voyager 1 edge of solar system

Voyager 1 Now Most Distant Human-Made Object in Space 

In a dark, cold, vacant neighborhood near the very edge of our solar system, the Voyager 1 spacecraft is set to break another record and become the explorer that has traveled farthest from home.

At approximately 2:10 p.m. Pacific time on February 17, 1998, Voyager 1, launched more than two decades ago, will cruise beyond the Pioneer 10 spacecraft and become the most distant human-created object in space at 10.4 billion kilometers (6.5 billion miles.) The two are headed in almost opposite directions away from the Sun. As with other spacecraft traveling past the orbit of Mars, both Voyager and Pioneer derive their electrical power from onboard nuclear batteries.

"For 25 years, the Pioneer 10 spacecraft led the way, pressing the frontiers of exploration, and now the baton is being passed from Pioneer 10 to Voyager 1 to continue exploring where no one has gone before," said Dr. Edward C. Stone, Voyager project scientist and director of NASA's Jet Propulsion Laboratory.

"At almost 70 times farther from the Sun than the Earth, Voyager 1 is at the very edge of the Solar System. The Sun there is only 1/5,000th as bright as here on Earth -- so it is extremely cold and there is very little solar energy to keep the spacecraft warm or to provide electrical power. The reason we can continue to operate at such great distances from the Sun is because we have radioisotope thermal electric generators (RTGs) on the spacecraft that create electricity and keep the spacecraft operating," Stone said. "The fact that the spacecraft is still returning data is a remarkable technical achievement."

Voyager 1 was launched from Cape Canaveral on September 5, 1977. The spacecraft encountered Jupiter on March 5, 1979, and Saturn on November 12, 1980.

Then, because its trajectory was designed to fly close to Saturn's large moon Titan, Voyager 1's path was bent northward by Saturn's gravity, sending the spacecraft out of the ecliptic plane - the plane in which all the planets except Pluto orbit the Sun.

Launched on March 2, 1972, the Pioneer 10 mission officially ended on March 31, 1997. However NASA's Ames Research Center, Moffet Field, CA, intermittently receives science data from Pioneer as part of a training program for flight controllers of the Lunar Prospector spacecraft now orbiting the Moon.

"The Voyager mission today presents an unequaled technical challenge. The spacecraft are now so far from home that it takes nine hours and 36 minutes for a radio signal traveling at the speed of light to reach Earth,"said Ed B. Massey, project manager for the Voyager Interstellar Mission. "That signal, produced by a 20 watt radio transmitter, is so faint that the amount of power reaching our antennas is 20 billion times smaller than the power of a digital watch battery,"

Having completed their planetary explorations, Voyager 1 and its twin, Voyager 2, are studying the environment of space in the outer solar system. Although beyond the orbits of all the planets, the spacecraft still are well within the boundary of the Sun's magnetic field, called the heliosphere. Science instruments on both spacecraft sense signals that scientists believe are coming from the outermost edge of the heliosphere, known as the heliopause.

The heliosphere results from the Sun emitting a steady flow of electrically charged particles called the solar wind. As the solar wind expands supersonically into space in all directions, it creates a magnetized bubble -- the heliosphere -- around the Sun. Eventually, the solar wind encounters the electrically charged particles and magnetic field in the interstellar gas. In this zone the solar wind abruptly slows down from supersonic to subsonic speed, creating a termination shock. Before the spacecraft travel beyond the heliopause into interstellar space, they will pass through this termination shock.

"The data coming back from Voyager now suggest that we may pass through the termination shock in the next three to five years," Stone said. "If that's the case, then one would expect that within 10 years or so we would actually be very close to penetrating the heliopause itself and entering into interstellar space for the first time."

Reaching the termination shock and heliopause will be major milestones for the mission because no spacecraft have been there before and the Voyagers will gather the first direct evidence of their structure. Encountering the termination shock and heliopause has been a long-sought goal for many space physicists, and exactly where these two boundaries are located and what they are like still remains a mystery.

Science data are returned to Earth in real-time to the 34- meter Deep Space Network (DSN) antennas located in California, Australia and Spain. Both spacecraft have enough electricity and attitude control propellant to continue operating until about 2020, when electrical power produced by the RTGs will no longer support science instrument operation. At that time, Voyager 1 will be almost 150 times farther from the Sun than the Earth -- more than 20 billion kilometers (almost 14 billion miles) away.

On Feb. 17, Voyager 1 will be 10.4 billion kilometers (6.5 billion miles) from Earth and is departing the Solar System at a speed of 17.4 kilometers per second (39,000 miles per hour). At the same time, Voyager 2 will be 8.1 billion kilometers (5.1 billion miles) from Earth and is departing the solar system at a speed of 15.9 kilometers per second (35,000 miles per hour).

JPL, a division of the California Institute of Technology, manages the Voyager Interstellar Mission for NASA's Office of Space Science, Washington, D. C.

September 12, 2013

Voyager 1 Finally Leaves Solar System—for Real This Time

After much debate over the murky boundary of interstellar space, a solar eruption gives scientists the evidence to say Voyager 1 has finally crossed it

By Clara Moskowitz

Voyager 1 was starting to get a reputation as the spacecraft that cried wolf, after scientists repeatedly claimed it was leaving the solar system, only to change their minds and say it wasn’t quite there yet . Now researchers say new evidence shows Voyager really has departed the sun’s sphere of influence and become the first man-made object to reach interstellar space.

Voyager 1, launched in 1977, is speeding away from us, traveling about 3.5 times the Earth–sun distance every year. The probe is now about 18.2 billion kilometers from Earth, farther away than anything human beings have sent into space. (Its sister spacecraft, Voyager 2, launched more than a month earlier, took a more circuitous path from Earth and is now about 14.8 billion kilometers away.)

Scientists have long been expecting Voyager 1 to exit the bubble of space containing particles from the sun, called the heliosphere, and enter a region where particles are much more plentiful and come from ancient explosions of other stars. But because Voyager 1 has lost its ability to measure this particle plasma, there was no easy way to tell when the transition had occurred .

