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Voyager 2 illuminates boundary of interstellar space.

Anthony Greicius

Pushing through plasma, leaking particles, magnetic field mystery.

One year ago, on Nov. 5, 2018, NASA’s Voyager 2 became only the second spacecraft in history to leave the heliosphere — the protective bubble of particles and magnetic fields created by our Sun. At a distance of about 11 billion miles (18 billion kilometers) from Earth — well beyond the orbit of Pluto — Voyager 2 had entered interstellar space, or the region between stars. Today, five new research papers in the journal Nature Astronomy describe what scientists observed during and since Voyager 2’s historic crossing.

Each paper details the findings from one of Voyager 2’s five operating science instruments: a magnetic field sensor, two instruments to detect energetic particles in different energy ranges and two instruments for studying plasma (a gas composed of charged particles). Taken together, the findings help paint a picture of this cosmic shoreline, where the environment created by our Sun ends and the vast ocean of interstellar space begins.

The Sun’s heliosphere is like a ship sailing through interstellar space. Both the heliosphere and interstellar space are filled with plasma, a gas that has had some of its atoms stripped of their electrons. The plasma inside the heliosphere is hot and sparse, while the plasma in interstellar space is colder and denser. The space between stars also contains cosmic rays, or particles accelerated by exploding stars. Voyager 1 discovered that the heliosphere protects Earth and the other planets from more than 70% of that radiation.

When Voyager 2 exited the heliosphere last year , scientists announced that its two energetic particle detectors noticed dramatic changes: The rate of heliospheric particles detected by the instruments plummeted, while the rate of cosmic rays (which typically have higher energies than the heliospheric particles) increased dramatically and remained high. The changes confirmed that the probe had entered a new region of space.

Before Voyager 1 reached the edge of the heliosphere in 2012, scientists didn’t know exactly how far this boundary was from the Sun. The two probes exited the heliosphere at different locations and also at different times in the constantly repeating, approximately 11-year solar cycle, over the course of which the Sun goes through a period of high and low activity. Scientists expected that the edge of the heliosphere, called the heliopause, can move as the Sun’s activity changes, sort of like a lung expanding and contracting with breath. This was consistent with the fact that the two probes encountered the heliopause at different distances from the Sun.

The new papers now confirm that Voyager 2 is not yet in undisturbed interstellar space: Like its twin, Voyager 1, Voyager 2 appears to be in a perturbed transitional region just beyond the heliosphere.

“The Voyager probes are showing us how our Sun interacts with the stuff that fills most of the space between stars in the Milky Way galaxy,” said Ed Stone, project scientist for Voyager and a professor of physics at Caltech. “Without this new data from Voyager 2, we wouldn’t know if what we were seeing with Voyager 1 was characteristic of the entire heliosphere or specific just to the location and time when it crossed.”

The two Voyager spacecraft have now confirmed that the plasma in local interstellar space is significantly denser than the plasma inside the heliosphere, as scientists expected. Voyager 2 has now also measured the temperature of the plasma in nearby interstellar space and confirmed it is colder than the plasma inside the heliosphere.

In 2012, Voyager 1 observed a slightly higher-than-expected plasma density just outside the heliosphere, indicating that the plasma is being somewhat compressed. Voyager 2 observed that the plasma outside the heliosphere is slightly warmer than expected, which could also indicate it is being compressed. (The plasma outside is still colder than the plasma inside.) Voyager 2 also observed a slight increase in plasma density just before it exited the heliosphere, indicating that the plasma is compressed around the inside edge of the bubble. But scientists don’t yet fully understand what is causing the compression on either side.

If the heliosphere is like a ship sailing through interstellar space, it appears the hull is somewhat leaky. One of Voyager’s particle instruments showed that a trickle of particles from inside the heliosphere is slipping through the boundary and into interstellar space. Voyager 1 exited close to the very “front” of the heliosphere, relative to the bubble’s movement through space. Voyager 2, on the other hand, is located closer to the flank, and this region appears to be more porous than the region where Voyager 1 is located.

An observation by Voyager 2’s magnetic field instrument confirms a surprising result from Voyager 1: The magnetic field in the region just beyond the heliopause is parallel to the magnetic field inside the heliosphere. With Voyager 1, scientists had only one sample of these magnetic fields and couldn’t say for sure whether the apparent alignment was characteristic of the entire exterior region or just a coincidence. Voyager 2’s magnetometer observations confirm the Voyager 1 finding and indicate that the two fields align, according to Stone.   

The Voyager probes launched in 1977, and both flew by Jupiter and Saturn. Voyager 2 changed course at Saturn in order to fly by Uranus and Neptune, performing the only close flybys of those planets in history. The Voyager probes completed their Grand Tour of the planets and began their Interstellar Mission to reach the heliopause in 1989. Voyager 1, the faster of the two probes, is currently over 13.6 billion miles (22 billion kilometers) from the Sun, while Voyager 2 is 11.3 billion miles (18.2 billion kilometers) from the Sun. It takes light about 16.5 hours to travel from Voyager 2 to Earth. By comparison, light traveling from the Sun takes about eight minutes to reach Earth.

More information about Voyager is available at the following site:

https://voyager.jpl.nasa.gov/

Calla Cofield Jet Propulsion Laboratory, Pasadena, Calif. 626-808-2469 [email protected]

NASA's Voyager 2 Probe Enters Interstellar Space

For the second time in history, a human-made object has reached the space between the stars.

For the second time in history, a human-made object has reached the space between the stars. NASA's Voyager 2 probe now has exited the heliosphere - the protective bubble of particles and magnetic fields created by the Sun.

Members of NASA's Voyager team will discuss the findings at a news conference at 11 a.m. EST (8 a.m. PST) today at the meeting of the American Geophysical Union (AGU) in Washington. The news conference will stream live on the agency's website .

