Space

Voyager 40th anniversary: Tracing an epic journey of discovery

Voyager 40th anniversary: Trac...
An artist's impression of the Voyager spacecraft
An artist's impression of the Voyager spacecraft
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Engineers testing Voyager in 1976
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Engineers testing Voyager in 1976
Voyager 2 being encapsulated before launch in 1977
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Voyager 2 being encapsulated before launch in 1977
Titan-Centaur 7 lifting off on August 20, 1977, beginning the Voyager journey
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Titan-Centaur 7 lifting off on August 20, 1977, beginning the Voyager journey
This image was compiled from three separate shots taken by Voyager 2 when it was 7.25 million miles (11.66 million km) from Earth less than a month after being launched
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This image was compiled from three separate shots taken by Voyager 2 when it was 7.25 million miles (11.66 million km) from Earth less than a month after being launched
NASA's Goddard Space Flight Center Voyager 1’s shots of Jupiter taken in early 1979
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NASA's Goddard Space Flight Center Voyager 1’s shots of Jupiter taken in early 1979
NASA's Goddard Space Flight Center Voyager 1’s shots of Jupiter taken in early 1979
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NASA's Goddard Space Flight Center Voyager 1’s shots of Jupiter taken in early 1979
NASA's Goddard Space Flight Center Voyager 1’s shots of Jupiter taken in early 1979
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NASA's Goddard Space Flight Center Voyager 1’s shots of Jupiter taken in early 1979
NASA's Goddard Space Flight Center Voyager 1’s shots of Jupiter taken in early 1979
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NASA's Goddard Space Flight Center Voyager 1’s shots of Jupiter taken in early 1979
Voyager 1 image of Io showing active plume of Loki on limb – image is a mosaic of smaller Voyager snaps
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Voyager 1 image of Io showing active plume of Loki on limb – image is a mosaic of smaller Voyager snaps
Voyager 1 snapped this picture of Jupiter’s moon Io in 1979
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Voyager 1 snapped this picture of Jupiter’s moon Io in 1979
Jupiter’s largest moon, Ganymede, snapped by Voyager 1 in early March 1979
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Jupiter’s largest moon, Ganymede, snapped by Voyager 1 in early March 1979
Rhea, a moon of Jupiter that looks similar to our moon
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Rhea, a moon of Jupiter that looks similar to our moon
A transit of Io across Jupiter captured by Voyager 2 in 1979
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A transit of Io across Jupiter captured by Voyager 2 in 1979
Jupiter's moon Europa captured by Voyager 2
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Jupiter's moon Europa captured by Voyager 2
Callisto, a cratered Jupiter moon, captured by Voyager 2
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Callisto, a cratered Jupiter moon, captured by Voyager 2
Voyager 2 approaching Saturn in mid 1981
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Voyager 2 approaching Saturn in mid 1981
Mimas, a moon of Saturn, visited by Voyager 1 in late 1980
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Mimas, a moon of Saturn, visited by Voyager 1 in late 1980
Voyager 2 meeting Saturn’s moon Enceladus
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Voyager 2 meeting Saturn’s moon Enceladus
Saturn's moon Dione, seen from Voyager 1
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Saturn's moon Dione, seen from Voyager 1
Saturn's moon Dione, seen from Voyager 1
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Saturn's moon Dione, seen from Voyager 1
Voyager 1 image of Saturn from a distance of 5.3 million km four days after its closest approach
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Voyager 1 image of Saturn from a distance of 5.3 million km four days after its closest approach
Saturn in Violet, Blue, and Green (mapped to Blue, Green, Red, respectively), taken by Voyager II in August of 1981
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Saturn in Violet, Blue, and Green (mapped to Blue, Green, Red, respectively), taken by Voyager II in August of 1981
Voyager 2 image of the Saturnian satellite Titan from 4.5 million km
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Voyager 2 image of the Saturnian satellite Titan from 4.5 million km
The north polar region of Saturn is pictured in great detail in this Voyager 2 image obtained Aug. 25 from a range of 633,000 km (393,000 mi)
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The north polar region of Saturn is pictured in great detail in this Voyager 2 image obtained Aug. 25 from a range of 633,000 km (393,000 mi)
Uranus’ Moon Miranda – taken by Voyager 2 in 1986
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Uranus’ Moon Miranda – taken by Voyager 2 in 1986
Voyager 2 discovered 10 new moons during its encounter with Uranus in early 1986
