Spacewalking astronauts worked Saturday to complete repairs to a cosmic ray detector outside the International Space Station and give it new life. It was the fourth spacewalk since November for NASA's Andrew Morgan and Italy's Luca Parmitano to fix the Alpha Magnetic Spectrometer, the AP reports. They installed new coolant pumps last month to revive the instrument's crippled cooling system and needed to check for any leaks in the plumbing. Parmitano quickly discovered a slight leak and tightened the fittings. "Our day just got a little more challenging," Mission Control observed. Provided everything goes well, the $2 billion spectrometer—launched to the space station in 2011—could resume its hunt for elusive antimatter and dark matter next week, according to NASA.
"Good luck out there, have a lot of fun," astronaut Jessica Meir radioed from inside. NASA has described the spectrometer spacewalks as the most complicated since the Hubble Space Telescope repair missions decades ago. Unlike Hubble, this spectrometer was never intended for astronaut handling in orbit, and it took NASA years to devise a repair plan. The first three spacewalks went well. Morgan and Parmitano cut into stainless steel pipes to bypass the spectrometer's old, degraded coolant pumps, then spliced the tubes into the four new pumps—no easy job when working in bulky gloves. The system uses carbon dioxide as the coolant. Besides checking for leaks Saturday, the astronauts had to cover the spectrometer with thermal insulation. The 7½-ton spectrometer was shut down late last year for the repair work, after it had studied more than 148 billion charged cosmic rays. The repairs should allow the spectrometer to work for the rest of the space station's life, another five to 10 years.
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