NASA astronauts step out on Christmas Eve spacewalk

Two NASA astronauts stepped out Tuesday 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 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 57-foot (15-meter) 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 maneuvered 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 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. Orchestrating the spacewalks from inside the station's Destiny laboratory was Wakata of the Japan Aerospace Exploration Agency. He arrived at the space station in November for a half-year stay as part of the six-member international crew. In March, he will become the first Japanese commander of the space station, NASA said. Meanwhile, Mastracchio was wearing a different spacesuit than the one he donned on Saturday, a backup that was stored at the station and was resized to fit him over the weekend. On Saturday, a "small amount of water" had entered his suit's cooling system in the space station airlock after he finished the 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. As a backup measure, the astronauts are now outfitted with emergency snorkels in their spacesuits and extra pads to absorb any leaking water in their helmets. NASA officials have said the suits, which were designed 35 years ago, are safe, and stressed that Saturday's problem did not put Mastracchio in any danger. The spacewalk marks the second of Hopkins' career, and the eighth for Mastracchio. 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. 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.