Alpha Magnetic Spectrometer gets new cooling pump
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European Space Agency astronaut Luca Parmitano rides the station’s robotic arm to the Alpha Magnetic Spectrometer during U.S. EVA-60 on Nov. 22. Credit: NASA
NASA astronaut Drew Morgan and European Space Agency astronaut Luca Parmitano competed the third of four planned spacewalks to repair the Alpha Magnetic Spectrometer particle physics experiment at the International Space Station.
The outing, dubbed U.S. EVA-61, started at 11:31 UTC Dec. 2, 2019, and involved installing a new cooling pump system on the outside of the device. This was the fifth spacewalk for Parmitano’s career and the sixth for Morgan.
Launched to the ISS aboard a space shuttle in 2011 and attached to the S3 truss segment, the Alpha Magnetic Spectrometer was designed to last three years. However, it continued to work for more than five years beyond that life expectancy.
The experiment collects cosmic ray particles and records their mass, velocity, charge and direction of travel. According to NASA, the instrument collected data for over 140 billion cosmic ray events during its roughly 8.5 years in orbit.
The primary part of the experiment is called the tracker and it collects data on particles as they go through the detector. However, it requires cooling. There are four redundant cooling pumps inside the device — all but one had failed by 2017, and it was also starting to show signs of failure.
Since then, NASA has worked to design a new cooling system to prolong the instrument well into the 2020s. This series of spacewalks is said to be the most challenging since the Hubble servicing missions in the space shuttle era as the Alpha Magnetic Spectrometer was never supposed to be serviced once at the ISS.
Engineers had to design special tools and procedures to tap into the existing cooling system and route fluid lines to the new system, which was brought to the outpost via the recent NG-12 Cygnus spacecraft in early November.
On Nov. 15 and Nov. 22, Morgan and Parmitano ventured outside the ISS on spacewalks to prepare the spectrometer to receive this new cooling system. They were required to remove a debris panel, install new handrails and cut eight steel fluid lines.
For the third spacewalk, the duo brought the upgraded tracker thermal pump system, also called the UTTPS, to the Alpha Magnetic Spectrometer, bolted it to the side of the experiment and began installing power and data cables before splicing the cut fluid lines onto the new box via swaging.
Parmitano and Morgan breezed through the spacewalk and even had time to perform a get-ahead task — installing a thermal blanket at the base of the spectrometer.
From there, the two spacewalkers cleaned up their work area and made their way back to the airlock to conclude the outing some 6 hours, 2 minutes after it began.
This spacewalk essentially completes the repair work on the Alpha Magnetic Spectrometer.
However, the two astronauts will need to go outside one more time to check to ensure there are no leaks coming from the instrument. There are special indicators on the new box that will let the astronauts know if the line needs tightened.
However, if everything seems good to go, ground teams will begin bringing the particle physics experiment back to life.
That final spacewalk, likely to be dubbed U.S. EVA-62, is tentatively scheduled for Dec. 8. However, it is unclear exactly when NASA will schedule the outing as the six-person Expedition 61 crew has to juggle up to three visiting vehicles arriving at the ISS within the next two-and-a-half weeks.
U.S. EVA-61 was the 224th spacewalk in support of ISS assembly and maintenance since 1998. This means astronauts have spent a total of 58 days, 15 hours and 43 minutes working outside the station.