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A boon came from an eruption on the sun in March 2012, which sent waves of solar material out into space. When this ejection reached Voyager 1 13 months later in April 2013, it set the local plasma vibrating. Voyager 1's plasma wave instrument (separate from the defunct plasma particle detector) was able to measure the pitch of these vibrations, which in turn reflected the density of plasma around the spacecraft. The results show that Voyager 1 is surrounded by plasma more than 40 times denser than it encountered earlier, when it was in the heliosphere. “Because there’s no other possible conclusion, I think we’re forced to and obliged to conclude that we’re truly in the interstellar medium,” physicist Gary Zank of the University of Alabama in Huntsville said during a press conference today.

Based on abrupt changes in the apparent plasma density around the spacecraft, the researchers were even able to pinpoint August 25, 2012 as the most likely date that Voyager 1 left the solar system , crossing the heliopause, the boundary between the heliosphere and the interstellar medium.

The “little spacecraft that could,” in the words of project manager Suzanne Dodd of the NASA Jet Propulsion Laboratory in Pasadena, Calif., is getting old in years and is technologically weak: the average smartphone has thousands of times more memory than the spacecraft. Yet most of Voyager 1’s instruments still work, and they continue to send signals back to Earth. The team estimates the probe still has enough power from its plutonium power plant to operate all its instruments through 2020, when it will begin shutting them off one by one, until it goes dark in 2025. That still gives Voyager 1 more than a decade to study the realm of the universe it has entered. “It marks the beginning of a new era of exploration for Voyager: the exploration of the space between the stars,” said Ed Stone, Voyager’s longtime project scientist.

The new findings represent a turnaround for the Voyager team, which as recently as June predicted the spacecraft may have years to go before it reached interstellar space. But the latest data remove most of the team members’ doubts, Stone said.

The new report, published online today in Science, also agrees with the conclusions of a separate paper claiming Voyager 1 had left the solar system, based on magnetic field data, which was published August 14 in The Astrophysical Journal Letters. The lead author of that paper, University of Maryland, College Park, physicist Marc Swisdak, says the two projects are complementary. “I thought the authors make an excellent case for their measurements and their interpretation,” Swisdak says.

Over the course of 36 years, between the two of them, the Voyager probes have visited all the outer planets of the solar system and discovered 23 moons around these worlds. They also each carry time capsules in the form of phonograph records loaded with recordings of music, natural sounds, voice greetings in 56 languages, and photographs and diagrams of life on Earth. Voyager 1 is on a course that should eventually take it within 1.6 light-years of a star called AC+79 3888, which lies in the constellation of Camelopardalis. It’s due to arrive in about 40,000 years, long after the spacecraft loses its ability to tell whomever is on Earth what comes of that encounter.

Voyager 1 finds a surprise at the edge of the solar system

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Voyager 1, the spacecraft famous for beaming back striking photos of Jupiter, Saturn and their moons more than 30 years ago, has made still another surprising discovery: the existence of an unexpected zone at the very edge of the solar system.

It had been thought that the NASA probe was already passing through the outermost section of the solar system on its way toward the heliopause — the boundary where the solar wind ends and interstellar space begins. For that reason, the existence of yet another district at our cosmic neighborhood’s edge was completely unexpected, said Stamatios Krimigis, a solar physicist at the Johns Hopkins Applied Physics Laboratory in Laurel, Md., and leader of the team that operates Voyager’s low-energy charged particle instrument.

“Nature is imaginative,” he said Monday.

PHOTOS: Images of space

Speaking to reporters from the annual meeting of the American Geophysical Union in San Francisco, Krimigis and former Jet Propulsion Laboratory Director Edward Stone described the newly discovered region as a “magnetic highway” that connects the heliosphere, the bubble surrounding the solar system, to the vast expanse of space beyond.

NASA researchers said in September that they thought that Voyager 1 might pass out of the solar system by the end of the year. As the craft neared the heliopause, scientists expected to detect fewer particles of solar wind and more cosmic rays pouring in from interstellar space. They also expected the magnetic field to change direction.

Since late July, Krimigis said, the intensity of the solar wind particles had decreased a thousand-fold, while cosmic ray intensities rose.

“If we had looked at particle data alone, we would have said, ‘We’re out! Goodbye, solar system!’” he said.

Although they could tell the strength of the magnetic field had increased, Voyager’s instruments never detected the anticipated change in the field’s direction, said Leonard Burlaga, a member of the team that operates Voyager’s magnetometer from NASA’s Goddard Space Flight Center in Greenbelt, Md.

For this reason, he said, “there’s no evidence we’ve entered interstellar space.”

Rather, the highway region, which is created by a magnetic field originating from the southern hemisphere of the sun, appears to allow particles from within the heliosphere to escape into interstellar space while permitting particles from the outside to pour in.

Gary Zank, a space physicist at the University of Alabama-Huntsville, said he wasn’t convinced Voyager 1 was still contained within the solar system and that it would take several months to figure out whether the probe had crossed the heliopause after all.

Different theoretical models predict a different looking boundary, he said. Either way, he said, it was “a major discovery.”

“As ever, Voyager seems to have a remarkable capacity for providing observations that suggest ... we’re almost right,” he said. “It would be nice for the theory and the observations to agree all at once. But it may not ever happen that way.”

Voyager 1 is about 11 billion miles from the sun, making it the most distant man-made object in space, according to NASA. Its twin probe, Voyager 2, is about 9 billion miles from the sun.

Launched in 1977, they are the elder statesmen of the working NASA fleet. Their scientific instruments, which are fueled by radioactive plutonium-238, will begin powering down in 2020 and are expected to stop operating in 2025.

The Voyagers should pass through the heliopause before then.

Stone, who continues to work as a Voyager project scientist at Caltech, said that researchers at NASA think the magnetic highway might be about 5 to 10 astronomical units thick — that is, 5 to 10 times the distance from the Earth to the sun. If they are right, it would take two to three years for Voyager 1 to cross the region, he said.

Then again, Stone cautioned, NASA hadn’t predicted the existence of the highway in the first place, so making precise guesses about when the spacecraft will leave the solar system isn’t really possible — nor is foreseeing exactly what the spacecraft might see on the other side of the bubble.

The magnetic field should still shift direction, Stone said. But he said he thought other details would remain a surprise.

“We won’t know until we finally actually leave the bubble,” he said.

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(CNN) -- The Voyager 1 spacecraft has arrived at the boundary of the solar system and is flying into a region of space that has never been explored before, NASA announced Wednesday.

