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Two astronauts are spacewalking today to repair the space station’s robotic arm

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One of its latching mechanisms needs to be replaced

This morning, two NASA astronauts will do a spacewalk outside the International Space Station in order to repair the orbiting lab’s main robotic appendage: the Canadian robotic arm. A latching mechanism on the end of the arm isn’t working properly, and the two astronauts are tasked with replacing it. Their spacewalk is the first of three planned for October that revolve around getting the Canadian robotic arm in good shape for doing work outside the ISS.

The arm, informally known as Canadarm2, is one of the most crucial tools on the ISS. The dexterous snake-like instrument can extend up to nearly 60 feet into space and “grab” onto large objects. Canadarm2 was instrumental in the station’s assembly in the early 2000s, helping to move and install large pieces of equipment. Today, it’s routinely used to do inspections on the outside of the ISS, as well as grab and dock incoming cargo spacecraft.

Canadarm2 was launched in 2001, so it’s starting to experience some wear and tear. Specifically, the two latching mechanisms at each end of the arm, called Latching End Effectors, or LEEs, have been deteriorating. One LEE typically stays attached to the ISS, anchoring the arm to the station; the other is extended out into space to grab objects. (The two LEEs can be interchanged.) They’re incredibly complex devices, incorporating sensors, electronics, and a camera.

One of the LEEs on Canadarm2
Image: NASA

Originally, NASA had intended to replace one of the LEEs that looked as if it had degraded significantly. But then in August, the latches on the other LEE stalled during one of the arm’s robotic maneuvers, so NASA decided that one was a higher priority to replace first. The space agency is eager to get this done soon, since the next cargo spacecraft from Orbital ATK is slated to launch to the station in early November. Faulty latches could compromise Canadarm2’s ability to capture the vehicle. NASA still plans to replace the other LEE, but that will happen in January now.

NASA astronauts Randy Bresnik and Mark Vande Hei are tasked with replacing the LEE with another spare one that’s currently attached to the outside of the space station. This is Bresnik’s third spacewalk and the first for Vande Hei. The pair are scheduled to emerge from the ISS at 8:10AM ET, and will likely work on the replacement for the entire six and a half hours allotted for the spacewalk.

On October 10th, Bresnik and Vande Hei will do another spacewalk to lubricate the new LEE on Canadarm2, and then replace a camera on the outside of the station. NASA astronaut Joe Acaba will then join Bresnik during a third spacewalk on October 15th, replacing Vande Hei, to do more lubrication and another camera replacement.

NASA’s coverage of this morning’s spacewalk is set to begin at 6:30AM ET, and the event should last well into the afternoon.