US Spacewalk 95: NASA Astronauts Repair Space Station's 18-meter Canadarm2

Members of the Expedition 74 crew, NASA astronauts Chris Williams and Jessica Meir on Tuesday (June 30), completed US Spacewalk 95, a seven-hour and 20-minute extravehicular activity (EVA) outside the International Space Station (ISS) to repair the Canadarm2 remote manipulator system (RMS).

The spacewalkers replaced a malfunctioning 90-kilogram wrist joint that had failed during routine operations on May 27 due to a seized motor-gearbox assembly.

Canadarm2 is ~18 meters when fully extended, about 1,800 kg (or 1,497 kg to 1,960 kg depending on specific configuration and source). It features seven motorized joints, providing a range of motion similar to a human arm but with the ability to rotate joints 270 degrees. The arm can handle payloads up to 116,000 kg and is capable of "cosmic catches," such as grappling visiting cargo spacecraft.

The repair was critical as Canadarm2, the station’s primary tool for capturing cargo vehicles like SpaceX Dragon and Cygnus, is essential for station operations through its planned decommissioning in 2030. Canadarm2, a space station workhorse, has been in regular use since it was installed on the orbiting outpost in April 2001.

Williams (EV1) and Meir (EV2), each wearing a NASA extravehicular mobility unit (EMU), floated outside the Quest airlock soon after switching the spacesuits to battery power at 1220 UTC. They made quick work of transitioning to their work station, where they retrieved a spare wrist joint by using a power tool (pistol grip unit) to unbolt it from an exterior equipment panel.

The pair were supported from inside the station, by Jack Hathaway (SpaceX Crew-12) and Sophie Adenot (ESA), who operated Canadarm2’s remaining functional joints to position the arm for the repair, guided by mission control from Jenny Gibbons (Canadian Space Agency).

Working meticulously, Williams and Meir removed the old unit and installed the new joint (no. 5), bolting it in place. The astronauts completed their work on the arm by reattaching its latching end effector, or hand, which the arm uses to grapple objects and inchworm across the exterior of the station. Mission Control confirmed that the arm had good power connections after the astronauts' work. They brought the faulty joint back into the space station to be returned to Earth for analysis and possible refurbishment.

The successful repair restored the arm’s full range of motion, clearing the path for the upcoming Soyuz MS-29 crew launch scheduled for July 14. Although designed for a 15-year lifespan, the 25-year-old arm was engineered with modular, replaceable components to allow for in-orbit maintenance. The spare joint was already stored aboard the ISS.

"For over 25 years, the Canadarm2 has been a crucial part of the International Space Station. The arm was key to our orbiting laboratory and continues to be a workhorse that we rely on. Whether it is performing maintenance or replacing equipment, moving and operating payloads, catching cargo vehicles or helping us out during spacewalks, the arm has played and will continue to play an essential role in our work on orbit," Williams said as the spacewalk ended. "It is also a testament to international cooperation. Canada, the U.S. and the world have come together to make this program a success. We are honored … that we were able to give the arm a helping hand."

Tuesday's EVA marked the fourth time in history that spacewalkers have worked to service the Canadarm2. Previously, another wrist joint was replaced and both of the arm's end effectors were swapped out for spares.

Williams and Meir returned to the Quest airlock and began its depressurization at 1940 UTC, marking an end to the spacewalk, Tuesday. "We are thrilled to have repaired the mighty Canadarm2 just in time for Canada Day tomorrow! We hope that all in Canada and everyone around the globe can celebrate this achievement," Meir said.

Today's EVA was the 280th spacewalk in ISS history and marked Williams’ second and Meir’s fifth career spacewalk. Williams has now logged 14 hours and 22 minutes, including a previous EVA with Meir. Meir has totaled 36 hours and 6 minutes, including the first all-female EVA in 2019.