An artist’s concept depicts NASA’s Voyager 1 spacecraft entering interstellar space on a journey which has lasted 47 years so far (Picture: Caltech/NASA-JPL)
The Voyager probes are said to be ‘far from finished’ despite their power supplies dwindling in the farthest reaches of space ever traversed by human-made objects.
NASA engineers have had to turn off instrumentation and last month overcame a communications blackout with Voyager 1 after it stopped sending data back to Earth.
The two 1970s-designed probes are travelling at around 38,000 mph through interstellar space and are each carrying Earthly sounds for potential alien life to listen to.
While NASA has said they could keep going into the late 2020s, the communication failure which was resolved last month has highlighted the ageing nature of the craft.
However Christopher Phillips, an astrophysicist at the University of Warwick, believes the ‘ambassadors of humanity’ still have a crucial role to play in space exploration.
He said: ‘Voyager’s power source, a small nuclear generator, is running out of fuel. To keep the science going, engineers have had to turn off heaters, instruments, and other systems one by one – sacrifices that are made for the sake of the mission.
‘The Voyager probes are like ocean explorers sailing uncharted waters, navigating farther from the shoreline than anyone thought possible.
‘Their sails are worn, and supplies are running low, but their mission is far from over. They’re still charting the cosmic currents and sending back messages about the mysterious depths they traverse.’
Launched on rockets a few weeks apart in late 1977, the explorers were designed to explore the outer planets in the solar system.
Voyager 1 reached the interstellar boundary in 2012, with its slower twin following six years later. The former is now around 15.5 billion miles from Earth and the latter 12.9 billion miles.
Neptune as captured by Voyager 1 in 1989 before the craft headed on a course for Interstellar space (Picture: NASA, @NASAVoyager)
As they hurtle into the unknown outside the protective heliosphere, they are losing power at a rate of 4 watts a year and will cool as the bar dips.
Camera technology is turned off and it is unlikely it could be revived.
‘Despite these challenges, Voyager still sends back whispers of the interstellar medium — the space between the stars,’ said Phillips, of the Astronomy and Astrophysics Group, part of the Physics Department.
‘This is a place we’ve never been, and Voyager is our eyes and ears in this mysterious realm. And let’s not forget the sheer distance involved.
‘Voyager 1 is over 15 billion miles away from us, and it takes more than 22 hours for its messages to reach Earth.
‘Communicating with these probes is like asking a question over the phone and then waiting an entire day for a response.’
An artist’s concept depicts NASA’s Voyager 1 spacecraft entering interstellar space, or the space between stars (Picture: Caltech/NASA-JPL)
One of the gold-plated records being readied for travel onboard the Voyager probes (Picture: Space Frontiers/Archive Photos/Getty Images)
Each Voyager probe contains a 12-inch, gold-plated phonograph disc containing encoded images and sounds including surf, wind, thunder, birds and greetings in 55 languages.
A diverse 90-minute selection of music includes Bach, Beethoven, Mozart, Chuck Berry and Blues singer Blind Willie Johnson.
Each record is encased in a protective aluminium jacket and comes with a cartridge, needle and instructions.
The late Carl Sagan, a planetary scientist who chaired a committee which selected the contents, said the records will only be played if there are ‘advanced spacefaring civilizations in interstellar space.’
‘The Voyager probes aren’t just spacecraft; they’re ambassadors of humanity and pioneers of exploration,’ Phillips said.
‘Their importance lies in their ability to give us a perspective we’ve never had before. By travelling beyond the influence of our Sun’s magnetic field and into interstellar space, they provide a direct look into the space between the stars — a realm that had previously only been theorized.’
Voyager 1 suffered a communications blackout for nearly a month due to power supply issues which began in October.
Voyager 1’s capture of Jupiter in 1979 compiled from two sets of frames (Picture: NASA/JPL/Ian Regan via The Planetary Society, http://www.planetary.org)
NASA managed to restore communications by turning back on the X-band transmitter, which sends science and engineering data. The blip is one of a number of issues that the agency has had to overcome.
Remarkably, both probes continue to work despite extremely small power margins and are carrying out their primary mission to study particles, plasma and magnetic fields in interstellar space.
‘Every bit of data they send back helps scientists refine our understanding of the nature of interstellar space, cosmic radiation, magnetic fields, the boundaries of the heliosphere – the bubble of solar wind that surrounds our solar system,’ Phillips said.
Discovery in the unknown
The two Voyager spacecraft launch weeks apart on rockets taking off from NASA’s Kennedy Space Centre
The craft has a close encounter with Saturn and several of its icy moons including Rhea (pictured). It reveals a weather system around Saturn’s north pole
At a distance of about 4 billion miles, Voyager 1 takes the last images of the mission, showing Earth as a tiny spec in an image called the Pale Blue Dot.
Voyager 1 becomes the first human-made object to cross beyond the heliopause, the boundary between the solar system and matter ejected by exploding stars
Voyager 1 observes a unique pressure front from the Sun that has crossed into interstellar space, which NASA has nicknamed Pf2
‘These insights are crucial for future space exploration, especially as we dream of sending humans to Mars and beyond.
‘The Voyagers remind us that even small, intrepid steps into the unknown can yield discoveries that transform how we see the universe.’
The ageing Voyagers continue to function amid new delays to NASA’s Artemis programme to send humans to the moon, with the next mission pushed back to 2026.
They have already completed a ‘grand tour’ of all the giant planets in the outer solar system: Jupiter, Saturn, Uranus and Neptune and 48 of their moons. Voyager 2 alone discovered 10 new moons as it flew past Uranus, which were given Shakespearean titles including Puck, Portia and Juliet.
Charting the unexplored reaches of space, the probes are acting as pathfinders for missions which may take place in hundreds, if not thousands, of years’ time.
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‘Looking ahead, even as its power dwindles, Voyager can continue to teach us about the nature of space in 2025 and beyond,’ Phillips said.
‘Its findings could influence how we design spacecraft to withstand the harsh environment of interstellar travel, laying the groundwork for humanity’s first true starships.
‘It’s a bit like mapping a new ocean before building the ships to cross it.’
Earthshot: An image of the origin planet entitled ‘Pale Blue Dot’ taken by Voyager 1 in 1990 (Picture: NASA/JPL-Caltech)
While the best shot of finding alien life is next-generation telescopes and missions searching for biosignatures on exoplanets, the probes and their discs are a statement of intent, according to Phillips.
‘They’re a symbol of our desire to connect with something greater and to show we are here,’ he said.
‘While Voyager might not be our best shot at contacting alien life, it’s certainly a poetic one.’
Voyager 1’s projected itinerary includes a rendezvous with an obscure star in the Ursa Minor constellation called AC+79 3888.
Space enthusiasts needn’t wait — even if its systems somehow lasted, the encounter would not take place until 40,272 AD.
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