"This is a very exciting time, said Voyager project scientist Edward Stone. "Voyager is beginning to explore the final frontier of the solar system."

Scientists analyzing data from Voyager 1 disagree as to whether the probe has yet crossed over the critical boundary that marks the transition from our solar system into interstellar space. But even dissenters agree that if it has not crossed that boundary, called terminal shock, it is very close.

"We're in the neighborhood. This is sort of a Lewis and Clark space expedition: We're in the foothills, and we'll soon be getting to the mountains, in our view," said Frank McDonald, a research scientist at the University of Maryland.

Voyager 1's journey marks a major scientific milestone: For the first time, a man-made object has traveled 8.4 billion miles (13.5 billion kilometers), about 90 times the distance between the Earth and sun. Ahead lies the journey to the star next door. Traveling at its predicted speed, Voyager 1 will get there in about 40,000 years.

Launched in 1977, Voyager 1 and its twin, Voyager 2, were the first space probes to explore the outer planets of our solar system. Voyager 1's primary mission ended in 1980 when it completed its observations of Saturn. Since then, it has been headed into deep space. In 1998, it passed the Pioneer 10 space probe and became the most distant man-made object from Earth.

'First taste' of the beyond

Now, scientists from the Johns Hopkins University's Applied Physics Laboratory and colleagues believe Voyager 1 crossed into the area marking the edge of the solar system.

"Voyager 1 is giving us our first taste of interstellar space," said Tom Krimigis, of the Applied Physics Laboratory, in a written statement. "This is our first look at the incredibly dynamic activity in the solar system's outer limits."

Contrary to popular belief, space is not an empty void. Rather, our solar system is awash in the solar wind, the charged gases that flow off our sun at supersonic speed. At the termination shock boundary, the solar wind dissipates and begins to give way to the interstellar medium -- the gases that float in the void between stars.

Instruments aboard Voyager 1 are able to measure the speed of the solar wind, and the Applied Physics Lab's analysis of that data suggests the spacecraft has hit the terminal shock boundary. The findings are published in the November 6 edition of the journal Nature.

A different view

A second article in Nature offers a more conservative analysis. The University of Maryland team interprets additional data from Voyager 1 to mean the spacecraft is approaching the termination shock boundary, but has yet to hit it.

"What we see, the observations agree very well with what Tom has described," said McDonald with the University of Maryland. "We just interpret them differently. That we're in the neighborhood of the termination shock, and we haven't crossed it."

Whichever the case, scientists are particularly excited as the 26-year-old probe still has operating scientific instruments. NASA says Voyager 1 still has enough power to beam back data through about the year 2020.

By that time, experts hope to also monitor the spacecraft's journey through something called the heliopause, the outer boundary delineating the edge of interstellar space. As these outer reaches of the solar system have never been explored, it is unclear exactly where these boundaries lie.

Voyager 1 and 2 both carry a so-called "golden record" -- a 12-inch gold-plated copper disk that is actually a phonograph record. The disk carries greetings and an overview of our culture to extraterrestrials that may one day stumble across one of these man-made craft.

The record includes samples of music; nature sounds such as thunder, waves crashing, bird songs; and greetings in multiple languages, including from then President Jimmy Carter and U.N. Secretary-General Kurt Waldheim. Pictographs on the disk explain how it should be played. A phonograph needle is included.

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After 35 Years, Voyager Nears Edge Of Solar System

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The Voyager 1 spacecraft's 35th anniversary is proving to be unexpectedly exciting, as scientists gathered this week to examine new hints that the spacecraft is on the verge of leaving our solar system.

Voyager 1 is now more than 11 billion miles away from Earth. It blasted off in September 1977, on a mission to Jupiter and Saturn. But it also carried a Golden Record filled with music and the sounds of our planet, in case it encountered intelligent life as it moved out toward the stars.

Scientists have been eagerly waiting for Voyager 1 to become the first human-made object to leave the solar system. And in recent weeks, the spacecraft has sent back intriguing signs that it might be getting close, to the delight of researchers who have been working on it for decades.

One of those scientists is Norman Ness, a professor at the University of Delaware who sent NASA a proposal for a Voyager instrument back in 1969. That December, he recalls, he received a telegram from NASA saying it had been selected.

The Golden Record

Tucked aboard each Voyager spacecraft was a 12-inch, gold-plated, copper phonograph disc "containing sounds and images selected to portray the diversity of life and culture on Earth," according to NASA. Below is a sampling of the 115 images and audio clips, selected by a committee chaired by Carl Sagan. The images were encoded in analog form. The audio was designed to be played at 16 2/3 rpm; a needle, cartridge and symbolic instructions for using the record were also included.

Urdu: "Peace on you. We the inhabitants of this Earth send our greetings to you."

Latin: "greetings to you, whoever you are; we have good will towards you and bring peace across space.", sounds of birds, hyenas and elephants, sounds of a train.

He was ecstatic, because these probes were going to visit far-off giant planets. The prospect of leaving the solar system, and exploring interstellar space, was not really on his mind. After all, the spacecraft might not live long enough. And, Ness notes, "we didn't know if NASA was going to continue to support the mission after the primary mission had been accomplished."

But NASA kept funding it. And even though Voyager's technology is primitive by today's standards — for example, each spacecraft has an on-board eight-track tape recorder — the probes just keep working.

"So we're getting anywhere from five to eight hours of data every day from each of these spacecraft, and it's quite remarkable," says Ness.

Of the two, Voyager 1 is the farthest away from Earth. Don Gurnett of the University of Iowa, who has worked on the mission since the mid-1970s, says Voyager 1's radio signals now take more than 16 hours to reach us.

"Astronomers like to think of distances in terms of 'light-years.' Well, we're not anything like a 'light-year,' but we're now a substantial fraction of a 'light-day' from the Earth," says Gurnett. "And I just find that extremely impressive."

Out Beyond The Planets

When will Voyager 1 finally leave our solar system? It's already way beyond the planets — it even looked back and snapped photos of them, including a famous one of Earth, looking like a pale blue dot . For years, scientists have been waiting for Voyager 1 to exit the bubble of charged particles that stream out from our sun, because then it would truly be in the space between stars.

