when was the voyager program started

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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.

Learn more Voyager Mission Status Bulletin Archives Experience A Message From Earth - Inspired by the Voyager Golden Record Neptune, planet of wind and ice

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Voyager, NASA’s Longest-Lived Mission, Logs 45 Years in Space

This archival image taken at NASA’s Jet Propulsion Laboratory on March 23, 1977, shows engineers preparing the Voyager 2 spacecraft ahead of its launch later that year.

Launched in 1977, the twin Voyager probes are NASA’s longest-operating mission and the only spacecraft ever to explore interstellar space.

NASA’s twin Voyager probes have become, in some ways, time capsules of their era: They each carry an eight-track tape player for recording data, they have about 3 million times less memory than modern cellphones, and they transmit data about 38,000 times slower than a 5G internet connection.

Yet the Voyagers remain on the cutting edge of space exploration. Managed and operated by NASA’s Jet Propulsion Laboratory in Southern California, they are the only probes to ever explore interstellar space – the galactic ocean that our Sun and its planets travel through.

The Sun and the planets reside in the heliosphere, a protective bubble created by the Sun’s magnetic field and the outward flow of solar wind (charged particles from the Sun). Researchers – some of them younger than the two distant spacecraft – are combining Voyager’s observations with data from newer missions to get a more complete picture of our Sun and how the heliosphere interacts with interstellar space.

NASA’s Solar System Interactive lets users see where the Voyagers are right now relative to the planets, the Sun, and other spacecraft. View it yourself here . Credit: NASA/JPL-Caltech

“The heliophysics mission fleet provides invaluable insights into our Sun, from understanding the corona or the outermost part of the Sun’s atmosphere, to examining the Sun’s impacts throughout the solar system, including here on Earth, in our atmosphere, and on into interstellar space,” said Nicola Fox, director of the Heliophysics Division at NASA Headquarters in Washington. “Over the last 45 years, the Voyager missions have been integral in providing this knowledge and have helped change our understanding of the Sun and its influence in ways no other spacecraft can.”

The Voyagers are also ambassadors, each carrying a golden record containing images of life on Earth, diagrams of basic scientific principles, and audio that includes sounds from nature, greetings in multiple languages, and music. The gold-coated records serve as a cosmic “message in a bottle” for anyone who might encounter the space probes. At the rate gold decays in space and is eroded by cosmic radiation, the records will last more than a billion years.

45 Years of Voyager I and II

Launched in 1977, NASA’s twin Voyager spacecraft inspired the world with pioneering visits to Jupiter, Saturn, Uranus, and Neptune. Their journey continues 45 years later as both probes explore interstellar space, the region outside the protective heliosphere created by our Sun. Researchers – some younger than the spacecraft – are now using Voyager data to solve mysteries of our solar system and beyond.

This archival photo shows engineers working on vibration acoustics and pyro shock testing of NASA’s Voyager on Nov. 18, 1976. Credit: NASA/JPL-Caltech

NASA’s Voyager 1 acquired this image of a volcanic explosion on Io on March 4, 1979, about 11 hours before the spacecraft’s closest approach to the moon of Jupiter.

Neptune’s green-blue atmosphere was shown in greater detail than ever before in this image from NASA’s Voyager 2 as the spacecraft rapidly approached its encounter with the giant planet in August 1989.

This updated version of the iconic "Pale Blue Dot" image taken by the Voyager 1 spacecraft uses modern image-processing software and techniques to revisit the well-known Voyager view while attempting to respect the original data and intent of those who planned the images.

This illustrated graphic was made to mark Voyager 1’s entry into interstellar space in 2012. It puts solar system distances in perspective, with the scale bar in astronomical units and each set distance beyond 1 AU (the average distance between the Sun and Earth) representing 10 times the previous distance.

This graphic highlights some of the Voyager mission’s key accomplishments. Credit: NASA/JPL-Caltech Full image details

This graphic provides some of the mission’s key statistics from 2018, when NASA’s Voyager 2 probe exited the heliosphere. Credit: NASA/JPL-Caltech Full image details

Beyond Expectations

Voyager 2 launched on Aug. 20, 1977, quickly followed by Voyager 1 on Sept. 5. Both probes traveled to Jupiter and Saturn, with Voyager 1 moving faster and reaching them first. Together, the probes unveiled much about the solar system’s two largest planets and their moons. Voyager 2 also became the first and only spacecraft to fly close to Uranus (in 1986) and Neptune (in 1989), offering humanity remarkable views of – and insights into – these distant worlds.

While Voyager 2 was conducting these flybys, Voyager 1 headed toward the boundary of the heliosphere. Upon exiting it in 2012 , Voyager 1 discovered that the heliosphere blocks 70% of cosmic rays, or energetic particles created by exploding stars. Voyager 2, after completing its planetary explorations, continued to the heliosphere boundary, exiting in 2018 . The twin spacecraft’s combined data from this region has challenged previous theories about the exact shape of the heliosphere.

Voyager 1 and 2 have accomplished a lot since they launched in 1977. This infographic highlights the mission’s major milestones, including visiting the four outer planets and exiting the heliosphere, or the protective bubble of magnetic fields and particles created by the Sun.

“Today, as both Voyagers explore interstellar space, they are providing humanity with observations of uncharted territory,” said Linda Spilker, Voyager’s deputy project scientist at JPL. “This is the first time we’ve been able to directly study how a star, our Sun, interacts with the particles and magnetic fields outside our heliosphere, helping scientists understand the local neighborhood between the stars, upending some of the theories about this region, and providing key information for future missions.”

The Long Journey

Over the years, the Voyager team has grown accustomed to surmounting challenges that come with operating such mature spacecraft, sometimes calling upon retired colleagues for their expertise or digging through documents written decades ago.

Each Voyager is powered by a radioisotope thermoelectric generator containing plutonium, which gives off heat that is converted to electricity. As the plutonium decays, the heat output decreases and the Voyagers lose electricity. To compensate , the team turned off all nonessential systems and some once considered essential, including heaters that protect the still-operating instruments from the frigid temperatures of space. All five of the instruments that have had their heaters turned off since 2019 are still working, despite being well below the lowest temperatures they were ever tested at.