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Voyager 2 discovered 10 new moons during its encounter with Uranus in early 1986
A false color shot from Voyager reveals concentric clouds on the South Pole of Uranus
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A false color shot from Voyager reveals concentric clouds on the South Pole of Uranus
Voyager 2 discovered two previously unknown rings during its visit to Uranus
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Voyager 2 discovered two previously unknown rings during its visit to Uranus
A parting snap as Voyager 2 said goodbye to Uranus on its way to Neptune
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A parting snap as Voyager 2 said goodbye to Uranus on its way to Neptune
Scientists pore over pictures of Neptune delivered by Voyager 2 in 1989
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Scientists pore over pictures of Neptune delivered by Voyager 2 in 1989
One of the most famous images of Neptune taken by Voyager 2 in 1989
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One of the most famous images of Neptune taken by Voyager 2 in 1989
A computer-generated montage of two Voyager 2 images showing Neptune’s moon Triton in the foreground
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A computer-generated montage of two Voyager 2 images showing Neptune’s moon Triton in the foreground
Neptune’s moon Triton in 1989
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Neptune’s moon Triton in 1989
Voyager 2 capturing cloud streaks on Neptune
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Voyager 2 capturing cloud streaks on Neptune
Umbriel, one of Neptune’s moons
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Umbriel, one of Neptune’s moons
Neptune in 1989 by Voyager 2
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Neptune in 1989 by Voyager 2
Neptune’s southern Hemisphere
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Neptune’s southern Hemisphere
Voyager says goodbye to Neptune in 1996
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Voyager says goodbye to Neptune in 1996
These six narrow-angle color images were made from the first ever images group of the Solar System taken by Voyager 1, which was more than 4 billion miles from Earth and about 32 degrees above the ecliptic. These blown-up images, left to right and top to bottom are Venus, Earth, Jupiter, and Saturn, Uranus, Neptune
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These six narrow-angle color images were made from the first ever images group of the Solar System taken by Voyager 1, which was more than 4 billion miles from Earth and about 32 degrees above the ecliptic. These blown-up images, left to right and top to bottom are Venus, Earth, Jupiter, and Saturn, Uranus, Neptune
This narrow-angle color image of the Earth, dubbed "Pale Blue Dot", is a part of the first ever "portrait" of the Solar System taken by Voyager 1 – Earth appears as a few blue pixels about halfway down the orange band on the right
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This narrow-angle color image of the Earth, dubbed "Pale Blue Dot", is a part of the first ever "portrait" of the Solar System taken by Voyager 1 – Earth appears as a few blue pixels about halfway down the orange band on the right
This is an image of Voyager 1’s signal taken from Earth by a radio telescope array in 2013 – Voyager 1 is 11.5 billion miles (18.5 billion km) away in this photograph
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This is an image of Voyager 1’s signal taken from Earth by a radio telescope array in 2013 – Voyager 1 is 11.5 billion miles (18.5 billion km) away in this photograph
An artist's impression of the Voyager spacecraft
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An artist's impression of the Voyager spacecraft
The status of both Voyager spacecraft as of Tuesday, 15th August 2017
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The status of both Voyager spacecraft as of Tuesday, 15th August 2017
The status of the Voyager instruments as of August 2017
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The status of the Voyager instruments as of August 2017
An impression of the expansive heliosphere and the four current objects on their way out of our solar system – Voyager 1 is the fastest and furthest of all the objects shown
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An impression of the expansive heliosphere and the four current objects on their way out of our solar system – Voyager 1 is the fastest and furthest of all the objects shown
A map of the Voyager journey
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A map of the Voyager journey
Happy 40th birthday Voyager!
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Happy 40th birthday Voyager!
View gallery - 47 images

On August 20, 1977, Voyager 2 was launched, beginning humanity's most epic astronomical adventure. Two weeks later its sister spacecraft, Voyager 1, was launched, and the two explorers set out to shed light on the mysteries of our solar system by getting up close and personal with our distant neighbors for the first time ever. Forty years later, both pioneers are still operating, sending back data, and heading on their way out of our solar system to explore further than any spacecraft ever launched.

