The Voyager Spacecraft
45:48 Share

This is the sleepy history of the Voyager spacecraft, narrated by Simon Mattox, written by Leila Weir. Have you ever wondered what lies beyond the farthest reaches of our solar system? Right now, a pair of small space probes, Voyager 1 and 2, are exploring that vast unknown. They are the first human-made objects to travel so far from Earth.

and theirs is a tale of adventure and curiosity, of scientific ingenuity and futuristic achievements, and of the undauntable human drive to understand our universe. So just relax and let your mind drift as we explore the sleepy history of the Voyager spacecraft. When you look up at the night sky,

You're likely to see the flashing lights of airplanes and the wandering pinpricks of satellites weaving among the gently winking stars whose light comes to us across hundreds or thousands of years. If you're lucky, you'll see a brighter band of stars across one part of the sky. This is the Milky Way.

our own galaxy, viewed from our vantage point on one side of it. And there, in the vastness of the Milky Way, out beyond our solar system, are two explorers, emissaries of Earth. They're twin, uncrewed spaceships that fly through the galaxy, sending back data about interstellar space.

and carrying a gold-plated message of goodwill for any alien intelligence they may encounter. These are the Voyager space probes, the first objects made by humans to enter interstellar space and, as it turns out, to communicate with home about it. Now, that wasn't always the plan, mind you.

The Voyager probes were launched in the 1970s on a mission to fly near Jupiter and Saturn and beam back information about them. To that end, they were originally built to last five years. But with some science fiction-level ingenuity, mission controllers remotely reprogrammed the Voyagers over the decades. From hundreds of millions of miles away,

They endowed the spaceships with additional capabilities and prepared them for a new voyage of discovery into interstellar space, the region between stars. The twin Voyager craft have now been exploring for roughly half a century. Their power will eventually run out and we'll lose communication with them.

but the ships will likely continue to wander the galaxy on into the far distant future. Eventually, in just about 40,000 years, the probes will wind up near another planetary system. And who knows? If there's any other intelligent life out there, perhaps they'll encounter these envoys from Earth, just in case each Voyager carries a golden record of images, greetings,

and music depicting life on our planet. This is the story of the Voyager space probes. It all began in the United States in Cape Canaveral, Florida, on the 20th of August 1977. The Voyager 2 space probe was launched from the NASA Kennedy Space Center, headed for Jupiter, more than 300 million miles away.

A couple of weeks later, its twin, Voyager 1, was launched on the 5th of September 1977. Voyager 1 was also headed for Jupiter, but on a shorter route that would get it there faster, while bypassing some of the views Voyager 2 would encounter.

The probes were, and remain, small, funny-looking craft, designed for scientific discovery. Their main cabins are tiny. After all, they don't need to hold any people. They're dwarfed behind large dish antennas, set up for communication with Earth.

Around the antennas, a profusion of cameras and scientific instruments stick out in what looks like a haphazard array. Though, of course, it is anything but. A long rod protrudes far past the antenna on each probe. This holds instruments called magnetometers, which measure magnetic fields.

Two thin, reed-like rod antennas extend the other way in order to pick up radio waves coming from planets and other clues from space. Not that NASA is expecting to tune into any alien radio stations. Radio waves occur naturally in the universe. In a canister between the rod antennas on each craft,

Generators produce electricity to power the probe's systems, and inside their main cabins lay the craft's all-important computers, navigation systems, and radio transmitters. All these instruments of scientific study and navigation are of very practical importance to the mission.

But the two Voyager probes each also carry other things of perhaps a more whimsical nature. Items that have enraptured the public imagination for generations now. These are phonograph records, what people played music on before CDs and long before streaming services were available.

They hold recorded greetings to any alien intelligence that might someday encounter the spacecraft in the far reaches of the galaxy. In many ways, the records epitomize the human capacity to dream and to envision something bigger than ourselves. It's something like a person planting a tree

knowing that future generations will benefit from its shade and fruit, but on a much larger scale. The records are made of copper, plated with gold, and covered with aluminum jackets, designed to last through eons in space. Their creators filled them with sounds and images selected to convey something of the diversity of life on Earth.

Picture symbols explaining how to play the records are provided, along with the simple hardware necessary to play them. The symbols also indicate the origin of the probes: our planet. The records contain greetings spoken in 55 different languages.

These range from Akkadian, the language of the ancient Sumerian civilization some 6,000 years ago, to Wu, a modern Chinese dialect. Each speaker shows the specifics of what they said, and the messages are all different, but they all convey warm and friendly wishes to any alien lifeforms.

The English greeting says "Hello" from the children of planet Earth. One in Latin states "Greetings to you, whoever you are. We have goodwill towards you and bring peace across space." The ancient Akkadian message declares simply "May all be very well." While one in a language called Amoy says hospitably "Friends from space, how are you all?"

