NASA's Voyager spacecraft have been exploring interstellar space since 1977, making them NASA's longest-operating missions.
It is fitting to say that NASA’s twin Voyager probes have become time capsules of their era. Data is recorded on 8-track tapes on both spacecraft, they have about 3 million times less memory than a modern cellphone, and they transmit data about 38,000 times slower than a 5G connection.
But this doesn’t matter.
As far as space exploration is concerned, the Voyagers remain the leaders. Until now, they have been the only probes that have visited interstellar space – the galactic ocean that our Sun and planets travel through.
Solar wind (charged particles from the Sun) and the Sun’s magnetic field create the heliosphere, a protective bubble that shelters the Sun and planets. To better understand our Sun and how the heliosphere interacts with interstellar space, researchers are combining the observations of Voyager with data from newer missions.
“The heliophysics mission fleet provides invaluable insights into our Sun, from understanding the corona or the outermost part of the Sun’s atmosphere to examining the Sun’s impacts throughout the solar system, including here on Earth, in our atmosphere, and on into interstellar space,” said Nicola Fox, director of the Heliophysics Division at NASA Headquarters in Washington. Over the last 45 years, the Voyager missions have provided this knowledge, helping us understand the sun and its influence in ways that no other spacecraft can.”
It is also an honor for the Voyagers to serve as ambassadors because each of them carries a golden record that includes images of Earth, diagrams of basic scientific principles, and audio that includes sounds from nature, greetings in multiple languages, and music.
With the rate gold decays in space and is eroded by cosmic radiation, the gold-coated records will last over a billion years if encountered by any intelligent beings out there. They serve as a cosmic “message in a bottle” for any future visitors.
The Voyager 2 spacecraft launched on Aug. 20, 1977, followed by the Voyager 1 spacecraft on Sept. 5. Both probes visited Jupiter and Saturn, but Voyager 1 went faster and reached them first. The two probes together revealed a great deal about our solar system’s two largest planets and their moons. In 1986 and 1989, Voyager 2 became the first and only spacecraft to fly as close as possible to Uranus and Neptune, providing humanity with a glimpse into these distant worlds.
After conducting these flybys, Voyager 1 began approaching the heliosphere’s boundary in 2012. After leaving the heliosphere in 2012, Voyager 1 discovered that the heliosphere blocks 70% of cosmic rays, which are energetic particles created when stars explode. In 2018, Voyager 2 exited the heliosphere boundary after completing its planetary explorations.
The combined data from both spacecraft has challenged previous theories of the heliosphere’s shape. The Voyagers are exploring uncharted territory as they explore interstellar space today, said Linda Spilker, deputy project scientist at JPL.
“This is the first time we’ve been able to directly study how a star, our Sun, interacts with the particles and magnetic fields outside our heliosphere, helping scientists understand the local neighborhood between the stars, upending some of the theories about this region, and providing key information for future missions.”
Through the years, the Voyager team has come to appreciate the challenges of operating such an old spacecraft, sometimes searching through historical documents and consulting retired colleagues for help.
The Voyagers are powered by a thermoelectric generator containing radioactive plutonium that generates heat that changes into electricity. The heat output decreases as the plutonium decays.
For compensation, the team turned off all non-essential systems, including heaters, to protect still-operating instruments from space’s frigid temperatures. Despite being well below the lowest temperatures they were ever tested at, all five instruments that have been turned off from heaters since 2019 are still working.
A recent issue on Voyager 1 caused status information about one of its onboard systems to become garbled. In spite of this, the spacecraft and system continue to operate normally, suggesting the problem is not with the system itself but with the way the status data is produced. While engineers try to fix the problem or find a way around it, the probe continues sending back science observations.
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