Comparing data from different instruments aboard the trailblazing spacecraft, mission scientists determined the probe crossed the outer edge of the heliosphere on Nov. 5. This boundary, called the heliopause, is where the tenuous, hot solar wind meets the cold, dense interstellar medium. Its twin, Voyager 1 , crossed this boundary in 2012, but Voyager 2 carries a working instrument that will provide first-of-its-kind observations of the nature of this gateway into interstellar space.

Voyager 2 now is slightly more than 11 billion miles (18 billion kilometers) from Earth. Mission operators still can communicate with Voyager 2 as it enters this new phase of its journey, but information - moving at the speed of light - takes about 16.5 hours to travel from the spacecraft to Earth. By comparison, light traveling from the Sun takes about eight minutes to reach Earth.

The most compelling evidence of Voyager 2's exit from the heliosphere came from its onboard Plasma Science Experiment ( PLS ), an instrument that stopped working on Voyager 1 in 1980, long before that probe crossed the heliopause. Until recently, the space surrounding Voyager 2 was filled predominantly with plasma flowing out from our Sun. This outflow, called the solar wind, creates a bubble - the heliosphere - that envelopes the planets in our solar system. The PLS uses the electrical current of the plasma to detect the speed, density, temperature, pressure and flux of the solar wind. The PLS aboard Voyager 2 observed a steep decline in the speed of the solar wind particles on Nov. 5. Since that date, the plasma instrument has observed no solar wind flow in the environment around Voyager 2, which makes mission scientists confident the probe has left the heliosphere.

"Working on Voyager makes me feel like an explorer, because everything we're seeing is new," said John Richardson, principal investigator for the PLS instrument and a principal research scientist at the Massachusetts Institute of Technology in Cambridge. "Even though Voyager 1 crossed the heliopause in 2012, it did so at a different place and a different time, and without the PLS data. So we're still seeing things that no one has seen before."

In addition to the plasma data, Voyager's science team members have seen evidence from three other onboard instruments - the cosmic ray subsystem, the low energy charged particle instrument and the magnetometer - that is consistent with the conclusion that Voyager 2 has crossed the heliopause. Voyager's team members are eager to continue to study the data from these other onboard instruments to get a clearer picture of the environment through which Voyager 2 is traveling.

"There is still a lot to learn about the region of interstellar space immediately beyond the heliopause," said Ed Stone, Voyager project scientist based at Caltech in Pasadena, California.

Together, the two Voyagers provide a detailed glimpse of how our heliosphere interacts with the constant interstellar wind flowing from beyond. Their observations complement data from NASA's Interstellar Boundary Explorer ( IBEX ), a mission that is remotely sensing that boundary. NASA also is preparing an additional mission - the upcoming Interstellar Mapping and Acceleration Probe ( IMAP ), due to launch in 2024 - to capitalize on the Voyagers' observations.

"Voyager has a very special place for us in our heliophysics fleet," said Nicola Fox, director of the Heliophysics Division at NASA Headquarters. "Our studies start at the Sun and extend out to everything the solar wind touches. To have the Voyagers sending back information about the edge of the Sun's influence gives us an unprecedented glimpse of truly uncharted territory."

While the probes have left the heliosphere, Voyager 1 and Voyager 2 have not yet left the solar system, and won't be leaving anytime soon. The boundary of the solar system is considered to be beyond the outer edge of the Oort Cloud , a collection of small objects that are still under the influence of the Sun's gravity. The width of the Oort Cloud is not known precisely, but it is estimated to begin at about 1,000 astronomical units (AU) from the Sun and to extend to about 100,000 AU. One AU is the distance from the Sun to Earth. It will take about 300 years for Voyager 2 to reach the inner edge of the Oort Cloud and possibly 30,000 years to fly beyond it.

The Voyager probes are powered using heat from the decay of radioactive material, contained in a device called a radioisotope thermal generator ( RTG ). The power output of the RTGs diminishes by about four watts per year, which means that various parts of the Voyagers, including the cameras on both spacecraft, have been turned off over time to manage power.

"I think we're all happy and relieved that the Voyager probes have both operated long enough to make it past this milestone," said Suzanne Dodd, Voyager project manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. "This is what we've all been waiting for. Now we're looking forward to what we'll be able to learn from having both probes outside the heliopause."

Voyager 2 launched in 1977, 16 days before Voyager 1, and both have traveled well beyond their original destinations. The spacecraft were built to last five years and conduct close-up studies of Jupiter and Saturn. However, as the mission continued, additional flybys of the two outermost giant planets, Uranus and Neptune, proved possible. As the spacecraft flew across the solar system, remote-control reprogramming was used to endow the Voyagers with greater capabilities than they possessed when they left Earth. Their two-planet mission became a four-planet mission. Their five-year lifespans have stretched to 41 years, making Voyager 2 NASA's longest running mission.

The Voyager story has impacted not only generations of current and future scientists and engineers, but also Earth's culture, including film, art and music. Each spacecraft carries a Golden Record of Earth sounds, pictures and messages. Since the spacecraft could last billions of years, these circular time capsules could one day be the only traces of human civilization.

Voyager's mission controllers communicate with the probes using NASA's Deep Space Network ( DSN ), a global system for communicating with interplanetary spacecraft. The DSN consists of three clusters of antennas inGoldstone, California; Madrid, Spain; and Canberra, Australia.

The Voyager Interstellar Mission is a part of NASA's Heliophysics System Observatory, sponsored by the Heliophysics Division of NASA's Science Mission Directorate in Washington. JPL built and operates the twin Voyager spacecraft. NASA's DSN, managed by JPL, is an international network of antennas that supports interplanetary spacecraft missions and radio and radar astronomy observations for the exploration of the solar system and the universe. The network also supports selected Earth-orbiting missions. The Commonwealth Scientific and Industrial Research Organisation, Australia's national science agency, operates both the Canberra Deep Space Communication Complex, part of the DSN, and the Parkes Observatory, which NASA has been using to downlink data from Voyager 2 since Nov. 8.

