NASA fixes a 21-year-old fault aboard Voyager 1 that no one thought could ever be solved

NASA has managed to revive thrusters aboard the Voyager 1 spacecraft that stopped working in 2004. The engineers studied the problem and deemed that the problem could not be fixed. Since then, Voyager 1 has been depending solely on its backup roll thrusters.

Voyager 1 was launched in 1977 and is zooming through interstellar space at a speed of 56,000 kph. Currently, it is 25 billion kilometres from Earth. The thrusters help the Voyager keep the antennas directed towards Earth to continue sending data and receiving commands. The spacecraft moves in different directions using these thrusters. The primary set of thrusters carries the other thrusters that control the spacecraft’s roll motion.

Thrusters keep Voyager moving towards a guide star

NASA said that "the roll motion rotates the antenna like a vinyl record to keep each Voyager pointed at a guide star it uses to orient itself." For this roll motion, the Voyager has a primary and backup set. There is an additional set of thrusters that helps it change trajectory when it comes close to a planet in outer space. They were fixed in 2018 and 2019, however, these cannot induce roll motion.

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Tubes in the thrusters are at risk of clogging, which is why scientists switch between the three types of thrusters. Voyager 1 lost power in two small internal heaters 21 years ago, after which its primary thrusters stopped working. Engineers opted to rely solely on Voyager 1’s backup roll thrusters to orient the star tracker, since they were in perfectly good condition, said Kareem Badaruddin, Voyager mission manager at JPL, which manages the mission for NASA.

NASA engineers were worried the secondary thrusters on Voyager would stop working soon

They were also not hopeful that Voyager would continue to travel through space 20 years later. But now that it is still working, NASA engineers are worried about the backup thrusters. If they also stopped working, then the spacecraft wouldn't be able to make a roll motion. So they decided to reexamine the primary thrusters.

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They figured out that "an unexpected change or disturbance in the circuits that control the heaters’ power supply had effectively flipped a switch to the wrong position." They now needed to turn the switch back to its original position, as that might provide a chance for the heaters to work again.

NASA faced a tough deadline to fix Voyager 1 thrusters

They needed to solve the problem before May 4, 2025, since from then onwards till February 2026, Deep Space Station 43 (DSS-43) in Australia would be offline for upgrades, opening only for small periods in August and December. Engineers were worried that by August, the primary thrusters might be completely clogged. So they wanted to ensure the primary thrusters were up and running by that time.

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The DSS-43 is a 230-foot-wide antenna in Canberra, Australia, that’s part of NASA’s Deep Space Network. California and Madrid also have two such complexes, but the one in Canberra is the only dish with enough signal power to send commands to the Voyagers.

NASA engineers saw their plan become a success 23 hours later

On March 20, they witnessed their commands being executed on the spacecraft, almost a day later than it actually happened, since the radio signal takes over 23 hours to travel from the spacecraft to Earth.

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Voyager 1 might have been doomed if the plan failed. However, within 20 minutes, the temperature of the thruster heaters rose, and the NASA engineers knew they had cracked the 21-year-old puzzle.

“It was such a glorious moment. Team morale was very high that day,” said Todd Barber, the mission’s propulsion lead at JPL.