Two space station astronauts popped in a new pump during a rare Christmas Eve spacewalk Tuesday, eager to wrap up urgent repairs to a cooling system.

It was the second spacewalk in four days for U.S. astronauts Rick Mastracchio and Michael Hopkins, and only the second Christmas Eve spacewalk in NASA history.

NASA ordered up the spacewalks to revive a critical cooling loop at the International Space Station. All nonessential equipment had to be turned off when the line conked out Dec. 11, and many science experiments halted.

Mastracchio and Hopkins removed the faulty ammonia pump during Saturday’s outing. On Tuesday, they installed the fresh pump 260 miles above the planet.

“It’s like Christmas morning opening up a little present here,” Mastracchio said as he checked his toolkit. Later, as he worked to remove the spare pump from its storage shelf, he commented: “Now it really feels like I’m unwrapping a present.”

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