For more information about the Voyager mission, visit:

https://voyager.jpl.nasa.gov/

https://www.nasa.gov/voyager

More information about NASA's Heliophysics missions is available online at:

https://www.nasa.gov/sunearth

News Media Contact

Calla Cofield

Jet Propulsion Laboratory, Pasadena, Calif.

626-808-2469

[email protected]

Dwayne Brown / Karen Fox

202-358-1726 / 301-286-6284

[email protected] / [email protected]

How the Voyager Space Probes Work (Infographic)

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Voyager 1 and 2: The Interstellar Mission

An image of Neptune taken by the Voyager 2 spacecraft. Image credit: NASA

NASA has beautiful photos of every planet in our solar system. We even have images of faraway Neptune , as you can see in the photo above.

Neptune is much too distant for an astronaut to travel there with a camera. So, how do we have pictures from distant locations in our solar system? Our photographers were two spacecraft, called Voyager 1 and Voyager 2!

An artist’s rendering of one of the Voyager spacecraft. Image credit: NASA

The Voyager 1 and 2 spacecraft launched from Earth in 1977. Their mission was to explore Jupiter and Saturn —and beyond to the outer planets of our solar system. This was a big task. No human-made object had ever attempted a journey like that before.

The two spacecraft took tens of thousands of pictures of Jupiter and Saturn and their moons. The pictures from Voyager 1 and 2 allowed us to see lots of things for the first time. For example, they captured detailed photos of Jupiter's clouds and storms, and the structure of Saturn's rings .

Image of storms on Jupiter taken by the Voyager 1 spacecraft. Image credit: NASA

Voyager 1 and 2 also discovered active volcanoes on Jupiter's moon Io , and much more. Voyager 2 also took pictures of Uranus and Neptune. Together, the Voyager missions discovered 22 moons.

Since then, these spacecraft have continued to travel farther away from us. Voyager 1 and 2 are now so far away that they are in interstellar space —the region between the stars. No other spacecraft have ever flown this far away.

Where will Voyager go next?

Watch this video to find out what's beyond our solar system!

Both spacecraft are still sending information back to Earth. This data will help us learn about conditions in the distant solar system and interstellar space.

The Voyagers have enough fuel and power to operate until 2025 and beyond. Sometime after this they will not be able to communicate with Earth anymore. Unless something stops them, they will continue to travel on and on, passing other stars after many thousands of years.

Each Voyager spacecraft also carries a message. Both spacecraft carry a golden record with scenes and sounds from Earth. The records also contain music and greetings in different languages. So, if intelligent life ever find these spacecraft, they may learn something about Earth and us as well!

A photo of the golden record that was sent into space on both Voyager 1 and Voyager 2. Image credit: NASA/JPL-Caltech

More about our universe!

Where does interstellar space begin?

Searching for other planets like ours

Play Galactic Explorer!

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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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Major Accomplishments of NASA’s Voyager 1 and 2 Spacecraft

By Elizabeth Landau, Jet Propulsion Laboratory August 1, 2017

This montage of images of the planets visited by Voyager 2 was prepared from an assemblage of images taken by the 2 Voyager spacecraft. Credit: NASA/JPL

Below is a short list of the major accomplishments to date of NASA ’s groundbreaking Voyager 1 and 2 Spacecraft during their 40 years of exploration.

Planetary Firsts

Launched in 1977, the Voyagers delivered many surprises and discoveries from their encounters with the gas giants of the outer solar system: Jupiter , Saturn , Uranus and Neptune . Between 1977 and 1990, the mission attained these distinctions:

• First spacecraft to fly by all four planets of the outer solar system (Voyager 2)
• 3 new moons at Jupiter
• 4 new moons at Saturn
• 11 new moons at Uranus
• 6 new moons at Neptune
• First spacecraft to fly by four different target planets (Voyager 2)
• First spacecraft to visit Uranus and Neptune (Voyager 2)
• First spacecraft to image the rings of Jupiter, Uranus and Neptune (Voyager 2)
• First spacecraft to discover active volcanoes beyond Earth (on Jupiter’s moon Io — Voyager 1)
• First spacecraft to detect lightning on a planet other than Earth (at Jupiter — Voyager 1)
• First spacecraft to find suggestions of an ocean beyond Earth (at Jupiter’s moon Europa — both spacecraft)
• First spacecraft to detect a nitrogen-rich atmosphere found beyond our home planet (at Saturn’s moon Titan — Voyager 1)

Heliophysics Firsts

After Voyager 1 departed from Saturn in November 1980, it began a journey to where no human-made object had ever gone before: the space between the stars. On August 25, 2012, it crossed over into interstellar space, leaving behind the heliosphere — the enormous magnetic bubble encompassing our Sun, planets, and solar wind. Voyager 2 set course for interstellar space after departing from Neptune in August 1989, and is expected to enter interstellar space in the next few years. Together the Voyagers have taught us a great deal about the extent of our sun’s influence and the very nature of the space that lies beyond our planets.

• First spacecraft to leave the heliosphere and enter interstellar space (Voyager 1)
• First spacecraft to measure full intensity of cosmic rays — atoms accelerated to nearly the speed of light — in interstellar space (Voyager 1)
• First spacecraft to measure magnetic field in interstellar space (Voyager 1)
• First spacecraft to measure density of interstellar medium — material ejected by ancient supernovae (Voyager 1)
• First spacecraft to measure solar wind termination shock — the boundary where solar wind charged particles slow below the speed of sound as they begin to press into the interstellar medium (Voyager 2)

Engineering and Computing Firsts and Records

The Voyagers, which launched with nearly identical configurations and instruments, were designed to withstand the harsh radiation environment of Jupiter — the greatest physical challenge they would ever encounter. Preparations for the peril at Jupiter ensured that the Voyagers would be well-equipped for the rest of their journeys, too. Engineering and computing advances that the Voyagers debuted set the stage for future missions.

