Voyager 1 continues to do well, despite its advanced age and 14.5 billion miles (23.3 billion km) from Earth. It can receive and carry out commands sent from NASA, as well as collect scientific data and send it back.
But the readings from the Expression and Attitude Control System, which controls the spacecraft’s orientation in space, don’t match what Voyager is actually doing. The Expression and Attitude Control System, or AACS, ensures that the probe’s high-gain antenna remains pointed toward Earth so Voyager can send data back to NASA.
Due to Voyager’s interstellar position, light takes 20 hours and 33 minutes to travel in one direction, so it takes two days to communicate and respond to a single message between NASA and Voyager.
So far, the Voyager team believes AACS is still working, but the instrument’s data readings seem random or impossible. The system issue hasn’t caused anything to put the spacecraft into “safe mode” yet. That’s when only basic operations occur so that engineers can diagnose a problem that would put the spacecraft at risk.
And the Voyager signal is as strong as ever, which means the antenna is still pointed at Earth. The team is trying to determine if this incorrect data comes directly from this tool or if another system is causing it.
According to the NASA release, “Until the nature of the problem is better understood, the team cannot predict whether this might affect how long the spacecraft can collect and transmit scientific data.”
“A puzzle like this is a bit like the course at this point in the Voyager mission,” Susan Dodd, Voyager 1 and 2 project manager at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., said in a statement.
“The spacecraft is about 45 years old, which is far beyond what the mission planners expected. We are also in interstellar space – a highly radioactive environment where no spacecraft has flown before. So there are some big challenges for the engineering team. But I think it’s If there is a way to solve this problem with AACS, our team will find it.”
If the team doesn’t identify the source of the problem, Dodd said, they may adapt. Or if they can find it, the problem may be resolved by making a software change or relying on a redundant hardware system.
Voyager has already relied on backup systems to last its life. In 2017, the probe launched thrusters that were used during its initial planetary encounters during the 1970s – and are still operating after being unused for 37 years.
Old probes produce very little energy per year, so subsystems and heaters have been turned off over the years so that scientific platforms and instruments can continue to function.
The Voyager 2 spacecraft, a twin spacecraft, continues to do well in interstellar space 12.1 billion miles (19.5 billion km) from Earth. By comparison, Neptune, the farthest planet from Earth, is only 2.9 billion miles away at most. Both probes were launched in 1977 and far exceeded their original goal of flying over planets.
Now, they’re the only two spacecraft to collect data from interstellar space and provide insights into the heliosphere, or the bubble created by the sun that extends beyond the planets in our solar system.