Engineers investigate NASA Voyager 1 telemetry data

NASA’s Voyager 1 spacecraft, shown in this illustration, has been exploring our solar system since 1977, along with its twin, Voyager 2. Credit: NASA/JPL-Caltech

As the Voyager 1 spacecraft continues to return science data and operate normally, the mission team searches for the source of a system data problem.

NASA’s Voyager 1 spacecraft engineering team attempts to solve a mystery: the interstellar explorer is operating normally, receiving and executing commands from Earth, and collecting and returning scientific data. But readings from the probe’s articulation and attitude control system (AACS) don’t reflect what’s actually happening on board.

The AACS controls the orientation of the 45-year-old spacecraft. Among other duties, he keeps Voyager 1’s high-gain antenna pointed precisely at Earth, allowing him to send data home. All signs suggest AACS is still working, but the telemetry data it returns is invalid. For example, the data may appear to be randomly generated or may not reflect any possible state the AACS might be in.

The problem did not trigger any onboard fault protection system, designed to put the spacecraft into “safe mode”, a state in which only essential operations are performed, giving engineers time to diagnose a problem. Voyager 1’s signal also did not weaken, suggesting that the high-gain antenna remains in its prescribed orientation with Earth.

The team will continue to monitor the signal closely while continuing to determine if the invalid data is coming directly from the AACS or from another system involved in producing and sending telemetry data. Until the nature of the problem is better understood, the team cannot predict whether it could affect how long the spacecraft can collect and transmit scientific data.

Voyager 1 is currently 14.5 billion miles (23.3 billion kilometers) from Earth, and it takes light 20 hours and 33 minutes to travel that difference. This means it takes about two days to send a message to Voyager 1 and get a response – a time frame the mission team is well used to.

“A mystery like this is kind of normal at this point in the Voyager mission,” said Suzanne Dodd, project manager for Voyager 1 and 2 at NASA’s Jet Propulsion Laboratory in Southern California. “The spacecraft are both nearly 45 years old, which is far beyond what mission planners had anticipated. We are also in interstellar space – a high-radiation environment in which no spacecraft can ‘ve flown before. So there are big engineering challenges. But I think if there’s a way to solve this problem with AACS, our team will find it.”

It’s possible the team won’t find the source of the anomaly and instead adapt to it, Dodd said. If they find the source, they may be able to fix the problem by modifying the software or possibly by using one of the spacecraft’s redundant hardware systems.

It wouldn’t be the first time the Voyager team had relied on backup hardware: in 2017, Voyager 1’s main thrusters showed signs of degradation, so engineers switched to a different set of thrusters. which had originally been used during the spacecraft’s planetary encounters. These thrusters worked, despite having been unused for 37 years.

Voyager 1’s twin, Voyager 2 (currently 12.1 billion miles, or 19.5 billion kilometers, from Earth), continues to function normally.

Launched in 1977, the two Voyagers have operated far longer than expected by mission planners and are the only spacecraft to collect data in interstellar space. The information they provide about this region has led to a better understanding of the heliosphere, the diffuse barrier that the sun creates around the planets of our solar system.

Each spacecraft produces about 4 watts less electrical power per year, which limits the number of systems the craft can operate. The mission’s engineering team shut down various subsystems and heaters to reserve power for science instruments and critical systems. No science instruments have yet been shut down due to power depletion, and the Voyager team is working to keep both spacecraft operational and make science unique beyond 2025.

As engineers continue to work to solve the mystery Voyager 1 has presented to them, mission scientists will continue to make the most of data from the spacecraft’s unique vantage point.

Voyager 2 engineers are working to restore normal operations

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Provided by Jet Propulsion Laboratory

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