WATCH LIVE: NASA Christmas Eve spacewalk

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NASA spacewalk


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(CNN) — While many people may spend Christmas Eve doing last-minute shopping, two American astronauts have a more challenging matter to attend to Tuesday.

In orbit more than 200 miles above Earth, flight engineers Rick Mastracchio and Mike Hopkins embarked on a spacewalk Tuesday morning to repair part of the International Space Station’s cooling system.

More than three hours into the job, the two astronauts had successfully bolted a replacement ammonia pump module into its location and were working to connect lines to allow the ammonia to flow, NASA said in a tweet.