Get the Latest JPL News

Recently, Voyager 1 began experiencing an issue that caused status information about one of its onboard systems to become garbled. Despite this, the system and spacecraft otherwise continue to operate normally, suggesting the problem is with the production of the status data, not the system itself. The probe is still sending back science observations while the engineering team tries to fix the problem or find a way to work around it.

“The Voyagers have continued to make amazing discoveries, inspiring a new generation of scientists and engineers,” said Suzanne Dodd, project manager for Voyager at JPL. “We don’t know how long the mission will continue, but we can be sure that the spacecraft will provide even more scientific surprises as they travel farther away from the Earth.”

More About the Mission

A division of Caltech in Pasadena, JPL built and operates the Voyager spacecraft. The Voyager missions are a part of the NASA Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate in Washington.

For more information about the Voyager spacecraft, visit:

https://www.nasa.gov/voyager

News Media Contact

Calla Cofield

Jet Propulsion Laboratory, Pasadena, Calif.

626-808-2469

[email protected]

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40 years and counting: the team behind Voyager’s space odyssey

In 1977, Voyager 1 and 2 started their one-way journey across our galaxy, travelling a million miles a day. Jonathan Margolis meets the dedicated team keeping the craft moving

O n a chilly March morning, Steve Howard, aged 65, is at work in his office on the northern edge of Pasadena, California. Two computer screens are squeezed on to his corner desk along with family photos, a tissue box and tins of Altoids Curiously Strong Peppermints. The office is in a quiet business park by a workaday main road. Next to it is a McDonald’s, where people linger for hours over a $1 coffee, seemingly to keep warm. Over the road there’s a scruffier burger joint, Jim’s, with an M missing from its sign – and, visible from Howard’s window, a landscaping supplies yard.

If the few people walking by on West Woodbury Road, Altadena, or popping into the landscaping place for some patio paving slabs were to peer into Howard’s office, they might guess, seeing the graph-covered twin screens and a third PC at the other end of the desk, that he was, perhaps, a financial adviser or a day trader. But what Steve Howard is actually doing makes this very ordinary all-American scene quite extraordinary.

Howard is a Nasa mission controller. He is sending instructions to a probe in interstellar space, 12 billion miles from Earth, beyond Pluto and escaping our Solar System at 1 million miles a day. The 815kg craft, Voyager 1 , is one of two identical machines that for many years now have been the furthest human-made objects from Earth. Howard’s computer code takes 17 hours at the speed of light to reach Voyager 1, the furthest travelled. Voyager 2, which is leaving the solar system in a different direction, is 3bn miles closer. The responses, from transmitters on the twin probes running 23 watts of power – have the power of a billionth of a billionth of a watt by the time they reach Earth.

“So here, see, I have Voyager 1’s status and information up, at least as it was 17 hours ago,” Howard explains. “Right now I’m connected to our Canberra station, and these are seven commands, set to radiate one every five minutes starting 30 minutes from now. They’re to verify that the spacecraft can receive and reset its timer. Such is the speed of light, I will not get confirmation that all is OK until late tomorrow night, but it will have entailed a 25bn-mile round trip, so that’s not too bad.”

It is no hyperbole to say, then, that the man tapping away at his keyboard on the office park next to McDonald’s is a key figure in the greatest-ever feat of human exploration. There was nothing like the Voyager 1 and 2 missions to the outer planets before they launched in 1977, and although three outer planet probes launched last decade are still on mission, no new ventures into deep space are planned.

Space exploration tends to be more inward looking today than in the so-called Space Age. The famous Curiosity rover is of course still working wonders on Mars, but almost all the US’s coming spacecraft will be restricted to studying our own planet, with special attention to environmental issues. The Voyagers and the people like Howard who still work on them full-time – having, in many cases, done so their entire adult life – are from a different era, when budgets were unrestrained, audaciousness (and showing off to the Soviets) was in vogue and the environment was a concern only for hippies.

Voyager’s spindly limbed, Transit-van-sized machines have been travelling at around 37,000mph for almost 38 years. When they were launched, wooden-framed Morris 1000 Traveller cars had only recently stopped being produced by British Leyland in Oxford. The Voyagers’ on-board computers are early 1970s models that were advanced then but are puny now – an iPhone’s computer is some 200,000 times faster and has about 250,000 times more memory than Voyager’s hardware.

The Voyager mission’s early 70s-inspired and -equipped trip, originally meant to last four years, took the craft initially to Jupiter, then Saturn, then, as a bonus since everything was working well, to Uranus and finally Neptune, after which they spun off into their journey around the Milky Way. Against all expectations their vintage electronics and thrusters are still, mostly, working in the intense -253C cold of outer space. What’s more, their sensors are sending data all day every day, as some will continue to do until 2036. That said, by 2025 almost all the instruments sending worthwhile scientific information will be turned off as the ships’ tiny plutonium-238 power sources dwindle.

The on-board camera on each Voyager, for instance, was deactivated to save power 25 years ago last Valentine’s Day. This was after Voyager 1 took a now-iconic “family portrait” of the solar system from almost 4bn miles out. It captured Neptune, Uranus, Saturn, Jupiter, Venus, Earth (seen, in the late astrophysicist Carl Sagan ’s phrase, as a “pale blue dot”) and the Sun, by then just a tiny point of light. By 2036 the craft will be nearly out of the solar system altogether and will remain dead, although in perfect condition, probably for eternity.

It is the Voyager spacecrafts’ longevity, despite their becoming a bit arthritic in later years, that has led to their Mission Control being moved out to an office park. The problem for Nasa – more correctly for the California Institute of Technology’s Jet Propulsion Laboratory , which runs most robotic missions for Nasa – is that high-profile later expeditions, most notably Curiosity, have used the available space on CalTech’s campus. Proud as JPL is of the amazing Voyager story, the craft are not taking photos or doing a lot of sexy science any more and may not encounter anything of much interest for another 40,000 years, by which time they will be deaf and mute. So, like a great grandfather who stubbornly refuses to do the decent thing, the Earth end of the Voyager programme and the spacecraft’s devoted carers have been put in a somewhat off-piste rest home.

