In the fall of last year, one of NASA’s most venerable spacecraft started beaming home nonsense. Its usual string of 1’s and 0’s—binary code that collectively told of its journey into the unknown—became suddenly unintelligible.
Some 15 billion miles from Earth, beyond the protective bubble blown by the sun and in interstellar space, Voyager 1 was in trouble.
“We’d gone from having a conversation with Voyager, with the 1’s and 0’s containing science data, to just a dial tone,” says Linda Spilker, Voyager project scientist at NASA’s Jet Propulsion Laboratory (JPL).
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Spilker joined JPL in 1977, the same year that NASA launched Voyager 1 and its twin, Voyager 2, on what, in a way, was an endless odyssey: from Earth, to the outer solar system and ultimately to interstellar infinity. Today there are several billion people on Earth who have never taken a breath without the Voyagers in our sky, people who, like me, have only ever existed in a cosmos shared with these talkative twin spacecraft. But like people, spacecraft get old. They break down.
And all good things—and even great ones—must come to an end. After days, and weeks and then months of nothing but indecipherable binary babbling, Voyager 1’s earthbound stewards had to reckon with the idea that maybe, after more than 46 years, its time had at last run out.
The Voyager 1 team at JPL had traced the problem to the spacecraft’s Flight Data System, an onboard computer that parses and parcels engineering and science measurements for subsequent radio transmittal to Earth. One possibility was that a high-energy cosmic particle had struck Voyager 1 and caused a bit flip within the system’s memory — something that has happened more frequently as the craft navigates the hostile wilds of interstellar space. Normally, the team would simply ask the spacecraft for a memory readout, allowing its members to find and reset the errant bit.
“We’ve recovered from bit flips before. The problem this time is we don’t know where the bit flip is because we can’t see what the memory is,” says Suzanne Dodd, Voyager project manager at JPL, who, like Spilker, began her long career with work on the probes. “It’s the most serious issue we’ve had since I’ve been the project manager, and it’s scary because you lose communication with the spacecraft.”
Yesterday, the team announced a significant step in breaking through to Voyager 1. After months of stress and unsuccessful answers they have managed to decode at least a portion of the spacecraft’s gobbledygook, allowing them to (maybe) find a way to see what it has been trying to say.
“It’s an excellent development on Voyager,” says Joe Westlake, director of NASA’s heliophysics division, which oversees the mission.
In the time it will take you to read this story, Voyager 1 will have traversed approximately 10,000 miles of mostly empty space; in the weeks it took me to report it, the probe traveled some 26 million miles. And since its communication first became garbled last November, the spacecraft has sailed another 10 light-minutes away from home. Voyager 1 and its twin are slipping away from us as surely as the passage of time itself. Sooner or later, these hallowed space-age icons will fall silent, becoming no more than distant memories.
And even among the space community, which of course loves all of its robotic explorers equally, the Voyagers are special. “They are incredibly important and much beloved spacecraft,” says Nicola Fox, NASA’s associate administrator for science. “Voyager 1 is a national treasure, along with Voyager 2.”
As envisioned, the Voyager mission would exploit a once-in-175-year alignment of Jupiter, Saturn, Uranus and Neptune to slingshot through the solar system’s sparsely charted hinterlands. Legend has it that NASA’s administrator sold the project to President Richard Nixon by noting that the last time the planets were so favorably arranged, Thomas Jefferson was living in the White House. Outfitted with nuclear power sources, the Voyagers were built to last—in utter defiance of the adage that what must go up, must come down. Neither was ever intended to make planetfall again; instead they were bound for the stars. And now, nearly a half-century later, the pair have become the longest-lived and farthest-flung probes ever dispatched by humankind. (Voyager 1 is the front-runner, with its sibling trailing close behind.)
Spilker was straight out of college when she started working on the Voyagers, eager to see the outer solar system through their robotic eyes as they surfed the rare celestial alignment. “I had a telescope in third grade that I used to look at Jupiter and Saturn,” she says. “I wanted to get up really close and get a look at what these planets look like.”
Between 1979 and 1981, Voyager 1 and Voyager 2 zipped by the gas giants, returning stunning images of banded Jupiter and buttery Saturn and their bewildering collection of moons. Voyager 2 went on to scrutinize the ice giants: Uranus in 1986 and Neptune in 1989. These were the first and only times anyone had seen each of these bluish ringed worlds up close.