• First spacecraft extensively protected against radiation, which also set the standard for radiation design margin still in use for space missions today
• First spacecraft protected against external electrostatic discharges
• First spacecraft with programmable computer-controlled attitude and articulation (which means the pointing of the spacecraft)
• First spacecraft with autonomous fault protection, able to detect its own problems and take corrective action
• First use of Reed-Solomon code for spacecraft data — an algorithm to reduce errors in data transmission and storage, which is widely used today
• First time engineers linked ground communications antennas together in an array to be able to receive more data (for Voyager 2’s Uranus encounter)

Beyond that, the Voyager spacecraft continue setting endurance and distance records:

• Longest continuously operating spacecraft (Voyager 2, which passed Pioneer 6’s record on August 13, 2012)
• Most distant spacecraft from the Sun (Voyager 1, which passed Pioneer 10’s distance on February 17, 1998 and is currently about 13 billion miles, or 21 billion kilometers, away)

The Voyager spacecraft were built by NASA’s Jet Propulsion Laboratory, Pasadena, California, which continues to operate both. JPL is a division of Caltech in Pasadena. The Voyager missions are a part of the NASA Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate in Washington.

More on SciTechDaily

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Voyager 2 Illuminates Boundary of Interstellar Space 11 Billion Miles From Earth

Voyager 2 Probe Enters Interstellar Space, Over 18 Billion Kilometers from Earth

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Great Craft ! Great contribution.. The twin Voyager 1 and 2 spacecraft are exploring where nothing from Earth has flown before. Continuing on their more-than-40-year journey Regards Dav

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Voyager 1 & 2

• Launched on September 5, 1977
• Surveyed the Jupiter and Saturn systems
• First spacecraft to reach interstellar space
• RTGs still operating
• Currently exploring beyond our solar system
• Launched on August 20, 1977
• Only spacecraft to visit Jupiter, Saturn, Uranus and Neptune
• Currently exploring the edge of the solar system

Each powered by:

• 3 Multi-Hundred Watt (MHW) RTGs stacked in a series on a boom, producing about 158 W e each, at launch.

As the electrical power decreases, power loads on the spacecraft must be turned off in order to avoid having demand exceed supply. As loads are turned off, some spacecraft capabilities are eliminated.

Voyager Goals & Accomplishments

Voyager 1 and 2 were designed to take advantage of a rare planetary alignment to explore the outer solar system. Voyager 1 targeted Jupiter and Saturn before continuing on to chart the far edges of our solar system. Voyager 2 targeted Jupiter, Saturn, Uranus and Neptune before joining its sister probe on their interstellar mission.

Voyager proved to be one of the greatest missions of discovery in history. Among their many revelations about the solar system are:

• Rings around Jupiter
• Volcanoes on Jupiter's moon Io
• Moons of Saturn that shepherd its rings
• New moons around Uranus and Neptune
• Geysers of liquid nitrogen on Neptune's moon Triton
• Revealed and crossed the farthest boundary of our solar system

Voyager 2 is the only spacecraft to study all four of the solar system's giant planets at close range. The Voyagers are now exploring the outermost reaches of our sun's influence, where the solar wind mixes with the interstellar wind of our galaxy. Their long-lived power source has enabled these explorers to continue teaching us about our solar system for more than years after they left earth.

• Go to Voyager Homepage
• Go to Voyager Image Gallery
• Status: Where are the Voyagers?

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Voyager 1 and 2, Humanity’s Interstellar Envoys, Soldier On at 45

Today is the 45th anniversary of the launch of Voyager 1, one of humanity’s iconic twin emissaries to the cosmos. (Its sibling, Voyager 2, launched a couple of weeks earlier.) Now in the dark, far reaches of interstellar space—more than 10 billion miles from home, where our sun looks like any other bright star—the pair are still doing science. They carry with them the Golden Records, bearing the sounds and symbols of Earth, should some extraterrestrial ever rendezvous with one of the spacecraft and become curious about its distant sender.

“I’ve been following the arc of Voyager over my career,” says Linda Spilker, Voyager’s deputy project scientist at NASA’s Jet Propulsion Laboratory, who started at the agency in 1977, the year the probes launched. “I’m amazed at how long both of these spacecraft, Voyager 1 and Voyager 2, have been able to keep going and return unique science about new places that no spacecraft has visited before. And now they’ve become interstellar travelers. How cool is that?”

The two car-sized probes, each with a 12-foot antenna mounted on top, had one primary task: to visit the gas giants in our own solar system. After their launches, the Voyagers’ paths diverged, but they both took advantage of a rare planetary lineup, snapping groundbreaking photos as they flew by Jupiter, Saturn, Uranus, and Neptune and revealed tantalizing details about the planets’ moons. By the end of 1989, they’d completed that mission. In 1990, Voyager 1 capped it by turning around and taking a poignant image of our own world, which astronomer and science communicator Carl Sagan dubbed the Pale Blue Dot .  

“Look 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, has lived out their lives,” Sagan wrote. The image of the Earth from a cosmic perspective—a mere “mote of dust suspended in a moonbeam,” as he put it—became nearly as memorable as the Earthrise photo taken by an Apollo 8 astronaut showing the planet as seen from the moon.

The two probes, which run on nuclear-powered systems called radioisotope thermoelectric generators (RTGs), kept flying. Our solar system has no clear boundary, but in the 2000s they crossed the “termination shock,” where solar wind particles abruptly slow below the speed of sound due to pressure from the gas and magnetic fields in interstellar space. Then in the 2010s, they breached the heliopause, the boundary between the solar wind and the interstellar wind. 

