and spacewalkers during maintenance operations. ISS operations and integration manager Bill Spetch said, "Systems like Canadarm2 were designed from the beginning with replaceable components and were planned with maintenance in mind. This is no exception." He added, "There's not a time where we say hey, we're just done repairing the arm. Overall, the arm is critical for station operations and continued maintenance of it throughout to the end of life."