“They were small little pinpoints of light, and now you’re flying close,” Spilker says. “And you see the cliffs of Miranda”—a bizarre Uranian moon—“and Triton, with active geysers going off.” (Nobody had expected to see an active icy world in orbit around Neptune, and even now Voyager’s 35-year-old image is still the best we have of that strange little moon.)
When the Voyagers left the realm of the known planets, each followed a different path into darkness: Voyager 1 arced up and out of the plane of the solar system, and Voyager 2 looped downward. Spilker also followed her own path: she went to graduate school and earned her doctorate in planetary science using Voyager data—not knowing that several decades later, after leading NASA’s Cassini mission to Saturn, she’d again be part of the mission that started it all.
“The chance came to go back to Voyager,” she says. “And I said, ‘Of course. I’d love to go back.’”
In the interim, as the Voyagers sailed farther from their Earthly harbor, teams shut down many of the onboard instruments, including the cameras. But the pair kept studying the space that they alone were visiting. Their main job was now to characterize the heliosphere—the solar-system-encompassing, cosmic-ray-blocking bubble formed by our sun’s wind and magnetic field. They would document the alien mix of particles and fields that pervade near nothingness. And maybe, if they got lucky, the twins would each escape the protective solar caul entirely to be reborn as true interstellar wanderers.
In 2012 Voyager 1 transcended this boundary, known as the heliopause, where the sun’s influence wanes. Before that scientists could only guess at what lay beyond this barrier and could only model how it shielded Earth from the harshness of the void. Now Voyager 1 could tell us directly about the stuff between the stars. Voyager 2 followed in 2018, and Fox—then the new chief of NASA’s heliophysics division—was in the midst of the action.
“You’re looking at the cosmic rays going up and the solar wind going down, and it was one of those ‘oh, my god, this is so exciting’ moments,” Fox recalls. “I think of the Voyagers as one mission,” she says. “We’re putting all the data together, but they’re the ones that are out there. They’re the brave spacecraft that have left the protective bubble of the heliosphere and are out exploring interstellar space. It’s hard not to be excited by them.”
This wasn’t the first time Voyager 1 had started speaking an unintelligible language. In 2022, when the probe suffered an earlier bout of garbled telemetry, JPL engineer Bob Rasmussen was shaken out of retirement. The lab wanted to know if Rasmussen, who’d joined the spacecraft’s systems engineering team in 1975, was willing to have a think about the situation.
“I’d been happily retired for a bit more than a year at that point, with plenty else to keep me busy,” Rasmussen says. “But I like solving puzzles, and this was a tough one that I just couldn’t pass up. Cracking it took a few months, but the puzzle stream hasn’t slowed since then.”
Afterward, he stayed on-call. So last November, when Voyager 1 again started transmitting nonsense, Rasmussen was ready for more problem-solving. He was joined by a hand-picked team of specialists, and together they dove into the details for getting the ailing spacecraft back in action.
The problems were at least three layers deep. First, it takes a long time to communicate with Voyager 1. Traveling at the speed of light, the radio signals used to command the spacecraft take 22.5 hours to travel 15 billion miles—and 22.5 hours to come back. Second, the Voyagers are not exactly modern technology.
“Most things don’t last 46 years. Your clock radio and toaster aren’t going to last 46 years,” says Dodd, who started on the Voyager project straight out of school, then worked on other missions and is now back on this one.
Plus, many of the people who built and developed the spacecraft in the 1970s aren’t around to explain the rationale behind the designs.
And third, unluckily enough, whatever had mangled the spacecraft had managed to take out Voyager 1’s ability to send meaningful communications. The team was in the dark, trying to find the invisible source of an error. (Imagine trying to revive a stalled desktop computer with a frozen screen: you can’t see your cursor, and your clicks risk causing more problems—except in this case each input carries a multiday lag and could damage a precious, misbehaving artifact that is more than 15 billion miles away.) Perhaps the most vexing part was the team’s knowledge that Voyager 1 was otherwise intact and functioning as it should be.
“It’s still doing what it’s supposed to be doing,” Westlake says. “It just can’t quite figure out how to send the correct message home.”