With four instruments operating on Voyager 1 and five aboard Voyager 2, they now have a new job: measuring the magnetic field strength, the density of the plasma, and the energy and direction of charged particles in the environment they’re traveling through. “The purpose of the interstellar mission is to measure the sun’s effects as we go further and further from Earth. We’re trying to find out how the sun’s heliosphere interacts with interstellar space,” says Suzanne Dodd, project manager of the Voyager interstellar mission at JPL. Voyager 1 is currently 14.6 billion miles from home, and Voyager 2 is 12.1 billion miles away, but for perspective, the nearest star is some 25 trillion miles away. (NASA maintains a tracker of their journeys .) It’s a remarkable coda for their mission, decades after the probes completed their main goals. 

Andy Greenberg

Matt Burgess

Caroline Haskins

Jessica Rawnsley

But they’ve always had a secondary task: conveying a message to any aliens from beyond the solar system who might one day peek inside a craft. Each one carries a Golden Record, which looks like vinyl but is made of metal. A team of scientists and artists, including Sagan and Frank Drake , who died last Friday, packed music, nature sounds, messages, photos, and more on each record—and they included players and instructions, should anyone find them. The ambitious project seeks to tell a story about humanity, what humans aspire to, and our world. It includes the music of Bach and Chuck Berry, and images of families, homes, and scientific advances. “The purpose of the record was to try to answer questions that we would have,” says Jon Lomberg, a scientific artist and the designer for the Golden Records team. “What were the beings like who sent it? What do they look like? What do they act like? What was their world like? So it’s really a self-portrait.”

Unlike the search for extraterrestrial intelligence , or SETI, the records are not designed to be a prelude to first contact. In fact, the Golden Records might be found millions of years from now, perhaps when human civilizations no longer exist. “It’s more like finding a fossil,” says Lomberg. “You can’t talk to the dinosaurs. This is a relic—our obituary in a way, the memento that we were once here.”

The Voyager probes were preceded by the Pioneer missions, which carried small metal plaques with symbolic messages . (The pair of Pioneers left the solar system in the 1980s and ’90s, but they’re no longer functioning.) But no space mission since has incorporated a similar record of humanity—though NASA’s New Horizons , for example, which flew by Pluto in 2015, offered another chance. That was a missed opportunity, Lomberg says, although it might still be possible to send a digital message to the spacecraft’s computer. That would be durable, but it would not last as long as the Golden Records.

The Voyagers have had a tangible influence on space exploration ever since. Their success inspired NASA and other agencies to revisit the outer planets, especially Jupiter and Saturn, and their myriad moons. These subsequent missions include Galileo , Juno , Cassini , and the European Space Agency’s Huygens lander, plus new probes in the works, such as the Europa Clipper , Dragonfly , ESA’s JUICE, and potential voyages to Uranus and Saturn’s moon Enceladus .

The Voyagers influenced pop culture too. The first Star Trek movie in 1979 included an alien spacecraft called “V’ger,” which was actually an altered fictional “Voyager 6.” Voyager and the Golden Records have turned up in TV shows like Saturday Night Live , The West Wing , and—of course— The X-Files . The composer Dario Marianelli even wrote a Voyager-inspired violin concerto.

The pair of spacecraft have lasted far longer than anyone imagined—and, Dodd says, the instruments are working and the data is still great. But they’re showing signs of age. In May, she and her team encountered a glitch in Voyager 1’s telemetry data, which would normally provide information to scientists back home about what the probe’s instruments are doing and whether they’re working properly. The data had been coming back garbled. Addressing the issue was complicated by the vast distance involved, since messages to and from Voyager 1 now take nearly 22 hours. 

Then last week, the team figured out what was wrong. Apparently, the attitude control system had suddenly started sending the telemetry data through the wrong computer, which was no longer working properly. They resolved the problem by routing the data back to the correct computer. “The spacecraft is healthy, it’s happy. It’s returning science data just beautifully,” Spilker says.

Even if Dodd, Spilker, and their colleagues can keep resolving these kinds of technical issues, however, the spacecraft have a more enduring problem: their power supplies. Their RTG systems provide power by converting heat from the radioactive decay of plutonium-238 into electricity. But after 45 years, the fuel is now generating 4 watts less per year. Dodd and her team have turned off any systems and instruments not involved in the interstellar mission—and in 2019, they started turning off heaters in some of the instruments that are still running. That added a couple of years to the spacecrafts’ lifespans.

Nevertheless, the Voyager probes might only have a few years, or perhaps a decade, left in them. Eventually, their dwindling power won’t be sufficient to run their instruments. “At that point, the Voyagers will become our silent ambassadors,” Spilker says.

As they hurtle at 35,000 miles per hour into the unknown with their powered-down machines, they will still carry humanity’s message in a bottle. “The Golden Record, a piece of human civilization, a piece of technology with a 1970s stamp on it—that is going to persevere. It’s not degrading. It’s going to last for billions of years. It’s going to outlast the planet that it came from. That’s mind-blowing kind of stuff,” says Jim Bell, a planetary scientist at Arizona State University and the author of a book on the Voyager mission’s 40th anniversary.

Bell speculates that it might not be aliens, but our own descendants, who ultimately spot the far-flung spacecraft. “My prediction is that the message really is going to be for us. We’re going to be the ones who go find it—in the far future, when it becomes easy to travel and be tourists and see the Voyagers,” he says. “We’ll be thinking: Wasn’t that one of the most amazing things we did as a species in the 20th century?”

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• The Contents
• The Making of
• Where Are They Now

Frequently Asked Questions

• Q & A with Ed Stone

golden record

Where are they now.

• frequently asked questions
• Q&A with Ed Stone

Can the Voyager imaging cameras be turned back on?

What instruments on the spacecraft are still working and what have been turned off?

