NASA investigates mysterious problem on Voyager 1 spacecraft, launched in 1977

The Voyager 1 probe is still exploring interstellar space 45 years after launch, but it has encountered a problem that puzzles the spacecraft team on Earth.

Voyager 1 continues to operate well despite its advanced age and distance of 23.3 billion kilometers from Earth. It can receive and execute commands sent from NASA, as well as collect and send back scientific data.

But the readings from the articulation and attitude control system, which controls the spacecraft’s orientation in space, don’t match what Voyager is actually doing. The articulation and attitude control system, or AACS, ensures that the spacecraft’s high-gain antenna remains pointed at Earth so Voyager can send data back to NASA.

Due to Voyager’s interstellar location, it takes 20 hours and 33 minutes to travel one way, so the call and response of a message between NASA and Voyager takes two days.

So far, the Voyager team believes that the AACS is still working, but the instrument’s data reads seem random or impossible. So far, the system issue has not triggered anything that could put the spacecraft into “safe mode,” which is when only essential operations occur so engineers can diagnose a problem that would put the spacecraft at risk.

And Voyager’s signal is stronger than ever, which means the antenna is still pointed at Earth. The team is trying to determine if this incorrect data is coming directly from this instrument or if another system is causing the problem.

“Until the nature of the problem is better understood, the team cannot predict whether it might affect how long the spaceship can collect and transmit scientific data,” according to a NASA statement.

“A mystery like this is kind of the course at this stage of the Voyager mission,” Suzanne Dodd, project manager for Voyager 1 and 2 at NASA’s Jet Propulsion Laboratory in Pasadena, California, said in a statement.

“Both spacecraft are nearly 45 years old, which is far beyond what mission planners anticipated. We are also in interstellar space – a high-radiation environment that no spacecraft has flown before. So there are some big challenges for the engineering team. But I think if there is a way to solve this problem with AACS, our team will find it.”

If the team doesn’t determine the source of the problem, it may simply adapt to it, Dodd said. Or, if they can find it, the problem can be resolved by making a software change or relying on a redundant hardware system.

Voyager once relied on backup systems to last as long as they did. In 2017, the spacecraft fired thrusters that were used during its initial planetary encounters during the 1970s — and they still worked after lying unused for 37 years.

Older probes produce very little power per year, so subsystems and heaters have been shut down over the years so that critical systems and scientific instruments can continue to operate.

Voyager 2, a twin spacecraft, continues to operate well in interstellar space 19.5 billion kilometers from Earth. By comparison, Neptune, the furthest planet from Earth, is at most only 2.9 billion kilometers away. Both probes were launched in 1977 and far exceeded their original purpose of flying by planets.

Now, they have become the only two spacecraft to collect data from interstellar space and provide information about the heliosphere, or the bubble created by the sun that extends beyond the planets in our solar system.