Have you eaten yet? Come visit us if you have time. The records also hold nature and animal sounds like surf, wind, thunder, and bird and whale calls. Then there's 90 minutes of music from different eras and cultures.

Aside from the sounds, the records hold 115 images and printed messages from then-U.S. President Jimmy Carter and the Secretary General of the United Nations. Legendary scientist Carl Sagan of Cornell University headed up the committee that chose what to put on the records for NASA. Sagan commented on the endeavor:

likening it to a person placing a message in a bottle and throwing it into the sea in the hopes that someone, somewhere, would see it someday. Sagan said the spacecraft will be encountered and the record played only if there are advanced spacefaring civilizations in interstellar space. But the launching of this bottle into the cosmic ocean

says something very hopeful about life on this planet. Now, around half a century later, those high-tech bottles with their gold-plated messages still hurtle through the deep space of our galaxy. But on their way out into the Milky Way, they recorded sights never seen before by human eyes.

They sent back pictures and data that immensely expanded our knowledge of the solar system. The Voyager mission had been planned to leverage a rare opportunity. This was a special alignment of the outer planets in our solar system, which are often called the gas giants because, as you might infer,

They're huge and composed largely of gas, rather than solid matter like Earth. During the 1970s and 1980s, the gas giants Jupiter, Saturn, Uranus, and Neptune were positioned in such a way that a spaceship could visit them in less time and with less fuel than usual.

they presented an exceptional opportunity for exploration because it only happens once every 175 years or so. The position of the planets meant that a spaceship launched on the right trajectory could use each planet's gravity to fling it towards the next one. Every time the craft passed one of the gas giants,

the planet's gravity would bend the spaceship's flight path and increase its speed, swinging it on towards the next destination. This gravity assist, or slingshot technique, cut the flight time to the farthest planet, Neptune, from 30 years to just 12.

Now, at the time of the Voyager launches, the gas giants were arranged in a way that would make it possible to slingshot past all four of them. But planners thought it would be too expensive to build a ship that could go so far and last so long, carrying all the instruments necessary to study the planets. So, funding was allocated only to cover in-depth studies of Jupiter and Saturn.

and the probes were built to last five years, not long enough to reach Neptune in working condition. Still, when NASA planned the probe's trajectories, Voyager 2 was sent on a route that could carry it on to Uranus and Neptune too, just in case. Both probes' paths would lead them close to Jupiter and Saturn,

as well as near enough to each planet's large moon to study those, too. In early 1979, less than two years after it lifted off from Cape Canaveral, Voyager 1 approached Jupiter, the first stop for the mission. The probe took thousands of pictures of the planet, reaching its closest approach on the 5th of March.

it sent back photographs that greatly outstripped the best images ever captured of Jupiter from Earth, along with many valuable scientific measurements. By April, Voyager 1's flyby of Jupiter was complete, as it swung around the planet and off towards Saturn. But Voyager 2 had arrived, and it also began capturing images of Jupiter.

Together, the two craft took more than 33,000 close-up pictures of Jupiter and its moons. Back on Earth, the world watched in awe as the distant planet was revealed in cosmic beauty hardly dreamt of in all the millennia that people had observed the skies.

The striking images showed colorful swirls and bands in brightly contrasting tones. These were the planet's cloud formations, wild winds, and raging storms seen from space. Despite centuries of astronomical observation of Jupiter from Earth's surface, the probe's close encounter with the planet and its moons yielded many surprises.

For example, they discovered a faint ring system around Jupiter that had been hitherto unknown. They also found active volcanoes on one of Jupiter's moons, Io. The first time volcanic activity was observed anywhere in the solar system besides on Earth. From Jupiter, the space probes hurtled on towards Saturn.

whose ring, visible with telescopes, had fascinated viewers for so long. On the 12th of November, 1980, Voyager 1 arrived at the so-called "ringed planet." As Saturn had come to be known, before scientists understood there were rings around other gas giants as well.

Nine months later, Voyager 2 also got to Saturn on the 25th of August, 1981. The two craft sent home high-resolution photos and data that shed new light on that planet, as well as on its much-admired ring. The probes also returned other scientific observations that profoundly changed and increased human knowledge of Saturn.

Voyager 1 found that some 7% by volume of Saturn's upper atmosphere is helium, while most of the rest is hydrogen. As it turns out, Saturn is the only planet in our solar system that is less dense than water. What that means, in the words of an unnamed NASA writer, is that in the unlikely event that a lake could be found large enough,

Saturn would float in it. Now there's a mental image. Speaking of images, the Voyager photos of Saturn showed subtler color contrasts compared to the bright streaks and swirls of Jupiter. In the pictures, the planet is encircled by bands of warm tones, what we might call earth tones in other circumstances.

