NASA astronauts have successfully wrapped up a Christmas Eve spacewalk to make repairs at the orbiting International Space Station, the US space agency has said.
"We have a pump that is alive and well," said a NASA commentator on live television on Tuesday after a successful jump-start test to the newly installed ammonia pump module, a bulky piece of gear the size of a refrigerator.
More checks would be done later, but the pump appeared to be in good shape and would be fully activated in the coming hours, a NASA commentator said from mission control in Houston.
American astronauts NASA Rick Mastracchio, 53, and Mike Hopkins, 44, made the only second Christmas Eve spacewalk in in NASA's history on Tuesday. The first was 14 year ago.
They managed to complete almost two days' worth of work in a single outing that lasted just five and a half hours, ending an hour earlier than planned.
Mastracchio and Hopkins made swift work of their first spacewalk on Saturday, disconnecting and pulling out the old cooling pump that regulates the temperature of equipment at the orbiting space lab.
Tuesday's spacewalk was the second of Hopkins' career, and the eighth for Mastracchio.
The shutdown of one of the two external cooling lines forced the six-man crew of the International Space Station to turn off all non-essential equipment, including experiments.
Later this week, Russian cosmonauts Oleg Kotov and Sergey Ryazanskiy will make a spacewalk on December 27 to install a pair of high-fidelity cameras on the Zvezda service module and to do maintenance on the Russian segment of the station.
Flight Engineer Koichi Wakata of the Japan Aerospace Exploration Agency operated the space station's 17-meter robotic arm, which hoisted Hopkins and the new, refrigerator-sized pump module from its stowage platform to the place it was to be installed.
Wakata arrived at the space station in November for a half-year stay as part of the six-member international crew.
He will become the first Japanese commander of the space station in March.
During the space walk on Tuesday, Mastracchio wore a different spacesuit than he did Saturday, a back-up that was stored at the station and was resized to fit him.
A "small amount of water" entered the suit's cooling system in the space station airlock after Mastracchio finished the last spacewalk, NASA said.
But the US space agency said the problem was not related to the water leak in a helmet that cut short Italian astronaut Luca Parmitano's spacewalk in July and risked drowning him.
NASA is still investigating what went wrong in that case.
Despite the concerns about leaking spacesuits, neither astronaut reported any problems during the seven and a half hour outing.
NASA said the last time astronauts embarked on a Christmas Eve spacewalk was 14 years ago, when space shuttle Discovery astronauts Steve Smith and John Grunsfeld stepped out to install upgrades and new insulation on the Hubble Space Telescope.