Engineers are not given to emotion, but the romance of this incredible voyage of discovery has, by their own account, kept the ageing mission team together. Even latecomers, who were at school when Voyager was launched, have been working on the same mission for 30 years and more. “I’m in my mid-50s and treat the craft like my ageing parents,” says Suzy Dodd , who was 16 at launch, joined as a graduate student and whose card now proclaims surely one of the cooler job titles in science: Project manager, Voyager Interstellar Mission.

“You treat them with a certain amount of reverence; you know they’re stately spacecraft, venerable senior citizens, and you want to do everything possible for them to have a healthy lifetime,” she says. “You need to help them a bit because things have failed and you want to be careful other things don’t. Most of the engineers here have dedicated their career to this project. They have turned down opportunities for promotions and other things because they like Voyager so much they want to stay with it.”

It is clear talking to Voyager staff that they genuinely love their spacecraft, even though most were too young to see them before they flew, and it is more than possible that the older ones will have died before the Voyagers bleep their last. But as engineers, they have mixed feelings about the most famous aspect of that romance, the “golden record” that each craft carries. This is a gold-covered copper LP, packed with a needle and cartridge (plus instructions), and containing, in groove form, 115 photos from Earth, a selection of natural sounds from surf to whales, music from a variety of cultures and eras (the modern west is represented by Chuck Berry’s “Johnny B Goode”) and spoken greetings in 55 languages, from Akkadian, spoken in Sumer about 6,000 years ago, to Welsh.

Carl Sagan, who had the initial idea for the record, wrote in the 1970s: “The spacecraft will be encountered and the record played only if there are advanced spacefaring civilisations in interstellar space. But the launching of this bottle into the cosmic ocean says something very hopeful about life on this planet.” Sagan’s son Nick, then an infant, now a science-fiction novelist and screenwriter (his credits include Star Trek episodes), recorded the English message: “Hello from the children of planet Earth.” But one sure to make many tear up is the Mandarin: “Hope everyone’s well. We are thinking about you all. Please come here to visit when you have time.” (The messages are on the Voyager website, voyager.jpl.nasa.gov ).

Voyager’s mission controllers are less starry-eyed than Sagan about the golden records. You sense some feel that it was too much of a bow to religious sentiment. Steve Howard is one of the more positive on the record question. “Even though Earth may not be here, some intelligent being could pick it up and detect it. I would say that many of the civilisations are much more advanced and would detect something like that and simply go in and decipher it,” he says.

Suzy Dodd’s view is more typical of the team’s. “I think it’s a great idea to get humans and mankind thinking what-ifs. Let’s send a picture of ourselves vintage 1977 and put it on a spacecraft and send it out there forever. I think it’s done to connect us to the spacecraft more than for an alien running into it. I’m of the opinion that space is very empty and the chances of something finding it are remote. But that doesn’t diminish the fact that we’ve got a little time capsule out there travelling through space and now orbiting around in our galaxy. And that’s us.”

For the mission’s much-honoured chief scientist and spokesman since 1972, CalTech professor Ed Stone, aged 79, the romance of Voyager lies more in what it has discovered since he joined the project aged 36. “Yes, the Space Age was a young man’s game back then,” he says, not a little ruefully, sitting on a park bench on the green university campus. “We all knew we were on a mission of discovery. We just had no idea how much discovery there would be. We just kept finding things we didn’t know were there to be found.

“For example, before Voyager, the only known volcanoes in the solar system were here on Earth. Then we flew by Jupiter’s moon, Io, which had 10 times the volcanic activity of Earth. Ten times! We detected hot lakes of lava on the surface. That was the first major discovery and it set the tone for the rest of the mission. And there are five instruments still working. But by 2025 the last will go off.”

He doesn’t quite add that by then he will be nearly 90, but does say, smiling: “Thing is, if you want to do space experiments, you have to be optimistic that it’s all going to work and that you’re going to find something worth the work. And you have to be patient, because nothing happens fast in space.”

Stone explains how, although it’s widely considered freakish that the Voyager crafts are still working so well – a TV left permanently on since Jim Callaghan’s day would be hardly working today – it’s less surprising to people like him who built them. To anyone familiar with the inside of a vintage radio or TV, the hand-soldered circuit boards, capacitors, transistors, resistors and so on that run a Voyager would look reassuringly familiar, which isn’t the case with a modern computer or phone, whose microchip-studded innards look more like something out of a UFO.

But the parts in Voyager weren’t as ordinary as they looked. Suzy Dodd, a “newcomer” to the project with just over 30 years’ service, has also been intrigued by the spacecraft’s durability. “The robustness is unique,” she says. “If you talk to the older engineers, they’ll say: ‘Well, we were told to make a four-year mission, but we realised if you just used this higher-rated component, it would last twice as long.’ So they did that. They just didn’t tell anybody. The early engineers were very conscious of trying to make this last as long as possible and, quite frankly, being not as forthcoming with information about the types of parts they were using.”

Even so, Ed Stone says, there have been problems. A ground controller’s error in April 1978 meant that Voyager 2 switched itself irretrievably to its back-up receiver – meaning that the craft has been receiving transmissions from Earth on a dodgy back-up radio for almost the entire mission. One of the original thrusters also failed.

For spacecraft 12bn miles from home and in their dotage, the Voyagers are quite tranquil machines today, but they do need watching. As Steve Howard is in his office inputting code in primordial programming language, on the floor of what passes for the main mission control Enrique Medina, 65, is watching streams of engineering data from the craft. A computer engineer, Medina is another of the eight full- and part-time controllers.

“One of us is always on call,” he says. “We’re all connected all the time by our smartphones. We will hear, that way, which engineering channel is out of tolerance and then we will connect from home with secure IDs and special codes, troubleshoot, determine and sometimes fix it from home. Or in some cases, one of us will drive in. That usually happens four to five times a month.

