NASA’s Voyager 1 spacecraft, which is currently the farthest human-made object from Earth, experienced a data glitch earlier this year that affected its communication with Earth. The problem was traced to a faulty onboard computer that corrupted the telemetry data sent by the probe’s attitude articulation and control system (AACS). The AACS is responsible for keeping Voyager 1’s antenna pointed at Earth, and it was sending garbled information about its health and activities to mission controllers. However, the rest of the probe was operating normally and continued to gather and return science data.
The NASA engineers at the Jet Propulsion Laboratory (JPL) in California, who are in charge of the Voyager mission, managed to fix the glitch by commanding the AACS to resume sending the data to the right computer. They suspected that the AACS had started routing the telemetry data to an onboard computer that was known to have stopped working years ago, and that was the source of the corruption. The engineers don’t yet know why the AACS switched to the wrong computer, but they think it was due to a faulty command generated by another onboard computer. They are still investigating the root cause of the problem, but they don’t think it poses a threat to the long-term health of Voyager 1.
“We’re happy to have the telemetry back,” said Suzanne Dodd, Voyager’s project manager at JPL. “We’ll do a full memory readout of the AACS and look at everything it’s been doing. That will help us try to diagnose the problem that caused the telemetry issue in the first place. So we’re cautiously optimistic, but we still have more investigating to do.”
The Legacy of Voyager 1
Voyager 1 and its twin, Voyager 2, were launched in 1977 to explore the outer planets of the solar system. They both completed their primary mission in 1989, after visiting Jupiter, Saturn, Uranus and Neptune. Since then, they have continued to travel farther away from the sun, reaching interstellar space, the region beyond the heliosphere, or the bubble of energetic particles and magnetic fields from the sun. They are the only spacecraft to have entered this uncharted territory, and they are still sending back valuable data about the interstellar medium.
Voyager 1 is currently about 15 billion miles (24 billion kilometers) from Earth, or more than four times the distance between the sun and Pluto. It takes about 21 hours for a signal from Voyager 1 to reach Earth, and vice versa. Voyager 2 is about 13 billion miles (21 billion kilometers) from Earth, and it takes about 18 hours for a signal to travel between the spacecraft and Earth. Both probes are expected to keep operating until at least 2025, when their radioisotope thermoelectric generators, which provide power and heat, will run out of fuel.
The Future of Interstellar Exploration
The Voyager spacecraft are not only scientific instruments, but also cultural ambassadors. They carry golden records that contain sounds and images of Earth, as well as greetings in 55 languages, in case they encounter any intelligent life forms in the vastness of space. The records also include a map of the solar system and the location of Earth, as well as a message from then-President Jimmy Carter, who said: “This is a present from a small, distant world, a token of our sounds, our science, our images, our music, our thoughts and our feelings. We are attempting to survive our time so we may live into yours.”
The Voyager mission has inspired generations of scientists, engineers, and explorers, and has paved the way for future interstellar missions. NASA is currently developing the Interstellar Probe, a concept for a spacecraft that would travel 10 times farther than Voyager 1 in half the time. The Interstellar Probe would study the heliosphere, the interstellar medium, and the local galactic environment, as well as search for exoplanets and potential signs of life. The mission is still in the early stages of planning, and it could launch in the 2030s or 2040s.