voyager 1 2 wikipedia

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The Voyager missions

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

What are the Voyager missions?

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

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

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

How the Voyagers work

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

Jupiter findings

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

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

Saturn findings

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

Uranus and Neptune findings

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

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

Interstellar space

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

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

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

The golden records

Each Voyager spacecraft has a golden phonograph record affixed to its side, intended as time capsules from Earth to any extraterrestrial life that might find the probes sometime in the distant future. They are inscribed with a message from Jimmy Carter, the U.S. President at the time of launch, which reads: “This is a present from a small, distant world, a token of our sounds, our science, our images, our music, our thoughts and our feelings. We are attempting to survive our time so we may live into yours.”

The covers of the records have several images inscribed, including visual instructions on how to play them, a map of our solar system’s location with respect to a set of 14 pulsars, and a drawing of a hydrogen atom. They are plated with uranium – its rate of decay will allow any future discoverers of either of the records to calculate when they were created.

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

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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. 

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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Five Things About NASA's Voyager Mission

Here are five things you should know about NASA's twin Voyager 1 and 2 spacecraft, the longest continuously-operating spacecraft in deep space.

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First to visit all four giant planets

Voyager 2 is the only spacecraft to visit Uranus and Neptune. The probe is now in interstellar space, the region outside the heliopause, or the bubble of energetic particles and magnetic fields from the Sun.

Mission Type

What is Voyager 2?

NASA's Voyager 2 is the second spacecraft to enter interstellar space. On Dec. 10, 2018, the spacecraft joined its twin – Voyager 1 – as the only human-made objects to enter the space between the stars.

• Voyager 2 is the only spacecraft to study all four of the solar system's giant planets at close range.
• Voyager 2 discovered a 14th moon at Jupiter.
• Voyager 2 was the first human-made object to fly past Uranus.
• At Uranus, Voyager 2 discovered 10 new moons and two new rings.
• Voyager 2 was the first human-made object to fly by Neptune.
• At Neptune, Voyager 2 discovered five moons, four rings, and a "Great Dark Spot."

In Depth: Voyager 2

The two-spacecraft Voyager missions were designed to replace original plans for a “Grand Tour” of the planets that would have used four highly complex spacecraft to explore the five outer planets during the late 1970s.

NASA canceled the plan in January 1972 largely due to anticipated costs (projected at $1 billion) and instead proposed to launch only two spacecraft in 1977 to Jupiter and Saturn. The two spacecraft were designed to explore the two gas giants in more detail than the two Pioneers (Pioneers 10 and 11) that preceded them.

In 1974, mission planners proposed a mission in which, if the first Voyager was successful, the second one could be redirected to Uranus and then Neptune using gravity assist maneuvers.

Each of the two spacecraft was equipped with a slow-scan color TV camera to take images of the planets and their moons and each also carried an extensive suite of instruments to record magnetic, atmospheric, lunar, and other data about the planetary systems.

The design of the two spacecraft was based on the older Mariners, and they were known as Mariner 11 and Mariner 12 until March 7, 1977, when NASA Administrator James C. Fletcher (1919-1991) announced that they would be renamed Voyager.

Power was provided by three plutonium oxide radioisotope thermoelectric generators (RTGs) mounted at the end of a boom.

Voyager 2 at Jupiter

Voyager 2 began transmitting images of Jupiter April 24, 1979, for time-lapse movies of atmospheric circulation. Unlike Voyager 1, Voyager 2 made close passes to the Jovian moons on its way into the system, with scientists especially interested in more information from Europa and Io (which necessitated a 10 hour-long “volcano watch”).

During its encounter, it relayed back spectacular photos of the entire Jovian system, including its moons Callisto, Ganymede, Europa (at a range of about 127,830 miles or 205,720 kilometers, much closer than Voyager 1), Io, and Amalthea, all of which had already been surveyed by Voyager 1.

Voyager 2’s closest encounter to Jupiter was at 22:29 UT July 9, 1979, at a range of about 400,785 miles (645,000 kilometers). It transmitted new data on the planet’s clouds, its newly discovered four moons, and ring system, as well as 17,000 new pictures.