“Sometimes people are away, but we love Voyager so much that though it’s not part of our employment we’ll come in and do it anyway. Attitude control is my sub-system, but if the propulsion or the power needs attention, we all do multiple jobs,” he adds. “I’ve been working on Voyager since the Uranus encounter in 1986, and I will retire when Voyager retires in 2025. My wife doesn’t like that idea at all, as we already have a retirement place by the beach back in Mexico.”

Medina’s devotion to the Voyager is clear to see. “This has been part of my life for so long, and they pay us to do it, so how can you stop doing something you love? I even talk about the spacecraft like it’s a person, especially if it’s my sub-system.”

Steve Howard feels the same. “I just love to think of everything, all those 65,000 parts on each craft, working up there,” he says. “Oh man, it really is something. Every time we come in here, it’s just a gift. And you know that one day it could stop.”

Do these engineers ever think it might be more fun to be at the controls of Curiosity on the CalTech campus a couple of miles away?

“Yes, maybe,” says Medina, “but after so many years, you’re invested. It’s like being married to someone. It would be interesting to go out with Angelina Jolie, but do I want to give up my wife of 44 years, and my grandkids? I don’t think so. I would not give this up for something more interesting or newer.”

For the most part, Voyager is the reality of space – slow, patient science, humdrum perhaps, but real. It’s only a 20-minute drive from Altadena to Hollywood, where brilliant fake versions of space exploration like Christopher Nolan’s recent Interstellar are confected.

But Voyager, starring real people who keep tissues and tins of Altoids on their desks and real buildings rather than set designers’ glamorous fantasies, just happens to be the only real interstellar mission there will probably be in the lifetime of anyone alive today. It is surely one of the most amazing things in human history.

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Everything you need to know about the Voyager mission

The Voyager space probes will outlast our Sun as they travel through interstellar space – here are the key facts and figures we’ve learned in these past 40 years.

Amy Godfrey

For more than 40 years Voyager 1 and Voyager 2 have been travelling through our Solar System, unveiling the mysteries of the outer planets and discovering new moons. We’re still receiving data from the Voyager probes as they make their epic journey through interstellar space, but what will it teach us, and how long will they continue to communicate? Here are the key facts and figures covering everything you need to know about this historic mission:

Why was Voyager launched?

BeforeVoyager, our knowledge of the giants, Jupiter, Saturn, Uranus and Neptune was minimal, having only visited Jupiter twice and Saturn once by human probes. There were many uncertainties regarding the four planets, including their compositions, moons, magnetic fields and potential ring systems, which the Voyager probes would explore and discover, rewriting the textbooks in the process. A chance interaction between the planets also made such a mission all the more feasible.

Read more about the Voyager program:

• Voyager: a brief history of the interstellar spacecraft
• A message to ET: 47 images from the Voyager Golden Record

What was Voyager’s route?

An intern at the Jet Propulsion Laboratory (JPL), Gary Flandro, realised that the four outermost planets would be aligned during the late 1970s - “the chance of three lifetimes”. So a route for a single probe to complete ‘The Grand Tour’ was clear, using the gravity of one planet to move on the next in a gravity-assisted trajectory. However, this initial plan was seen as too expensive after planetary exploration funds were slashed, so the race was on to find a cheaper alternative, yet still take advantage of the rare planetary alignment.

A pair of identical probes was to be built to replace the earlier plan, and in a competition run by NASA, the new mission was named Voyager. Voyager 1 was set to closely flyby Jupiter and Saturn, while Voyager 2 would pass these planets from slightly further out, and follow its own trajectory to explore Uranus and Neptune.

What's on the Voyager probes?

The twin probes each weighed 722kg, full of scientific instruments, radio systems and their power sources. Solar energy was not an option given that Voyager 1 would be travelling 778 million km from the Sun, and Voyager 2 needed to be functional as far as 4.5 billion km from the Sun . The best alternative was nuclear power, in the form of Radioisotope Thermoelectric Generators (RTGs), containing plutonium-238 that would decay to produce heat, which was converted to electricity.

Each probe holds 11 instruments for analysis. These include examining atmospheric chemistry, magnetic fields, detecting aurorae, measuring charged particles, using radio signals to determine physical properties of the planets, and detecting solar wind through plasma measurements.

When were the Voyager probes launched?

On 20 August 1977 Voyager 2launched from Cape Canaveral, Florida, soon followed by Voyager 1 on 5 September. But the question on most peoples lips was ‘why was Voyager 2 launched before Voyager 1?’. This was due to the different trajectories of the two craft. Voyager 2 needed to travel much further to the two outermost planets so was launched first due to the preferable planetary conditions. Voyager 1 would be launched second, for its much shorter journey, but would still overtake Voyager 2 before reaching Jupiter.

What did the Voyager twins discover?

After a 15-month journey, Voyager 1 arrived at Jupiter , soon followed by Voyager 2 a few months later. One of the first surprises was the discovery that its moon Io appeared to be geologically active, a trait known only to belong to Earth. At a third the size of our planet, Io’s volcanic activity yields twice as much energy, making it the most geologically active place in the Solar System.

Data from Voyager also revealed that Jupiter’s magnetosphere was much larger than previously thought, extending as far as the orbit of Saturn. Infrared measurements indicated the composition of Jupiter to be mostly hydrogen with some helium and trace amounts of water, methane, ammonia and rock. After Voyager 1’s closest approach, it captured another astonishing image. It depicted a narrow ring, closely surrounding the planet, something that had been thought impossible for Jupiter to sustain. Comprised of dark rocky grains, it prompted speculation that the ring was made from the debris of an ancient moon, with similar compositions to the newly discovered moons; Thebe, Metis and Adrastea. The heavily cratered moon Ganymede, the largest satellite in the Solar System , was found to have a very thin atmosphere.

