who worked on the voyager mission

The Voyager spacecraft will probably last a billion years, says a scientist on the mission for nearly 5 decades

• Alan Cummings has worked on the Voyager mission for over 50 years.
• Since their launch, the two Voyager spacecraft have made breakthrough discoveries that keep Cummings engaged.
• Cummings thinks they will continue traveling for a billion years.

The twin Voyager spacecraft launched almost five decades ago, and there's no reason they shouldn't keep going for a billion years, one of its scientists, Alan Cummings told Business Insider.

Cummings started working on the Voyager mission when he was a graduate student at Caltech in 1973, about four years before the two spacecraft launched.

Now a senior research scientist at Caltech, Cummings has seen the program dwindle from over 300 people to fewer than a dozen.

Voyagers 1 and 2 have traveled over 10 billion miles into space, further than any human-made object. Cummings said being a part of this historic mission for so many decades has been the backbone of his career.

"The Hubble Telescope is a great mission," he said. " JWST is a great mission, but I think Voyager's in that kind of category."

Voyagers' endurance

The Voyager mission has been gathering groundbreaking data and photos since the beginning.

The first time Cummings saw Jupiter's moon Io in 1979, for example, he thought it was a joke. "It looked like a poorly made pizza," he said.

Its colorful, volcano-covered surface looked so different from Earth's gray, pockmarked moon . "This can't be real," he said, "and it was real."

The Voyagers offered us a new perspective on our outer solar system, unlike anything we could have imagined.

They discovered Saturn wasn't the only planet with rings — Jupiter has them too. They revealed new moons around Jupiter and Saturn.

In total, the two spacecraft snapped 67,000 images of our solar system, the final of which was the "pale blue dot" photo made famous by Carl Sagan who said:

"To my mind, there is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world."

"It rewrote the textbooks," Cummings said of the mission.

Both Voyagers were initially planned as five-year missions, but Cummings said, from the beginning, he expected the spacecraft to last at least 30 to 40 years.

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"A remarkable engineering team has kept this thing going," Cummings said.

Now, as the two spacecraft approach their 50th anniversaries, they're running low on fuel.

Engineers have had to shut down different instruments to keep them going and the data coming in.

Cummings said once the Voyagers lose power and communication, they'll continue traveling. "I think it's going to go for a billion years," he said. "There's nothing to stop it."

Joining Voyager

If it weren't for an unfortunate accident, Cummings may never have joined the Voyager mission.

Before Voyager, Cummings was part of an experiment to measure cosmic rays using a balloon.

For several summers, he had released the balloon from northern Manitoba, Canada.

But during its final flight, the balloon didn't descend as expected and ended up over Russia, instead.

By the time Cummings got to Russia, the instrument was destroyed.

"It was very fortunate for me," he said, because he was able to then join the Voyager mission.

He put his cosmic ray experience to use, working on telescopes for the mission's experiments.

"I have my little initials scratched on one of those" telescopes he said, "so I guess I'm going to be immortal."

Interstellar space

Cummings has worked on other projects over the decades, but Voyagers' continual transmission of new data has kept him excited and involved.

"There's always some new phenomenon that you see," he said.

In fact, Voyager's data has become increasingly more interesting to Cummings in recent years because the two spacecraft are now in interstellar space , the region of space beyond our sun's influence.

After passing by the four giant planets of Jupiter, Saturn, Neptune, and Uranus, many of the instruments were still in working order. So, the spacecraft transitioned to an interstellar mission.

In 2012, Voyager 1 became the first human-made spacecraft to enter interstellar space and Voyager 2 followed six years later.

"That is really what I was most interested in anyway," Cummings said, since cosmic rays are his field of expertise and in interstellar space, those rays aren't disrupted by the sun, Earth, and other obstructions in our solar system.

Voyager is "making its most interesting measurements in some ways right now," he said.

Currently, Voyager 1 is having issues with one of its onboard computers that could compromise the mission.

Cummings hopes the Voyagers can hang on a little longer, especially since interstellar space is a long way off for any other spacecraft.

Watch: NASA released this 5-year time-lapse of Mars from its Curiosity rover — and the footage looks amazing

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The Loyal Engineers Steering NASA’s Voyager Probes Across the Universe

As the Voyager mission is winding down, so, too, are the careers of the aging explorers who expanded our sense of home in the galaxy.

Larry Zottarelli, who recently retired from the Voyager flight crew. Credit... Graeme Mitchell for The New York Times

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By Kim Tingley

• Aug. 3, 2017

I n the early spring of 1977, Larry Zottarelli, a 40-year-old computer engineer at NASA’s Jet Propulsion Laboratory in Pasadena, set out for Cape Canaveral, Fla., in his Toyota Corolla. A Los Angeles native, he had never ventured as far as Tijuana, but he had a per diem, and he liked to drive. Just east of Orlando, a causeway carried him over the Indian and Banana Rivers to a triangular spit of sand jutting into the Atlantic, where the Air Force keeps a base. His journey terminated at a cavernous military hangar.

A fleet of JPL trucks made the trip under armored guard to the same destination. Their cargo was unwrapped inside the hangar high bay, a gleaming silo stocked with tool racks and ladder trucks. Engineers began to assemble the various pieces. Gradually, two identical spacecraft took shape. They were dubbed Voyager I and II, and their mission was to make the first color photographs and close-up measurements of Jupiter, Saturn and their moons. Then, if all went well, they might press onward — into uncharted territory.

It took six months, working in shifts around the clock, for the NASA crew to reassemble and test the spacecraft. As the first launch date, Aug. 20, drew near, they folded the camera and instrument boom down against the spacecraft’s spindly body like a bird’s wing; gingerly they pushed it, satellite dish first, up inside a metal capsule hanging from the high bay ceiling. Once ‘‘mated,’’ the capsule and its cargo — a probe no bigger than a Volkswagen Beetle that, along with its twin, had nevertheless taken 1,500 engineers five years and more than $200 million to build — were towed to the launchpad.

By T-minus two hours, a select few engineers, too nervous to sit down, stood at computers outside the high bay, overseeing the spacecraft telemetry. Elsewhere in the hangar, scientists, NASA brass from Washington and several dozen ‘‘nonessential’’ engineers — Zottarelli among them — huddled around TV monitors. At T-minus 30 seconds, the spacecraft’s engines roared to life, and many of the nonessentials took off running out of the room and toward the exit — ‘‘seven, six, five.’’ They burst out into the morning. Shielding their eyes, they peered across a flat expanse at smoke billowing on the horizon. Slowly and silently, the capsule rose out of the cloud, its rockets trailing flames. In an instant, there came a terrific boom as the sound waves from blastoff hit the hangar like a gong, ringing it as the spacecraft disappeared.

Two weeks later, after the second launch, everyone headed home. The show was over — both spacecraft were performing flawlessly — but behind the scenes, the mission, on a tight budget, lagged in hiring the more than 200 computer engineers needed to shepherd the spacecraft through a planetary encounter. Many of those on the flight team were fresh out of college, running the most sophisticated electronics systems in the world. They had barely had a chance to jell, when, in April 1978, not yet halfway to Jupiter, Voyager 1 experienced a problem. Its scan platform, where the cameras and instruments are mounted, got stuck.

As the engineers scrambled to figure out what they could do from more than 100 million miles away, someone forgot to send a weekly command to reset a timer on the other spacecraft. When it ran down without hearing from Earth, it triggered so-called fault-protection software, 600 lines of code that respond to malfunctions automatically. In this instance, fault protection assumed the radio receiver was broken and switched to the backup. On the mission-control monitors in a situation like this, the crawl of numbers reporting the status of the receivers would have turned crimson: a ‘‘red alarm.’’

Voyager’s 40th Anniversary

Long after they have stopped communicating with earth, the twin voyager spacecraft will forever drift among the stars..

Forty years ago, in August and September of 1977, a band of humans launched a pair of robots to explore the solar system and probe the infinite darkness beyond. “3, 2, 1. We have ignition and we have liftoff!” Taking advantage of a rare planetary alignment, the twin Voyager spacecraft raced outward toward Jupiter, then used the giant planet’s gravity to slingshot on to Saturn. At Saturn they parted company. Voyager 1 turned upward, leaving the plane of the planets and heading toward interstellar space. But Voyager 2 kept trekking, spiraling outward on a grand tour of the outer planets, toward distant Uranus and Neptune. At each planetfall, fuzzy dots bloomed into worlds. Every image sent back to Earth was another lesson on nature’s ability to surprise. Voyager saw swirls within swirls in Jupiter’s banded jet streams. Volcanoes spouting sulphur on Jupiter’s moon Io, a tormented world twisted and pulled by gravity. And eggshell-smooth Europa, an icy shell around a hidden ocean. Two years after Jupiter, the Voyagers approached Saturn, jewel of the solar system. Its broad rings dissolved into thousands of grooves, like a phonograph record. Braided, kinked and patrolled by tiny moonlets. Voyager probed the methane skies of Titan. It slid past two-faced Iapetus, with light and dark sides. Giovanni Cassini’s disappearing moon. And Enceladus. Trapped under its crust of ice is another dark ocean, and perhaps living creatures. After Saturn, Voyager 1 turned away from the planets but Voyager 2 sailed on. Voyager found ghostly Uranus tipped on its side, its south pole facing the sun. A blue-green bulls eye with faint rings. Voyager slipped passed methane-blue Neptune, a pacific-looking world bruised with dark, violent hurricanes. Antennas on Earth strained to hear the trickle of data from almost 3 billion miles out. Voyager 2’s last port of call was Triton, Neptune’s biggest moon. A mottled ball of exotic ices, plumed with dark geysers of nitrogen. One final world added to Voyager’s tally. But the Voyager mission was not only to observe. Each spacecraft carried a message. A gold record, with a needle and instructions on how to play it. A time capsule from the 1970s, grooved with the sights and sounds of Earth. “I send greetings on behalf of the people of our planet. We step out of our solar system, into the universe, seeking only peace and friendship, to teach if we are called upon, to be taught if we are fortunate.” Of all the voices ever recorded, of all the photographs ever taken, these few will survive the end of our planet. Scratches on gold, adrift in the void. A time capsule from the 1970s, grooved with the sights and sounds of Earth. Of all the voices ever recorded, of all the photographs ever taken, these few will survive the end of our planet. Scratches on gold, adrift in the void. As Voyager 1 climbed away from the planets, it turned its cameras backward. To snap a family portrait of the worlds it was leaving behind forever. The Earth appears as a bright pixel in a wash of scattered sunlight. A “Pale Blue Dot” in the words of astronomer and cosmic sage, Carl Sagan: “Consider again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. ... The Earth is a very small stage in a vast cosmic arena.” No other spacecraft have gone so far, or explored so many new worlds. In the fullness of galactic time the Voyagers might yet be found, but by then the human race could be long extinct. Long after they have ceased speaking to us, the twins will forever drift among the stars. Mute, but carrying sounds and greetings from home. “Hello from the children of Planet Earth” The last lonely evidence that we too once lived in this starry realm, on an island of ice and rock. As Carl Sagan put it: “A dust mote in a sunbeam.”

Realizing their mistake, the engineers tried to stop the fault-protection routine, but the newly awakened backup receiver would not register their command. Helpless, they waited for the spacecraft to reason its way back to the original receiver; when it did, and the command went through normally, they were giddy with relief. They were still high-fiving when the working receiver shorted out like a blown fuse. Now it really was dead.

Fortunately, the malfunctioning backup receiver was still drawing current. They guessed that its oscillator, which allows it to accept a wide range of frequencies, had quit, essentially shrinking the target for transmissions from Earth. Assuming a much narrower bandwidth, and manually subtracting the Doppler effect, they recalibrated their signal. It worked — but to this day, the same calculation must precede every command. The original receiver remains useless: one engineer’s simple oversight nearly doomed humankind’s lone visit to Uranus and Neptune . ‘‘You like to think you have checks and balances,’’ Chris Jones, JPL’s chief engineer, who designed Voyager’s fault protection, told me. ‘‘In reality, we all worry about being that person.’’

Today the Voyagers are 10 billion and 13 billion miles away, the farthest man-made objects from Earth. The 40th anniversary of their launch will be celebrated next month. We tend to think of space as vacant, but it is actually matter, created, as everything in the universe is, by the explosions of ancient stars. Within our planetary neighborhood, this ‘‘space’’ is made up of different particles than the space outside is, because of supersonic wind that blows out from the surface of our sun at a million miles per hour. The wind generates a bubble around our solar system called the heliosphere. Five years ago, Voyager 1 reached the boundary where the heliosphere gives way to interstellar space, a region as novel to us — and potentially relevant — as the Pacific was to Europeans 500 years ago. The data the probes are collecting are challenging fundamental physics and will provide clues to the biggest of questions: Why did our sun give birth to life only here? Where else, within our solar system or others, are we most likely to find evidence that we are not alone?

The mission quite possibly represents the end of an era of space exploration in which the main goal is observation rather than commercialization. In internal memos, Trump-administration advisers have referred to NASA’s traditional contractors as ‘‘Old Space’’ and proposed refocusing its budget on supporting the growth of the private ‘‘New Space’’ industry, Politico reported in February. ‘‘Economic development of space’’ will begin in near-Earth orbit and on the moon, according to the president’s transition team, with ‘‘private lunar landers staking out de facto ‘property rights’ for Americans on the moon, by 2020.’’

All explorations demand sacrifices in exchange for uncertain outcomes. Some of those sacrifices are social: how many resources we collectively devote to a given pursuit of knowledge. But another portion is borne by the explorer alone, who used to be rewarded with adventure and fame if not fortune. For the foreseeable future, Voyager seems destined to remain in the running for the title of Mankind’s Greatest Journey, which might just make its nine flight-team engineers — most of whom have been with the mission since the Reagan administration — our greatest living explorers. They also may be the last people left on the planet who can operate the spacecraft’s onboard computers, which have 235,000 times less memory and 175,000 times less speed than a 16-gigabyte smartphone. And while it’s true that these pioneers haven’t gone anywhere themselves, they are arguably every bit as dauntless as more celebrated predecessors. Magellan never had to steer a vessel from the confines of a dun-colored rental office, let alone stay at the helm long enough to qualify for a senior discount at the McDonald’s next door.

Their fluency in archaic programming languages will become only more crucial as the years go on, because even as the probes harvest priceless information from the cosmos, they are running out of fuel. (Decaying plutonium supplies their power.) By 2030 at the latest, they will not have enough juice left to run a single experiment. And even that best case comes with a major caveat: that the flight-team members forgo retirement to squeeze the most out of every last watt.

