Two NASA astronauts headed outside the International Space Station today, Dec. 24, for the second and last spacewalk to repair a faulty cooling system, according to Reuters.

Astronauts Mike Hopkins and Rick Mastracchio will spent approximately six hours outside the ISS to install the new ammonia cooling system pump.

The faulty cooling system was removed during a spacewalk on Dec. 21, according to Reuters. The spacewalk is being broadcasted on NASA TV.

This is Hopkins second spacewalk whereas Mastracchio has been apart seven spacewalks.

"Let's get to work," Hopkins said as left the station around 7 a.m.

The second spacewalk would have been Dec. 23, but it was pushed a day so that Mastracchio could "swap suits" according to AP.

Mastracchio accidentally hit the water switch in the air lock after they were done working on Dec. 21, and engineers believe that water was able to get into his suit.

The suit now has to dry for another three or four days before it can be used again, according to AP.

Mastracchio and Hopkins spent their off day on Dec. 22 to make a new spacesuit from spare components already on the space station.

"It's like Christmas morning opening up a little present here," Mastracchio said as he was outside the ISS, according to Reuters. "Now it really feels like I'm unwrapping a present."The only other Christmas Eve spacewalk took place in 1999 during a Hubble Space Telescope repair effort.

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