Just in the past couple of months, researchers have been getting some tantalizing hints that Voyager 1 might be almost there.

Ed Stone, the Voyager project scientist at Caltech, showed off some brand new data this week during a public lecture at NASA's Jet Propulsion Laboratory. Voyager 1 has been seeing decreases in the number of lower-energy particles that come from inside our solar system, he said. Meanwhile, it's been seeing increases in the high-energy particles that come from outside our solar system.

"So there is some kind of connection between where Voyager is and the outside, which lets the particles that are inside out, and lets particles outside in," explained Stone.

This is uncharted territory, and no one really knows just what the boundary with interstellar space is like. So Stone can't say how long it will be before Voyager passes through it.

"I can't tell you whether it's days, months or years. I really can't tell you," he said. "That's the nice thing. From a science point of view, there is so much that we're learning that we had no way of really understanding before Voyager."

Still, scientists are extremely excited that they could be getting there. Robert Decker of The Johns Hopkins University Applied Physics Laboratory, who has worked on Voyager since 1980, says the rapid changes being seen now are extremely unusual, and they come after a number of years when not much seemed to be happening.

This artist's drawing shows one of the Voyager probes, which were launched in 1977. Voyager 1 is hurtling toward the edge of the solar system and might be close to reaching interstellar space, researchers say. NASA/JPL hide caption

"And the way that the changes are taking place — that is, the low energy is going down and the high energy is going up — certainly is evidence to me that we're very close to the interstellar medium," says Decker, "because that is what you would expect to happen as you get into the interstellar medium."

In the weeks ahead, scientists will be looking for more indicators that Voyager 1 is finally moving out. For example, they'll analyze the direction of the magnetic field, to see if it has changed.

Voyager 1 can keep talking to Earth for about another decade. That's how long the plutonium that powers it should last. After it falls silent, it will still keep going. But it will be about 40,000 years before it wanders close to another star.

Scientists Have Calculated How Long It'll Take to Reach Distant Stars

Are we there yet?

• The researchers compared the predicted paths of four spacecraft to the paths of nearby stars, as measured by the Gaia space telescope, to see where and when they might overlap.
• According to their work , posted to the online pre-print server arXiv, it would take about 90,000 years for Pioneer 10 to swing within striking distance of a nearby star.

The intrepid Voyager 1 and 2 spacecrafts were launched in 1977, and despite having a roughly 12-year mission lifespan, are still hurtling through space and returning data to eager scientists on Earth. They’ve broken through barrier that protects our solar system and are now zipping through the interstellar medium along with Pioneer 10 and 11.

But how long might it take them, or another spacecraft, to actually reach another star system?

A team of scientists—Coryn Bailer-Jones of the Max Planck Institute for Astronomy in Switzerland and Davide Farnocchia of NASA’s Jet Propulsion Laboratory—have done the calculations. Essentially, the pair found a way to chart how long it would take a spacecraft to get from our humble solar system to the next system over, according to a paper uploaded to the pre-print server arXiv.

In the quest for answers, Farnocchia and Bailer-Jones turned to the European Space Agency’s Gaia space telescope for help. For more than five years, Gaia has been gathering data on billions of stars , charting their orbits and path through the cosmos.

Using this data and data about the projected paths of both the voyager spacecrafts as well as Pioneer 10 and 11, which are careening toward the outer reaches of the solar system, the researchers were able to create a timeline of when these crafts might reach distant star systems. For those eager to visit other worlds, brace for some bad news.

Should they continue their transit, the four spacecraft will come within striking distance of approximately 60 stars in the next million years. And in that same amount of time, they’ll get even closer—try two parsecs, the equivalent of 6.5 light years—to about 10 stars.

Who will have the best shot at reaching and exploring a distant star? Pioneer 10 will swing within .231 parsecs the star system HIP 117795 in the Cassiopeia constellation in approximately 90,000 years. And how long before one of these spacecrafts is hijacked by the orbit of one of these stars? It’ll be about 1,000,000,000,000,000,000,000 years.

You'll have some time to kill.

Jennifer Leman is a science journalist and senior features editor at Popular Mechanics, Runner's World, and Bicycling. A graduate of the Science Communication Program at UC Santa Cruz, her work has appeared in The Atlantic, Scientific American, Science News and Nature. Her favorite stories illuminate Earth's many wonders and hazards.

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Voyager 1 at the edge of the solar system

This image shows that the inner edge of the stagnation region is located about 113 astronomical units from the Sun. Voyager 1 is currently about 119 astronomical units from the sun. The distance to the outer edge is unknown, but Voyager 1 should cross it eventually.

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

by Daniel Strain, University of Colorado at Boulder

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Provided by University of Colorado at Boulder

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Going, Going, Still Going? Voyager 1 at Solar System’s Edge

By Kenneth Chang

• June 27, 2013

At the edge of the solar system, there are no signs that proclaim, “You are now entering interstellar space.”

NASA’s Voyager 1 spacecraft, launched more than 35 years ago and now 11.5 billion miles from where it started, is closing in on this boundary. In recent years scientists have been waiting eagerly for it to become the first artificial object to leave the solar system and enter the wider reaches of the Milky Way, which they fully expect it to do. But there has been at least one false alarm.

On Thursday, scientists reported that, no, Voyager 1 still had not reached interstellar space, but it had entered a region that no one expected and no one can yet explain, a curious zone that is almost certainly the last layer of our Sun’s empire — technically speaking, the heliosphere. Three papers published in the journal Science describe in detail the sudden and unpredicted changes encountered in the surroundings of Voyager 1, which left Earth about three months after the original “Star Wars” movie was released and is heading for the cosmos at 38,000 miles per hour.

Scientists had expected that Voyager 1 would detect two telltale signs as it passed through the heliosheath, the outermost neighborhood of the solar system, which is thought to abut the heliopause, as the actual boundary is known. Happily, the key instruments on Voyager 1, as well as those on its twin, Voyager 2, are still working after all these years, and its nuclear power source will last until at least 2020.

Last summer, one of the two events occurred, but not the other, leaving scientists perplexed. Scientists had predicted that at the boundary between solar system and interstellar space, the solar wind — a stream of charged particles blown out by the Sun — would fade away, and that Voyager 1 would no longer detect it. That happened.