When the earlier Pioneers flew by Jupiter, they detected few atmospheric changes from one encounter to the second, but Voyager 2 detected many significant changes, including a drift in the Great Red Spot as well as changes in its shape and color.

With the combined cameras of the two Voyagers, at least 80% of the surfaces of Ganymede and Callisto were mapped out to a resolution of about 3 miles (5 kilometers).

Voyager 2 at Saturn

Following a course correction two hours after its closest approach to Jupiter, Voyager 2 sped to Saturn – its trajectory determined to a large degree by a decision made in January 1981, to try to send the spacecraft to Uranus and Neptune later in the decade.

Its encounter with the sixth planet began Aug. 22, 1981, two years after leaving the Jovian system, with imaging of the moon Iapetus. Once again, Voyager 2 repeated the photographic mission of its predecessor, although it actually flew about 14,290 miles (23,000 kilometers) closer to Saturn. The closest encounter to Saturn was at 01:21 UT Aug. 26, 1981, at a range of about 63,000 miles (101,000 kilometers).

The spacecraft provided more detailed images of the ring “spokes” and kinks, and also the F-ring and its shepherding moons, all found by Voyager 1. Voyager 2’s data suggested that Saturn’s A-ring was perhaps only about 980 feet (300 meters) thick.

As it flew behind and up past Saturn, the probe passed through the plane of Saturn’s rings at a speed of 8 miles per second (13 kilometers per second). For several minutes during this phase, the spacecraft was hit by thousands of micron-sized dust grains that created “puff” plasma as they were vaporized. Because the vehicle’s attitude was repeatedly shifted by the particles, attitude control jets automatically fired many times to stabilize the vehicle.

During the encounter, Voyager 2 also photographed the Saturn moons Hyperion (the “hamburger moon”), Enceladus, Tethys, and Phoebe, as well as the more recently discovered Helene, Telesto and Calypso.

Voyager 2 at Uranus

Although Voyager 2 had fulfilled its primary mission goals with the two planetary encounters, mission planners directed the veteran spacecraft to Uranus—a journey that would take about 4.5 years.

In fact, its encounter with Jupiter was optimized in part to ensure that future planetary flybys would be possible.

The Uranus encounter’s geometry was also defined by the possibility of a future encounter with Neptune: Voyager 2 had only 5.5 hours of close study during its flyby.

The first human-made object to fly past Uranus, Voyager 2's long-range observations of the planet began Nov. 4, 1985, when signals took approximately 2.5 hours to reach Earth. Light conditions were 400 times less than terrestrial conditions. Closest approach to Uranus took place at 17:59 UT Jan. 24, 1986, at a range of about 50,640 miles (81,500 kilometers).

During its flyby, Voyager 2 discovered 10 new moons (given such names as Puck, Portia, Juliet, Cressida, Rosalind, Belinda, Desdemona, Cordelia, Ophelia, and Bianca – obvious allusions to Shakespeare, continuing a naming tradition begun in 1787), two new rings in addition to the “older” nine rings, and a magnetic field tilted at 55 degrees off-axis and off-center.

The spacecraft found wind speeds in Uranus’ atmosphere as high as 450 miles per hour (724 kilometers per hour) and found evidence of a boiling ocean of water some 497 miles (800 kilometers) below the top cloud surface. Its rings were found to be extremely variable in thickness and opacity.

Voyager 2 also returned spectacular photos of Miranda, Oberon, Ariel, Umbriel, and Titania, five of Uranus’ larger moons. In flying by Miranda at a range of only 17,560 miles (28,260 kilometers), the spacecraft came closest to any object so far in its nearly decade-long travels. Images of the moon showed a strange object whose surface was a mishmash of peculiar features that seemed to have no rhyme or reason. Uranus itself appeared generally featureless.

The spectacular news of the Uranus encounter was interrupted the same week by the tragic Challenger accident that killed seven astronauts during their space shuttle launch Jan. 28, 1986.

Voyager 2 at Neptune

Following the Uranus encounter, the spacecraft performed a single midcourse correction Feb. 14, 1986 – the largest ever made by Voyager 2 – to set it on a precise course to Neptune.