The discoveries made by the Voyager team on the approach to Saturn started with the flyby of its moon Titan. Known to have a thick atmosphere, it was uncovered to be much more substantial than predicted when Voyager 1 drifted beneath its orange clouds. Until then, Titan was thought to be the largest moon in the Solar System, but the diameter of the solid centre was found (through radio signals) to be smaller than Jupiter’s Ganymede. Titan also has an axial tilt, and Voyager 1 was able to witness distinct seasons as the gases migrated from each hemisphere.

Voyager was also tasked with photographing Saturn’s intricate ring system, revealing thin bands, spokes and gaps produced by ‘shepherd moons’ Prometheus and Pandora. Further discoveries into the moons influence in the ring structure unveiled a new moon, Pan, a tiny speck in an image captured by Voyager 2 of the Encke Gap. This flyby of Saturn marked the end of Voyager 1’s planetary expedition.

After Voyager 2’s five-year hibernation it finally reached Uranus in 1986, a mysterious new world. The probe captured images of the aquamarine coloured planet, confirmed the main constituents to be hydrogen and helium, recorded an uniform temperature of -216 degrees centigrade across Uranus’ atmosphere, and magnetometer data measured the ‘day’ to be 17.25 hours.

Voyager 2 also observed polar aurorae, in different positions to the planets rotational poles. Uranus’ aurorae produced powerful high-energy radiation, stripping any atmosphere from its moons, shown by the Voyager 2’s imaging of the dark, dusty natural satellites. Due to Voyagers trajectory, it was able to closely image the moon Miranda, whose craters and canyons inferred that it had been previously destroyed then reaggregated. Alongside these findings, 10 new moons were discovered, and only 2 moons were found to ‘shepherd’ Uranus’ rings, Ophelia and Cordelia.

Three years later, in 1989, Voyager 2 reached its final planetary destination, Neptune . A sky-blue planet composed of primarily hydrogen and helium, but with notable abundances of ammonia, methane and hydrogen cyanide. The probe measured Neptune’s day at 16.1 hours, discover six new moons, and revealed an eagerly awaited ring system. The outermost ring had an inconsistent width, leading scientists to believe that the debris was from ancient moons, and the small moons Thalassa and Naiad would later contribute to the system.

To avoid the icy debris in the rings, the path of Voyager was altered so that it would still pass by Triton, the largest of Neptune’s moons. Nicknamed the ‘cantaloupe’ due to its scaly looking surface, Triton revealed its most surprising feature: erupting geysers. At 4.5 billion km from the Sun, active volcanism was unexpected, and became only the third known body in the Solar System to harbour this trait.

What happened once the Voyager probes completed their missions?

Voyager 1 completed its mission after passing Saturn, and continued its trajectory into the outer Solar System, overtaking Pioneer 10 to be the furthest human-made object from the Sun, in 1998. Before this, in 1990 the probe captured the iconic image of Earth, the Pale Blue Dot, as it looked back towards our Solar System.

The journey then fell quiet for Voyager 1 until 2002, when it started to detect energetic particles, inferring it had reached a boundary of the Solar System, known as Termination Shock. This boundary is the point at which the solar wind abruptly slows down, as it encounters interstellar winds, resulting in the particles bunching up, enough for the increase to be detected. The Voyager Interstellar Mission (VIM) team then took almost two years to confirm Voyager 1’s position, as the plasma detector (best suited for measuring solar winds) had previously stopped working during the Saturn flyby. Voyager 2 crossed this region three years later at a different point, so was able to confirm that our solar system is not round, but is in fact squashed.

Read more about Voyager 1 and 2 missions:

• Mind-blowing things we learned watching the new Voyager film The Farthest
• Mission timeline: Voyager’s landmark moments

By 2012, Voyager 1 had travelled to the outermost boundary between our system and interstellar space - the heliopause, where the solar winds are forced back around the Heliosphere, by the interstellar winds from the milky way and nearby supernovae. The iconic Voyager 1 is now humanity’s first interstellar traveller, collecting further information on the importance of the heliosphere, which protects our Solar System from 75 per cent of galactic cosmic rays, which have the ability to wreak havoc with our precious ozone layer and destroy DNA.

How much longer will Voyager last in Interstellar space?

From 2020, the scientific instruments aboard each craft will be turned off one by one to conserve the remaining power supplied via the decaying RTGs. The final instruments will be shut down by 2025, when only a periodic, faint electronic blip will be received, indicating the pairs positions beyond the Solar System for the following few years.

What can voyager reveal about interstellar space?

Initially presumed to be a vast empty expanse, analysis of the interstellar medium could help scientists understand dark matter, the birth of stars and the origins of life.

Dark matter, the elusive material that holds the Milky Way together, could be studied by the Voyager probes in the Interstellar medium. The current proposal is that dark matter in formed of Weakly Interacting Massive Particles (WIMPs), which cannot be analysed by the 40 year-old instruments on the probes. However, in theory they could detect the particles produced when two WIMPs collide, in a process known as annihilation.

Read more about space exploration:

• Space exploration: how might the next 50 years progress?
• 50 beautiful photos of the Moon landing missions from the Project Apollo Archives

Scientists also hope to use the pair to study the interstellar matter, and uncover more about the life cycle of stars and galaxies. The death of a star results in the emission of the heavy elements formed from nuclear fusion (the process which powers stars). These include carbon, oxygen and iron, the abundances of which can be measured over time. With fewer lighter elements, such as hydrogen and helium in the interstellar medium, the fewer stars are born, and fewer systems like ours will be formed.

The VIM team aim to use Voyagers remaining eight years to learn as much as possible about the outer Solar System. Key objectives of the mission include: understanding how the Sun’s magnetic field wraps around the heliosphere by measuring the changes in the density of particle detection, revealing new information about interstellar winds by listening to plasma oscillations caused by coronal mass ejections, and exposing the interactions between the solar atmosphere and interstellar winds. They are also eagerly awaiting data from Voyager 2, to confirm the boundary position of the heliopause with its fully functioning plasma detector.

What is the Golden Record?

As the voyager twins continue on their travels through interstellar space, they are tasked with one final mission: greeting extraterrestrial civilisations.