Rasmussen and his colleagues set out to understand the spacecraft in as much detail as possible. That meant poring over the original design schematics, now yellowed and pinned to various walls—an effort that resembled “a bit of an archaeology dig,” Dodd says—and studying how past teams had addressed anomalies. That was tricky, Dodd says, because even though the team members could figure out how engineers solved a problem, they couldn’t necessarily discern the rationale behind various solutions. They’d send commands to Voyager 1 about once a week—usually on Fridays—and by Sunday, they’d hear back from the spacecraft.
“There’s suspense after each cautious move, hope with each piece that falls into place, disappointment if our hunches are wrong,” Rasmussen says.
Progress was slow. And as time crept on, the team grew more concerned. But no one was giving up, at any level of leadership.
“I will rely on the Voyager team to say, ‘Hey, Nicky, we’ve done everything,’” Fox says. “We wouldn’t make any decisions until we knew that every single thing had been tried and tried again because we really do want to get Voyager 1 back talking to us.”
And then, in early March, something changed. In response to a command, instead of beaming back absolute gibberish, the spacecraft sent a string of numbers that looked more familiar. It proved to be a Rosetta stone moment. Soon an unnamed engineer at NASA’s Deep Space Network—the globe-girdling array of radio dishes that relays information from Earth to spacecraft—had learned how to speak Voyager 1’s jumbled language.
After translating that vaguely familiar portion of the spacecraft’s transmission, the team could see that it contained a readout of the flight data system’s memory. Now they face new questions: Can they find and correct the source of the mutated code? Can they learn whether the spacecraft is sending useful science data? Can they restore Voyager 1’s lexicon to its original state—or will they need to continue speaking in the probe’s new postheliopause patois? “The hope is that we’ll get good science data back,” Westlake says. “Thinking about something that’s been a constant throughout my entire career going away is really tough to think about.”
But either by glitch or time’s slow decay of radioactive power sources, the Voyagers will, of course, eventually fade away. Each year they lose four watts of power, and they grow ever colder. “Whether it’s this particular anomaly that gets us or one downstream, or the spacecraft gets old enough and cold enough —one day you’ll go to look for it and it has just stopped working,” Spilker says.
Like silent ambassadors or wordless emissaries, the Voyagers will keep sailing outward, still carrying us with them into the stars—“sort of like a message a bottle,” Spilker says.
Besides their science payloads, a fraction of each spacecraft’s mass was devoted to casting a cosmic message into the interstellar ocean from a lonely island called Earth. Mounted to each probe is a golden record etched with grooves encoding a selection of sights and sounds from our small corner of space and time. An accompanying stylus is positioned to play the record from the beginning, alongside a pictographic and arithmetic instruction manual.
The records are gold because gold is stable for eons, and they’re records because that was the best way to store a lot of information in the 1970s. Should they ever be recovered and decoded, the message will tell the stories of we humans—at least as envisioned (and in some cases performed) by a small group of folks that included my parents (the late astrophysicist Frank Drake and his surviving spouse Amahl Shakhashiri Drake), astronomer Carl Sagan, documentary producer Ann Druyan and science writer Timothy Ferris. Those stories are imperfect. They’re filled with lopsided optimism and scrubbed of references to war, famine, poverty and most any other Earthly failing—a deliberate decision to hide the defects of our broken world. I know this because my dad, the record’s technical director and a pioneer in the scientific quest to find cosmic civilizations, told me about the hard choices he’d made in selecting the photographs. And I know it because my mom, who recorded the message’s Arabic greeting (“Greetings to our friends in the stars. We wish that we will meet you someday”), helped, too.
For me, as the Voyagers travel through space, they’re not only helping us understand the cosmic context in which we exist; they’re also bearing a memento of my parents into the stars. These spacecraft—and their gleaming paean to Earth—will survive for billions of years. Long after our world, our sun and everything we hold dear becomes unrecognizable, the Voyagers will remain, resolutely speeding ever farther from a home that no longer exists and containing artifacts of a civilization that once was.
That’s why, over nearly half a century, the Voyagers and their interstellar tidings have come to be bigger than the already audacious mission they were designed to accomplish. Their reach is broader. And their inevitable silence will be profound.
“The thought that they’re out there on their own and you can no longer communicate with them—it’s traumatic,” Fox says. “It’s sad. It’s really sad.”
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