In May, NASA scientists said the Voyager 1 spacecraft was returning inaccurate data from its altitude control system. The mysterious issue is still ongoing, according to the mission’s engineering team. Now, in order to find a solution, engineers are digging through decades-old textbooks.
Voyager 1, along with its twin Voyager 2, was launched in 1977 with a five-year lifespan to closely study Jupiter, Saturn, Uranus, Neptune and their respective moons.
After nearly 45 years in space, both spacecraft are still functioning. In 2012, Voyager 1 became the very first man-made object to venture beyond the limit of our sun’s influence, known as the heliopause, and into interstellar space. It is now about 14.5 billion kilometers from Earth and is sending back data from beyond the solar system.
“No one thought it would last this long,” Suzanne Dodd, project manager for the Voyager mission at NASA’s Jet Propulsion Laboratory, told Insider, adding, “And here we are.”
Voyager 1 was designed and built in the early 1970s, complicating efforts to fix the spacecraft’s problems.
Although Voyager’s current engineers have documentation—or order media, the technical term for documents containing details of the spacecraft’s design and procedures—from those early mission days, other important documents may have been lost or misplaced.
During the first 12 years of the Voyager mission, thousands of engineers worked on the project, according to Dodd. “When they retired in the 70s and 80s, there wasn’t a lot of pressure to have a library of project materials. People would take their boxes home to their garage,” Dodd added. In modern missions, NASA maintains stronger documentation archives.
There are a few boxes with documents and schematics stored offsite from the Jet Propulsion Laboratory, and Dodd and the rest of Voyager’s handlers can request access to these records. Still, it can be a challenge. “To get that information, you have to figure out who’s working in that area on the project,” Dodd said.
For Voyager 1’s latest issue, mission engineers had to specifically search boxes under the names of engineers who helped design the altitude control system. “It’s a process that takes time,” Dodd said.
The spacecraft’s altitude control system, which sends telemetry data back to NASA, indicates Voyager 1’s orientation in space and keeps the spacecraft’s high-gain antenna pointed at Earth, allowing it to to send the data home.
“Telemetry data is essentially a state of system health,” Dodd said. But the telemetry readings that spacecraft handlers get from the system are garbled, according to Dodd, meaning they don’t know if the altitude control system is working properly.
So far, Voyager engineers haven’t been able to find the root cause of the problem, mainly because they haven’t been able to reset the system, Dodd said. Dodd and his team believe this is due to an aging game. “Not everything works forever, even in space,” she said.
Voyager’s glitch may also be influenced by its location in interstellar space. According to Dodd, data from the spacecraft suggests that high-energy charged particles are in interstellar space. “It’s unlikely anyone will hit the spacecraft, but if it did, it could cause more damage to the electronics,” Dodd said, adding, “We can’t identify that as the source of the the anomaly, but that could be a factor.”
Despite the spacecraft’s orientation problems, it still receives and executes commands from Earth, and its antenna is still pointed towards us. “We saw no degradation in signal strength,” Dodd said.
As part of an ongoing power management effort that has intensified in recent years, engineers have turned off non-technical systems aboard the Voyager probes, such as its science instrument heaters, in hopes of maintain them until 2030.
From the discovery of unknown moons and rings to the first direct evidence of the heliopause, the Voyager mission has helped scientists understand the cosmos. “We want the mission to last as long as possible, because science data is very valuable,” Dodd said.
“It’s really remarkable that both spacecraft are still working and working well – small issues, but working extremely well and still returning this valuable data,” Dodd said, adding, “They’re still talking to us.”