They also expected that the direction of the magnetic field would change as Voyager 1 emerged from the Sun’s magnetic bubble. That did not.

“Nature is far more imaginative than we are,” said Stamatios M. Krimigis, a scientist at the Johns Hopkins Applied Physics Laboratory who is the principal investigator of an instrument that records charged particles hitting Voyager 1. Dr. Krimigis is an author of one of the papers in Science .

Last July, the spacecraft — which is roughly 1,600 pounds and would fit inside a cube about 13 feet on each side, according to NASA — observed a momentary dip in the intensity of the solar wind. “It was exciting,” said Edward C. Stone, the project scientist for the two Voyagers. “We had never seen such a drop before. It happened in less than a day. Then five days later, it was back up.”

In mid-August, there was a deeper momentary dip.

Then, on Aug. 25, the solar wind dropped by a factor of more than a thousand, vanishing to imperceptible levels, and it has remained at essentially zero since. At the same time, the number of cosmic rays from outside the solar system jumped by 9.3 percent .

“It looked like we were outside,” Dr. Stone said.

But the magnetic field has steadily, stubbornly pointed in the same direction, indicating that Voyager 1 is still ensconced within the Sun’s magnetic field. Scientists guess that in this region the magnetic fields of the solar system partly connect to those of the surrounding interstellar space, allowing the solar particles to escape. (Charged particles travel along magnetic field lines.) They have named the zone through which Voyager 1 is hurtling the heliosheath depletion region .

“I think it’s clear we do not have a model which explains all of this,” Dr. Stone said.

Voyager 2, which is moving slightly more slowly and is not as far from the Sun, has not yet encountered this region.

Dr. Stone noted that when the two Voyagers launched in 1977 on a grand tour of Jupiter, Saturn, Uranus and Neptune, the space age was just 20 years old, and there was no way to know that NASA had built something that would last 35 years, long after it passed the planets. But the designers of the mission were prescient to be prepared if they lasted that long.

“It turns out that in fact we designed the cosmic ray instrument specifically for this phase of this mission,” Dr. Stone said. “We were planning, and it really paid off. We’ve begun to see what’s outside even though the magnetic field says you’re not outside.”

As for actually reaching the outside of the solar system, Dr. Stone said, “it could be a few months, or it could be several more years.”

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The Oort Cloud: A Distant Realm at the Edge of Our Solar System

Far beyond the familiar planets and even the distant Kuiper Belt lies a vast, spherical cloud of icy bodies surrounding our solar system. This region, known as the Oort cloud, represents the outer boundary of the Sun’s gravitational influence and serves as a reservoir for long-period comets that occasionally visit the inner solar system. Though it has never been directly observed, the existence of the Oort cloud is widely accepted by astronomers based on compelling evidence from comet observations and theoretical models. This article explores what we currently know about the Oort cloud – its structure, composition, origins, and significance for our understanding of the solar system.

Discovery and History

The concept of a distant cloud of comets was first proposed in 1950 by Dutch astronomer Jan Oort, after whom it is named. Oort was attempting to resolve a paradox about the origins of long-period comets. These comets have very elongated orbits that take them far beyond the planets, yet they also appeared to be relatively new objects that had not made many passes by the Sun. Oort hypothesized that there must be a vast reservoir of icy bodies in the outer solar system that occasionally get perturbed into orbits bringing them into the inner solar system.

Interestingly, Estonian astronomer Ernst Öpik had proposed a similar idea in 1932. For this reason, the Oort cloud is sometimes referred to as the Öpik-Oort cloud. However, it was Oort’s more detailed analysis that brought the concept widespread attention in the astronomical community.

While the existence of the Oort cloud remains theoretical, as no direct observations have confirmed it, the idea is now widely accepted. Decades of comet observations have provided strong circumstantial evidence supporting Oort’s hypothesis. The Oort cloud model elegantly explains the observed population of long-period comets and has become an integral part of our understanding of solar system structure and evolution.

Location and Structure

The Oort cloud is believed to form a vast sphere enveloping the entire solar system at an immense distance from the Sun. Its exact boundaries are not precisely known, but most estimates place the inner edge at about 2,000 to 5,000 astronomical units (AU) from the Sun. One AU is the average distance between the Earth and Sun, equivalent to about 93 million miles or 150 million kilometers. This means that even the inner part of the Oort cloud begins nearly 50 times farther out than the orbit of Neptune.

The outer boundary of the Oort cloud is even more uncertain, but it may extend as far as 100,000 to 200,000 AU from the Sun. At this distance, the Sun’s gravitational influence becomes very weak, and objects are easily affected by the gravity of passing stars and the overall gravitational field of the Milky Way galaxy. This region essentially marks the edge of the Sun’s gravitational dominion and thus the outer limit of our solar system.

To put the scale of the Oort cloud in perspective, consider that light from the Sun takes about 8 minutes to reach Earth. It would take over a year for that same light to reach the outer regions of the Oort cloud. The nearest star to our solar system, Proxima Centauri, is about 268,000 AU away – not much farther than the outer edge of the Oort cloud.

The overall structure of the Oort cloud is thought to consist of two main regions:

• The outer Oort cloud: This is a roughly spherical region extending from about 20,000 AU to the outer edge. Objects here have no preferred orbital plane and can orbit the Sun in any direction.
• The inner Oort cloud: Also called the Hills cloud, this is a doughnut-shaped region extending from the inner edge to about 20,000 AU. It is thought to be denser than the outer cloud and may contain many more objects.

The entire cloud is believed to contain trillions of icy bodies, most just a few kilometers across but some potentially reaching sizes of 100 km or more. Despite this vast number of objects, they are spread over such an enormous volume that the cloud is incredibly sparse. The average separation between objects may be millions of kilometers.

Composition

Our knowledge of Oort cloud composition comes primarily from studies of long-period comets believed to originate there. Based on this evidence, Oort cloud objects are thought to consist mainly of a mixture of ices – water ice, dry ice (frozen carbon dioxide), methane, ammonia, carbon monoxide, and other frozen gases. These are likely mixed with dust and rocky material.

This composition is similar to what we see in comets and in the icy moons of the outer solar system. It represents some of the most primitive material left over from the formation of the solar system, preserved in deep freeze far from the Sun for billions of years.