The brownish-orangish images evoke something like a round clay bowl spinning on a potter's wheel. But not surprisingly, the real star of the Saturn photos was the planet's large and distinct ring system. As it turned out, the planet doesn't have a ring, but rather rings plural, full of myriad twists and turns.

What's more, these twisting, turning rings are accompanied by many smaller ringlets. In an image captured by Voyager 2 on the 11th of August, at about 8.6 million miles from Saturn, the rings cast a noticeable shadow around the planet's middle, its equator.

The Voyager craft also recorded information about Saturn that revealed it to be a cold and windy place, to say the least. Easterly winds blow at around 1,100 miles an hour, so strong as to make Earth's strongest gale force wind seem like a mild breeze.

For contrast, our planet's strongest wind ever recorded blew at around 250 miles per hour, meaning Saturn's gales beat our world record more than four times over. Meanwhile, temperatures were recorded in the range of -200 to 300 degrees Fahrenheit, or about -130 to 180 degrees Celsius.

More than a tad chilly. The measurements conjured an understanding of the gas giant as a freezing and blustery place, way out there in the far reaches of our solar system.

Meanwhile, the distant planet spins through space at a faster rotation than our cozier home, too, with a Saturn day measuring just 10 hours, 39 minutes, and 24 seconds to Earth's 24-hour day. The Voyager mission to Jupiter and Saturn had proven a resounding success, and to add to that success,

Scientists then showed that Voyager 2 could continue on to Uranus, with its scientific instruments still functioning. The opportunity was too good to pass up. NASA allocated more funding to keep operating the probes. Voyager 2 would become the only spacecraft to visit the outermost gas giants.

That's when mission scientists and engineers at the Jet Propulsion Laboratory, or JPL, in Pasadena, California, engaged in some science fiction-sounding work. They remotely programmed those craft, flying through distant space, giving them new capacities that exceeded their original design.

From many hundreds of millions of miles away, they updated the probes, readying them for their new mission. And so, the tuned-up Voyager 2 approached Uranus, the seventh planet from our Sun, on the 24th of January, 1986. Flying far above the cloud tops of Uranus, the probe sent back stunning photos of the gas giant.

along with images of its moons and its dark rings. Besides thousands of pictures, Voyager 2 also transmitted scientific data about the planet's atmosphere, interior, magnetic field, and other features.

It revealed 11 previously unknown moons of Uranus, as well as two new rings, in addition to other rings around the planet that had already been observed from Earth. It also enabled the discovery of a substantial magnetic field around the gas giant. The spaceship took detailed images of the planet's five biggest moons,

telling scientists a great deal about those moons' histories and formation. And it measured a day on Uranus, which proved to be 17 hours, 14 minutes long. With all these discoveries and data flowing in, and the remotely programmed spacecraft still going strong, NASA couldn't stop there. So, the space agency authorized the Jet Propulsion Laboratory

to continue the mission onto Neptune. The probe reached that distant place, which is some 30 times farther away from the Sun than Earth is, in late August 1989. That was around three and a half years after its closest approach to Uranus, and 12 years after it had left Earth.

Voyager 2 had traveled at an average speed of around 42,000 miles an hour to get to Neptune, the final planet it would approach, at least for another 40,000 years. There, the investment in continuing the mission was richly rewarded once again, as the probe studied Neptune over several months.

Its observations revealed six moons, along with three rings around Neptune. Billions of miles from Earth, Voyager 2 flew just 3,000 miles over Neptune's North Pole. A hop, skip, and a jump in astronomical distances. This was the closest it got to any planet, apart from our own, of course.

Just five hours after that, the probe soared past Triton, Neptune's largest moon. This was a goodbye of sorts, as it was the last solid body the Voyager mission would observe. But, as they say, whenever one door closes, another opens. And as the Voyager probe left that final planetary system,

it got a new, and if possible, even more science fiction-like mission: the Voyager Interstellar Mission. Just as it sounds, this new mission was for the Voyager craft to explore interstellar space, meaning the space between stars.

This region outside the area, dominated by our Sun, and in between the domains of other stars, is devoid of cosmic bodies like planets or stars. But it's hardly empty, as it contains material left over from the long-ago death of nearby stars. Material like the cosmic plasma, or electrically charged particles.

Astonishingly, decades after leaving Earth and after their planned demise, the Voyager probes were remotely reprogrammed again. Mission specialists pushed the boundaries of scientific possibility to once more do what had never been done before. Their objective

Keep the Voyagers going to transmit observations from beyond our solar system, taking measurements and communicating with Earth from far out in the Milky Way. To that end, Mission Control turned off some of the probe's scientific instruments that they wouldn't need for interstellar observations. This allowed the ships enough power to keep going.

