NASA

MIT

Michele Famiglietti

NASA

NASA

NASA

NASA

NASA

NASA

NASA

The Alpha Magnetic Spectrometer has served during the last six years as a silent witness to the formation of the universe, quietly collecting about 100 billion cosmic rays, particles, and nuclei with energies up to 1 trillion electron volts. "The results show unexpected phenomena—they are not predicted by current cosmic ray models—and this is changing our understanding of the cosmos," principal investigator Sam Ting told Ars.

But as this publication recently reported, there is a problem with the AMS particle detector's cooling system, and NASA is planning an extensive set of repairs. This will likely include a series of "Hubble-esque" spacewalks in 2018 to install a new cooling system for the $2 billion instrument. After the initial story, Ting provided Ars with more information about the scope and timing of the repairs.

According to Ting, there are four redundant pumps in the cooling system that keep AMS' silicon tracker at a constant 10 degrees Celsius, plus or minus three degrees. The system was originally designed to last three years in space, but now after almost six years two of the four pumps have stopped functioning. The experiment is using the third pump, which is operating normally. The fourth pump has shown signs of malfunctioning and is therefore kept in reserve.

Given that the rest of the experiment is continuing to function beyond its design lifetime, both the AMS scientists and NASA would like to see the experiment continue and are preparing to fix a machine that wasn't designed with on-orbit servicing in mind. The repairs will therefore involve several tricky spacewalks, for which NASA has had teams of astronauts, engineers, and flight directors training for more than a year. Ting explained that the repair plans are still not final, but are coming into shape.

"Together with the NASA Johnson Space Center, we have improved the pump design to extend the lifetime of AMS to coincide with the lifetime of the ISS," he said. "Twelve new pumps have been ordered and will be delivered in September of this year. After extensive tests, four of the new pumps are scheduled to be sent to the space station in the later part of 2018 as replacements."

Despite the cost (one person involved in the planning said that under some scenario, the repairs could cost as much as $100 million), researchers say the additional time collecting data is critical to the experiment's success. "By collecting data until at least 2024, we should be able to make a statement on the origin of dark matter and antimatter," Ting said. "So far, all other the instruments are operating normally and we expect to stay operational on the space station for its lifetime."

Listing image by NASA