How long can Voyager 1 and 2 continue to function?

Voyager 1 is expected to keep its current suite of science instruments on through 2021. Voyager 2 is expected to keep its current suite of science instruments on through 2020.

The radioisotope thermoelectric generator on each spacecraft puts out 4 watts less each year. Because of this diminishing electrical power, the Voyager team has had to prioritize which instruments to keep on and which to turn off. Heaters and other spacecraft systems have also been turned off one by one as part of power management.

The Voyager team has chosen to keep operating the instruments that are the most likely to send back key data about the heliosphere and interstellar space -- the fields and particles instruments. Engineers expect to begin turning off fields and particles science instruments one by one, starting in 2020 for Voyager 2. Voyager 2 will have to start turning science instruments off sooner because it is currently operating one more instrument than Voyager 1. Engineers expect each spacecraft to continue operating at least one science instrument until around 2025.

Even if science data won't likely be collected after 2025, engineering data could continue to be returned for several more years. The two Voyager spacecraft could remain in the range of the Deep Space Network through about 2036, depending on how much power the spacecraft still have to transmit a signal back to Earth.

Where are Voyager 1 and 2 today? How do they compare to other spacecraft on an outbound trajectory?

Where is Voyager 1 going? When will it get there? How about Voyager 2?

Where do we consider our solar system to end; Pluto's orbit? Solar apex?

Have any human-made objects ever exited the solar system?

Are the distance counters rolling backwards?

Did either of the Voyagers visit Pluto? Why didn't the Voyagers fly by Pluto?

When we send spacecraft through the asteroid belt to the outer planets, how do we navigate the craft through the belt?

I was reading Dr. Carl Sagan's biography recently and found that he persuaded NASA administrators to turn one of the Voyager space probes around in order to take a last image of the solar system. Is this true? Do the craft send back any images of where they are?

I can not locate a copy of the Murmurs of Earth CD. Would you know of a vendor that might sell copies of it?

Who was on the committee with Dr. Sagan regarding the development of the Golden Record? Both American or foreign scientists?

If there is intelligent life in our universe and they were not a peace loving species, wouldn't the information on the Voyager be enough to destroy human kind?

What were the most important discoveries of the Voyager space probes?

How big is Voyager? How much does it weigh?

Is it true that a sketch by Da Vinci is included in the "Message to the Universe" of Voyagers 1 and 2?

What kind of computers are used on the Voyager spacecraft?

How fast are the Voyager computers?

What is the "direction" (constellation and/or star) both VOYAGER 1 & 2 and the Pioneers are "aimed" for, at present.

Where can I find pictures of what the Voyager spacecraft took?

Is there some sort of plate with pictograms on the Voyager 1 spacecraft? Also is it similar to the Pioneer spacecraft plaque?

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Hope returns —

Nasa knows what knocked voyager 1 offline, but it will take a while to fix, "engineers are optimistic they can find a way for the fds to operate normally.".

Stephen Clark - Apr 6, 2024 12:28 am UTC

Engineers have determined why NASA's Voyager 1 probe has been transmitting gibberish for nearly five months, raising hopes of recovering humanity's most distant spacecraft.

Voyager 1, traveling outbound some 15 billion miles (24 billion km) from Earth, started beaming unreadable data down to ground controllers on November 14. For nearly four months, NASA knew Voyager 1 was still alive—it continued to broadcast a steady signal—but could not decipher anything it was saying.

Confirming their hypothesis, engineers at NASA's Jet Propulsion Laboratory (JPL) in California confirmed a small portion of corrupted memory caused the problem. The faulty memory bank is located in Voyager 1's Flight Data System (FDS), one of three computers on the spacecraft. The FDS operates alongside a command-and-control central computer and another device overseeing attitude control and pointing.

The FDS duties include packaging Voyager 1's science and engineering data for relay to Earth through the craft's Telemetry Modulation Unit and radio transmitter. According to NASA, about 3 percent of the FDS memory has been corrupted, preventing the computer from carrying out normal operations.

Optimism growing

Suzanne Dodd, NASA's project manager for the twin Voyager probes, told Ars in February that this was one of the most serious problems the mission has ever faced. That is saying something because Voyager 1 and 2 are NASA's longest-lived spacecraft. They launched 16 days apart in 1977, and after flying by Jupiter and Saturn, Voyager 1 is flying farther from Earth than any spacecraft in history. Voyager 2 is trailing Voyager 1 by about 2.5 billion miles, although the probes are heading out of the Solar System in different directions.

Normally, engineers would try to diagnose a spacecraft malfunction by analyzing data it sent back to Earth. They couldn't do that in this case because Voyager 1 has been transmitting data packages manifesting a repeating pattern of ones and zeros. Still, Voyager 1's ground team identified the FDS as the likely source of the problem.

The Flight Data Subsystem was an innovation in computing when it was developed five decades ago. It was the first computer on a spacecraft to use volatile memory. Most of NASA's missions operate with redundancy, so each Voyager spacecraft launched with two FDS computers. But the backup FDS on Voyager 1 failed in 1982.

Due to the Voyagers' age, engineers had to reference paper documents, memos, and blueprints to help understand the spacecraft's design details. After months of brainstorming and planning, teams at JPL uplinked a command in early March to prompt the spacecraft to send back a readout of the FDS memory.

The command worked, and Voyager1 responded with a signal different from the code it had been transmitting since November. After several weeks of meticulous examination of the new code, engineers pinpointed the location of the bad memory.

"The team suspects that a single chip responsible for storing part of the affected portion of the FDS memory isn’t working," NASA said in an update posted Thursday. "Engineers can’t determine with certainty what caused the issue. Two possibilities are that the chip could have been hit by an energetic particle from space or that it simply may have worn out after 46 years."