One of the greatest obstacles to planetary science has always been the human life span: Typically, for instance, a direct flight to Neptune would take about 30 years. But in the spring of 1965, Gary Flandro, a doctoral student at Caltech, noticed that all four outer planets — Jupiter, Saturn, Uranus and Neptune — would align on the same side of the sun in the 1980s. If a spacecraft were launched in the mid- to late 1970s, it could use the gravity of the first body to slingshot to the second, and so on. Such a trajectory would add enough speed to shorten the total journey by almost two-thirds. What’s more, this orbital configuration would not appear again for 175 years.

The Voyagers carried cameras and instruments for analyzing atmospheric temperatures, moon masses, gravitational and magnetic fields and radiation levels. Reaching Jupiter in 1979, they captured images of lightning in its cloud tops and astounded scientists — who had assumed all moons were as barren as our own — with pictures of eight active volcanoes on its satellite Io; Europa, another Jovian moon, was encased in a shell of water ice, cracked in places by what appeared to be the tides of an ocean below. The photographs revealed themselves on control-room monitors pixel by pixel, row by row. ‘‘I would be sitting in here at night sometimes when the Voyager mission was flying,’’ Esker Davis, project manager for the Saturn encounter, told David W. Swift, who published an oral history of the mission in 1997, after Davis’s death. ‘‘And my wife would call up and ask what I was doing. I said, ‘Just watching pictures come in, being the first person to see this picture.’ ’’

The mission would have ended there, but President Ronald Reagan bestowed an extension, possibly swayed by the real-time briefings hosted by Ed Stone, the project’s lead scientist, on the occasion of every planetary encounter. Hundreds of reporters, as well as politicians and celebrities, attended, packing into a cramped JPL auditorium for the debuts of Uranus in 1986 and Neptune in 1989.

The final flyby, of Neptune’s moon Triton, took place on a hot August night. Afterward, everyone celebrated with Champagne, cold cuts and drunken singing; on the JPL lawn, Chuck Berry performed ‘‘Johnny B. Goode,’’ one of the tracks included on gold-plated records of human sights and sounds attached to the spacecraft for any intelligent life that might find them. Then, gradually, the hallways grew quiet. Stone and his colleagues moved on to new projects while analyzing Voyager data part time; the flight team laid off 150 engineers (many of whom went on to staff subsequent missions). The probes’ new goal was to reach interstellar space. But though scientists had measured the speed of the solar wind that forms the heliosphere, the properties of the matter beyond it had never been analyzed. How much pressure it exerted on the bubble, and thus the size of the bubble, were a mystery. So, too, was how long — years? decades? — it might take a craft to escape it.

At the mission’s outset, the flight-team members were mischievous kids. They relieved stress with games and pranks: bowling in the hallway, using soda cans as pins; filling desk drawers with plastic bags of live goldfish; making scientists compete in disco-pose contests. Now, by 1990, they were older, with kids of their own. They had experienced the deaths of colleagues and watched others’ marriages falter as a result of long hours at the lab. With no planets to explore, they spent the decade doing routine spacecraft maintenance with a fraction of their bygone manpower. Six of the current nine engineers were on the team then. Sun Kang Matsumoto, who joined the mission in ’85, studied so diligently to master the new roles pressed upon her that her sons learned the spacecraft contours by osmosis. When her eldest was 8, he surprised her with a perfect Lego model; now in college, ‘‘he calls and asks, ‘How is Voyager?’ Like, ‘How is Grandma?’ ’’ Matsumoto says.

The mission originally occupied three floors of Building 264 on the JPL campus, home to many of the lab’s highest-profile projects. But soon after Neptune, says Jefferson Hall, who joined the project in 1978, ‘‘we were booted out.’’ Their first move was into the former offices of a mainframe-computer company in Sierra Madre. In 2002, after more staff cuts, they moved to a rental suite in Altadena. NASA reviewed the mission to determine if it should be canceled altogether.

The scientists’ models, meanwhile, began to reveal subtle changes in the raw data. By late 2004, it was clear that Voyager 1’s magnetometer had detected an abrupt increase in the strength of the surrounding magnetic field, suggesting the probe had entered the outermost layer of the heliospheric bubble, the ‘‘heliosheath.’’ This is where the solar wind ions abruptly slow as they press outward against the surrounding interstellar matter and swerve to create a cometlike tail. A wind of interstellar ions flows around the outside of the bubble like water around the bow of a ship. Finally, on Aug. 25, 2012, the density of particles around the spacecraft precipitously increased, as though it had plunged from sky to sea. It had crossed the threshold of interstellar space.

I n 2016, the year he turned 80, Zottarelli, the flight team’s most experienced programmer, gave six months’ notice and spent the time training a successor. None of the other engineers, only one of whom is under 50, have a replacement in waiting in the event that they abdicate more suddenly. Unlike the astrophysicists who devise experiments for Voyager and who interpret the results, the core flight-team members don’t have the luxury of being able to work simultaneously on other missions. Over decades, the crew members who have remained have forgone promotions, the lure of nearby Silicon Valley and, more recently, retirement, to stay with the spacecraft. NASA funding, which peaked during the Apollo program in the 1960s, has dwindled, making it next to impossible to recruit young computer-science majors away from the likes of Google and Facebook.

Last autumn, I drove through the San Gabriel Valley to a squat concrete building beside Scott-Fox Puppy Preschool. Suzanne Dodd, 56, the mission’s project manager, answered the door. She wore red-framed glasses over sharp blue eyes, and her fair hair was cut short. She escorted me past the vestibule to a common room ringed by office doors. Hanging over the cubicle partitions in the center was a shingle that read ‘‘Mission Control.’’

‘‘You can see where we are in the culture,’’ she said, with a mild sweep of her palm. Voyager was her first job. She pointed out a used microfiche reader that Tom Weeks, a hardware engineer and the self-described mission librarian, purchased on eBay to read old diagnostics reports. To conserve power on the spacecraft, the engineers must decide what to turn off when, and for how long — which means estimating how cold they can let each component get. (On Voyager 2, because of the broken oscillator, any change in temperature also tweaks the receiver frequency.) Turning the heaters off for a while is the safest way to get enough power to run the instruments, but the lower the overall wattage drops, the faster parts will freeze. One of the team’s most valuable insights so far: Spinning the wheels of an eight-track tape recorder — the spacecrafts’ only data-storage option — generates a bit of additional heat.

Enrique Medina, the power subsystem expert, was preparing to implement a ‘‘patch,’’ an update that would turn off a heater on Voyager 2 in order to run the gyroscope, roll the spacecraft and calibrate the magnetometer. Even though they simulate every patch with software, there is plenty of room for human error. Far more often, hardware fails for no evident reason. In 1998, Voyager 2 reacted to a command by going silent. For 64 hours straight, the flight team studied the specific instruction — consisting of 18 bits, or 1s and 0s — that preceded the blackout. Bits have been known to ‘‘flip’’ to the opposite value, changing the instruction the same way that swapping a single letter turns ‘‘cat’’ into ‘‘cut.’’ The question was: What instruction had they accidentally given and how could they undo it? At last, modeling the outcome of each possible bit, they discovered one that turned off the exciter, which generates the spacecraft’s radio signal; when they turned it back on, the transmissions resumed. A similar scare took place in 2010, when a bit involved in formatting telemetry flipped, turning the transmissions to gibberish. ‘‘A lot of our anomalies we’ve come up with workarounds for, and at the time we didn’t know why it happened,’’ Weeks explained. Dodd added, ‘‘The No. 1 rule with spacecraft is: Don’t change it if you don’t have to.’’

In the mission-control cubby, Medina, who is 68 and a grandfather of four, with a husky voice and a Tom Selleck mustache, rolled a chair over to two pairs of monitors labeled with construction-paper signs that read: ‘‘Voyager Mission Control Hardware, PLEASE DO NOT TOUCH.’’ He jiggled a mouse, and one of the screens woke to a stream of numbers and letters describing the health of Voyager 1.

Because they have only four kilobytes of computer storage, the spacecraft transmit data 24/7, but the radio signals take 19 hours and 12 hours to reach Earth. The three antenna dishes big enough to register them are shared, so Voyager gets only four to six hours of reception time per spacecraft per day; outside these often odd windows, their data dissipate into the ether. Medina gestured to another computer in the corner that monitors the telemetry that comes in when the office is empty and, if it detects an anomaly, phones an on-call engineer: the Voyager Alarm Monitor Processor Including Remote Examination tool. ‘‘We call it Vampire,’’ Medina said, ‘‘because it works in the middle of the night.’’

In March 2014, after news broke that Voyager 1 had crossed into interstellar space, I spoke with Medina over the phone. ‘‘I would not leave my wife to go with Angelina Jolie, as exciting as that sounds,’’ he told me. ‘‘And I would not leave Voyager to go to the new Mars missions. I will not leave Voyager until it ceases to exist. Or until I cease to exist.’’

A ll the billions of stars in the universe, hosts to billions of planets, have a heliosphere. Understanding the properties of our own will help us interpret observations of those systems. Voyager 1 has shown that it blocks 75 percent of cosmic radiation, which at extreme levels is toxic to life as we know it. This is not a static number: Our sun is orbiting the galaxy at 125 miles per second; its interstellar environment — and thus the size and shape of its heliosphere — is constantly in flux.

‘‘If the pressure outside got high enough, and there are some areas in the Milky Way galaxy where it would be high enough, it could compress the heliosphere down to where in fact the boundary is almost to where we are. And that would change the radiation environment of the planets, which is important when you want to try to understand anything about the origin of life,’’ Ed Stone, the science-team leader, told me when I visited him at Caltech last fall. ‘‘Here on Earth, wherever there’s liquid water, whether it’s boiling water coming out of the vents or frozen water, there are microbes there. So life is remarkably robust where there’s water.’’

He went on: ‘‘I think that one of the biggest questions is, Can we find a spot here in the solar system where there’s microbial life? If there’s no microbial life anywhere else, that would be surprising, given here on Earth it appeared fairly quickly after the end of the bombardment,’’ an epic rain of asteroids some four billion years ago. ‘‘If one could ever find some evidence of it here in the solar system where we could get a sample, then one could look at the DNA. All life on Earth has a related DNA. Is that true for everywhere? Either answer would be amazing. Either there’s only one way that life evolves, or no, there’s more than one way.’’

In his office, Stone stood on tiptoe to lift an intricate model of Voyager from the top of a bookcase. At 81, he moves more stiffly than the Stone of NASA archival footage. Otherwise, he is remarkably unchanged. On a bulletin board behind his computer, he pins the latest graphs of the rate of charged particles that each spacecraft has detected. A drastic dip in low-energy ones is what convinced him that Voyager 1 had exited the heliosphere, and he is eager for Voyager 2, which entered the heliosheath from a different angle in 2007, to see a comparable drop before it goes quiet.

‘‘When we started this, I realized we were on a mission of discovery,’’ he said. ‘‘I just had no idea how much discovery there was going to be. And I certainly had no idea that it would last as long as it has.’’ After we lose contact with them, the spacecraft will continue to orbit the galaxy for billions of years, never striking another star. ‘‘Space,’’ Stone said, ‘‘is really empty.’’

Astrophysicists who study the heliosphere wage a constant battle against apathy when it comes to invisible substances nearly 100 times farther away from us than the sun is. ‘‘I hear a lot of people saying, ‘So what?’ I try to explain: ‘It’s like your home,’ ’’ Merav Opher, a professor of astrophysics at Boston University and a member of the Voyager science team, told me. ‘‘You just found out the walls aren’t walls. They’re porous. I think it’s existential.’’ In 2006, Opher and Stone published a landmark paper in The Astrophysical Journal predicting that Voyager 2 would encounter the heliosphere boundary closer to the sun than its twin had, pointing to a startling contradiction: The heliosphere must be asymmetrical; it is not a ‘‘sphere’’ after all.

There is passionate disagreement about what its exact shape is. (The Voyager scientists argue over practically every scrap of data; a few holdouts insist that Voyager 1 has yet to reach interstellar space.) In 1961, Eugene Parker, the renowned astrophysicist who first predicted the existence of a heliosphere, hypothesized that it might look like a comet — compressed in front with a tail in back. Earlier this year, Tom Krimigis, the emeritus head of the Space Department at the Applied Physics Laboratory at Johns Hopkins University and the principal investigator for Voyager’s Low-Energy Charged Particle Experiment, published a paper in Nature Astronomy showing that the heliosphere has a very short tail and ‘‘kind of moves through space like a clenched fist.’’ His instrument has also shown that cosmic rays — expected to flow toward the heliosphere uniformly from across interstellar space — actually move quite differently depending on their orientation to the interstellar magnetic field. ‘‘Every once in a while, a tsunami passes Voyager,’’ Krimigis told me, referring to these waves. ‘‘The galaxy was supposed to be a calm sea, and that’s not what we find.’’

Opher believes that the influence of the sun’s magnetic field may warp the heliosphere into the shape of a ‘‘croissant.’’ At its plump center, interstellar matter presses in closer than previously thought — which would mean we are less isolated from the rest of the galaxy than we believe.

Last Sept. 29, a Thursday, Larry Zottarelli awoke before 7, as he did most weekdays, and dressed quietly so as not to disturb his sleeping wife. He raked a comb through his silver hair, donned trifocals and a calculator watch and drove to the office. He brewed his first mug of coffee in the efficiency kitchen and carried it to his desk. He’d been on the job for 40 years; the next day would be his last. A printed-out email taped to his computer hutch had instructions for handing in his badge and parking pass and collecting his final paycheck. He had cleared out most of his belongings, except two gallon-size Ziploc bags, in which he had sealed the plastic arms of his office chair to protect them from disintegrating under the daily weight of his elbows. Sitting facing the door, backed by a windowless, conch-pink brick wall, he brought to mind a hermit crab wearing a seashell.

Later that morning, when Zottarelli entered the conference room to attend his last daily flight-team briefing, his colleague Adans Ko, 58, was arranging takeout containers of dim sum on the table for a celebration. He threw an arm around his shoulders and said, ‘‘Larry is going to give me a kiss today!’’ Matsumoto, who was holding a camera, said, ‘‘O.K., look at me.’’ She was making a photo album for him. When the party broke up, I found Zottarelli’s replacement, Lu Yang, at her desk. I asked her if he had given her any specific advice. ‘‘Whatever the problem, you go there and solve it,’’ she said, and laughed.

In retirement, Zottarelli told me, he would like to see Florida again. He wonders how it has changed. In his garage is a 1954 Swallow Doretti, a fixer-upper. ‘‘It probably needs new brakes,’’ he said. I asked him if there was anywhere he liked to drive for fun. ‘‘No,’’ he replied. ‘‘Not anymore.’’

I had stopped by his office to say goodbye and ask him what he planned to do with his newfound freedom. I pictured him in the Doretti, flying down the Pacific Coast Highway, wind in his hair. But he seemed to be in no mood for talking. I wished him well and turned to go. Then he spoke. ‘‘I expect my second stroke will be on the 17th of November,’’ he said ruefully, gesturing toward his empty wall calendar. ‘‘Life expectancy is five to seven years at my age on retiring, so —’’ He paused. ‘‘That was humor, I guess. I’m not looking forward to being even older. Got no choice in the matter.’’

