Two NASA astronauts have stepped out on a rare Christmas Eve spacewalk to wrap up repairs to an equipment cooling system at the International Space Station.
Americans Rick Mastracchio, 53, and Mike Hopkins, 44, floated outside the orbiting lab on Tuesday on a second outing to replace an ammonia pump whose internal control valve failed on December 11.
Their task was to retrieve a spare pump module from an external stowage platform and install it.
Despite recent concerns about leaking spacesuits, the spacewalk got off to a smooth start.
After about two hours outside the station, Hopkins, riding a 15-metre robotic arm operated from inside the station by Japanese astronaut Koichi Wakata, managed to unhook the connectors on the spare.
“Okay, my friend you have yourself a pump module,” said a NASA official at mission control in Houston, overheard in footage broadcast live on the space agency’s online television station.
With his boots affixed to the Canadian-made arm, Hopkins’ grasped the refrigerator-sized pump module as Wakata manoeuvred him over to its installation location.
Then, Hopkins and Mastracchio pushed the module into its slot and began affixing it in place.
Hopkins and Mastracchio must complete five electrical connections and four fluid connections before the pump can be activated.
Tuesday’s spacewalk was expected to last six and a half hours, which the US space agency estimated would be enough time to complete the repair job.
NASA said tests would be done on the new pump later on Tuesday to see how well it is working.
Earlier in the day, Mastracchio reported seeing a tiny piece of space junk strike the space station near where the spare pump was stowed.
A NASA commentator said: “micrometeoroid debris … is not uncommon to strike station structures in this 15 years that the International Space Station has been flying in orbit.”
The team made swift work of the first spacewalk on Saturday, disconnecting and pulling out the old cooling pump that regulates the temperature of equipment at the orbiting space lab.
They managed to complete what had been seen as almost two days’ worth of work in a single outing that lasted just five and a half hours, ending an hour earlier than planned.