Long after Earth has lost contact with the Voyager probes, the golden records attached to the outside of each craft have the potential to connect our world with any other intelligent life they may encounter.

In 1977, a time capsule in the form of a 12-inch disc was commissioned to adorn each of Voyager 1 and 2, containing a wealth of information to depict Earth and humanity. As well as inscriptions in the gold-plated copper disc on how to read it, there is also an ultra-pure sample of uranium-238 to determine the age of the probe once it reaches life (due to the rate of radioactive decay), alongside a map to locate our Sun with reference to 14 known pulsars. Thecontents of the Golden Record, including 116 analogue-encoded images, greetings in 55 languages, 12 minutes of natural sounds from Earth, and 90 minutes of music, was chosen by Carl Sagan and SETI’s Frank Drake after collaborating with historians, artists, folklorists and ethnomusicologists to create the best first impression of our home planet.

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Stephen Clark, Ars Technica

How NASA Repaired Voyager 1 From 15 Billion Miles Away

Engineers have partially restored a 1970s-era computer on NASA's Voyager 1 spacecraft after five months of long-distance troubleshooting , building confidence that humanity's first interstellar probe can eventually resume normal operations.

Several dozen scientists and engineers gathered Saturday in a conference room at NASA's Jet Propulsion Laboratory, or connected virtually, to wait for a new signal from Voyager 1. The ground team sent a command up to Voyager 1 on Thursday to recode part of the memory of the spacecraft's Flight Data Subsystem (FDS) , one of the probe's three computers.

“In the minutes leading up to when we were going to see a signal, you could have heard a pin drop in the room,” said Linda Spilker, project scientist for NASA's two Voyager spacecraft at JPL. “It was quiet. People were looking very serious. They were looking at their computer screens. Each of the subsystem (engineers) had pages up that they were looking at, to watch as they would be populated.”

Finally, a Breakthrough

Launched nearly 47 years ago, Voyager 1 is flying on an outbound trajectory more than 15 billion miles (24 billion kilometers) from Earth, and it takes 22.5 hours for a radio signal to cover that distance at the speed of light. This means it takes nearly two days for engineers to uplink a command to Voyager 1 and get a response.

In November, Voyager 1 suddenly stopped transmitting its usual stream of data containing information about the spacecraft's health and measurements from its scientific instruments. Instead, the spacecraft's datastream was entirely unintelligible. Because the telemetry was unreadable, experts on the ground could not easily tell what went wrong. They hypothesized the source of the problem might be in the memory bank of the FDS.

There was a breakthrough last month when engineers sent up a novel command to “poke” Voyager 1's FDS to send back a readout of its memory. This readout allowed engineers to pinpoint the location of the problem in the FDS memory . The FDS is responsible for packaging engineering and scientific data for transmission to Earth.

After a few weeks, NASA was ready to uplink a solution to get the FDS to resume packing engineering data. This datastream includes information on the status of the spacecraft—things like power levels and temperature measurements. This command went up to Voyager 1 through one of NASA's large Deep Space Network antennae on Thursday.

Then, the wait for a response. Spilker, who started working on Voyager right out of college in 1977, was in the room when Voyager 1's signal reached Earth on Saturday.

“When the time came to get the signal, we could clearly see all of a sudden, boom, we had data, and there were tears and smiles and high fives,” she told Ars. “Everyone was very happy and very excited to see that, hey, we're back in communication again with Voyager 1. We're going to see the status of the spacecraft, the health of the spacecraft, for the first time in five months.”

Reece Rogers

Steven Levy

Brenda Stolyar

Throughout the five months of troubleshooting, Voyager's ground team continued to receive signals indicating the spacecraft was still alive. But until Saturday, they lacked insight into specific details about the status of Voyager 1.

“It’s pretty much just the way we left it,” Spilker said. “We're still in the initial phases of analyzing all of the channels and looking at their trends. Some of the temperatures went down a little bit with this period of time that's gone on, but we're pretty much seeing everything we had hoped for. And that's always good news.”

Relocating Code

Through their investigation, Voyager's ground team discovered that a single chip responsible for storing a portion of the FDS memory had stopped working, probably due to either a cosmic ray hit or a failure of aging hardware. This affected some of the computer's software code.

“That took out a section of memory,” Spilker said. “What they have to do is relocate that code into a different portion of the memory, and then make sure that anything that uses those codes, those subroutines, know to go to the new location of memory, for access and to run it.”

Only about 3 percent of the FDS memory was corrupted by the bad chip, so engineers needed to transplant that code into another part of the memory bank. But no single location is large enough to hold the section of code in its entirety, NASA said.

So the Voyager team divided the code into sections for storage in different places in the FDS. This wasn't just a copy-and-paste job. Engineers needed to modify some of the code to make sure it will all work together. “Any references to the location of that code in other parts of the FDS memory needed to be updated as well,” NASA said in a statement.

Newer NASA missions have hardware and software simulators on the ground, where engineers can test new procedures to make sure they do no harm when they uplink commands to the real spacecraft. Due to its age, Voyager doesn't have any ground simulators, and much of the mission's original design documentation remains in paper form and hasn't been digitized.

“It was really eyes-only to look at the code,” Spilker said. “So we had to triple check. Everybody was looking through and making sure we had all of the links coming together.”

This was just the first step in restoring Voyager 1 to full functionality. “We were pretty sure it would work, but until it actually happened, we didn't know 100 percent for sure,” Spilker said.

“The reason we didn’t do everything in one step is that there was a very limited amount of memory we could find quickly, so we prioritized one data mode (the engineering data mode), and relocated only the code to restore that mode,” said Jeff Mellstrom, a JPL engineer who leads the Voyager 1 “tiger team” tasked with overcoming this problem.

“The next step, to relocate the remaining three actively used science data modes, is essentially the same,” Mellstrom said in a written response to Ars. “The main difference is the available memory constraint is now even tighter. We have ideas where we could relocate the code, but we haven’t yet fully assessed the options or made a decision. These are the first steps we will start this week.”