In early 1998, almost 10 years after Voyager 2 left Neptune, its twin, Voyager 1, became the farthest away human-made object in the universe. And by 2004, both Voyager probes were far past Pluto, the most distant planet, or planetoid, traditionally recognized in our solar system. They were still within our system though,

as they remained in the area dominated by the Sun's magnetic field and its supersonic solar wind. But not for much longer. And still, they hurtled on, away from the Sun and towards the vast unknown that is the wide open space of our galaxy. They flew on, rocketing inevitably towards the outer reach of the Sun's influence.

where the solar winds slow from the million mile per hour range to around 250,000 miles per hour. And then, onwards they sped, past that boundary, called the heliopause. In August 2012, Voyager 1 crossed into interstellar space, 11 billion miles from the Sun.

it was the first thing created by humankind ever to exit our solar system. Voyager 2 followed suit in November 2018. Both spacecraft are now flying through the galaxy, collecting observations from interstellar space, and incredibly, sending them back to their earthly handlers in Pasadena.

The probes transmit their observations to Earth through something called the Deep Space Network. This is NASA's network of huge radio antennas located around the world and even some in orbit above it. The network uses three facilities spaced at equal distances across the globe. One is in California, another is in Spain, and the third is in Australia.

These carefully placed sites allow operators to remain in constant communication with spacecraft, even as the Earth rotates. When one site loses visibility with a spaceship that's fallen below the horizon, as day turns to night in its part of the world, one of the other sites can take over.

Like the Voyager mission itself, the Deep Space Network is run out of the Jet Propulsion Laboratory in Pasadena. The network is so powerful that it can reach not just spacecraft flying around our solar system, but even beyond it. Out to the Voyager probes, exploring interstellar space.

The probes are so far away that it takes many hours for a signal to travel between them and the Earth. Around 19 hours in the case of Voyager 2. Some of the Voyager probe's instruments have stopped working over time. Scientists have also remotely deactivated all of the probe systems that aren't absolutely essential to keeping them working.

This has made it harder to address problems that occur with the probes. For example, heaters were turned off, and remote repairs are more difficult on the now cold craft. But it has enabled the scientific miracle of continuing the craft's interstellar observations.

Most recently, in October 2024, the mission team turned off Voyager 2's plasma detector to keep that miracle going a bit longer. The plasma detector measured the amount of electrically charged atoms, called plasma, around the probe. But it wasn't collecting much data due to the ship's direction compared to the plasma's flow direction.

and the ship needed the power saved by deactivating it. This savings let the mission controllers continue to power several other instruments on board that are still working. Using the observations they record and transmit, scientists have been studying the Sun's magnetic field and its solar wind, along with other features about that distant region.

Science teams are also studying Voyager data about cosmic rays and radio emissions that seem to come from the boundary between the Sun's domain and interstellar space. The Voyager spacecraft have enough power and fuel to keep at least some of these scientific instruments operating for some years into the future. Even when their power and fuel do run out,

Their motion will keep them headed on a predictable path through the galaxy. Voyager 1 is speeding away from Earth and out into the space between stars more than 15 billion miles from the Sun. Its twin is doing the same on a different route, at well beyond 12 billion miles away. Someday, long, long after their instruments have gone silent and they've stopped communicating with the Earth,

the Voyagers will pass other stars, many light years from our Sun. In around 40,000 years, Voyager 1 will drift into the neighborhood of a star in the constellation of Camelopardalis, or the giraffe constellation. In cosmic terms, "in the neighborhood" means it will be less than two light years away from that star.

Meanwhile, somewhere around the same time, Voyager 2 will float to within 1.7 light-years of a star known as Ross 248. And still on, the probes will wander, assuming some other celestial body or, dare we imagine, alien intelligence doesn't encounter either of them and alter their paths. If not, in a few hundred thousand years,

Voyager 2 will approach Sirius, the brightest star in the sky, as seen from Earth. Sirius is also the focus of much mythology and lore from the earliest reaches of human memory. Some people even say that ancient myths and one modern tribe declare their long-ago ancestors were created by visitors who came to Earth from that distant star.

And now, a human-made object may go from Earth to Sirius in a time span that seems impossibly long to human perception and yet is like the blink of an eye in the cosmic timescale. Who knows? The Voyager spacecraft may continue their journey on into the unimaginable distances of the future. They may forever drift around the galaxy

carrying their precious cargo of gold-plated records bearing the message of earthly life and human goodwill into the depths of the universe. A message of hope and belief that may well inform a vision for humanity to carry forward through the space age and into the new age of interstellar exploration.