I asked if he ever found himself thinking about the billions of years that the Voyagers will circle the center of the galaxy, long after our sun has exploded, scattering more stardust throughout the universe. ‘‘Of course,’’ he said. ‘‘I was raised in the Roman Rite. I’m pretty much an atheist. But what is the meaning of life? It’s not Monty Python, O.K.?’’

Had he reached any conclusions about what it is? ‘‘Well, on Earth, yeah,’’ he said. ‘‘One species always prepares the way for the next generation — that’s all.’’

An article on Aug. 6 about the Voyager space probes misstated the title of Tom Krimigis. He is the emeritus head of the Space Department at the Applied Physics Laboratory at Johns Hopkins University, not the emeritus head of the entire laboratory.

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Kim Tingley is a contributing writer for the magazine. She last wrote about the future of automation .

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Voyager turns 45: What the iconic mission taught us and what's next

Can the first probe to visit Neptune and Uranus make it to its 50th anniversary?

Forty-five years ago, on Aug. 20, 1977, NASA's Voyager 2 spacecraft launched from Cape Canaveral, Florida, on a Titan III-Centaur rocket, embarking on a "grand tour" of the solar system that would include visits to the Jupiter and Saturn systems and would make it the first spacecraft to visit the ice giants Uranus and Neptune and their moons.  

Voyager 2 is now 12.1 billion miles (19.5 billion kilometers) away and still sending back data on the distant and unknown heliopause, and scientists are beginning to wonder how long the iconic space probe can keep going. 

Designed to take advantage of a once-every-176-years alignment in the 1970s that made it possible for spacecraft to take gravity-assist slingshots from planet to planet across the solar system , the Voyager mission consisted of two probes. Voyager 2 was the first to launch, with Voyager 1 following two weeks later. Both carried the famous " Golden Record ," a 12-inch gold-plated copper disc containing sounds and images portraying the diversity of life and culture on Earth . 

Now over 14.5 billion miles (23.3 billion km) away, Voyager 1 is the farthest artificial object from Earth. But Voyager 2 is arguably more iconic because of its incredible multidecade tour of the giant planets. 

Related: Celebrate 45 years of Voyager with these amazing images of our solar system (gallery)

Voyager's "grand tour"

Though it launched second, Voyager 1 was so called because it was to reach Jupiter and Saturn first — in March 1979 and November 1980, respectively — before exiting the plane of the planets where it took the famous "Pale Blue Dot" photo . Voyager 2 visited four planets: Jupiter in July 1979, Saturn in August 1981, Uranus in January 1986 and Neptune in August 1989. 

"Both Voyager 1 and Voyager 2 provided tremendous legacies for planetary exploration," Jonathan Lunine, a planetary scientist and physicist at Cornell University who is working on the Juno , Europa Clipper and James Webb Space Telescope missions, told Space.com. "Not only in what they accomplished in terms of science, but also demonstrating that it was really possible to explore the outer solar system with a couple of spacecraft."

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What did the Voyager probes reveal?

Voyager's discoveries are the stuff of legend among planetary scientists, many of whom still rely on the unique images from the spacecraft's wide-angle and narrow-angle cameras. The probes spotted volcanoes on Jupiter's moon Io , discovered that Jupiter's Great Red Spot is an Earth-size storm and found that the gas giant has faint rings. They studied Saturn's rings ; saw the giant moon Titan's thick, Earth-like atmosphere; and revealed the tiny moon Enceladus to be geologically active. 

Voyager 2 alone then visited Uranus and Neptune. The spacecraft's first-ever images of Uranus revealed dark rings, the planet's tilted magnetic field and its geologically active moon Miranda. Neptune, meanwhile, was also discovered to have rings and many more moons than scientists initially thought. We also got to see Triton , a geologically active moon that is orbiting "backward" and, like Pluto , is now believed to be a captured dwarf planet from the Kuiper Belt .  

Voyager as a catalyst 

In addition to making groundbreaking discoveries, the Voyager mission helped scientists determine what merited deeper exploration. The mission revealed Jupiter to be an incredibly complex planet, thus spurring NASA to launch the Galileo mission in 1989 and the Juno mission in 2011. The Voyager probes' work also helped to inspire the iconic Cassini mission to Saturn.

"Voyager 1's close flyby of Titan was the catalyst for the wonderful Cassini mission to Saturn and its Huygens probe," Lunine said. The Huygens probe landed on the surface of Titan in 2005 and sent back an incredible video . 

Voyager 2 has also been a catalyst for investigations into the role of the ice giant planets — not only in the solar system but also in distant star systems, since most of the exoplanets found so far are roughly the size of Neptune and Uranus. 

Voyager and NASA today 

NASA has spent decades following up on the Voyager missions, and those efforts continue today. The space agency's Dragonfly mission will reach Titan, Saturn's largest moon, in 2034, while Europa Clipper will study Jupiter's ocean moon, first imaged by Voyager, starting in 2030. In April, the National Academies Planetary Science Decadal Survey recommended that NASA send a $4.2 billion Uranus Orbiter and Probe mission to unveil the mysterious ice giant planet and its moons in the 2040s. 

It's the latest mission that's a direct consequence of Voyager 2's brief visit to the Uranus system in January 1986. "Voyager 2's flyby of Uranus was a bull's-eye — it went directly through the plane of the moons' orbits because of the orientation of Uranus' axis to the sun ," Lunine said. That made it unlike flybys at other planets, where the probes were able to visit one moon after another. "Voyager 2 got very brief images from these moons, so they're largely unexplored," Lunine said. 

Ariel and Miranda, in particular, are thought to be ocean worlds and so would be specifically targeted by the Uranus Orbiter and Probe. "It's been 45 years since the launch of Voyager 1 and Voyager 2, and here we are now finally talking about a Uranus Orbiter and Probe mission," Lunine said. "It seems like a long time because these missions take so long to conceive of, fund, build, launch and execute, but it all comes from the intriguing peeks that we got from Voyager 2." 

How long will Voyager last?

Both Voyager 1 and Voyager 2 still communicate with NASA's Deep Space Network (which itself was created to communicate with Voyager 2 at Uranus and Neptune), receiving routine commands and occasionally transmitting data to Earth. "We are still getting data from Voyager," Stamatios Krimigis, principal investigator for the Voyager 1 and 2 probes and the Voyager Interstellar Mission, said during a news conference held at COSPAR 22 in July. "We're looking forward to getting data for probably another five or six years."  

— What's next for NASA's Voyager 2 in interstellar space?

— Scientists' predictions for the long-term future of the Voyager Golden Records will blow your mind

— NASA's twin Voyager probes are nearly 45 — and facing some hard decisions  

Around the mid- to late 2020s , the probes' scientific instruments will be entirely switched off, and eventually, the spacecraft will go cold and silent — but their journeys into interstellar space will continue indefinitely. "My motto is, I want to be here after Voyager passes on," said Krimigis, who is in his 80s. "But I'm not sure that's going to happen."  

In around 300 years, Voyager 1 and 2 will enter the Oort cloud , the sphere of comets surrounding the solar system. About 30,000 years later, they'll exit the neighborhood and silently orbit the center of the Milky Way for millions of years. 

Their scientific work may be almost over, but the Voyager spacecraft have only just begun their journeys into the cosmos.

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Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: [email protected].

Jamie is an experienced science, technology and travel journalist and stargazer who writes about exploring the night sky, solar and lunar eclipses, moon-gazing, astro-travel, astronomy and space exploration. He is the editor of  WhenIsTheNextEclipse.com  and author of  A Stargazing Program For Beginners , and is a senior contributor at Forbes. His special skill is turning tech-babble into plain English.

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Carl Sagan in 1986: ‘Voyager has become a new kind of intelligent being—part robot, part human’

The renowned scientist reflected on the lesser-known triumphs and lofty ambitions of Voyager in Popular Science's October 1986 issue.

By Bill Gourgey | Published Mar 25, 2024 9:02 AM EDT

One of the worries that kept legendary astronomer Carl Sagan up at night was whether aliens would understand us. In the mid-1970s, Sagan led a committee formed by NASA to assemble a collection of images, recorded greetings, and music to represent Earth. The montage was pressed onto golden albums and dispatched across the cosmos on the backs of Voyagers 1 and 2 .

In a 1986 story Sagan wrote for Popular Science , he noted that “hypothetical aliens are bound to be very different from us—independently evolved on another world,” which meant they likely wouldn’t be able to decipher the golden discs. But he took assurance from an underappreciated dimension of Voyagers’ message: the designs of the vessels themselves.

“We are tool makers,” Sagan wrote. “This is a fundamental aspect, and perhaps the essence, of being human.” What better way to tell alien civilizations that Earthlings are toolmakers than by sending a living room-sized, aluminum-framed probe clear across the Milky Way. 

Although both spacecraft were only designed to swing by Jupiter and Saturn , Voyager 2’s trajectory also hurled it past Uranus and Neptune . Despite numerous mishaps along the way—and because of the elite toolmaker skills of NASA engineers—the probe was in good enough shape to send back close-ups of those distant worlds. In 2012, Voyager 1 became the first interstellar spacecraft , followed soon thereafter by Voyager 2 . “Once out of the solar system,” Sagan wrote, “the surfaces of the spacecraft will remain intact for a billion years or more,” so resilient is their design.

Today, the probes are 12–15 billion miles from Earth , still operable (despite experiencing recent communication difficulties ), and sailing through the relative calm of interstellar space. They are expected to continue to transmit data back to Earth for another year or so , or until their plutonium batteries quit. 

It was early 20th century wireless inventor Guglielmo Marconi who suggested that radio signals never die, they only diminish as they travel across space and time. Even after communications from the Voyager spacecraft cease, perhaps the tiny voices of Earth’s first emissaries, animated by NASA’s master toolmakers nearly half a century ago, will continue to drift through the cosmos for all time, accessible to far-flung civilizations equipped with sensitive enough receivers to listen.

“Voyager’s Triumph” (Carl Sagan, October 1986)

A noted scientist tells the little-known story of the remarkable feats of the Voyager engineers, a dedicated band who repeatedly overcame technical adversity to ensure the success of these historic expeditions to the outer solar system.

Carl Sagan is Director, Laboratory for Planetary Studies, Cornell University, and, since 1970, a member of the Voy­ager Imaging Science Team. His Cosmos: A Special Edition is televised this fall. 

On Jan. 25, 1986, the Voyager 2 robot probe entered the Uranus system and reported a procession of wonders. The encounter lasted only a few hours, but the data faithfully relayed back to Earth have revolu­tionized our knowledge of the aquamarine planet, its more than 15 moons, its pitch black rings, and its belt of trapped high-energy charged particles. Voyager 2 and its compan­ion, Voyager 1, have done this before. At Jupiter, in 1979, they braved a dose of trapped charged particles 1,000 times what it takes to kill a human being [PS, July ’79); and in all that radiation they discovered the rings of the largest planet, the first active volcanoes outside Earth, and a pos­sible underground ocean on an airless world—among a few hundred other major findings. At Saturn, in 1980 and 1981, the two spacecraft survived a pummeling by tiny icy particles as they plummeted through previously un­ known rings; and there they discovered not a few, but thou­ sands of Saturnian rings, icy moons recently melted through unknown causes, and a large world with an ocean of liquid hydrocarbons surmounted by clouds of organic matter IPS, March ’81 l. These spacecraft have returned to Earth four trillion bits of information, the equivalent of about 100,000 encyclopedia volumes. 

Because we are stuck on Earth, we are forced to peer at distant worlds through an ocean of distorting air. It is easy to see why our spacecraft have revolutionized the study of the solar system: We ascend to the stark clarity of the vacuum of space, and there approach our objectives, flying past them or orbiting them or landing on their surfaces. These nearby worlds have much to teach us about our own, and they will be—unless we are so foolish as to destroy ourselves—as familiar to our descendents as the neighboring states are to those who live in America today. 

Voyager and its brethren are prodigies of human inven­tiveness. Just before Voyager 2 was to encounter the Uranus system, the mission design had scheduled a final course correction, a short firing of the on-board propul­sion system to position Voyager correctly as it flew among the moving moons. But the course correction proved un­necessary. The spacecraft was already within 200 kilome­ters of its designed trajectory after a voyage along an arcing path five billion kilometers in length. This is roughly the equivalent of throwing a pin through the eye of a needle 50 kilometers away, or firing your target pistol in New York and hitting the bull’s eye in Dallas.

The lodes of planetary treasure were transmitted back to Earth by the radio antenna aboard Voyager; but Earth is so far away that by the time the signal was gathered in by radiotelescopes on our planet, the received power was only 10-16 watts (fifteen zeros after the decimal point). Comparing this weak signal with the power emitted by an ordinary reading lamp is like comparing the width of an atom with the distance between Earth and the moon. (Incidentally, the first photograph ever taken of Earth and the moon together in space was acquired by one of the Voyager spacecraft.)

We tend to hear much about the splendors returned, and very little about the ships that brought them, or the shipwrights. It has always been that way. Our history books do not tell us much about the builders of the Nina, Pinta, and Santa Maria, or even the principle of the caravel. De­spite ample precedent, it is a clear injustice: The Voyager engineering team and its accomplishments deserve to be much more widely known.

The Voyager spacecraft were designed and assembled, and are operated by the Jet Propulsion Laboratory (JPL) of the National Aeronautics and Space Administration in Pasadena, Calif. The mission was conceived during the late 1960s, first funded in 1972, but was not approved in its present form (which includes encounters at Uranus and Neptune) until after the 1979 Jupiter flyby. The two spacecraft were launched in late summer and early fall 1977 by a non-reusable Titan/Centaur booster configuration at Cape Canaveral, Fla. Weighing about a ton, a Voyager would fill a good-sized living room. Each spacecraft draws about 400 watts of power—considerably less than an average American home—from a generator that converts radioactive plutonium into electricity. The instrument that measures interplanetary magnetic fields is so sensitive that the flow of electricity through the innards of the spacecraft would generate spurious signals. As a result, this instrument is placed at the end of a long boom stretching out from the spacecraft. With other projections, it gives Voyager a slightly porcupine appearance. Two cameras, infrared and ultraviolet spectrometers, and an instrument called the photopolarimeter are on a scan platform; the platform swivels so these instruments can point toward a target world. The spacecraft antenna must know where Earth is if the transmitted data are to be received back home. The spacecraft also needs to know where the sun is and at least one bright star, so it can orient itself in three dimensions and point properly toward any passing world. It does no good to be able to return pictures over billions of miles if you can’t point the camera.

