WATCH LIVE: NASA Astronauts fix cosmic ray detector in spacewalk

CAPE CANAVERAL, Fla. (AP) — Astronauts have begun an extraordinarily complicated series of spacewalks to fix a cosmic ray detector at the International Space Station.

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Italian astronaut Luca Parmitano and U.S. astronaut Andrew Morgan ventured out Friday with dozens of tools and four new pumps for the Alpha Magnetic Spectrometer. NASA considers these spacewalks the most difficult since the Hubble Space Telescope repairs a few decades ago.

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Unlike Hubble, the spectrometer was never meant to undergo space surgery. After 8 ½ years in orbit, its cooling system is almost dead.

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Parmitano and Morgan will go out at least four times this month and next to revitalize the instrument. NASA describes the work as a heart bypass.

The $2 billion spectrometer is searching for elusive antimatter and dark matter. It’s already studied 148 billion cosmic rays.