NASA/JPL-Caltech
Since May, the engineering team with NASA's Voyager 1 spacecraft had been trying to solve a mystery. The 45-year-old spacecraft seemed to be in excellent condition, receiving and executing commands from Earth, along with gathering and returning science data – but the probe's attitude articulation and control system (AACS) was sending garbled information about its health and activities to mission controllers.
The AACS controls the spacecraft's orientation and keeps Voyager 1's high-gain antenna pointed precisely at Earth, enabling it to send data home. Though all signs suggested that the AACS was still working, the telemetry data was invalid. For instance, the data appeared to be randomly generated or did not reflect any possible state the AACS could be in.
However, in today's dose of good news, NASA reported that engineers had located the source of the junk data: The AACS had started sending the telemetry data through an onboard computer known to have stopped working years ago, and the computer corrupted the information.
Suzanne Dodd, Voyager’s project manager, said that when they suspected this was the issue, they opted to try a low-risk solution: commanding the AACS to resume sending the data to the correct computer.
The solution was low-risk but time-consuming. A radio signal takes nearly 22 hours to reach Voyager 1, which was 14.6 billion miles (23.5 billion kilometers) from Earth and growing farther by the second as of August 30.
While the problem has been solved, the team is uncertain why it occurred in the first place.
They suspect the interstellar explorer began routing its health and status telemetry through the dead computer after receiving a bad command from yet another onboard computer. That would suggest that some other problem lurked inside Voyager 1's computer brains. But, the mission managers don't think it threatens the spacecraft's long-term health.
NASA/JPL-Caltech
"We're happy to have the telemetry back," Dodd said in a statement. "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."
Nevertheless, they would like to know the source of the mystery.
"So we’re cautiously optimistic, but we still have more investigating to do," she added.
NASA launched the Voyager 1 spacecraft and its twin Voyager 2, in 1977, as part of the NASA Heliophysics System Observatory. The probes were on a mission to explore the solar system's outer planets. Both Voyagers have operated far longer than mission planners expected and are the only spacecraft to collect data in interstellar space, the region outside the heliopause, or the bubble of energetic particles and magnetic fields from the Sun. While Voyager 1 flew by Jupiter and Saturn during its primary mission and entered interstellar space in 2012, Voyager 2 reached the milestone in 2018.
The information the probes provide from this region has helped provide a deeper understanding of the heliosphere, the diffuse barrier the Sun creates around the planets in our solar system.
A division of Caltech in Pasadena, JPL, built and operates the Voyager spacecraft.
