Astronauts aboard the International Space Station have received a gift just in time for Christmas: a new pump module to repair their ailing cooling system and to restore the outpost to full power.

NASA astronauts Rick Mastracchio and Mike Hopkins embarked on their second spacewalk together, setting out at 6:53 a.m. EST (1153 GMT) on Tuesday (Dec. 24) to complete the work they began Saturday to remove and replace an ammonia pump module with a faulty flow control valve.

"Houston from the airlock, we'd just like to say thanks to all the great folks doing all this hard work to get this space station back up and running," Mastracchio radioed at the end of the spacewalk, which concluded at 2:23 p.m. EST (1923 GMT), seven hours and 30 minutes after it began. [See photos from the Christmas Eve spacewalk]

"No, thank you guys," astronaut capcom Doug Wheelock replied from NASA's Mission Control in Houston. "It is the best Christmas ever. Thanks, guys."

"I'd just like to add to that," Hopkins said. "Fantastic work, merry Christmas to everybody. It took a couple of licks to get her done, but we got it."

The Christmas Eve EVA extravehicular activity, NASAs term for a spacewalk had the two astronauts retrieve a spare of the refrigerator-size cooling system device and install it on the space stations starboard, or right, side backbone truss. The 780-pound (355 kg) pump module replaced a faulty unit Mastracchio and Hopkins successfully and speedily removed three days ago.

The removal, which came just 10 days after a valve inside the module ceased working properly, was originally slated to be part of this second outing, but Mastracchio and Hopkins made quick work of disconnecting the degraded unit, allowing them the time to also remove and stow the module during the spacewalk Saturday.

Their get-ahead work negated the need for a planned third spacewalk.

Pump module in place

The failure of the flow control valve, which regulates the temperature of the ammonia coolant passing through the pump, resulted in restricting the space station to the use of just half of its cooling loop system needed to maintain equipment temperatures inside and outside of the outpost. Non-critical systems and science experiment hardware in two of the stations laboratories have been without power since the valve malfunctioned on Dec. 11.

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Space Station Gets New Pump for Christmas