Spacewalkers replace the cooling pumps of the ISS cosmic particle detector

Matter and antimatter were created during the big bang in equal amounts. However, matter and antimatter annihilate each other and the reason why the universe is ruled by matter today is not clear. Then to shed more light on this phenomenon, the Alpha Magnetic Spectrometer (AMS) was launched in space and installed in May 2011 on the International Space Station (ISS) which orbits around Earth.

The AMS was built to study high-energy cosmic rays to gather clues about what happened to antimatter subsequent to the big bang. The AMS moreover may clarify the nature of the unseen dark matter permeating the universe and the mysterious dark energy that appears to be speeding up the expansion of the cosmos.

To achieve the required sensitivity, the AMS particle detectors must be chilled using carbon dioxide (CO₂) refrigerant circulating through thin lines. Originally designed to operate for just three years, the AMS chalked up eight years of operation before being hobbled by cooling pump failures.

The AMS was not designed to be serviced in orbit and connecting the small, relatively fragile coolant lines while working in pressurised spacesuits was considered an especially challenging task, rivaling work to repair some of the Hubble Space Telescope's most delicate systems.

So, during a 6.5-hour spacewalk, at the end of November 2019, two space astronauts, European Space Agency astronaut Luca Parmitano and NASA crewmate Drew Morgan successfully cut eight stainless steel tubes, including one that vented the remaining carbon dioxide from the old cooling pump. The crew members also prepared a power cable and installed a mechanical attachment device before setting up the new cooling system.

This work has cleared the way for Parmitano and Morgan’s following spacewalk early December 2019 whose objective has been to bypass the old thermal control system by attaching a new one off the side of the AMS, and then conduct leak checks during a final spacewalk on January 25, 2020.

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