On-orbit repairs

Each spacecraft costs about as much as a single modern strategic bomber. But unlike bombers, Voyager cannot, once launched, be returned to the hangar for repairs.

As a result, the spacecraft’s computers and electronics are designed redundantly. And when Voyager finds itself in trouble, the computers use branched contingency tree logic to work out the appropriate course of action. As the spacecraft journeys increasingly far from Earth, the round-trip light (and radio) travel time also increases, approaching six hours by the time Voyager is at the distance of Uranus.

Thus, in case of an emergency, the spacecraft needs to know how to put itself in a safe standby mode while awaiting instructions from Earth. As the spacecraft ages, more and more failures are expected, both in its mechanical parts and its computer system, although there is as yet no sign of a serious memory deterioration, some robot Alzheimer’s disease. When an unexpected failure occurs, special teams of engineers—some of whom have been with the Voyager program since its inception—are assigned to “work” the problem. They will study the underlying basic science and draw upon their previous experience with the failed subsystems. They may do experiments with identical Voyager spacecraft equipment that was never launched or even manufacture a large number of components of the sort that failed in order to gain some statistical understanding of the failure mode.

In April 1978, almost eight months after launch, an omitted ground command caused Voyager 2’s on-board computer to switch from the prime radio receiver to its backup.

During the next ground transmission to the spacecraft, the receiver refused to lock onto the signal from Earth. A component called a tracking loop capacitor had failed. After seven days in which Voyager 2 was out of contact, its fault protection software commanded the backup receiver to be switched off and the prime receiver to be switched back on. But, mysteriously, the prime receiver failed moments later: It never recovered. Voyager 2 was now fundamentally imperiled. Although the primary receiver had failed, the on-board computer commanded the spacecraft to use it. There was no way for the controllers on Earth to command Voyager to revert to the backup receiver. Even worse, the backup receiver would be unable to receive the commands from Earth because of the failed capacitor. Finally, after a week of command silence, the computer was programmed to switch automatically between receivers.

And during that week’s time the JPL engineers designed an innovative command frequency control procedure to make a few essential commands comprehensible to the damaged backup receiver.

This meant the engineers were able to communicate, at least a little bit, with the spacecraft. Unfortunately the backup receiver now turned giddy, becoming extremely sensitive to the stray heat dumped when various components of the spacecraft were powered up or down. Over the following months the JPL engineers designed and conducted a series of tests that let them thoroughly understand the thermal consequences of most operational modes of the spacecraft on its ability to receive commands from Earth. The backup-receiver problem was entirely circumvented. It was this backup receiver that acquired all the commands from Earth on how to gather data in the Jupiter, Saturn, and Uranus systems. The engineers had saved the mission. (But to be on the safe side, during most of Voyager’s subsequent flight there is in residence in the onboard computers a nominal data-taking sequence for the next planet to be encountered.)

Another heart-wrenching failure occurred just after Voyager 2 emerged from behind Saturn after its closest approach to the planet in August 1981. The scan platform had been moving rapidly in the azimuth direction—quickly pointing here and there among the rings, moons, and the planet itself during the time of closest approach. Suddenly, the platform jammed. A stuck scan platform obviously implies a severe reduction in future pictures and other key data. The scan platform is driven by gear trains called actuators, so first the JPL engineers ran an identical copy of the flight actuator in a simulated mission. The ground actuator failed after 348 revolutions: the actuator on the spacecraft had failed after 352 revolutions. The problem turned out to be a lubrication failure. Plainly, it would be impossible to overtake Voyager with an oil can. The engineers wondered whether it would be possible to restart the failed actuator by alternately heating and cooling it, so that the thermal stresses would cause the components of the actuator to expand and contract at different rates and un-jam the system. After gaining experience with specially manufactured actuators on the ground, the engineers jubilantly found that they were able to use this procedure to start the scan platform up again in space. More than this, they devised techniques to diagnose any imminent actuator failure early enough to work around the problem. Voyager 2’s scan platform worked perfectly in the Uranus system. The engineers had saved the day again.

Ingenious solutions

Voyager 1 and 2 were designed to explore the Jupiter and Saturn systems only. It is true that their trajectories would carry them to Uranus and Neptune, but officially these planets were never contemplated as targets for Voyager exploration: The spacecraft was not supposed to last that long. Because of trajectory requirements in the Saturn system, Voyager 1 was flung on a path that will never encounter any other known world; but Voyager 2 flew to Uranus with brilliant success, and is now on its way to an August 1989 encounter with the Neptune system.

At these immense distances, sunlight is getting progressively dimmer, and the spacecraft’s transmitted radio signals to Earth are getting progressively fainter. These were predictable but still very serious problems that the JPL engineers and scientists also had to solve before the encounter with Uranus.

Because of the low light levels at Uranus, the Voyager television cameras were obliged to take longer time exposures. But the spacecraft was hurtling through the Uranus system so fast (about 35,000 miles per hour) that the image would have been smeared or blurred—an experience shared by many amateur photographers. To overcome this, the entire spacecraft had to be moved during the time exposures to compensate for the motion, like panning in the direction opposite yours while taking a photograph of a street scene from a moving car. This may sound easier than it is: You have to compensate for the most casual of motions. At zero gravity, the mere start and stop of the on-board tape recorder that’s registering the image can jiggle the spacecraft enough to smear the picture. This problem was solved by commanding the spacecraft thrusters, instruments of exquisite sensitivity, to compensate for the tape-recorder jiggle at the start and stop of each sequence by turning the entire spacecraft just a little. To compensate for the low received radio power at Earth, a new and more efficient digital encoding algorithm was designed for the cameras, and the radiotelescopes on Earth were joined together with oth ers to increase their sensitivity. Overall, the imaging system worked, by many criteria, better at Uranus than it did at Saturn or even at Jupiter.

Voyager has become a new kind of intelligent being—part robot, part human. It extends the human senses to far-off worlds.

The ingenuity of the JPL engineers is growing faster than the spacecraft is deteriorating. And Voyager may not be done exploring after its Neptune encounter.

There is, of course, a chance that some vital subsystem will fail tomorrow, but in terms of the radioactive decay of the plutonium power source, the two Voyager spacecraft will be able to return data to Earth until roughly the year 2015. By then they will have traveled more than a hundred times Earth’s distance from the sun, and may have penetrated the heliopause, the place where the interplanetary magnetic field and charged particles are replaced by their interstellar counterparts; the heliopause is one definition of the frontier of the solar system.

Robot-human partnerships

These engineers are heroes of our time. And yet almost no one knows their names. I have attached a table giving the names of a few of the JPL engineers who played central roles in the success of the Voyager missions.

In a society truly concerned for its future, Don Gray, Charlie Kohlhase, or Howard Marderness, would be as well known for their extraordinary abilities and accomplishments as Dwight Gooden, Wayne Gretzky, or Kareem Abdul Jabbar are for theirs.

Voyager has become a new kind of intelligent being-part robot, part human. It extends the human senses to far-off worlds. For simple tasks and short-term problems, it relies on its own intelligence; but for more complex tasks and longer term problems, it turns to another, considerably larger brain—the collective intelligence and experience of the JPL engineers. This trend is sure to grow. The Voyagers embody the technology of the early 1970s; if such spacecraft were to be designed in the near future, they would incorporate stunning improvements in artificial intelligence, in data-processing speed, in the ability to self-diagnose and repair, and in the capacity for the spacecraft to learn from experience. In the many environments too dangerous for people, the future belongs to robot-human partnerships that will recognize Voyager as antecedent and pioneer.

Unlike what seems to be the norm in the so-called defense industry, the Voyager spacecraft came in at cost, on time, and vastly exceeding both their design specifications and the fondest dreams of their builders. These machines do not seek to control, threaten, wound, or destroy; they represent the exploratory part of our nature, set free to roam the solar system and beyond.

Once out of the solar system, the surfaces of the spacecraft will main intact for a billion years or more, as the Voyagers circumnavigate the center of the Milky Way galaxy.

This kind of technology, its findings freely revealed to all humans everywhere, is one of the few activities of the United States admired as much by those who find our policies uncongenial as by those who agree with us on every issue. Unfortunately, the tragedy of the space shuttle Challenger implies agonizing delays in the launch of Voyager’s successor missions, such as the Galileo Jupiter orbiter and entry probe. Without real support from Congress and the White House, and a clear long-term NASA goal, NASA scientists and engineers will be forced to find other work, and the historic American triumphs in solar-system exploration—symbolized by Voyager—will become a thing of the past. Missions to the planets are one of those things—and I mean this for the entire human species—that we do best. We are tool makers—this is a fundamental aspect, and perhaps the essence, of being human.

Greeting the aliens

Both Voyager spacecraft are on escape trajectories from the solar system. The gravitational fields of Jupiter, Saturn, and Uranus have flung them at such high velocities that they are destined ultimately to leave the solar system altogether and wander for ages in the calm, cold blackness of interstellar space—where, it turns out, there is essentially no erosion.

Once out of the solar system, the surfaces of the spacecraft will main intact for a billion years or more, as the Voyagers circumnavigate the center of the Milky Way galaxy. We do not know whether there are other space-faring civilizations in the Milky Way. And if they do exist, we do not know how abundant they are.

But there is at least a chance that some time in the remote future one of the Voyagers will be intercepted by an alien craft. Voyagers 1 and 2 are the fastest spacecraft ever launched by humans; but even so, they are traveling so slowly that it will be tens of thousands of years before they go the distance to the nearest star. And they are not headed toward any of the nearby stars. As a result there could be no danger of Voyager attracting “hostile” aliens to Earth, at least not any time soon.

So, it seemed appropriate to include some message of greeting from Earth At NASA’s request, a committee I chaired designed a phonograph record that was affixed to the outside of each of the Voyager spacecraft. The records contain 116 pictures in digital form, describing our science and technology, our institutions, and ourselves; what will surely be unintelligible greetings in many languages; a sound essay on the evolution of our planet; and an hour and a half of the world’s greatest music. But the hypothetical aliens are bound to be very different from us—independently evolved on another world. Are we really sure they could understand our message? Every time I feel these concerns stirring, though, I reassure myself: Whatever the incomprehensibilities of the Voyager record, any extraterrestrial that finds it will have another standard by which to judge us.

Each Voyager is itself a message. In its exploratory intent, in the lofty ambition of its objectives, and in the brilliance of its design and performance, it speaks eloquently for us.

Bill Gourgey is a Popular Science contributor and unofficial digital archeologist who enjoys excavating PopSci’s vast archives to update noteworthy stories (yes, merry-go-rounds are noteworthy).

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March 18, 2024

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As Voyager 1's mission draws to a close, one planetary scientist reflects on its legacy

by Daniel Strain, University of Colorado at Boulder

For nearly 50 years, NASA's Voyager 1 mission has competed for the title of deep space's little engine that could. Launched in 1977 along with its twin, Voyager 2, the spacecraft is now soaring more than 15 billion miles from Earth.

On their journeys through the solar system , the Voyager spacecraft beamed startling images back to Earth—of Jupiter and Saturn, then Uranus and Neptune and their moons. Voyager 1's most famous shot may be what famed astronomer Carl Sagan called the "pale blue dot," a lonely image of Earth taken from 6 billion miles away in 1990.

But Voyager 1's trek could now be drawing to a close. Since December, the spacecraft--which weighs less than most cars--has been sending nonsensical messages back to Earth, and engineers are struggling to fix the problem. Voyager 2 remains operational.

Fran Bagenal is a planetary scientist at the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder. She started working on the Voyager mission during a summer student job in the late 1970s and has followed the two spacecraft closely since.

To celebrate Voyager 1, Bagenal reflects on the mission's legacy—and which planet she wants to visit again.

Many are impressed that the spacecraft has kept going for this long. Do you agree?

Voyager 1's computer was put together in the 1970s, and there are very few people around who still use those computing languages. The communication rate is 40 bits per second. Not megabits. Not kilobits. Forty bits per second. Moreover, the round-trip communication time is 45 hours. It's amazing that they're still communicating with it at all.

What was it like working on Voyager during the mission's early days?

At the very beginning, we used computer punch cards. The data was on magnetic tapes, and we would print out line-plots on reels of paper. It was very primitive.

But planet by planet, with each flyby, the technology got a lot more sophisticated. By the time we got to Neptune in 1989, we were doing our science on much more efficient computers, and NASA presented its results live across the globe over an early version of the internet.

Think about it—going from punch cards to the internet in 12 years.

How did the Voyager spacecraft shape our understanding of the solar system?

First of all, the pictures were jaw-dropping. They were the first high-quality, close-up pictures of the four gas giant planets and their moons. The Voyagers really revolutionized our thinking by going from one planet to the other and comparing them.

Jupiter and Saturn's ammonia white and orange clouds, for example, were violently swept around by strong winds, while Uranus and Neptune's milder weather systems were hidden and colored blue by atmospheric methane. But the most dramatic discoveries were the multiple distinct worlds of the different moons, from Jupiter's cratered Callisto and volcanic Io to Saturn's cloudy Titan to plumes erupting on Triton, a moon of Neptune.

The Jupiter and Saturn systems have since been explored in greater detail by orbiting missions—Galileo and Juno at Jupiter, Cassini at Saturn.

Voyager 2 is the only spacecraft that has visited Uranus and Neptune. Do we need to return?

My vote is to return to Uranus—the only planet in our solar system that's tipped on its side.

We didn't know before Voyager whether Uranus had a magnetic field. When we arrived, we found that Uranus has a magnetic field that's severely tilted with respect to the planet's rotation. That's a weird magnetic field.

Jupiter, Saturn and Neptune all emit a lot of heat from the inside. They glow in the infrared, emitting two and a half times more energy than they receive from the sun. These things are hot.

Uranus isn't the same. It doesn't have this internal heat source. So maybe, just maybe, at the end of the formation of the solar system billions of years ago, some big object hit Uranus, tipped it on its side, stirred it up and dissipated the heat. Perhaps, this led to an irregular magnetic field .

These are the sorts of questions that were raised by Voyager 30 years ago. Now we need to go back.

Culturally, Voyager 1's most lasting impact may be the 'pale blue dot.' Why?

I have huge respect for Carl Sagan. I met him when I was 16, a high school student in England, and I shook his hand.

He pointed to the Voyager image and said, "Here we are. We're leaving the solar system. We're looking back, and there's this pale blue dot. That's us. It's all our friends. It's all our relatives. It's where we live and die."

This was the time we were just beginning to say, "Wait a minute. What are we doing to our planet Earth?" He was awakening or reinforcing this need to think about what humans are doing to Earth. It also evoked why we need to go exploring space: to think about where we are and how we fit into the solar system.

How are you feeling now that Voyager 1's mission may be coming to an end?

It's amazing. No one thought they would go this far. But with just a few instruments working, how much longer can we keep going? I think it will soon be time to say, "Right, jolly good. Extraordinary job. Well done."