Voyager 2’s encounter with Neptune capped a 4.3 billion-mile (7 billion-kilometer) journey when, on Aug. 25, 1989, at 03:56 UT, it flew about 2,980 miles (4,800 kilometers) over the cloud tops of the giant planet, the closest of its four flybys. It was the first human-made object to fly by the planet. Its 10 instruments were still in working order at the time.

During the encounter, the spacecraft discovered six new moons (Proteus, Larissa, Despina, Galatea, Thalassa, and Naiad) and four new rings.

The planet itself was found to be more active than previously believed, with 680-mile (1,100-kilometer) per hour winds. Hydrogen was found to be the most common atmospheric element, although the abundant methane gave the planet its blue appearance.

Images revealed details of the three major features in the planetary clouds – the Lesser Dark Spot, the Great Dark Spot, and Scooter.

Voyager photographed two-thirds of Neptune’s largest moon Triton, revealing the coldest known planetary body in the solar system and a nitrogen ice “volcano” on its surface. Spectacular images of its southern hemisphere showed a strange, pitted, cantaloupe-type terrain.

The flyby of Neptune concluded Voyager 2’s planetary encounters, which spanned an amazing 12 years in deep space, virtually accomplishing the originally planned “Grand Tour” of the solar system – at least in terms of targets reached, if not in science accomplished.

Voyager 2's Interstellar Mission

Once past the Neptune system, Voyager 2 followed a course below the ecliptic plane and out of the solar system. Approximately 35 million miles (56 million kilometers) past the encounter, Voyager 2’s instruments were put in low-power mode to conserve energy.

After the Neptune encounter, NASA formally renamed the entire project the Voyager Interstellar Mission (VIM).

Of the four spacecraft sent out to beyond the environs of the solar system in the 1970s, three of them – Voyagers 1 and 2 and Pioneer 11 – were all heading in the direction of the solar apex, i.e., the apparent direction of the Sun’s travel in the Milky Way galaxy, and thus would be expected to reach the heliopause earlier than Pioneer 10, which was headed in the direction of the heliospheric tail.

In November 1998, 21 years after launch, nonessential instruments were permanently turned off, leaving seven instruments still operating.

At 9.6 miles per second (15.4 kilometers per second) relative to the Sun, it will take about 19,390 years for Voyager 2 to traverse a single light year.

Asif Siddiqi

Beyond Earth: A Chronicle of Deep Space Exploration

Through the turn of the century, NASA's Jet Propulsion Laboratory (JPL) continued to receive ultraviolet and particle fields data. For example, on Jan. 12, 2001, an immense shock wave that had blasted out of the outer heliosphere on July 14, 2000, finally reached Voyager 2. During its six-month journey, the shock wave had plowed through the solar wind, sweeping up and accelerating charged particles. The spacecraft provided important information on high-energy shock-energized ions.

On Aug. 30, 2007, Voyager 2 passed the termination shock and then entered the heliosheath. By Nov. 5, 2017, the spacecraft was 116.167 AU (about 10.8 billion miles or about 17.378 billion kilometers) from Earth, moving at a velocity of 9.6 miles per second (15.4 kilometers per second) relative to the Sun, heading in the direction of the constellation Telescopium. At this velocity, it would take about 19,390 years to traverse a single light-year.

On July 8, 2019, Voyager 2 successfully fired up its trajectory correction maneuver thrusters and will be using them to control the pointing of the spacecraft for the foreseeable future. Voyager 2 last used those thrusters during its encounter with Neptune in 1989.

The spacecraft's aging attitude control thrusters have been experiencing degradation that required them to fire an increasing and untenable number of pulses to keep the spacecraft's antenna pointed at Earth. Voyager 1 had switched to its trajectory correction maneuver thrusters for the same reason in January 2018.

To ensure that both vintage robots continue to return the best scientific data possible from the frontiers of space, mission engineers are implementing a new plan to manage them. The plan involves making difficult choices, particularly about instruments and thrusters.

National Space Science Data Center: Voyager 2

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