It could take “a few weeks” to go through the sections of code responsible for packaging Voyager 1's science data in the FDS, Spilker said.

That will be the key payoff, Spilker said. Voyager 1 and its twin spacecraft, Voyager 2, are the only operating probes flying in the interstellar medium, the diffuse gas between the stars. Their prime missions are long over. Voyager 1 flew by Jupiter and Saturn in 1979 and 1980, then got a gravitational boost toward the outer edge of the Solar System. Voyager 2 took a slower trajectory and encountered Jupiter, Saturn, Uranus, and Neptune.

For the past couple of decades, NASA has devoted Voyager's instruments to studying cosmic rays, the magnetic field, and the plasma environment in interstellar space. They're not taking pictures anymore. Both probes have traveled beyond the heliopause, where the flow of particles emanating from the Sun runs into the interstellar medium.

But any scientific data collected by Voyager 1 since November 14 has been lost. The spacecraft does not have the ability to store science data onboard. Voyager 2 has remained operational during the outage of Voyager 1.

Scientists are eager to get their hands on Voyager 1's science data again. “With the results we got on Saturday, we have new confidence that we can put together the pieces we need to now get back the science data,” Spilker said.

“One thing I'm particularly excited about—there's this feature in the Voyager 1 data. We nicknamed it Pressure Front 2,” Spilker said. “Pressure Front 2 is a jump in both the density of the plasma around the spacecraft and the magnetic field. It's lasted for three-and-a-half years.”

“We'd like to see, is this still there?” she continued. “It's different from what we've seen in the past, and we're trying to figure out, is it some influence coming from the Sun, or is it actually something coming from interstellar space that's creating this feature? So we'd like to see it again, get more data, and be able to study it more carefully.”

This story originally appeared on Ars Technica .

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Voyager 1 was in crisis in interstellar space. NASA wouldn’t give up.

NASA engineers spent months doggedly trying to fix a computer on Voyager 1, a spacecraft launched in the 1970s that’s now exploring interstellar space.

For the past six months a team of engineers at NASA’s Jet Propulsion Laboratory has been trying to fix a glitchy computer. Three things make the repair job challenging:

The computer is highly customized and unlike anything on the market today.

It was built in the 1970s.

And it is 15 billion miles away.

The computer is on Voyager 1, the most distant human-made spacecraft ever launched. Far beyond the orbit of Pluto, it is riding point for all humanity as it hurtles through interstellar space.

But on Nov. 14, Voyager 1 suddenly stopped sending any data back to Earth. While it remained in radio contact, the transmission had, as NASA engineers put it, “flatlined.” So began the greatest crisis in the history of the fabled Voyager program.

Voyager 1 and its twin, Voyager 2, launched in 1977 and in the years that followed obtained stunning close-up images of Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune and is the only spacecraft to have visited those ice giants. The Voyagers blew past the heliopause, where the solar wind abates and interstellar space begins, and continued to send back science data about particles and magnetic fields in a realm never before visited.

The two Voyagers are powered by the radioactive decay of plutonium-238, and in the near future that power source will be too feeble to keep the spacecraft warm and functioning. But for now, they have operational scientific instruments that are sending back otherwise unobtainable data on the composition of space beyond the heliopause.

Fixing Voyager 1 quickly became a priority for NASA, and especially for Jeffrey Mellstrom, who has been at JPL in Pasadena for 35 years and is the chief engineer in the astronomy and physics directorate.

Mellstrom took on the challenge even as he planned for retirement in the spring. In January, Mellstrom told a colleague, “The one thing I’m going to regret is if I retire before we solve Voyager 1’s problem.”

Like kicking a vending machine

After initial attempts to resolve the issue went nowhere, JPL leadership created a “tiger team” made of a multigenerational crew of engineers, some of them veterans of the lab and some born long after the Voyagers launched.

“We didn’t know how to solve this in the beginning because we didn’t know what’s wrong,” said Mellstrom, the team’s leader.

Voyager 1 has three computers. One is the attitude and articulation control system, which makes sure the spacecraft is pointed in the right direction. Another is the command control system, which handles the commands coming from Earth. The third is the flight data subsystem, which takes science and engineering data and packages it for transmission home.

Something had gone wrong somewhere in that trio of computers. Maybe a “cosmic ray” — a particle from deep space — had smashed into a computer chip. Or maybe a piece of hardware just got so old it ceased to work.

“All we had was incoherent data, garbled data,” said Suzanne Dodd, the Voyager project manager since 2010. Dodd has been at JPL for four decades, and in her early years she wrote computer code for Voyager 2’s encounters with Uranus and Neptune. She vividly remembers that first close-up look of Neptune and an image of the ice giant with its huge moon Triton in the background.

“We didn’t know what part of the spacecraft was involved with this,” Dodd said.

So they poked it. They sent commands to Voyager 1, trying to jolt it back to coherence. The team had a list of potential failures and figured that one of the commands might have the equivalent effect of kicking a vending machine.

Here is where the troubleshooting encountered an inviolable obstacle: the speed of light. Even at 186,000 miles per second, a command sent to Voyager 1 would take 22½ hours to arrive. Then the engineers would have to wait another 22½ hours for the spacecraft to send a response.

The planet Earth is kind of a pain, too, because it spins inconveniently on its axis and moves restlessly around the sun. To communicate with distant spacecraft, NASA relies on the Deep Space Network, three arrays of huge radio telescopes in California, Spain and Australia. The idea is that, regardless of Earth’s movement, at least one array can be pointed toward a spacecraft at almost any time.

The tiger team developed a pattern of sending a command on a Friday and waiting for the return signal on Sunday. Some dark days and weeks followed.

“None of those commands that we sent were able to make any discernible difference whatsoever,” said David Cummings, an advanced flight software designer and developer.

In late February, the team sent a series of commands to prod the flight data subsystem to place software in each of 10 different “data modes.” The team waited, hoping for a breakthrough. After two days, Voyager responded — still without data. Engineer Greg Chin circulated a technical chart and summarized the situation: “So, at this time, no joy.”