Provided by University of Colorado at Boulder

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What did we learn from the Voyager mission?

Jim Green, director of planetary science at NASA, discusses the lasting influence of the epic Voyager programme to study the outer Solar System.

James Green

The Voyager mission not only transformed our knowledge of Jupiter, Saturn and their dozens of moons, it also gave us our first close-up look at the strange and wondrous planets Uranus and Neptune.

Voyager will be remembered as one of the greatest achievements in exploration. As you read this, the two Voyager probes are still operating and travelling where no spacecraft – or anything else touched by human hands – has ever gone before.

In August 2012, Voyager 1 left our planetary system and entered the mysterious region between the stars: interstellar space. Voyager 2 joined its pioneering twin in the outer limits of the Sun’s sphere of influence in 2018.

In the decades since the two craft were launched into space, Voyager 1 has travelled more than 20 billion km, while Voyager 2 has hit the 17 billion km mark.

It's worth pausing to reflect on the vision that inspired Voyager, its greatest achievements and its enduring legacy – how the two probes and their findings inspired those that followed and how they continue to influence NASA missions today.

In my quieter moments, I think about a time, billions of years from now, when our Sun has become a red giant. By then, Earth will no longer be habitable and, in order to survive, humans will have ‘left the nest’ for another home, following a path forged by the Voyager missions.

It's humbling and inspiring to think that, even then, the Voyagers will still be Earth’s ambassadors – each one a time capsule from an era when audacious explorers on our Pale Blue Dot reached out to the stars beyond our Solar System.

Curiosity is in our DNA. As humans, we’re compelled to explore, to find out what lies beyond the next hill.

Not only has the science produced by the Voyager mission been captivating, the probes themselves captured the world’s imagination by each carrying a greeting for extraterrestrial civilisations, in the form of the Golden Records.

While Pioneers 10 and 11 each carried small metal plaques detailing their origin and date of launch, the Voyagers’ Golden Records were considerably more ambitious.

The twin phonograph records brim with images and sounds that provide a snapshot of the diversity of life and culture on Earth to anyone that might discover them. As Carl Sagan noted, “The launching of this ‘bottle’ in the cosmic ocean says something very hopeful about life on this planet.”

Why were there two Voyager spacecraft?

The Voyager mission was as ambitious as it gets. Collectively, the Voyagers visited more planets, discovered more moons and imaged more places than any other spacecraft in NASA history.

One of the questions I’m often asked is: why were there two Voyagers? Voyager was an early NASA mission, at a time when flight systems were known to suffer many anomalies that would put them in safe mode, a condition that typically shuts down all science instruments and looks for commands from Earth.

Since the Voyager missions were flybys, anomalies that would require a lot of time to diagnose and correct could result in us missing an encounter and all the science that might derive from it.

By having two spacecraft we could increase the odds of the mission’s success. The same strategy was employed with the Mars exploration rovers, Spirit and Opportunity; having two rovers not only provides a redundancy and gives us a bigger margin for error.

It quickly became clear that this ‘one-two punch’ strategy was the best one to adopt. Voyager 1’s scan platform, the swivel that moves its cameras and instruments from side to side, became stuck for several weeks in 1978.

The same platform became stuck on Voyager 2’s as the spacecraft was pulling away from its closest approach with Saturn. Fortunately Voyager 2 produced fantastic results at Saturn despite the technical problems, but the anomalies reinforced the value of redundancy and having a second craft as a back-up.

As the first mission to take in the four giant planets in the outer Solar System, Voyager produced a bonanza of new science.

Among the mission’s accomplishments was the discovery of previously unknown moons and rings, the finding of active volcanoes on Io , Neptune’s Great Dark Spot and powerful winds and erupting geysers on Triton.

The discoveries didn’t stop with the probes’ last planetary flybys though. In 2012 Voyager 1 became the first spacecraft to leave the heliosphere, delivering the first measurements of the full intensity of cosmic rays and the galactic magnetic field from interstellar space.Voyager 2 provided the first measurements of the solar wind termination shock.

How Voyager influenced current Solar System exploration

NASA’s Planetary Science Division follows a paradigm for its exploration of the Solar System: flyby, orbit, land, rove and return samples.

The Voyagers were – and in some ways continue to be – the scouting party and the instigators of this paradigm. They forged the way with flybys that have enabled us to take the next steps.

Indeed, the Voyager spacecraft allowed us to survey what’s out there and decide on our priorities for further study. As flyby missions, the Voyagers reinforced the planetary science paradigm, which has been, and continues to be, tremendously successful.

Critical to the success of the Voyagers’ tours of the outer planets was the principle of gravity assist – using the mass of a planet or another object in space to alter the speed and trajectory of a spacecraft. Voyager 2 nailed the gravity assist to tour Jupiter, Saturn, Uranus and Neptune.

Since then, a number of missions have employed gravity assists to save fuel and dramatically reduce the amount of time it takes to reach destinations in the outer Solar System.

Voyager paved the way for a number of NASA missions: the Galileo and Juno missions to Jupiter, the Cassini mission to Saturn.

New Horizons flew by Pluto with a boost from Jupiter’s gravity. OSIRIS-REX , bound for asteroid 101955 Bennu, got a gravity assist from Earth to slingshot it more rapidly to its destination.

On the other hand, mission planners for Messenger used gravity assist not to speed the spacecraft up, but to slow it down, so it could successfully enter Mercury’s orbit.

Messenger received assists at Earth and Venus, and three separate assists from Mercury itself before being placed into Mercury’s orbit.

Cassini received two gravity assists at Venus and one each at Earth and Jupiter en route to Saturn. Cassini has mastered the art of gravity assists and uses close flybys of Saturn's largest moon Titan to continually reshape its orbit.

This has allowed Cassini to obtain new views of many of the Saturnian moons that would be otherwise inaccessible, and produced significant scientific results.

In order to observe Neptune’s moon Triton, Voyager 2 performed a very close flyby of Neptune that saw it pass about 5,000km above the planet’s north polar cloud tops.

This was the closest trajectory that any spacecraft had followed around one of the outer planets and initiated the development of precision trajectories for future flybys that would be even closer.

One such flyby took Cassini through the plumes bursting up from Enceladus , bringing the probe within 15km of the moon’s icy surface.

While the Voyagers had limited programmable memory, it proved to be a critical resource that was used extensively and reprogrammed on a number of occasions.Consequently, all subsequent planetary missions were given large programmable memories.

The Voyagers set the agenda for future planetary exploration.Though they taught us much about the ice giants and their moons, the relatively primitive instruments of those missions, and the relatively low volume of data returned raised more questions than answers.

The Voyagers piqued our curiosity about the internal structures and compositions of the giant planets. We have much to learn about their polar regions and the origin of their magnetic fields.

The Voyager mission was a case of the more we know, the more we appreciate what we need to learn. As such, Voyager paved the way for a number of NASA missions: both the Galileo and Juno missions to Jupiter, and the Cassini mission to Saturn with, appropriately, a gravity assist from Jupiter.

The Europa Clipper mission is an orbiter that also builds on the experience gained from Voyager. Clipper is scheduled to launch in the early 2020s and a subsequent lander mission would be a logical successor that could explore the surface but also seek evidence of life beyond Earth.

While the Voyagers' 'grand tours' didn’t include Pluto, the New Horizons mission ‘completed the set’ with a flyby of Pluto in July of 2015 – aided once again by a gravity assist from Jupiter.

Returning to the ice giants

The ice giants Uranus and Neptune have remained unexplored since Voyager 2, but that could change in the years to come. The current Planetary Science Decadal Survey, which covers 2013–2022, lists a return to Uranus or Neptune as a top priority.

A recent NASA-led pre-decadal survey explored a variety of potential mission concepts including orbiters, flybys and probes that would dive into Uranus’s atmosphere to study its composition, possibly in the late 2020s.

Voyagers’ discoveries also inspired a future mission to Jupiter’s fascinating volcanic moon Io, with an Io Observer listed as one of the priorities in NASA’s New Frontiers line of missions in 2003.

Very little is known about the magnetic fields and magnetospheres of Uranus and Neptune, aside from what was learned through the Voyager encounters more than two decades ago.

But questions remain about their magnetosphere-ionosphere coupling processes and their link to the aurorae and moons.

Also puzzling are Neptune’s heat flow, which is around 10 times larger than expected, and Uranus’s, which is about three times greater than anticipated. But the causes are unknown.

At Neptune, Voyager found nitrogen geysers erupting into the stratosphere from Triton’s ultra-cold surface.

We also still have much to learn about the final frontier of the Solar System, so visiting the heliopause with a more capable mission is on my bucket list.

Looking back on the Voyager mission, we can reflect on what drives us to understand our origins and what our future may hold. Curiosity is in our DNA. As humans, we’re compelled to explore, to find out what lies beyond the next hill.

The Voyager probes not only transformed our view of science and the Universe, they also changed us as people. Who isn’t awestruck and humbled by the iconic image of our home planet, that Pale Blue Dot, seen by Voyager 1 from a distance of six billion km?

We were compelled to repeat that experiment with Cassini as we viewed Earth through Saturn’s rings.

Voyager also taught us the art of patience. The time it took for the probes to complete their investigations required that the NASA scientists involved with the mission make a long-term investment in the project.

Any gratification that came from it would be severely delayed, but, as history show has shown, it would be worth the wait.

As a graduate student, I was transfixed by the Voyager flybys. Now, as NASA’s director of planetary science, I yearn

to return to the outer Solar System, to go back to Uranus and Neptune and discover even more about the ice giants.

There are still legacies of the Voyager mission out there waiting to be fulfilled.

James Green is director of planetary science at NASA.

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Inside NASA's 5-month fight to save the Voyager 1 mission in interstellar space

After working for five months to re-establish communication with the farthest-flung human-made object in existence, NASA announced this week that the Voyager 1 probe had finally phoned home.

For the engineers and scientists who work on NASA’s longest-operating mission in space, it was a moment of joy and intense relief.

“That Saturday morning, we all came in, we’re sitting around boxes of doughnuts and waiting for the data to come back from Voyager,” said Linda Spilker, the project scientist for the Voyager 1 mission at NASA’s Jet Propulsion Laboratory in Pasadena, California. “We knew exactly what time it was going to happen, and it got really quiet and everybody just sat there and they’re looking at the screen.”

When at long last the spacecraft returned the agency’s call, Spilker said the room erupted in celebration.

“There were cheers, people raising their hands,” she said. “And a sense of relief, too — that OK, after all this hard work and going from barely being able to have a signal coming from Voyager to being in communication again, that was a tremendous relief and a great feeling.”

The problem with Voyager 1 was first detected in November . At the time, NASA said it was still in contact with the spacecraft and could see that it was receiving signals from Earth. But what was being relayed back to mission controllers — including science data and information about the health of the probe and its various systems — was garbled and unreadable.

That kicked off a monthslong push to identify what had gone wrong and try to save the Voyager 1 mission.

Spilker said she and her colleagues stayed hopeful and optimistic, but the team faced enormous challenges. For one, engineers were trying to troubleshoot a spacecraft traveling in interstellar space , more than 15 billion miles away — the ultimate long-distance call.

“With Voyager 1, it takes 22 1/2 hours to get the signal up and 22 1/2 hours to get the signal back, so we’d get the commands ready, send them up, and then like two days later, you’d get the answer if it had worked or not,” Spilker said.

The team eventually determined that the issue stemmed from one of the spacecraft’s three onboard computers. Spilker said a hardware failure, perhaps as a result of age or because it was hit by radiation, likely messed up a small section of code in the memory of the computer. The glitch meant Voyager 1 was unable to send coherent updates about its health and science observations.

NASA engineers determined that they would not be able to repair the chip where the mangled software is stored. And the bad code was also too large for Voyager 1's computer to store both it and any newly uploaded instructions. Because the technology aboard Voyager 1 dates back to the 1960s and 1970s, the computer’s memory pales in comparison to any modern smartphone. Spilker said it’s roughly equivalent to the amount of memory in an electronic car key.

The team found a workaround, however: They could divide up the code into smaller parts and store them in different areas of the computer’s memory. Then, they could reprogram the section that needed fixing while ensuring that the entire system still worked cohesively.

That was a feat, because the longevity of the Voyager mission means there are no working test beds or simulators here on Earth to test the new bits of code before they are sent to the spacecraft.

“There were three different people looking through line by line of the patch of the code we were going to send up, looking for anything that they had missed,” Spilker said. “And so it was sort of an eyes-only check of the software that we sent up.”

The hard work paid off.

NASA reported the happy development Monday, writing in a post on X : “Sounding a little more like yourself, #Voyager1.” The spacecraft’s own social media account responded , saying, “Hi, it’s me.”

So far, the team has determined that Voyager 1 is healthy and operating normally. Spilker said the probe’s scientific instruments are on and appear to be working, but it will take some time for Voyager 1 to resume sending back science data.

Voyager 1 and its twin, the Voyager 2 probe, each launched in 1977 on missions to study the outer solar system. As it sped through the cosmos, Voyager 1 flew by Jupiter and Saturn, studying the planets’ moons up close and snapping images along the way.

Voyager 2, which is 12.6 billion miles away, had close encounters with Jupiter, Saturn, Uranus and Neptune and continues to operate as normal.

In 2012, Voyager 1 ventured beyond the solar system , becoming the first human-made object to enter interstellar space, or the space between stars. Voyager 2 followed suit in 2018.

Spilker, who first began working on the Voyager missions when she graduated college in 1977, said the missions could last into the 2030s. Eventually, though, the probes will run out of power or their components will simply be too old to continue operating.

Spilker said it will be tough to finally close out the missions someday, but Voyager 1 and 2 will live on as “our silent ambassadors.”

Both probes carry time capsules with them — messages on gold-plated copper disks that are collectively known as The Golden Record . The disks contain images and sounds that represent life on Earth and humanity’s culture, including snippets of music, animal sounds, laughter and recorded greetings in different languages. The idea is for the probes to carry the messages until they are possibly found by spacefarers in the distant future.

“Maybe in 40,000 years or so, they will be getting relatively close to another star,” Spilker said, “and they could be found at that point.”

Denise Chow is a reporter for NBC News Science focused on general science and climate change.

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The Voyager missions

Highlights Voyager 1 and Voyager 2 launched in 1977 and made a grand tour of the solar system's outer planets. They are the only functioning spacecraft in interstellar space, and they are still sending back measurements of the interstellar medium. Each spacecraft carries a copy of the golden record, a missive from Earth to any alien lifeforms that may find the probes in the future.

What are the Voyager missions?

The Voyager program consists of two spacecraft: Voyager 1 and Voyager 2. Voyager 2 was actually launched first, in August 1977, but Voyager 1 was sent on a faster trajectory when it launched about two weeks later. They are the only two functioning spacecraft currently in interstellar space, beyond the environment controlled by the sun.

