ISS Crew Repairs $2 Billion Dark Matter Detector

A decade ago, NASA, CERN, and dozens of other institutions banded together to build the Alpha Magnetic Spectrometer (AMS) at a cost of $2 billion. This advanced instrument has helped scientists study dark matter from its perch on the International Space Station, but components have started failing in recent years. The AMS was never intended to be serviceable, but after a series of spacewalks, astronauts have managed to resurrect this spendy science module

The AMS arrived at the International Space Station in 2011 on one of the final Space Shuttle cargo runs. The team didn’t believe it would be possible to repair the instrument in orbit, so it wasn’t designed with repairs in mind. The AMS was only supposed to operate for three years, but the insights it provided into the nature and quantity of dark matter proved extremely valuable. As the instrument’s cooling pumps began failing, space agencies decided to take a shot at repairing the AMS. 

NASA sent specialized tools and replacement parts to the ISS last year in preparation for the repair operation, which is expected to take as many as five spacewalks. There are four coolant pumps in the AMS, but only one of them was operational by 2019 when the first spacewalk took place. The ISS crew completed two spacewalks in November 2019, and a third happened in December 2019. Last weekend, European Space Agency astronaut Luca Parmitano and Andrew Morgan of NASA completed the repairs on the fourth and final spacewalk. 

The AMS mounted to the exterior of the ISS.

Repairing the AMS consisted of installing new cooling pumps (seen in the top image), replacing the power and data cabling, and repressurizing the liquid carbon dioxide coolant. Most of the hardware work was completed in the previous three spacewalks, but Parmitano and Morgan needed to go over the instrument and check every fitting and cable before pressurizing the new cooling system. The pair did spot a minor leak in one of the cooling lines, but they were able to rectify that by tightening the fitting. 

The ground team has confirmed that early testing shows the AMS operating as expected. However, it’s not ready to do science yet. The cooling system has to run for several more days to stabilize temperatures across the instrument, and then the team will power it on and run more tests. NASA believes the AMS will be operation again by the end of next week.

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