ISS astronauts repaired cosmic ray detector during a spacewalk

Over the weekend, a pair of astronauts aboard the ISS went on a spacewalk to work on an instrument that some believed unrepairable. The instrument that astronauts Andrew Morgan from NASA and Luca Parmitano from Italy worked on was the Alpha Magnetic Spectrometer. The duo worked on the same instrument last month.In the previous spacewalk, the duo installed new coolant pumps to fix the damaged cooling system and checked for leaks in the plumbing of the instrument. A leak was discovered, and the fittings were tightened to stop it. The spectrometer is a $2 billion instrument meant to search the heavens for antimatter and dark matter.

If the repairs went well, the instrument, which launched to the ISS in 2011, could resume its search next week. NASA says that the spacewalks to try and repair the instrument are the most complex since astronauts repaired the Hubble space telescope several decades ago. To fix the spectrometer, Morgan and Parmitano had to cut a stainless steel pipeline to bypass the degraded coolant pumps and splice the tubes into four new pumps.

The coolant was carbon dioxide, and in addition to checking for leaks of that coolant, the astronauts also installed thermal insulation. The spectrometer is a massive instrument that weighs 7.5 tons and was sent to the space station aboard the next to last space shuttle flight in 2011. The instrument was shut down late last year for repair work.

While it was operating, it studied more than 148 billion charged cosmic rays. The repairs would allow the spectrometer to continue to work for the remainder of the life of the ISS, which is another five to ten years. The original plan for the instrument was for it to operate for three years; it has already surpassed its expected lifetime.