The rare alignment

The Voyager dream began in the early 1960s, when aerospace engineer Gary Flandro discovered a rare planetary alignment would occur in the late 1970s. This perfect alignment of Jupiter, Saturn, Uranus, Neptune and Pluto occurs once every 175 years, and it meant a single spacecraft could quickly visit most of the Solar System's outer planets using gravitational slingshots to leap from planet to planet.

The original project was known as the Planetary Grand Tour, and for years NASA worked on the project until it was officially canceled in 1971 due to the nearly US$1 billion proposed cost. The following year President Nixon rekindled the project, but with a caveat – the project could only budget for two probes to visit two planets, Jupiter and Saturn.

The ambitious and talented NASA engineers set to work on developing the probes, secretly designing the spacecraft with further exploration in mind. Not content with just getting to Jupiter and Saturn, the team was determined to get the probes all the way to the outer Solar System.

A map of the Voyager journey
A map of the Voyager journey

Send more Chuck Berry!

As the project progressed the legendary astronomer Carl Sagan worked on a series of messages to attach to the probes. Eventually the messages took the form of a golden record conceived as a cosmic "message in a bottle". The now infamous Voyager Golden Records included aboard both Voyager spacecraft are encoded with a variety of images and music from our global culture. A curious alien species will find 115 images on each record, greetings in various Earth languages and a variety of lessons in our biochemistry.

Each record also holds 27 songs, designed to be a representation of music spanning all Earth cultures. Bach is well represented with three tracks, and a variety of traditional cultural selections, such as Peruvian panpipes and Navajo chanting, are included as well. Perhaps the most contentiously argued choices came when the selection committee focused on what songs to send to represent modern music.

A Louis Armstrong jazz track and a blues song by Blind Willie Johnson were relatively uncontroversial selections, but the choice of "Johnny B. Goode" by Chuck Berry was not unanimous. After initially hesitating, Carl Sagan ultimately defended the choice against some more conservative objections, although it wasn't his first choice for a modern song. The Beatles' "Here Comes the Sun" was on the hit list for some time, and despite the band themselves apparently supporting the idea, copyright holder EMI bizarrely refused to give permission.

The name of the Voyager project only came into being months before the launch in 1977. To that point the project had been clunkily labeled the Mariner Jupiter-Saturn mission. After a public competition organized by NASA, the name Voyager was chosen, and it was all systems go. The two Voyager probes were launched in August/September 1977 and then the waiting game commenced.

Titan-Centaur 7 lifting off on August 20, 1977, beginning the Voyager journey
Titan-Centaur 7 lifting off on August 20, 1977, beginning the Voyager journey

A journey of a billion miles begins...

In January 1979, Voyager began its approach of Jupiter sending back photographs and data offering insights scientists could only have dreamed of just a few years prior. Active volcanoes were unexpectedly seen on Jupiter's moon Io – the first time such features ever witnessed on another body in the Solar System. Rings were also discovered orbiting Jupiter and the volatile Great Red Spot was studied in astounding detail.

Next stop was Saturn, and the two Voyagers arrived in 1980/81. After providing more extraordinary insights into Saturn, the two probes parted ways. Voyager 1 altered its flightpath for a close flyby of Titan, Saturn's largest moon, revealing it to be a smog-enclosed world. The Voyager data also suggested possible oceans of liquid methane beneath the dense atmosphere, a hypothesis that was finally confirmed by the Cassini mission 25 years later.