Some larger Oort cloud objects may have undergone enough internal heating from radioactive decay to have differentiated, developing layered structures with rocky cores surrounded by mantles of ice. A few of the largest bodies could potentially qualify as dwarf planets. The object Sedna, orbiting in the inner Oort cloud region, is a possible example.

While most Oort cloud bodies are expected to be icy in nature, there is also evidence that the cloud may contain a small fraction of rocky asteroids as well. This mixture may provide clues about the complex dynamics involved in the cloud’s formation.

Origins and Evolution

The Oort cloud is believed to have formed early in the solar system’s history, about 4.6 billion years ago. There are two main theories about its origins:

• The primordial theory suggests that the Oort cloud formed in place as part of the original protoplanetary disk that gave rise to the planets. In this scenario, the material in the outermost parts of the disk was too sparse to form planets but remained in orbit around the Sun.
• The scattered disk theory proposes that the Oort cloud formed from objects that were originally closer to the Sun but were gravitationally scattered outward by the giant planets, particularly Jupiter and Saturn. Computer simulations have shown this to be a plausible mechanism.

The current scientific consensus favors a combination of these theories. Some of the Oort cloud material may have formed in place, while a significant portion was likely scattered outward from the inner solar system. This scattering process may have continued over hundreds of millions of years as the giant planets migrated to their current orbits.

Once established, the Oort cloud has not remained static. It is subject to ongoing perturbations from several sources:

• Passing stars can gravitationally influence Oort cloud objects, potentially dislodging them from their orbits.
• The overall gravitational field of the Milky Way galaxy exerts a tidal force on the cloud.
• Giant molecular clouds in interstellar space may occasionally pass near enough to have an effect.

These perturbations cause a constant trickling of Oort cloud objects into the inner solar system, where we observe them as long-period comets. At the same time, the giant planets continue to scatter some objects outward, helping to replenish the cloud. There is also a slow loss of objects that are ejected from the solar system entirely.

Over the very long term, the Oort cloud is gradually being depleted. However, this process is extremely slow, and the cloud is expected to persist for billions of years to come.

Significance for the Solar System

The Oort cloud plays several important roles in our understanding of the solar system:

• Comet source: It serves as the primary reservoir for long-period comets, those with orbital periods greater than 200 years. These comets provide valuable scientific data and occasionally put on spectacular celestial displays.
• Preserved early solar system material: Oort cloud objects are thought to be among the most primitive bodies in the solar system, preserving a record of the conditions present during planet formation.
• Dynamical tracer: The structure and composition of the Oort cloud provide clues about the early dynamical evolution of the solar system, including planet migration.
• Interstellar interface: The outer Oort cloud represents the boundary between our solar system and interstellar space, helping us understand how star systems interact with their galactic environment.
• Potential hazards: While very rare, it is possible for large Oort cloud objects to be perturbed into orbits that bring them into the inner solar system, posing a potential impact threat to Earth.

Exploration and Observation

Direct observation of the Oort cloud remains beyond our current technological capabilities. The objects are simply too small, too far away, and too dark to be seen by even our most powerful telescopes. Our knowledge of the cloud comes primarily from indirect evidence:

• Long-period comet observations
• Theoretical models of solar system formation and evolution
• Studies of extrasolar debris disks around other stars
• Observations of a few known objects with very distant orbits, like Sedna, that may represent an inner population of the Oort cloud

No spacecraft has yet reached the Oort cloud. The most distant human-made objects, Voyager 1 and Voyager 2, are traveling out of the solar system but won’t reach the inner edge of the Oort cloud for hundreds of years. Even at their speed of about 17 kilometers per second (38,000 mph), they would take tens of thousands of years to pass through the entire cloud.

Future observations may provide more direct evidence for the Oort cloud. Proposed space telescopes could potentially detect the combined infrared glow from many Oort cloud objects. Meanwhile, continued study of long-period comets and very distant solar system bodies will help refine our models of the cloud’s structure and composition.

Oort Clouds Around Other Stars

The concept of the Oort cloud has implications beyond our own solar system. Astronomers now believe that similar clouds of icy bodies likely surround many, if not most, other stars. These extrasolar Oort clouds would be the outer component of debris disks, which have been observed around numerous stars.

Studying these distant comet clouds could provide valuable insights:

• They may help us understand the diversity of planetary system architectures.
• They could serve as tracers of past gravitational interactions between stars in dense clusters.
• They may play a role in delivering water and organic compounds to planets, potentially contributing to the development of life.

Detecting Oort clouds around other stars is extremely challenging with current technology. However, future space-based telescopes may be able to observe them indirectly through their interactions with interstellar dust or by detecting comets falling toward their parent stars.

Mysteries and Open Questions

Despite decades of study, many aspects of the Oort cloud remain mysterious. Some of the key questions astronomers are still working to answer include:

• What is the exact structure and extent of the cloud?
• How many objects does it contain, and what is their size distribution?
• What is the total mass of the Oort cloud?
• How much material in the cloud originated in the inner solar system versus forming in place?
• Do other stars commonly steal or exchange Oort cloud objects when they pass nearby?
• Could the Oort cloud harbor a large, undiscovered planet (sometimes called “Planet Nine”)?
• How do Oort cloud-like structures differ around other types of stars?

Answering these questions will require continued theoretical work, advanced computer simulations, and new observational techniques. Each advance in our understanding of the Oort cloud helps to refine our overall picture of solar system formation and evolution.

The Oort cloud represents the outer frontier of our solar system, a vast and mysterious realm that we are only beginning to understand. This hypothetical cloud of icy bodies plays a crucial role in our solar system’s ecology, acting as a long-term reservoir for comets and preserving some of the most primitive material from the solar system’s formation.

While direct observation of the Oort cloud remains beyond our current capabilities, continued study of comets, improved theoretical models, and future space missions promise to shed more light on this distant region. As we learn more about the Oort cloud, we gain valuable insights into the history and evolution of our solar system, as well as the processes that shape planetary systems throughout the galaxy.

• Solar System

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Voyager 1 Distance from Earth

Voyager 1 distance from sun, voyager 1 one-way light time, voyager 1 cosmic ray data, voyager 2 distance from the earth, voyager 2 distance from the sun, voyager 2 one-way light time, voyager 2 cosmic ray data.