Voyager 2’s path took it past Jupiter in 1979, Saturn in 1981, Uranus in 1985, and Neptune in 1989. It is the only spacecraft to have visited Uranus or Neptune, and has provided much of the information that we use to characterize them now.

Because of its higher speed and more direct trajectory, Voyager 1 overtook Voyager 2 just a few months after they launched. It visited Jupiter in 1979 and Saturn in 1980. It overtook Pioneer 10 — the only other spacecraft in interstellar space thus far — in 1998 and is now the most distant artificial object from Earth.

How the Voyagers work

The two spacecraft are identical, each with a radio dish 3.7 meters (12 feet) across to transmit data back to Earth and a set of 16 thrusters to control their orientations and point their dishes toward Earth. The thrusters run on hydrazine fuel, but the electronic components of each spacecraft are powered by thermoelectric generators that run on plutonium. Each carries 11 scientific instruments, about half of which were designed just for observing planets and have now been shut off. The instruments that are now off include several cameras and spectrometers to examine the planets, as well as two radio-based experiments. Voyager 2 now has five functioning instruments: a magnetometer, a spectrometer designed to investigate plasmas, an instrument to measure low-energy charged particles and one for cosmic rays, and one that measures plasma waves. Voyager 1 only has four of those, as its plasma spectrometer is broken.

Jupiter findings

Over the course of their grand tours of the solar system, the Voyagers took tens of thousands of images and measurements that significantly changed our understanding of the outer planets.

At Jupiter, they gave us our first detailed ideas of how the planet’s atmosphere moves and evolves, showing that the Great Red Spot was a counter-clockwise rotating storm that interacted with other, smaller storms. They were also the first missions to spot a faint, dusty ring around Jupiter. Finally, they observed some of Jupiter’s moons, discovering Io’s volcanism, finding the linear features on Europa that were among the first hints that it might have an ocean beneath its surface, and granting Ganymede the title of largest moon in the solar system, a superlative that was previously thought to belong to Saturn’s moon Titan.

Saturn findings

Next, each spacecraft flew past Saturn, where they measured the composition and structure of Saturn’s atmosphere , and Voyager 1 also peered into Titan’s thick haze. Its observations led to the idea that Titan might have liquid hydrocarbons on its surface, a hypothesis that has since been verified by other missions. When the two missions observed Saturn’s rings, they found the gaps and waves that are well-known today. Voyager 1 also spotted three previously-unknown moons orbiting Saturn: Atlas, Prometheus, and Pandora.

Uranus and Neptune findings

After this, Voyager 1 headed out of the solar system, while Voyager 2 headed toward Uranus . There, it found 11 previously-unknown moons and two previously-unknown rings. Many of the phenomena it observed on Uranus remained unexplained, such as its unusual magnetic field and an unexpected lack of major temperature changes at different latitudes.

Voyager 2’s final stop, 12 years after it left Earth, was Neptune. When it arrived , it continued its streak of finding new moons with another haul of 6 small satellites, as well as finding rings around Neptune. As it did at Uranus, it observed the planet’s composition and magnetic field. It also found volcanic vents on Neptune’s huge moon Triton before it joined Voyager 1 on the way to interstellar space.

Interstellar space

Interstellar space begins at the heliopause, where the solar wind – a flow of charged particles released by the sun – is too weak to continue pushing against the interstellar medium, and the pressure from the two balances out. Voyager 1 officially entered interstellar space in August 2012, and Voyager 2 joined it  in November 2018.

These exits were instrumental in enabling astronomers to determine where exactly the edge of interstellar space is, something that’s difficult to measure from within the solar system. They showed that interstellar space begins just over 18 billion kilometers (about 11 billion miles) from the sun. The spacecraft continue to send back data on the structure of the interstellar medium.

After its planetary encounters, Voyager 1 took the iconic “Pale Blue Dot” image , showing Earth from about 6 billion kilometers (3.7 billion miles) away. As of 2021 , Voyager 1 is about 155 astronomical units (14.4 billion miles) from Earth, and Voyager 2 is nearly 129 astronomical units (12 billion miles) away.

The golden records

Each Voyager spacecraft has a golden phonograph record affixed to its side, intended as time capsules from Earth to any extraterrestrial life that might find the probes sometime in the distant future. They are inscribed with a message from Jimmy Carter, the U.S. President at the time of launch, which reads: “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 covers of the records have several images inscribed, including visual instructions on how to play them, a map of our solar system’s location with respect to a set of 14 pulsars, and a drawing of a hydrogen atom. They are plated with uranium – its rate of decay will allow any future discoverers of either of the records to calculate when they were created.

The records’ contents were selected by a committee chaired by Carl Sagan. Each contains 115 images, including scientific diagrams of the solar system and its planets, the flora and fauna of Earth, and examples of human culture. There are natural sounds, including breaking surf and birdsong, spoken greetings in 55 languages, an hour of brainwave recordings, and an eclectic selection of music ranging from Beethoven to Chuck Berry to a variety of folk music.

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Season 3, episode 10: a voyager’s view of earth.

The Voyager 1 spacecraft has traveled farther away from Earth than any human-made object. Candy Hansen and David Grinspoon talk about the Voyager mission, and its humbling perspective of our planet as a tiny blue dot in the blackness of space.

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(Voyager Golden Record greetings) French : “Hello everybody” Hindi: “Greetings from the inhabitants of this world.” Hebrew: “Peace.”

[0:08] Narrator: The Voyager 1 and Voyager 2 spacecraft left our planet 43 years ago, and they both carry something unique, something no other spacecraft has ever had. Affixed to their sides is a phonograph record, made of copper and coated in gold to keep it from interfering with spacecraft electronics.

The identical Golden Records contain greetings from Earth in 55 languages, from Arabic:

(Voyager Golden Record greetings: Arabic)

“Greetings to our friends in the stars. We wish that we will meet you someday.”

(Voyager Golden Record greetings: Zulu)

To Zulu: “We greet you, great ones. We wish you longevity.”

The reason to send greetings in so many languages was not to confuse potential extraterrestrials who might play the record someday, but instead, to have a diverse chorus that represents a broad sphere of humanity.

[1:10] The Golden Records also feature the songs of birds and humpback whales, and also crickets, frogs, a chimpanzee, a dog. There are sounds made by our planet, like volcanoes, earthquakes, thunder, and ocean surf. There are sounds of our vehicles, including a train, a plane, an automobile, and the lift-off of a Saturn V rocket. There are more personal human sounds like footsteps, a heartbeat, and a mother caring for her baby.

(note: sound effects follow each description)

[2:14] The Golden Records encoded more than 100 photographs depicting different scenes of Earth and its inhabitants. And of course, no record would be complete without music.

(Voyager Golden Record music: “Queen of the Night aria from Mozart’s “Magic Flute”)

Narrator: There’s Mozart’s Magic Flute. A Peruvian wedding song.

(Voyager Golden Record music: Wedding Song – Peru)

Narrator: Songs from Aboriginal Australia

(Voyager Golden Record music: “Morning Star and Devil Bird” – Australia)

Narrator: And, perhaps most famously, “Johnny B. Goode” by Chuck Berry.

(Voyager Golden Record music: “Johnny B. Goode” by Chuck Berry)

[3:04] Chuck Berry performed this song at NASA’s Jet Propulsion Laboratory in 1989, to celebrate Voyager 2 reaching the planet Neptune. Among those dancing along to the music was the astronomer Carl Sagan.

Carl was one of the scientists on the Voyager mission, which had been built and tested at JPL. The original goal of the mission had been to fly the two spacecraft past the gas giant planets Jupiter and Saturn, collecting images and information about them and their moons. The spacecraft were built to last 5 years, but if they could last even longer, the outer planets Uranus and Neptune were also within reach.

Normally visiting all those planets would be beyond the capabilities of most spacecraft, because of all the fuel and time needed to ping-pong around the solar system to intersect with each of the planets in their distant orbits around the Sun.

[4:09] But JPL engineer Gary Flandro figured out that during the 1980s, the outer planets would all line up on the same side of the Sun. This planetary alignment wouldn’t happen again for 176 years.

It would take several years for a spacecraft just to reach Jupiter, so Voyager 2 left Earth on August 20, 1977, and Voyager 1 followed a few days later, on September 5. Even though it launched after Voyager 2, Voyager 1 was on a shorter and faster route to Jupiter, and so would reach that planet first.

After the Voyagers completed their planetary tours, they would keep flying on, eventually leaving the solar system to head out into the galaxy. Carl reasoned, why not use this opportunity to also send a message to the stars, a shout of solidarity with our fellow space wanderers?

[5:11] This was a new variation on an earlier theme. The Pioneer 10 spacecraft, launched in 1972 for a Jupiter flyby, was the first NASA mission sent on a path that would eventually take it out of the solar system. It was quickly followed in 1973 by Pioneer 11, which visited both Jupiter and Saturn before heading outwards. Carl had helped ensure each of these future interstellar wanderers sported gold-plated plaques etched with drawings about Earth and humanity. The Voyagers would be going even faster than the Pioneers, and thus travel farther, and recorded messages could convey so much more.

(Voyager Golden Record music: Pygmy Girls Initiation Song, Zaire)

[5:59] The Golden Records may be forever silent, never to encounter other life in the galaxy. But if, by remote chance, one of the records finds itself speaking to an audience on some strange and distant shore, among the many voices of this alien world called Earth, they’ll hear one of Carl’s children. That message perhaps best sums up this auditory time capsule, regardless of your age.

( Voyager record greetings: “Hello from the children of planet Earth.”)

(Intro music and NASA montage)

[7:04] Narrator: Welcome to “On a Mission,” a podcast of NASA’s Jet Propulsion Laboratory. I’m Leslie Mullen, and in this third season, we’ve been following scientists to the ends of the Earth as they explore the many aspects of our home planet.

In the first episode of the season, we pulled back from Earth to see it from an astronaut’s perspective. In this final episode, we’ll gaze upon our planet from an even greater distance, the farthest any human-made object has ever traveled. This is episode 10: A Voyager’s View of Earth.

(NASA audio/Apollo 11) Neil Armstrong: “That’s one small step for (a) man, one giant leap for mankind”

Narrator: Like most space scientists who grew up in the 1960s, David Grinspoon was inspired by humanity’s first steps on the Moon during NASA’s Apollo 11 mission. But his household had an extra source of inspiration.

[8:01] David Grinspoon: I have this very specific memory, really my earliest vivid memory, of watching the Moon landing on TV late at night on the little scratchy black and white signal when I was in the fourth grade.

( NASA audio/Apollo 11) Neil Armstrong: “…but it’s adequate to get back up…” (beep)

David Grinspoon: And that blew my mind and help set me on the path I’m on. But in some ways, I had a kind of unusual childhood too, in that my dad’s best friend was Carl Sagan. And he was around our house a lot, and this was before he was famous.

David Grinspoon: My dad was a psychiatrist at Harvard, and he and Carl Sagan became really close friends in the mid-sixties because they were two of the Harvard faculty who were opposed to the Vietnam War, before it was popular to be opposed to the Vietnam War.

[9:00] So I had this guy, Uncle Carl, who was very much in my life when I was a kid, who was involved in some of the early space missions. And he’d show up at the house with an 8 by 10 glossy photograph from Mariner 9. And this was way before the internet when you could just download these things. And as a kid who had already been sparked by Apollo, that was amazing.

And I was very into science fiction and “2001: A Space Odyssey” was coming up and we were going to be going out to Jupiter and, you know, all that fiction and real science was all mixed up in my mind as this excitement about the future and excitement about exploring space.

And kind of also part of this utopian vision of humans solving problems and using science to create a better world. The vision of humans expanding into the Universe was mixed with the visions of humans being more enlightened, and there was a sort of utopian idea that we would become, you know, Homo cosmicus , the cosmic connection, where we would become star folk. ( laughs)

[10:10] David Grinspoon: I was definitely a teenage space geek, and my friends and I were part of something called the L5 society, where we thought we were all going to go live in cylinders in orbit designed by our other hero, Gerard O’Neill, who was this Princeton physicist who wrote this book called “The High Frontier,” and had this idea about space colonies. And they were going to be at the L5 point, which is the stable orbit point between the Earth and the Moon. And in high school, in the seventies, we had these buttons that said “L5 in 95.” Because we were convinced that by the 1990s, we’d be living in orbit. (laughs)

Narrator: David pursued his utopian vision for the future by studying planetary science at Brown University in Rhode Island. Some of his professors were working on NASA’s Viking Mars landers, and before long, David found himself at Mission Control.

[11:01] David Grinspoon: There was this magic land out in California; this place called JPL where all this incredible stuff happened, all these space missions. My first time out at JPL was during the Viking 2 landing on Mars in 1976.

David Grinspoon: I got to go out and stay in Pasadena with Carl Sagan and his son Dorion, who was my best friend. And the Viking 2 landing was incredibly exciting. When those first pictures came down, you know, the way the Viking cameras worked is it came in stripe by stripe. So you see this one little row, that doesn’t really make sense, of pixels, and then the next row, you could start to see all those rocks and those are dunes and you see the image assemble itself slowly in real time as it comes down.

Narrator: David returned to JPL three years later, this time to work as a student intern for the Voyager mission. Voyager 1 was nearing Jupiter, and Carl was on the imaging team responsible for taking photos of the planet and its many moons.

[12:06] David Grinspoon: That was just an amazing experience, being part of Voyager as a student and showing up and seeing all these scientists at work, running the spacecraft that was encountering the Jupiter system up close for the first time. And all these scientists that seemed like gods to me, and they still do, kind of. Not just Carl Sagan, but people like Andy Ingersoll and Gene Shoemaker and Candy Hansen. I could go on listing names, but all these people that were like, wow, these are the real deal. These are planetary scientists. I’m watching them explore planets and I’m helping them doing my little menial clerical tasks.

Although, Carl gave me a real research task that summer that was really hard. It had to do with the solar spectrum in the ultraviolet, and representing it in a specific way that, in order to give him what he wanted, I had to work out some quantum mechanics that I didn’t really know.

[13:09] But I really wanted to do it well and impress him and impress the other scientists. So I ended up going to Caltech and getting into the Millikan library and reading some books and doing some calculations. I have no idea if I even did it right. I probably screwed it up, but it was like, “Wow, I’m doing science!” (laughs)

But mostly just being there and being a fly on the wall was exciting. You know, if you’re in that room, you’re with that small group of humans that are seeing it for the first time. And the other people in that room are the people that built the spacecraft to send out there. Just that sense of discovery, and the latest images would be on the monitors there in the area where the imaging team worked.

The thing about these encounters of the Voyagers, they happen really fast. The spacecraft is approaching for years and months and the planets and the moons are just these single pixel dots. And then a few days before the planet’s starting to get close enough, so you can see it as more than a dot, you can start to make it out as a round object. And then you can start to see detail on the planet and then on the moons.

