NASA's Voyager 1 Spacecraft Mystery: Engineers Investigating Telemetry Data
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NASA’s Voyager 1 Spacecraft Mystery: Engineers Investigating Telemetry Data

While the spacecraft continues to return science data and otherwise operate normally, the mission team is investigating the cause of a system data problem.

The engineering team with NASA’s Voyager 1 spacecraft is trying to solve a mystery: The interstellar explorer is operating normally, receiving and executing commands from Earth, along with gathering and returning science data. However, readouts from the probe’s attitude articulation and control system (AACS) do not accurately reflect what is happening onboard.

The AACS controls the 45-year-old spacecraft’s orientation. Among other things, it keeps Voyager 1’s high-gain antenna accurately oriented at Earth, allowing it to transmit data back home. All signs indicate that the AACS is still operational, but the telemetry data it is returning is invalid. For example, the data may appear to be created at random or may not reflect any probable condition of the AACS.

The problem hasn’t triggered any onboard fault protection systems, which are meant to send the spacecraft into “safe mode” — a state in which only critical functions are performed, giving engineers time to detect a problem. The signal from Voyager 1 hasn’t weakened either, indicating that the high-gain antenna is still oriented correctly with Earth.

The team will continue to closely monitor the signal in order to determine whether the invalid data is coming directly from the AACS or from another system involved in the production and transmission of telemetry data. The team cannot predict how long the spacecraft will be able to gather and transmit science data until the nature of the problem is better understood.

Voyager 1 is currently 14.5 billion miles (23.3 billion kilometers) from Earth, and light travels that distance in 20 hours and 33 minutes. That means it takes about two days to send a message to Voyager 1 and receive a response – a delay that the mission team is used to.

“At this stage of the Voyager mission, a mystery like this is sort of par for the course,” said Suzanne Dodd, project manager for Voyager 1 and 2 at NASA’s Jet Propulsion Laboratory in Southern California. “The spacecraft are both almost 45 years old, which is far beyond what the mission planners anticipated. We’re also in interstellar space – a high-radiation environment that no spacecraft have flown in before. So there are some big challenges for the engineering team. But I think if there’s a way to solve this issue with the AACS, our team will find it.”

According to Dodd, it is feasible that the team will not uncover the source of the anomaly and will instead adapt to it. If they do locate the source, they may be able to address the problem with software adjustments or by utilizing one of the spacecraft’s redundant hardware systems.

It wouldn’t be the first time the Voyager team had to rely on backup equipment: When Voyager 1’s primary thrusters began to fail in 2017, engineers switched to another set of thrusters that had previously been used during the spacecraft’s planetary encounters. Despite having been inactive for 37 years, those thrusters worked.

Voyager 2 (now 12.1 billion miles or 19.5 billion kilometers from Earth) continues to operate normally.

Both Voyager spacecraft, launched in 1977, have operated significantly longer than mission planners anticipated, and are the only spacecraft to collect data in interstellar space. The data from this region has contributed to a better understanding of the heliosphere, the diffuse barrier that the Sun produces surrounding the planets in our solar system.

Each spacecraft uses around 4 watts less electrical power per year, limiting the amount of systems it can run. To save power for science instruments and essential systems, the mission engineering team turned off different subsystems and heaters. Because of the declining power, no science instruments have been turned off yet, and the Voyager team is attempting to keep the two spacecraft operational and returning unique science beyond 2025.

While the engineers try to solve the enigma presented by Voyager 1, the mission’s scientists will continue to make the most of the data coming down from the spacecraft’s unique vantage position.

More Information on the Mission

JPL built the Voyager spacecraft, which is still in operation. Caltech’s JPL division is based in Pasadena. The Voyager missions are part of the NASA Heliophysics System Observatory, which is sponsored by the Science Mission Directorate’s Heliophysics Division in Washington.

More information about the Voyager spacecraft can be found at: https://www.nasa.gov/voyager

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