Voyager 1's distance from Earth complicates the troubleshooting effort. The one-way travel time for a radio signal to reach Voyager 1 from Earth is about 22.5 hours, meaning it takes roughly 45 hours for engineers on the ground to learn how the spacecraft responded to their commands.

NASA also must use its largest communications antennas to contact Voyager 1. These 230-foot-diameter (70-meter) antennas are in high demand by many other NASA spacecraft , so the Voyager team has to compete with other missions to secure time for troubleshooting. This means it will take time to get Voyager 1 back to normal operations.

"Although it may take weeks or months, engineers are optimistic they can find a way for the FDS to operate normally without the unusable memory hardware, which would enable Voyager 1 to begin returning science and engineering data again," NASA said.

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Engineers Pinpoint Cause of Voyager 1 Issue, Are Working on Solution

Engineers have confirmed that a small portion of corrupted memory in one of the computers aboard NASA’s Voyager 1 has been causing the spacecraft to send unreadable science and engineering data to Earth since last November. Called the flight data subsystem (FDS), the computer is responsible for packaging the probe’s science and engineering data before the telemetry modulation unit (TMU) and radio transmitter send the data to Earth.

In early March , the team issued a “poke” command to prompt the spacecraft to send back a readout of the FDS memory, which includes the computer’s software code as well as variables (values used in the code that can change based on commands or the spacecraft’s status). Using the readout, the team has confirmed that about 3% of the FDS memory has been corrupted, preventing the computer from carrying out normal operations.

The team suspects that a single chip responsible for storing part of the affected portion of the FDS memory isn’t working. Engineers can’t determine with certainty what caused the issue. Two possibilities are that the chip could have been hit by an energetic particle from space or that it simply may have worn out after 46 years.

Although it may take weeks or months, engineers are optimistic they can find a way for the FDS to operate normally without the unusable memory hardware, which would enable Voyager 1 to begin returning science and engineering data again.

Launched in 1977 , the twin Voyager spacecraft flew by Saturn and Jupiter, and Voyager 2 flew by Uranus and Neptune. They are both exploring interstellar space, outside the bubble of particles and magnetic fields created by the Sun, called the heliosphere. Voyager 2 continues to operate normally.

News Media Contact Calla Cofield Jet Propulsion Laboratory, Pasadena, Calif. 626-808-2469 [email protected]

NASA Decodes the Reason Behind Voyager 1's Garbled Transmissions

For months, NASA's Voyager team has been struggling to translate garbled messages from beyond our solar system. Voyager 1 has been responding to NASA's data requests with tangles of 1s and 0s, none of which have made sense to anyone at the agency. But now, thanks to a "poke command" issued in March, the spacecraft seems to have helped scientists identify the error behind its wonky transmissions. 

NASA had just managed to solve an issue with Voyager 1's attitude articulation and control system (AACS) in 2022 when a new glitch arose, jumbling the probe's flight data. This raw data is supposed to convey information about what Voyager 1's various scientific instruments have gleaned from remote regions of the Milky Way, but instead, it was just a mysterious stream of unintelligible numbers. Getting the spacecraft to return to its original "language" has been a challenge ever since, in part because most of the folks who originally worked on Voyager 1 are no longer alive .

In March, NASA sent Voyager 1 a poke command, or a command that directly modifies a system's memory addresses. Though poke commands are a fairly antiquated concept, they're occasionally useful for low-level memory control—a stone the Voyager team couldn't leave unturned. Their command prompted Voyager 1's system into using a different readout sequence for its software package than it typically defaults to, and about 22 hours later, NASA found itself with a new clue.

According to a Voyager mission blog post , activity from one portion of Voyager 1's flight data system (FDS) stood out from the probe's previous unreadable transmissions. A single engineer involved in NASA's Deep Space Network saw that the data contained a readout of Voyager 1's full FDS memory. This, the engineer noticed, offered the team an opportunity to compare and contrast Voyager 1's previous FDS readout with the latest snapshot of its inner workings.   

NASA has since used the decoded readout to determine that roughly 3 percent of the probe's memory is corrupted. This may explain why restarting the FDS didn't resolve the issue back in November: If a system's memory has degraded, turning that system off and back on again won't do anything to bring it back. Luckily, engineers at the Voyager mission think the corruption is confined to just one chip, which could make the issue easier to circumvent or resolve. 

NASA Voyager 2 Could Be Nearing Interstellar Space

NASA's Voyager 2 probe, currently on a journey toward interstellar space, has detected an increase in cosmic rays that originate outside our solar system. Launched in 1977, Voyager 2 is a little less than 11 billion miles (about 17.7 billion kilometers) from Earth, or more than 118 times the distance from Earth to the Sun.

Since 2007 the probe has been traveling through the outermost layer of the heliosphere -- the vast bubble around the Sun and the planets dominated by solar material and magnetic fields. Voyager scientists have been watching for the spacecraft to reach the outer boundary of the heliosphere, known as the heliopause. Once Voyager 2 exits the heliosphere, it will become the second human-made object, after Voyager 1, to enter interstellar space.

Since late August, the Cosmic Ray Subsystem instrument on Voyager 2 has measured about a 5 percent increase in the rate of cosmic rays hitting the spacecraft compared to early August. The probe's Low-Energy Charged Particle instrument has detected a similar increase in higher-energy cosmic rays.

Cosmic rays are fast-moving particles that originate outside the solar system. Some of these cosmic rays are blocked by the heliosphere, so mission planners expect that Voyager 2 will measure an increase in the rate of cosmic rays as it approaches and crosses the boundary of the heliosphere.

In May 2012, Voyager 1 experienced an increase in the rate of cosmic rays similar to what Voyager 2 is now detecting. That was about three months before Voyager 1 crossed the heliopause and entered interstellar space.