[14:09] And it happens so fast, partly because the spacecraft is also accelerating as it’s pulled in by the gravity of Jupiter. But in a matter of days, it goes from being a dot to being these resolved objects.

And it felt like you were almost on the ship and looking out the window. You know, “It’s getting closer, it’s getting closer.” And you see it getting bigger and starting to reveal itself; that real-time sense of discovery, where it was almost like you were traveling with the spacecraft and seeing the Jupiter system go by.

( Voyager Golden Record music: “Tchakrulo,” by singers from Georgia )

Narrator: Each Voyager flyby revealed new details of the planets and their moons. They showed that Jupiter’s moon Io had volcanoes erupting lava hundreds of kilometers high into space. Jupiter’s frozen moon Europa had a strange cracked-ice surface that concealed a vast ocean below.

[15:07] The Voyagers examined the intricate woven threads of Saturn’s dusty rings, and saw that Saturn’s moon Titan was enveloped in a thick orange smog.

While Voyager 2 would go on to visit the cool blue gas giants Uranus and Neptune, Voyager 1’s path around Saturn sent it above the ecliptic, the disc-like region where the planets orbit the Sun, like a record spinning on a record player. From this point on, Voyager 1 would visit no more planets. Instead, all the planets would recede steadily from its view, once again becoming tiny points of light.

Carl wanted to maneuver Voyager 1 so that it could take photos of all those tiny dots, to create a family portrait of the planets of the solar system. But as imaging team member Candy Hansen explains, getting permission from NASA’s Voyager Project Office was no easy task.

[16:02] Candy Hansen: We asked for that picture a number of times, and the first time was in 1981. We asked in 1986 and we asked in 1988, and they just were never really willing to spend the resources.

There were two reasons that we were getting turned down. One was that every time we asked for it, it was either right after a flyby or right before a flyby, when they were either staffing up or staffing down, or in the middle where there was no staff. So there was always an issue with staffing. But there was always this feeling on the project that they didn’t want to pull out all the stops to get this observation, because they didn’t think it was that important.

Candy Hansen: The technical challenges had to do with pointing close to the Sun. And so there was always a concern, if we point too close to the Sun, then we might actually damage the camera, even that far away.

[17:04] And that may have been the reason that Carl waited until Voyager 1’s mission was essentially done in 1981. It was finished with its planetary exploration. And then it seemed like, “Okay, if we use Voyager 1, we’re not taking any risk for future flybys of Uranus and Neptune.” We wouldn’t want to damage the camera on Voyager 2 because it’s got work ahead of it. But it turned out that we actually used Voyager 1 quite a bit as a test bed for the things that we were going to do on Voyager 2. So people still did not want to take risks with the hardware, even if Voyager 1 didn’t really have a scientific need for it anymore.

But also, Voyager was what we call 3-axis stabilized. And what that means is that it had a fixed orientation. You held that fixed orientation with the Sun sensor knowing where the Sun was, and with a star sensor that we usually had parked on Canopus, because that’s the brightest star in the Southern Hemisphere.

[18:12] And so, in a way, the spacecraft was just rock steady in that orientation, and we knew it’s not going to overheat on one side or get too cold on the other. We knew those were stable orientations where kind of nothing could go wrong. So when you take it out of that well-understood configuration, what might go wrong? We took it off the star, will it be able to find it again?

And when we had to do maneuvers, which we actually had to do from time to time, every once in a while, we wouldn’t get the signal back. And everyone would panic, “Oh my God, we lost the spacecraft.” And then they would bring all the big antennas and next thing you know, you’d hear this little tiny whisper of a signal over the low-gain antenna, and everybody’d be like, “Oh, okay, okay, it’s okay.” And then we’d have to wait for it to do its star search till it finally found Canopus again. And then we’d get the big booming signal back again, but every time it was like, “Oh no, we lost Voyager!” (laughs)

[19:15] Narrator: The risk of turning Voyager 1 always outweighed the wish for a family portrait of the planets. After many requests were rejected over the years, time was running out – and not only because the planets were growing fainter in the distance.

Candy Hansen: In 1989, it was obvious that this was going to be our last chance. We knew that the project would be staffing down dramatically. The engineering expertise would be off working on other projects, and we knew we needed to start turning off the instruments because the spacecraft power level was dropping, and so we knew the cameras were going to be among the first instruments to be powered off.

[20:02] And so, there was this kind of band of advocates that were just like, “We’re not going to give up, we’ll just keep asking and keep coming up with ideas.” And Carl never gave up. I never gave up. Carolyn Porco and William Kosmann, they were part of our band of advocates. And then it was, like I said, the fact that we knew this is really our last chance. Carl went to headquarters, and there was a meeting here in Pasadena, and that was the meeting where they decided, “Okay, yes, the project will carry this out.”

But there was still a lot of, I don’t know, a lack of enthusiasm, I guess I would call it. So I kind of took it on myself to personally sell it. You know, tell people, “This is going to be great. Here’s why it’s going to be great. You’re going to love it.”

[20:59] Narrator: On February 14, 1990, Voyager 1 took 60 images of our solar system – the first time a spacecraft was far enough away to capture such a vast distance in a glance. On that Valentine’s Day, Voyager 1 was 3.7 billion miles away from the Sun, or 6 billion kilometers. Candy says the date of the photo session wasn’t deliberate.

Candy Hansen: It was a coincidence, but what a nice coincidence! It’s like Voyager’s Valentine to us.

The original idea that Carl had was to do a whole mosaic of the sky and get the whole stellar background. But the problem was, that was going to take far more images than we had space for on our tape recorder. And the exposure was too short to get stars. I think our cameras could get down to like 10th magnitude stars, but the Earth was brighter than that.

[21:58] And so we knew we wanted to do color of each of the planets, so that took up 18 images or however many it was. We would take the images through the different color filters, and then we would stack the different colors together and do color reconstruction. We had six or eight filters, but we didn’t have enough data volume to send all of them back all of the time. So we would typically pick out which ones sort of worked the best for different situations.

And then we did the wide-angle frames, the bigger ones. The narrow angle are the little ones that have the planets. And so, since we knew we couldn’t do the whole stellar background, we thought, “Well, we’ll just connect the dots.” And that’s why it’s that particular shape, and then we said, “We have a few left over, so let’s go around the Sun.” So this is the design process.

[22:56] Narrator: The photos that make up the solar system portrait are patched together in a long sinuous shape resembling a hobbyhorse, a toy horsehead with a stick protruding from beneath it for a child to ride on. For the Voyager mosaic, the head is made up of photos taken around the Sun — which includes Earth, Venus and Jupiter. Saturn and Uranus are in the body of the stick, and Neptune is at the bottom end. Mars and Mercury are not pictured – Mercury is too close to the Sun to be seen amid the bright glare, while the sunlight reflecting off Mars was too faint from the camera’s perspective.

After the last photo was taken, Voyager 1’s cameras were turned off, and it took more than two months for the spacecraft to send all the images back to Earth.

As expected, all the planets were mere dots, about a pixel in size or less. Earth’s pale blue dot was barely visible amid streaks of light emanating from the Sun. Carl Sagan famously said it looked as though our planet was a mote of dust suspended in a sunbeam.

[24:03] Candy Hansen: To this day, it still gives me shivers down my spine, that connection. That’s home. Voyager is way out there, and looking back at home, and that’s where we are.

You know, to see your home planet up close, it’s like, “There’s the ocean, there’s continents.” And the Pale Blue Dot is, “Take that perspective, but now move out to the outside, way outside.” And now you realize that that beautiful blue orb is this tiny little speck in space. And we’re alone out here, nobody’s going to come save us from ourselves.

(Voyager Golden Record music: Japan, shakuhachi, “Tsuru No Sugomori” (“Crane’s Nest,”) performed by Goro Yamaguchi )

Candy Hansen: I would say we need this image; we need to see how alone the Earth is in space, we need to see how far away any other planets are.

[25:04] If something goes awry here on planet Earth, we are not going to be able to move seven billion people to the Moon or to Mars. Those are not hospitable places, they’re not all that close, and so we really need to take care of our home planet.

And the thing that has really been amazing to me is to realize how timeless that message is, because when we planned that image, it was still the Cold War, and the United States and the Soviet Union had I don’t know how many thousands of nuclear warheads pointed at each other. And today, the existential threat is climate change. So Carl saw that picture as a way to communicate that we’re all in this together.

[26:05] Narrator: The creation of that far-distant image of our home planet bookends Candy’s journey with the Voyager mission, which began for her as a calculated maneuver to come back home to Los Angeles, where she’d grown up.

Candy Hansen: I had gone to Tucson to go to graduate school, but I was really homesick for California. And so, I talked my graduate school advisor, Brad Smith, into sending me to JPL for a summer, like an internship. And because my advisor was the leader of the Voyager imaging team, it was kind of natural for me to work for the imaging team.

Certainly, in my graduate courses, we were looking at images from space, and there’s certain things that you learn about the lighting, what’s good lighting, what’s not good. But mostly, honestly, it was an on-the-job learning experience. And that was okay, that was fine with me, I loved it. So I never did go back to Tucson. I did ultimately finish my PhD at UCLA.

[27:10] Narrator: While Candy was a student intern, she applied for a job with the Voyager mission, and later wrote her PhD dissertation using Voyager data. Since then, Candy has worked on other space missions like the Cassini mission to Saturn, the Mars Reconnaissance Orbiter, and the Juno mission to Jupiter. Her long career that started with Voyager is all the more remarkable considering Candy never intended to become a space scientist.

Candy Hansen: When I was around 12 or 13, I discovered the science fiction section of our local library, and I read every book on those shelves. But I never thought of it as a career. When I went to college, I was not planning to major in physics, I was planning to major in anthropology and accounting, because I had in mind I wanted to get a job in city government. I liked math, so that’s the accounting connection.

[28:08] My dad drove a bread truck for Oroweat and my mom was a housewife, so I didn’t get a lot of advice on what to do when I got to college. So I know today it sounds a little bit random, but I know I had a plan in my 18-year-old head. ( laughs )

But what happened was, I needed to have some general education classes including a science class. And this was of course all pre-Internet, so you had to actually stand in line for hours to sign up for your classes at Cal State Fullerton. And so I was standing in line and I had the course catalog, and I was looking through trying to decide what my general education science class should be. And the guy standing next to me said, “Oh, I had that physics class, it was really good.” And it was basically, “Intro to Physics for the Non-Science Major.” And so I looked at it and I’m like, “Oh yeah, well, actually that would fit pretty well in my schedule.”

[29:05] But when I got into the class, I loved it. So when you really love something, you tend to excel at it. And it turns out that at that moment, the physics department was trying to beef up their student population, and so they were watching these general education science classes for people that they might be able to pull into the department and get them to change their major.

So my professor one day calls me aside and he said, “You seem to really like this class.” And I’m like, “Oh yeah, I’m really enjoying it.” He said, “What do you think about being a physics major?” He said, “All you have to do is sign here.” Because they had, unbeknownst to me, filled out all the paperwork (laughs ). And so, I was thinking to myself, “Well, if it’s this easy to get into, it should be this easy to get out of again if I don’t like it.” So sure, signed my name.

[30:02] And then I really did like it, but I have to say at that point in time, it was the Vietnam War, and most of the jobs coming out of college with a bachelor’s degree in physics were doing things like weapons development and that sort of thing, and I didn’t want to do that, I knew that. And so, I was really flailing a little bit.

And one of my professors, Professor Wollum, had worked on the Apollo missions, on the surface-exposure experiments — the radiation, and what affect that had on materials in this harsh space environment. And she taught a class called, “Planetary Physics,” which I loved. And so she was the one who suggested that I might go to graduate school at the University of Arizona in Tucson, because the Lunar and Planetary Lab there was kind of a hotbed for this new field of planetary science.

[31:07] Candy Hansen: You know, before spacecraft, all planetary science was within the realm of astronomy. And it wasn’t until we really started flying spacecraft to these places that you could see the geology on the surface of Mars and know it’s a heavily-crated surface in many places. And so the field of geology expanded in that moment from being all about the Earth to, well, when we look at the Moon, when we look at Mars, when we look at Mercury, now we’ve got all these different instances of geology. And kind of the same thing, you know, with atmospheres. Meteorologists study storms on the Earth, but they also were starting to study storms on places like Jupiter.

[31:56] And so, the Voyager imaging team was this collection of people who were geologists who were used to looking for oil, and meteorologists who happened also to think that Jupiter was pretty darn interesting. But there were also astronomers who were used to looking at a point of light as it moved around the sky, and figuring out what you could tell about the surface from the way it was reflecting light. It was quite an interesting mix of scientists who had gone from looking at something on the Earth to looking at something in space. And so they were the first generation, really, of planetary scientists.

Narrator: The Voyager 1 images weren’t just a family portrait of the planets of the solar system. They also were a family portrait of the Voyager mission team, with each planet like a milestone in their lives.

Candy Hansen: When I was hired, there was kind of a flock of us 20-somethings that were all hired around the same time, and so we were all just out of college. So in those days we talked about who we were dating and what was the cool concert we had gone to.

[33:06] And then, as time went by, we bought cars, we bought houses, we got married and we had kids. And so at the end of that 12 years, in a person’s life, that’s where a lot of things happen, right? And we had all, as a group, kind of moved through it together, and all of us told time, in a sense, by the planets. So it was between Jupiter and Saturn that I bought a car, and it was between Saturn and Uranus that I bought a house.

So it was all very special and towards the end, very bittersweet. We learned a lot of really incredible things, a lot of astounding discoveries, but there was a heart to the project as well. We love those spacecraft. ( laughs) I know you shouldn’t love an inanimate object like that, but they are extensions of ourselves.

[34:05] And so that Pale Blue Dot picture was a bit of a gift to ourselves. You know, we’re not just going to shut down and move away. We’re going to do one more cool thing before we call it quits.

I was on Voyager for maybe another six or nine months after that because we were just wrapping up and boxing things up, and outside the door of my office was a bookcase, and in the bookcase we had albums full of hard copy. And the day that they came and took that to the Regional Planetary Imaging Facility, and it was only a couple of floors down, but it was no longer there, outside my door. ( laughs ) I went home that day, I was just kind of devastated, you know? I had this blank wall outside my door.

But when we got the Pale Blue Dot images, we had a big blank wall there, and so we, like a bulletin board, just stuck them up, and made that little hobbyhorse shape out of it, and put it to good use.

[35:08] Narrator: In addition to a child’s toy, a “hobbyhorse” is a term meaning a favorite topic or preoccupation. The Voyager family portrait certainly has been a favorite part of the mission for many of the scientists who worked on it, and for the general public as well. For a while, that hobbyhorse was displayed across 20 feet of wall in JPL’s von Kármán auditorium, and visitors to JPL got to see the solar system spread out before them.