“It was unbelievably depressing,” Cummings said. “Luckily the story doesn’t end there.”

Cracking the code

Just a day after the “no joy” email, the team felt a surge of optimism.

JPL has specialists in radio transmissions, and they noticed that in some “modes” the return signal from Voyager 1 had been modulated in a pattern consistent with the flight subsystem computer producing data, though not in any normal format. The modulation suggested that the processor was functioning and supported the team’s conjecture that some of the memory had been corrupted.

“That was huge,” Cummings said. “The processor was not dead.”

Painstakingly, the team at last tracked down the origin of the problem: a bad memory chip holding one bit — the smallest unit of binary data — for each of 256 contiguous words of memory.

The flight data subsystem was built with 8K memory, or more exactly 8,192 bytes. (A modern smartphone has something like 6G memory, or 6 billion bytes.)

The engineers came up with a plan: They would move the software to different parts of the flight data subsystem memory. Unfortunately they couldn’t just move the 256 words in a single batch, because there was no place roomy enough for all of it. They had to break it down into pieces. And they’d have to proofread everything. It was tedious, error-prone work.

Cummings called a young JPL flight software engineer named Armen Arslanian: “Do you want to help me relocate Voyager code?”

Arslanian was the right person for the job. Just six years out of college, he knew how to write code for spacecraft, and he knew how to deal with “assembly language,” the coding that underlies the common languages used by programmers today. That’s the language of Voyager’s 1970s-era computers.

“I ended up needing that skill,” Arslanian said.

The JPL teams had documentation from the 1970s describing the function of the software, but often the descriptions were contingent on other information that could not be found. The team also lacked the tools to verify their coding. They had to do everything essentially by hand. It wasn’t like trying to find a needle in a haystack so much as like trying to examine every piece of hay for possible flaws.

The team prioritized the software for the engineering data so that they could fully restore communication with the spacecraft. If that worked, they could fix the science data later.

On April 18, the team sent a package of commands to the spacecraft and then waited. Two days later the spacecraft sent back the first intelligible engineering data in more than five months.

There is more work to be done, but the end is in sight. The engineers are still working on transferring the code that controls the scientific data. But they know how to do this. They found the problem, figured out the workaround and are just grinding through the code transfer.

Mellstrom and Dodd are fully confident that Voyager 1 has been saved. Mellstrom said he can retire without regret.

“The spacecraft is working,” Dodd said. “Go Voyager!”

An earlier version of this story incorrectly said Jeffrey Mellstrom and Suzanne Dodd are married. They are married to other people. This story has been corrected.

NASA hears ‘heartbeat’ of Voyager 2 after losing communication

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The Voyager mission team at NASA has been able to detect a signal from Voyager 2 after losing contact with the spacecraft, which has been operating for nearly 46 years.

“We enlisted the help of the ( Deep Space Network ) and Radio Science groups to help to see if we could hear a signal from Voyager 2,” said Suzanne Dodd, Voyager’s project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California. “This was successful in that we see the ‘heartbeat’ signal from the spacecraft. So, we know the spacecraft is alive and operating. This buoyed our spirits.”

Commands sent to Voyager 2 on July 21 accidentally caused the spacecraft’s antenna to point 2 degrees away from Earth. The miniscule shift means that Voyager 2 can’t receive any commands from mission control or send data back to Earth from its location more than 12.3 billion miles (19.9 billion kilometers) in interstellar space.

The mission team was pleasantly surprised to be able to detect the spacecraft’s “carrier signal” using the Deep Space Network, an international array of massive radio antennas that allows NASA to communicate with missions across the cosmos.

Each of the three giant dishes are equidistant, meaning that one is always in communication with different spacecraft as Earth rotates. One radio antenna is located at Goldstone near Barstow, California, the second near Madrid, and the third near Canberra, Australia.

Now, the mission team will attempt to send a signal back to the spacecraft.

“We are now generating a new command to attempt to point the spacecraft antenna toward Earth,” Dodd said. “There is a low probability that this will work.”

‘Shouting’ into the cosmos

The signal, sent via the Deep Space Network, is basically an attempt to “shout” at Voyager 2 and try to get its attention, despite the fact that its antenna isn’t oriented in a way to receive the radio signal, according to NASA.

Given the distance between Voyager 2 and Earth, it takes about 18.5 hours for the signal to travel one way across the solar system to the spacecraft.

If the Earth-based signals don’t reach Voyager 2, the spacecraft is already programmed to reorient itself multiple times a year to keep its antenna pointing in Earth’s direction. The next reset was already scheduled for October 15, and the team is hopeful that this program will allow communications to resume with Voyager 2.

“But that is a long time to wait, so (we) will try sending up commands several times prior to that date,” Dodd said.

It’s not the first time that the aging twin probes, both launched in 1977, have experienced issues. As these “senior citizens” continue exploring the cosmos, the team has slowly turned off instruments to conserve power and extend their missions . Along the way, both Voyager 1 and 2 have encountered unexpected issues and dropouts, including a seven-month period where Voyager 2 and the Deep Space Network couldn’t communicate in 2020.

The team expects that Voyager 2 will remain on its planned trajectory, even without receiving commands. Meanwhile, Voyager 1, which is nearly 15 billion miles (24 billion kilometers) from Earth, continues to operate as expected and communicate with the Deep Space Network.

Both are in interstellar space and the only spacecraft to operate beyond the heliosphere, the sun’s bubble of magnetic fields and particles that extends well beyond the orbit of Pluto, collecting valuable data as they explore uncharted interstellar territory.

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Voyager 1 and Voyager 2

Where are they now.

Both Voyager 1 and Voyager 2 have reached "interstellar space" and each continue their unique journey deeper into the cosmos. In NASA's Eyes on the Solar System app, you can see the actual spacecraft trajectories of the Voyagers updated every five minutes.

Mission Status

Instrument status.

Voyager 1 Present Position

Voyager 2 present position, voyager's grand tour: 1977 - today.