Space photo of the week: 1st-ever close-up of Neptune is Voyager 2's final portrait of a planet

What it is: One of the final photographs of Neptune taken by NASA's Voyager 2 probe

Where it is: 2.8 billion miles (4.5 billion kilometers) from the sun

When it was taken: Aug. 25, 1989

When it was shared: Aug. 19, 2024

Why it's so special: Only one spacecraft has ever visited the eighth and most distant planet from the sun.

On Aug. 25, 1989, NASA's Voyager 2 spacecraft took the first-ever close-up images of Neptune. This one — among the last full-disk photos taken before the probe ended its "Grand Tour" of the planets — became one of the most iconic. It revealed Neptune as a deep azure blue, which colored the public's perception of the planet for decades. (That is, until a new treatment of Voyager 2's images earlier this year revealed Neptune's true color to be a much lighter blue green.)

Voyager 2's original images were taken in false color using filters — a standard technique used by planetary astronomers. In this case, blue and green filters were used alongside one that passes light at a wavelength absorbed by methane gas. According to scientists , hydrogen and helium dominate Neptune's atmosphere, but methane gives it its blue appearance by absorbing red light. The filters make methane look dark blue in this image, but they also reveal a semitransparent haze layer across the planet. The bright-red edge around Neptune is caused by the haze scattering sunlight at higher altitudes, above most of the methane.

Related: Uranus and Neptune aren't made of what we thought, new study hints

Voyager 2 took this shot almost precisely 12 years after it launched on a Titan-Centaur rocket from Cape Canaveral, Florida. Having visited Jupiter in 1979, Saturn in 1981 and Uranus in 1985, Voyager's closest approach to Neptune came on Aug. 25, 1989. During the flyby, Voyager also visited two of Neptune's moons, Triton and Nereid, and discovered six new moons and four rings .

Because Neptune is about 30 times farther from the sun than Earth is, it gets only a faction of a percent of Earth's sunlight, meaning Voyager 2 had to take long-exposure images. So engineers fired the fast-moving spacecraft's thrusters to have it rotate so the camera could remain focused.

Voyager 2's images from Neptune were its last, sent back as radio signals with 13-watt transmitters — about enough power to run a refrigerator light bulb, according to NASA — and took four hours to travel across the solar system to NASA's Deep Space Network of radio antennae across the world.

Neptune was Voyager 2's last stop before it traveled to the solar system's edge. The probe entered interstellar space on Nov. 5, 2018. Voyager 2 remains NASA's longest-running mission, even after encountering some communication problems last summer.

For more groovy space photos, check out our space photo of the week archives . New stories post every Sunday.

Personal Stories from the Mission

Voyager is a mission with no shortage of highlights, given its historic encounters with all the giant planets and the first-ever entry of a human-made object into interstellar space. We asked team members past and present and next-generation scientists and engineers inspired by Voyager to share their most meaningful moments over the decades.

From the first detection of active volcanoes outside Earth to the first up-close images of Neptune, the 40-year Odyssey of NASA's Voyager mission is full of unforgettable memories. Voyager 1, the farthest human-made object, launched on Sept. 5, 1977, and Voyager 2, the second farthest, launched on Aug. 20, 1977. In honor of their 40th launch anniversaries, we asked scientists and engineers who have worked with the spacecraft, as well as enthusiasts inspired by the mission, to share their most meaningful Voyager moments.

Some Voyager team members began their careers in the early days of the mission. Designing science sequences for the 1986 Uranus encounter was a first job after college for Suzanne Dodd, now the Voyager project manager: "We were making history," she said.

Jamie Rankin, who started working with Voyager Project Scientist Ed Stone just days after Voyager 1 entered interstellar space in 2012: "Every day as a graduate student here is like living in a legacy of discovery," she wrote.

We were making it happen. We were making history.

Suzanne "Suzy" Dodd

Voyager Project Manager

What is your most meaningful Voyager moment and why?

"I loved adventure stories as a child, turned to science fiction as a young adult, studied math and physics at Georgia Tech, often gazed at the night sky and dreamed of one day exploring the planets. After learning the tricks of the trade at the Jet Propulsion Laboratory, I was thrilled in late 1974 to receive a call from Bud Schurmeier, project manager of the Mariner Jupiter/Saturn 1977 mission (or simply MJS77), which was later named Voyager. He offered me the job of “mission analysis and engineering manager.” I would be working with the great team of dedicated people Bud had assembled."

Charley Kohlhase

"I was 9 in 1989 when my parents let me stay up to watch the PBS coverage of Voyager 2's flyby of Neptune. I remember my parents debating whether I would even be interested. I think I really wanted to see it because I'd heard about it. I was interested in space, and I wanted to be an astronaut, but only in a vague way."

Mark Wallace

"For me, the highlights of Voyager were clearly the planetary encounters. All six of them were wonderful experiences where every day we saw and learned new things. We had a lifetime of discovery packed into each one."

"My involvement with the Voyager mission started in 2001, when I started using and adapting a major computational code developed by the University of Michigan to study the outer layer of the heliosphere, where this bubble of plasma that the Sun blows around itself touches interstellar space."

"I arrived in Pasadena, California, to begin graduate school at Caltech on Friday, August 31, 2012 -- just six days after Voyager 1’s own interstellar arrival. My new advisor, Ed Stone, invited me to attend the Voyager Science Steering Group meeting which started the following Monday."

"I think back to the days we launched Voyager 40 years ago, and it seemed like one more shot into the unknown -- albeit rather ambitious. We just wanted to get to Jupiter and Saturn in the next four years and explore the “uncharted territory.”

"In late 1972, I was hired into NASA’s Jet Propulsion Laboratory to develop the Voyager power subsystem design. My background included engineering on the Phoenix missile and F-15 radar transmitter at Hughes Aircraft. The opportunity to work at a world-class laboratory like JPL was the pinnacle of my career aspirations."

"The five days of January 24 to 28, 1986 -- starting when Voyager 2 flew by Uranus (“the planet that got knocked on its side”) and ending with the painful tragedy of the Challenger accident -- are forever etched in my memory of unforgettable life experiences."

"In 1610, when Galileo (Galilei) was the first person in the world to look through a telescope at an astronomical object, he looked at Jupiter, and he saw four moons going around it. The historical importance of that event is it convinced him that Copernicus was right -- the Sun was the center of the solar system, and the planets were revolving around it."