The success of the Voyager program led to an inevitable mission extension and the foresight of the NASA engineers in secretly future-proofing the designs allowed Voyager 2 to quickly get on its way to explore Uranus and Neptune. Voyager 1's Titan mission meant its trajectory couldn't be altered back towards the outer planets, so it began an extended mission speeding towards interstellar space.

The Voyager 2 explorations of Uranus and Neptune remain to this day the only spacecraft we have sent to explore those planets. From Uranus' bizarre axial tilt to Neptune's extraordinarily violent storms, these observations are still some of the most valuable and direct insights ever collected on these mysterious outer planets.

A transit of Io across Jupiter captured by Voyager 2 in 1979
A transit of Io across Jupiter captured by Voyager 2 in 1979

Where no probe has gone before

From this point forward both Voyager spacecraft commenced their final, and most epic, mission phase – exiting the Solar System. In February, 1990, at the behest of Carl Sagan, Voyager 1 turned its camera around to take a "family portrait" of our solar system from the most distant vantage point ever. One of the images became known as the Pale Blue Dot, an awe-inspiring photograph where the Earth is seen as nothing more than a tiny blue dot suspended in the vastness of space.

For the next two decades scientists tracked the Voyager craft, discovering the extent of the Sun's solar winds, known as the heliosphere. The heliosphere is the bubble-like sphere of influence of the solar winds and its outermost stretches are known as the heliopause. This is the theoretical edge of our solar system, where the sun's solar winds are brought to an end by the pressure of interstellar space.

An impression of the expansive heliosphere and the four current objects on their way out of our solar system – Voyager 1 is the fastest and furthest of all the objects shown
An impression of the expansive heliosphere and the four current objects on their way out of our solar system – Voyager 1 is the fastest and furthest of all the objects shown

How far out our heliosphere stretched was unknown, and it wasn't until the middle of 2012 when Voyager 1 suddenly started registering spikes in certain high energy particles that scientists began to suspect the spacecraft had finally left the Solar System. By the end of 2013 it was finally confirmed that Voyager 1 had indeed entered interstellar space as of August 2012. Voyager 2, traveling a different trajectory, and slightly slower, is expected to cross into interstellar space in late 2019 or early 2020.

Both craft are estimated to still have enough power to return minor levels of data until at least 2025, at which point they will fall silent but continue their remarkable journey out into the galaxy. In 300 years Voyager 1 will reach the mysterious Oort cloud, and in about 40,000 years it will come within one light year of the star Gliese 445, in the constellation Camelopardalis.

Voyager 2, on the other hand, will come close to the star Ross 248 in about 40,000 years, but if undisturbed it will reach the brightest star in our sky Sirius, in about 296,000 years.

It's not hyperbolic to say the Voyager program is one of the greatest human achievements to date. Whatever happens to humanity here on Earth, hundreds of thousands of years from now the intrepid spacecraft will likely still be hurtling through the galaxy. They could still be going strong years after the Sun consumes the Earth, providing evidence of our existence long after we're gone.

Safe travels Voyager – and happy 40th birthday. Here's to a billion more!

Take a pictorial trip through the spacecrafts' remarkable journeys in our Voyager mission gallery.

View gallery - 47 images
5 comments
Brian M
Puts everything else into perspective!
Lardo
I'm planning a big "Glad to Meet You" party for August 20, 298,017. You're all invited. Siriusly.
Brainfarth
Time to watch the Star Trek movie again.
amazed W1
Truly amazing and vital to our understanding of what there is! Most congratulations to the "techies", from another techy, for concealing the true value of what you were doing from that heap of adminstrative illogic that tends to rule us all. You won't get the praise you deserve but then you have the techy's joy of seeing what you were responsible for working exactly as intended and even beyond its design life.
mike_edward
This to me is truly our greatest achievement of all time. Those craft are way out there, gone for good. It will be interesting if say, in 50 years time we have super fast travel methods and to a flyby of one of the craft!