What Voyager 1's Near-Death Experience Reveals About the Future of Space Exploration

Last April, more than 15 billion miles away, NASA engineers began repairing a spacecraft headed toward the constellation Ophiuchus, even though it won’t arrive for another 38,000 years. NASA launched Voyager 1 in 1977 and it has already exceeded expectations, but the space agency hopes to continue receiving data from the probe until at least 2030. However, after Voyager 1 suffered a computer glitch in November, it began transmitting garbled data (not entirely uncharacteristic of the spacecraft), prompting NASA to initiate these long-distance repairs.

After some hesitation about the effectiveness of these repairs, they were successfully carried out. Better yet, when Salon spoke with NASA about the problem of repairing deep spacecraft, experts were optimistic about their future and what it means for space exploration in general.

To understand why, we must first analyze what happened to Voyager 1. In November, the spacecraft sent a signal that contained no data. Engineers figured out that the problem was either with the Flight Data Subsystem (FDS) or the Telemetry Modulation Unit (TMU). During the last week of February, NASA sent a “poke” to Voyager 1 to ask the FDS to send a memory readout with data. Not only did it succeed, but NASA quickly downloaded a separate command that caused Voyager 1 to respond with a full memory readout that helped them pinpoint the specific problem with the FDS.

“The team confirmed that the problem was in the FDS,” Calla Cofield, a media relations specialist at NASA’s Jet Propulsion Laboratory, told Salon. “A chip that stores 256 words of FDS memory has a stuck bit (code is stuck at 0 or 1), which indicates that the part is defective, either due to age or damage from external particles. This section represents about 3 percent of the FDS memory. The team is expected to relocate the portion of the software code stored on the damaged chip.”

During the April mission, NASA transmitted a command to Voyager 1 to move the impacted portion of the FDS software code and redirect references to that code to other locations in the spacecraft software.

“On April 20, the team received technical data from the spacecraft indicating that the command was successful,” Cofield said. “Everything indicates that the spacecraft is doing well after five months without contact.”

The team began receiving science data from Voyager 1 again on May 19, and in June, all of Voyager 1's science instruments began sending usable data again. Even so, Cofield added that “maintenance tasks [is] “still in progress with the spaceship”.

Of course, the problem doesn't end there. Voyager 1 isn't the only spacecraft that might need repairs. Currently, two other spacecraft have left the solar system and are still operational, Voyager 2 and New Horizons. In addition, NASA has sent two other probes that are now decommissioned, Pioneer 10 and Pioneer 11. Can the lessons that allowed NASA to repair Voyager 1 be applied to these and other deep spacecraft?

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“The future is not about fixing problems, but about finding ways around them,” said Bob Rasmussen, a member of the Voyager flight team. “We know several factors that limit the life of the spacecraft, and we have strategies to preserve capabilities for as long as possible. However, we can't predict total failures, so we have to manage them as they occur.”

That’s not to say Rasmussen is entirely optimistic about NASA’s ability to save the malfunctioning probes. In 2019, the agency had to turn off the heater on Voyager 2’s cosmic-ray subsystem instrument to save the probe’s power. In April, NASA kept Voyager 2 running by tapping into a small backup power tank that powers the onboard safety mechanism. By doing so, NASA believes it can keep the craft powered with enough energy that it won’t need to shut down a science instrument until 2026.

Voyager 1 and 2, meanwhile, are still on the verge of a more lasting failure. Even if all their systems function optimally in the future, the spacecraft are not expected to survive beyond the 2030s. That they have lasted this long is a testament to the skill and dedication of the engineers who built them in the 1970s. Unfortunately, there may come a day when many of their vital systems simply stop working properly.

“The worst-case scenario is that both systems could fail at any time,” Rasmussen said. “Not all failures are recoverable. For many of them, we would never be able to tell what happened because contact would simply cease.”

Rasmussen added that the best-case scenario would be for Voyager 1 to continue operating for another five to 10 years. “We have a long-term strategy to wind down operations as power declines and to use degraded modes of operation,” Rasmussen said. “But we also know what happens to the best-laid plans.”

June also marked the death of Ed Stone, the man who pioneered the Voyager missions and led their missions for half a century. In its obituary for the former director of the Jet Propulsion Laboratory, NASA wrote that Stone was “a pioneer who dared extraordinary things in space” and “took humanity on a planetary tour of our solar system and beyond, sending NASA where no spacecraft had gone before.”