Candy Hansen: The person who was in charge of the von Kármán exhibits at that time was Jurrie van der Woude, and he was this delightful Dutch guy. And after it had been up on the wall of von Kármán for three or maybe four years at that point, he told me the story that people would admire the whole thing, and then they’d walk up and they would have to touch the Earth. You know, that connection of, “That’s us.” And so, he had to frequently replace that picture, because it was continually getting worn. (laughs)

[36:15] Narrator: It’s amazing that just a simple tap, from enough people, can be so destructive over time, like drops of water that eventually wear down a stone. Since that photo of our pale blue dot was snapped thirty years ago, from the Voyagers’ perspective, Earth has disappeared into the darkness.

Candy Hansen: I’m going to guess that Voyager could still see the big planets, Jupiter and Saturn. It can probably still see Uranus and Neptune. I’m very, very doubtful that it has the sensitivity to see the Earth. Because the Earth, even back then, was smaller than a pixel, and now it’s much smaller.

[37:02] And the Voyagers are out in interstellar space now. That was so exciting when the first one left, and now they’re both out there, and it took a lot longer to get there than anyone would’ve predicted. But that teaches us, right?

Narrator: All the planets and the Sun travel together through the galaxy in a sort of bubble, which scientists call the heliosphere, created by the particles and magnetic field of the Sun’s solar wind. There were lots of ideas for how big the heliosphere could be, but no one really knew how far it extended.

Then Voyager 1 crossed over in 2012, at a distance of about 18 billion kilometers from the Sun, or more than 11 billion miles. Voyager 2, following its own path past Neptune, left the heliosphere in 2018, when it also was about 18 billion kilometers from the Sun.

[37:59] Candy Hansen: It was surprising that it took that long, but I’m so glad that they both are operating long enough to be able to tell us where’s the edge of our bubble that the Sun provides for us, magnetically speaking. And just the thought that they’re on this no-return journey, and they’re going to probably outlive the Earth. Because someday, our star is going to turn into a red giant, and that’ll be that, billions of years from now.

And they’re just going to be out there, scooting along with our Golden Record, and it’s a little piece of not only ourselves, but our time, of what was happening right here, right now.

( Voyager Golden Record music: 31/31 String Quartet No. 13 In B Flat, Opus 130, Cavatina, Beethoven )

(Voyager Golden Record greetings)

Armenian: “To all those who exist in the universe, greetings.”

Mandarin Chinese: “Hope everyone’s well. We are thinking about you all. Please come here to visit when you have time.”

Nepali: “Wishing you a peaceful future from the Earthlings.”

Narrator: We’re still talking to the Voyagers, but not for long. Mission scientists estimate in the next few years the spacecraft will run out of power and no longer be able to speak to us.

When we finally say goodbye, the Voyagers will have a long, silent journey ahead of them. It will take many thousands of years for them to fully leave our solar system, where the boundary is marked by a region of comets known as the Oort Cloud. Once they pass through that, given the vast distances between stars, the Voyagers likely will only ever encounter interstellar dust.

(Voyager Golden Record music: Dark was the Night, Cold was the Ground, Blind Willie Johnson )

[40:11] Narrator: When our Sun evolves into a red giant star 5 billion years from now, consuming the inner planets of the solar system in its expansion, including Earth, the Voyagers will still be orbiting the center of the galaxy. From the Voyagers’ view, the end of their birthplace will be signaled by a distant background star shining just a little bit brighter, a little redder than before.

The Voyager spacecraft and their Golden Records are our messages in a bottle, set adrift on the cosmic sea. After Earth is long gone, the Voyagers will be our legacy, still speaking our messages of welcome, and singing our songs.

(music continues)

Narrator: If you like this podcast, please subscribe, rate us on your podcast platform, and share us on social media. We’re “On a Mission,” a podcast of NASA’s Jet Propulsion Laboratory.

[run time = 41:31]

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Voyager 1 transmitting data again after Nasa remotely fixes 46-year-old probe

Engineers spent months working to repair link with Earth’s most distant spacecraft, says space agency

Earth’s most distant spacecraft, Voyager 1, has started communicating properly again with Nasa after engineers worked for months to remotely fix the 46-year-old probe.

Nasa’s Jet Propulsion Laboratory (JPL), which makes and operates the agency’s robotic spacecraft, said in December that the probe – more than 15bn miles (24bn kilometres) away – was sending gibberish code back to Earth.

In an update released on Monday , JPL announced the mission team had managed “after some inventive sleuthing” to receive usable data about the health and status of Voyager 1’s engineering systems. “The next step is to enable the spacecraft to begin returning science data again,” JPL said. Despite the fault, Voyager 1 had operated normally throughout, it added.

Launched in 1977, Voyager 1 was designed with the primary goal of conducting close-up studies of Jupiter and Saturn in a five-year mission. However, its journey continued and the spacecraft is now approaching a half-century in operation.

Voyager 1 crossed into interstellar space in August 2012, making it the first human-made object to venture out of the solar system. It is currently travelling at 37,800mph (60,821km/h).

Hi, it's me. - V1 https://t.co/jgGFBfxIOe — NASA Voyager (@NASAVoyager) April 22, 2024

The recent problem was related to one of the spacecraft’s three onboard computers, which are responsible for packaging the science and engineering data before it is sent to Earth. Unable to repair a broken chip, the JPL team decided to move the corrupted code elsewhere, a tricky job considering the old technology.

The computers on Voyager 1 and its sister probe, Voyager 2, have less than 70 kilobytes of memory in total – the equivalent of a low-resolution computer image. They use old-fashioned digital tape to record data.

The fix was transmitted from Earth on 18 April but it took two days to assess if it had been successful as a radio signal takes about 22 and a half hours to reach Voyager 1 and another 22 and a half hours for a response to come back to Earth. “When the mission flight team heard back from the spacecraft on 20 April, they saw that the modification worked,” JPL said.

Alongside its announcement, JPL posted a photo of members of the Voyager flight team cheering and clapping in a conference room after receiving usable data again, with laptops, notebooks and doughnuts on the table in front of them.

The Retired Canadian astronaut Chris Hadfield, who flew two space shuttle missions and acted as commander of the International Space Station, compared the JPL mission to long-distance maintenance on a vintage car.

“Imagine a computer chip fails in your 1977 vehicle. Now imagine it’s in interstellar space, 15bn miles away,” Hadfield wrote on X . “Nasa’s Voyager probe just got fixed by this team of brilliant software mechanics.

Voyager 1 and 2 have made numerous scientific discoveries , including taking detailed recordings of Saturn and revealing that Jupiter also has rings, as well as active volcanism on one of its moons, Io. The probes later discovered 23 new moons around the outer planets.

As their trajectory takes them so far from the sun, the Voyager probes are unable to use solar panels, instead converting the heat produced from the natural radioactive decay of plutonium into electricity to power the spacecraft’s systems.

Nasa hopes to continue to collect data from the two Voyager spacecraft for several more years but engineers expect the probes will be too far out of range to communicate in about a decade, depending on how much power they can generate. Voyager 2 is slightly behind its twin and is moving slightly slower.

In roughly 40,000 years, the probes will pass relatively close, in astronomical terms, to two stars. Voyager 1 will come within 1.7 light years of a star in the constellation Ursa Minor, while Voyager 2 will come within a similar distance of a star called Ross 248 in the constellation of Andromeda.

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25 Years Later, Voyager Mission Keeps Pushing the Space Envelope

A quarter-century after NASA's twin Voyager spacecraft departed Earth to visit outer planets, the historic mission is flying a race against time.

During the first 12 years after launch in 1977, the Voyagers chalked up a wealth of discoveries about four planets and 48 moons, including fast winds on Neptune, kinks in Saturn's rings and volcanoes on Jupiter's moon Io. As scientists and engineers mark the mission's silver anniversary, they hope at least one Voyager will pass beyond the boundary of the Sun's influence before the onboard nuclear power supply wanes too low to tell us what's out there. Voyager 1 is now the most distant human-made object, about 85 times as far from the Sun as Earth is. Voyager 2 is now about 68 times the Sun-Earth distance.

"After 25 years, the spacecraft are still going strong," said Dr. Edward Stone, Voyager project scientist since 1972 and former director of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Back in 1977, we had no way to know they would last so long. We were initially just on a four-year journey to Jupiter and Saturn."

The Voyager team at JPL still receives information almost daily from the durable spacecraft traveling beyond all the planets. The Voyagers are examining the far reaches of the solar wind, a gusty flow of particles hurled outward by the Sun. The eventual goal is to become the first spacecraft to taste interstellar space. Voyager 1, which launched on Sept. 5, 1977, flew past Jupiter and Saturn, then angled northward out of the plane of the planets' orbits. After Voyager 2 launched on Aug. 20, 1977, and completed its tour of Jupiter and Saturn, NASA extended the spacecraft's adventure with flybys of Uranus in 1986 and Neptune in 1989.

"A radio signal traveling at the speed of light takes nearly 12 hours to travel between Voyager 1 and Earth. That raises operational concerns," said Ed Massey, Voyager's project manager at JPL. " If something went wrong on board, at least a full day would lapse before a signal revealing the problem could reach Earth and commands to fix it could be returned. It could be too late." So the project team tries to anticipate any emergencies and program the spacecraft's computers with advance instructions on how to react to them, he said.

Both spacecraft are studying the vast bubble the Sun inflates around itself by outward pressure of the solar wind. The bubble has a boundary, called the heliopause, where this outward pressure is counterbalanced by inward pressure of the interstellar wind in our neck of the galaxy. The interstellar wind outside that boundary is a flow of atoms and other particles blasted from explosions of dying stars. The location of the heliopause varies with the level of solar activity during the Sun's 22-year sunspot cycle and with changes in the interstellar wind, Stone said. Some scientists suggest that, on a much longer time scale, the interstellar wind may occasionally press the boundary far enough inward to sway Earth's climate.

Voyager 1 is rushing toward the heliopause at about 1.6 million kilometers (about one million miles) a day. Whether it gets there before about 2020, while it still has adequate electrical power, depends on how far away the heliopause is. Recent estimates are that, depending on that distance, it would take Voyager 1 between seven and 21 years to reach the heliopause.

Voyager 1 has already discovered that the outbound solar wind around it is slowing from effects of inbound interstellar particles leaking through the boundary. A much better prediction of the boundary's location will come when the spacecraft encounters the termination shock, the zone where the solar wind begins piling up against the heliopause. That encounter may come within the next three years, Stone estimates.

Whatever their future holds, Voyager 1 and Voyager 2 have already earned a prominent place in the history of exploration. Among their big surprises: Jupiter's moon Io has active volcanoes. Jupiter's atmosphere has dozens of huge storms. Saturn's rings have kinks and spoke-like features. The hazy atmosphere of Saturn's moon Titan extends far above the surface. Miranda, a small moon of Uranus, has a jumble of old and new surfacing. Neptune has the fastest winds of any planet. Neptune's moon Triton has active geysers.

Long after they fall silent, the Voyager twins will keep speeding away from our solar system, each carrying an "interstellar outreach program" of recorded sounds and images from Earth, Massey said.

Further information about Voyager's past discoveries, current interstellar mission and messages from Earth is available at https://voyager.jpl.nasa.gov . JPL, a division of the California Institute of Technology in Pasadena, manages Voyager for NASA's Office of Space Science, Washington, D.C.

NASA’s Voyager 1 Resumes Sending Engineering Updates to Earth

NASA’s Voyager 1 spacecraft is depicted in this artist’s concept traveling through interstellar space, or the space between stars, which it entered in 2012.

After some inventive sleuthing, the mission team can — for the first time in five months — check the health and status of the most distant human-made object in existence.

For the first time since November , NASA’s Voyager 1 spacecraft is returning usable data about the health and status of its onboard engineering systems. The next step is to enable the spacecraft to begin returning science data again. The probe and its twin, Voyager 2, are the only spacecraft to ever fly in interstellar space (the space between stars).

Voyager 1 stopped sending readable science and engineering data back to Earth on Nov. 14, 2023, even though mission controllers could tell the spacecraft was still receiving their commands and otherwise operating normally. In March, the Voyager engineering team at NASA’s Jet Propulsion Laboratory in Southern California confirmed that the issue was tied to one of the spacecraft’s three onboard computers, called the flight data subsystem (FDS). The FDS is responsible for packaging the science and engineering data before it’s sent to Earth.

After receiving data about the health and status of Voyager 1 for the first time in five months, members of the Voyager flight team celebrate in a conference room at NASA’s Jet Propulsion Laboratory on April 20.

The team discovered that a single chip responsible for storing a portion of the FDS memory — including some of the FDS computer’s software code — isn’t working. The loss of that code rendered the science and engineering data unusable. Unable to repair the chip, the team decided to place the affected code elsewhere in the FDS memory. But no single location is large enough to hold the section of code in its entirety.

So they devised a plan to divide the affected code into sections and store those sections in different places in the FDS. To make this plan work, they also needed to adjust those code sections to ensure, for example, that they all still function as a whole. Any references to the location of that code in other parts of the FDS memory needed to be updated as well.

The team started by singling out the code responsible for packaging the spacecraft’s engineering data. They sent it to its new location in the FDS memory on April 18. A radio signal takes about 22 ½ hours to reach Voyager 1, which is over 15 billion miles (24 billion kilometers) from Earth, and another 22 ½ hours for a signal to come back to Earth. When the mission flight team heard back from the spacecraft on April 20, they saw that the modification worked: For the first time in five months, they have been able to check the health and status of the spacecraft.

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During the coming weeks, the team will relocate and adjust the other affected portions of the FDS software. These include the portions that will start returning science data.

Voyager 2 continues to operate normally. Launched over 46 years ago , the twin Voyager spacecraft are the longest-running and most distant spacecraft in history. Before the start of their interstellar exploration, both probes flew by Saturn and Jupiter, and Voyager 2 flew by Uranus and Neptune.

Caltech in Pasadena, California, manages JPL for NASA.

News Media Contact

Calla Cofield

Jet Propulsion Laboratory, Pasadena, Calif.

626-808-2469

[email protected]

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Good news from Voyager 1, which is now out past the edge of the solar system

Nell Greenfieldboyce

In mid-November, Voyager 1 suffered a glitch, and it's messages stopped making sense. But the NASA probe is once again sending messages to Earth that make sense.

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golden record

Where are they now.

• frequently asked questions
• Q&A with Ed Stone

Mission Status

Instrument status.

Where are the Voyagers now?

To learn more about Voyager, zoom in and give the spacecraft a spin. View the full interactive experience at Eyes on the Solar System . Credit: NASA/JPL-Caltech

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Space Flight Operations Schedule (SFOS)

SFOS files showing Voyager activity on Deep Space Network (DSN)

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