It wasn't just that it was a technically great mission. The people who I worked with, the generosity and kindness with which they treated me, has stayed with me always.

Steve Squyres

Role on Voyager: Graduate Student

"Voyager was one of the most wonderful, formative, unforgettable experiences of my entire career. I was very, very fortunate that in graduate school I worked with several members of Voyager imaging team."

"There was great excitement in the office as the scientists started arriving in the weeks leading up to the flyby. I got to meet Carl Sagan and had him autograph my copy of Cosmos."

"I started working for the Voyager Imaging Team in 1977, shortly before launch, and continued on through the Neptune encounter. There were so many memorable moments, but one of my favorites occurred in the spring of 1990..."

"A single paper plot over a quarter of a mile long showed the attenuation of the starlight by the ring material, at a resolution of greater than 20 meters, for the entire 70 million-meter length of the cut through the rings’ radius. What a spectacular event that unfolded after so much hard work by so many people!"

"One of my favorite stories in science history is Voyager’s observation of tidally driven volcanic activity at Jupiter’s tiny moon Io, first theorized just prior to the mission’s arrival at Jupiter. As I grew up I knew I wanted to contribute to answering big questions, including, "Are we alone in the universe?" The Voyager Golden Record, which carries a capsule of sounds and images from Earth in the chance that some day an alien civilization might recover the spacecraft, came to symbolize for me humanity's commitment to pursuing the answers to such questions and the hope that our better nature will see us through to the future."

Steve Vance

"Working on a mission like Voyager, with the opportunity to explore the planets, was something I dreamed about since first looking at Jupiter and Saturn in third grade with my tiny telescope. I wondered what these worlds looked like up close and Voyager gave me a chance to find out."

"One of my more memorable moments, after watching Voyager 1 launch from the Cape in September of 1977, was focused on whether Neptune had a magnetosphere... Part of the challenge was that certain conclusions could only be drawn from actually 'being there,' and in mid-August 1989, Voyager was bearing down on its rendezvous with Neptune."

"Back in 1989, I was hired by NASA’s Jet Propulsion Laboratory to work on the General Science Data Team for the Voyager project’s Neptune flyby. Incredible! My first job at JPL was on what could reasonably be argued as the best mission ever flown by JPL at the peak of its experience and capabilities."

"When I was graduating from college in Texas with a computer science degree, I was all set to go to work for IBM in San Jose (IBM back then for many of us was like Google now); I had never heard of the Jet Propulsion Laboratory or Voyager. However, fate brought me to JPL and to the Voyager project."

"I have had the unspeakably good fortune to have worked on Voyager throughout my entire career and to continue to do so. As a graduate student, I worked on the Plasma Wave Science (PWS) instruments prior to launch. (I placed a 'Uranus or Bust' sticker on the Voyager 2 PWS shipping container – how little I knew about how far it would go!)."

"Finally, for me, a cosmic-ray physicist, one of the highlights by far has been the crossing of the heliopause, the boundary of the Sun’s magnetic bubble, into interstellar space by Voyager 1. The Voyagers will orbit the center of the galaxy forever. It is humbling to think that I’ve been a part of such a fantastic mission."

My daily interactions across the JPL engineering matrix on Voyager-specific issues and problems provided me with a host of friendships and a knowledge base on implementation of a long-lived spacecraft. Who could have predicted that this hardware would still be functional some 40 years after launch?

Robert Detwiler

Power System Cognizant Engineer

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India to launch Gaganyaan crew capsule test flight by end of 2024

India aims to fly Gaganyaan uncrewed this December, in a crucial trial ahead of astronaut missions.

India plans to launch a key test of its Gaganyaan crew vehicle before the end of the year as the country gears up for human spaceflight missions.

Some rocket hardware for the uncrewed Gaganyaan test flight has arrived at the Satish Dhawan Space Centre, on the huge barrier island Sriharikota, Chairman of the Indian Space Research Organisation (ISRO) S Somanath revealed on Aug. 16. 

"Today, we are working on the first mission of the Gaganyaan, called G1. The first unmanned mission. The status today is the rocket , the S200 stage, the L1, [and] C32 stage are all at Satish Dhawan Space Centre," Somanath said, as reported by the Economic Times.

That rocket is the Launch Vehicle Mark-3, or LVM3 for short. Meanwhile, the crew module and service module for the uncrewed flight are undergoing integration at Vikram Sarabhai Space Centre and U R Rao Satellite Centre, respectively. 

"All systems will reach Sriharikota in one and a half months, and the launch will be in December," Somanath said, according to the Times of India.

Related: India wants to land astronauts on the moon in 2040

—  India launches test flight for future Gaganyaan astronaut mission (video, photos)

— India tests parachutes for Gaganyaan crew capsule using a rocket sled (video)

— Fly along with India's crew capsule on crucial test flight (video)

India Prime Minister Narendra Modi formally announced the Gaganyaan (Sanskrit for "celestial vehicle") human spaceflight program in 2018. It seeks to make India only the fourth country to attain independent human spaceflight capabilities, following Russia (the former Soviet Union), the United States and China.

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The upcoming demonstration flight, G1, will test all systems for a full crewed flight, including the rocket modified for human spaceflight, the crew and service modules, reentry, parachute deployment and a splashdown in the Bay of Bengal.

Though it will be uncrewed, G1 will carry the " Vyomitra " (Sanskrit for "space friend") humanoid robot to help verify systems. Two further uncrewed test missions, G2 and G3, are expected to follow in 2025. 

If those trials are successful, the first crewed flight, called H1, will carry astronauts into low Earth orbit for the first time. ISRO shortlisted four "astronaut-designates" for the mission in February this year. The exact timing of the H1 mission has yet to be revealed.

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Andrew is a freelance space journalist with a focus on reporting on China's rapidly growing space sector. He began writing for Space.com in 2019 and writes for SpaceNews, IEEE Spectrum, National Geographic, Sky & Telescope, New Scientist and others. Andrew first caught the space bug when, as a youngster, he saw Voyager images of other worlds in our solar system for the first time. Away from space, Andrew enjoys trail running in the forests of Finland. You can follow him on Twitter  @AJ_FI .

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