Italian astronaut Luca Parmitano and NASA crewmate Drew Morgan stepped outside the International Space Station Friday for the second of four spacewalks to repair a $2 billion cosmic ray detector.
Floating in the Quest airlock compartment, the astronauts switched their spacesuits to battery power at 7:02 a.m. EST, officially kicking off the year’s tenth spacewalk, the 223rd since station assembly began in 1998. A few moments later, they made their way outside to continue work to upgrade the Alpha Magnetic Spectrometer’s coolant system.
For identification once the spacewalk begins, Parmitano, call sign EV-1, is wearing a suit with red stripes and is using helmet camera 11 while Morgan, EV-2, is wearing an unmarked suit with helmetcam 18.
The 7.5-ton AMS, mounted on the right side of the station’s power truss, was not designed to be serviced by spacewalking astronauts, and fixing its failing cooling system is considered the most challenging repair work since shuttle astronauts serviced the Hubble Space Telescope.
During an initial outing last Friday, Parmitano and Morgan removed a debris shield from the AMS, installed handrails, cut zip ties holding cables and coolant lines in place and pulled back insulation, getting well ahead of schedule and carrying out several tasks originally planned for the second excursion.
Today’s revised spacewalk is focused on prepping power and data cables needed by a new coolant pump module; installing a mounting bracket to hold the new pump package in place; cutting a 6-millimeter-wide line to vent carbon dioxide coolant overboard; and cutting eight more even smaller lines that carry CO2 through the instrument.
During a third spacewalk Dec. 2, the astronauts will attach the new pump module and splice, or swage, new coolant lines to the ones that were cut earlier. A fourth spacewalk is planned to close out the overhaul and address any follow-up work that might be needed after a series of tests.
The Alpha Magnetic Spectrometer was designed to detect high-energy cosmic rays in long-term research to learn what happened to the antimatter presumably cooked up in the big bang. It also is looking for clues about the nature of unseen dark matter and the equally mysterious dark energy that is speeding up the expansion of the universe.
Launched to the station in 2011 aboard the next-to-last space shuttle mission, the AMS was designed to operate for three years. But the instrument managed an additional five years before being hobbled by coolant pump failures, and NASA opted to attempt the spacewalk repair job to extend its life.
“It’s not only replacing the pumps, it’s replacing the accumulator, its replacing the heat exchangers, heaters, valves, that whole pump package,” said Ken Bollweg, the AMS project manager at the Johnson Space Center in Houston. “It’s a whole new package that’s designed to extend the life until the end of space station.”