However, Voyager team members note that the increase in cosmic rays is not a definitive sign that the probe is about to cross the heliopause. Voyager 2 is in a different location in the heliosheath -- the outer region of the heliosphere -- than Voyager 1 had been, and possible differences in these locations means Voyager 2 may experience a different exit timeline than Voyager 1.

The fact that Voyager 2 may be approaching the heliopause six years after Voyager 1 is also relevant, because the heliopause moves inward and outward during the Sun's 11-year activity cycle. Solar activity refers to emissions from the Sun, including solar flares and eruptions of material called coronal mass ejections. During the 11-year solar cycle, the Sun reaches both a maximum and a minimum level of activity.

"We're seeing a change in the environment around Voyager 2, there's no doubt about that," said Voyager Project Scientist Ed Stone, based at Caltech in Pasadena. "We're going to learn a lot in the coming months, but we still don't know when we'll reach the heliopause. We're not there yet -- that's one thing I can say with confidence."

The Voyager spacecraft were built by NASA's Jet Propulsion Laboratory in Pasadena, California, which continues to operate both. JPL is a division of Caltech. The Voyager missions are a part of the NASA Heliophysics System Observatory, managed by the Heliophysics Division of the Science Mission Directorate in Washington.

For more information about the Voyager spacecraft, visit:

• https://www.nasa.gov/voyager
• https://voyager.jpl.nasa.gov

News Media Contacts Calla Cofield Jet Propulsion Laboratory, Pasadena, Calif. 626-808-2469 [email protected] Jia-Rui Cook Jet Propulsion Laboratory, Pasadena, Calif. 818-354-0724 [email protected] Karen Fox NASA Headquarters, Washington 301-286-6284 [email protected]

News Release: 2018-232

Engineers attempt to fix a computer glitch on Voyager 1

Voyager 1's system that sends data home is malfunctioning, preventing the computer from operating as it should.

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Last November, the Voyager 1 spacecraft began sending gibberish radio signals back to Earth. Engineers have now identified the problem, but trying to repair a 46-year-old device on a craft 24 billion kilometres from Earth is not easy.

Voyager 1 and its twin Voyager 2 were both launched in 1977 on a reconnaissance mission to Jupiter and Saturn. They were designed to fly past the giant planets to obtain closeup images of those distant worlds and their myriad of moons.

Both spacecraft performed beyond expectations, discovering many new moons — some covered in ice , one with active volcanoes , another with a thick atmosphere and closeup details of Saturn's rings .  

Following the Saturn encounter, Voyager 1 was flung upwards by Saturn's gravity on a trajectory northward, above the orbital plane in which most of the planets orbit the Sun, out of our solar system. NASA extended its mission and from there it went on to become the first human-made object to venture into interstellar space in 2012. 

Voyager 2, however, was aimed toward Uranus and Neptune, which were conveniently positioned in a rare alignment with Jupiter and Saturn making it the only spacecraft to visit those distant worlds.

Following the grand tour of the outer solar system, Voyager 2 was also tossed out toward interstellar space in 2018 when its mission was extended and where it continues on its journey today. 

• After a 42-year journey, Voyager 2 goes interstellar
• Voyager 1 picks up the 'hum' of interstellar space

While their primary missions were over, both spacecraft were still in good health, thanks largely to their nuclear power sources or Radioisotope Thermoelectric Generators (RTG). These containers hold small amounts of plutonium which provide heat that is turned directly into electricity with no moving parts. They have an expected lifetime of around 50 years and have kept the Voyagers' instruments running.

Now, as both spacecraft continue their journey through the space between the stars, they are showing signs of their age.

For Voyager 1, the problem seems to be in the flight data subsystem (FDS) that packages data from the scientific instruments for transmission to Earth. The scientists don't know if the faulty module was corrupted by cosmic rays or just worn out, but they say they're optimistic they may be able to work around the problem, although it will take some time.

Engineers have confirmed that corrupted memory aboard my twin <a href="https://twitter.com/hashtag/Voyager1?src=hash&amp;ref_src=twsrc%5Etfw">#Voyager1</a> has been causing it to send unreadable data to Earth. It may take months, but our team is optimistic they can find a way for the FDS to operate normally again: <a href="https://t.co/qe5iQUu4Oj">https://t.co/qe5iQUu4Oj</a> <a href="https://t.co/AGFBZFz53v">https://t.co/AGFBZFz53v</a> &mdash; @NASAVoyager

The challenge is that the computers were built in the 1970s using old code and send data very slowly by today's standards.

In addition, these computers are so deep in space, it takes 22.5 hours for a radio signal from Voyager 1 to reach Earth. That means the controllers on the ground have to wait 45 hours for each two-way communication with the spacecraft.

Given how very, very far they are from home, if something goes wrong with them, it's up to engineers on the ground to fix it by sending radio signals since reaching them for repair missions isn't possible. We're a long way from the fictional warp drive and sub-space communication that made life so easy on the Starship Enterprise of Star Trek fame. 

The twin Voyagers are now the most distant objects ever sent from Earth; a demonstration of how vast space is and how slow our spacecraft are. In 1977, I attended the launch of Voyager 2 when my hair was black and skin was smooth. This one mission with Voyager 1 and 2 has occupied a good chunk of my lifetime.

In another few years, the RTGs on both Voyagers are expected to run down to the point where the spacecraft will no longer be able to communicate with Earth. They will just continue to drift in silence among the stars of the Milky Way for billions of years. 

However, there is one item on both Voyagers that will continue to function, the Golden Record, which carries a message from Earth to anyone out there who may find the spacecraft in the future.

The chances of them being found are astronomically small, but they will become the longest running experiment in human history.

ABOUT THE AUTHOR

Bob McDonald is the host of CBC Radio's award-winning weekly science program, Quirks & Quarks. He is also a science commentator for CBC News Network and CBC TV's The National. He has received 12 honorary degrees and is an Officer of the Order of Canada.

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