Spacewalking astronauts making repairs on International Space Station in Oct.

The first six-hour walk unfolded Thursday morning with Commander Randy Bresnik and Flight Engineer Mark Vande Hei, the space agency said.

Bresnik, on his third walk, and Vande Hei, on his first, are tasked with fixing the orbiting lab's crucial robotic arm, called the Canadarm2, according to NASA officials.

“One of the Canadarm2 grappling mechanisms experienced a stall of its motorized latches last month,” the space agency said.

The problem did not impact ISS operations, but the arm's hand, or Latching End Effector (LEE), needs repair.

The arm is integral to space station operations and can extend 60 feet off ISS, grabbing visiting cargo vehicles and payloads. The LEEs, located at either end of the arm, also provide other crucial data through complex electronics, camera and sensors, NASA officials said, but the arm was launched over 15 years ago and is in need of repair.

The station has a spare LEE stored outside the ISS, which the astronauts retrieved to make the repair.

Two more walks are scheduled, one on Oct. 10 and the other this month on Oct. 18.

These spacewalks will include lubricating the new LEEs on the robotic arm and replacing cameras on the ISS's truss and on the U.S. Destiny lab.