On this day in 1977 NASA launched the Voyager probes (1 and 2) to explore the outer solar system. These spacecraft are, in my opinion, one of humanity’s most impressive technological accomplishments. Unlike anything here on Earth, they are artefacts that shall endure long after we as a species have ceased to exist; a testament to the space-faring aspirations of a band of primates on a tiny planet in the corner of the Milky Way. The Voyager probes are marvels of scientific ingenuity and wonderful tributes to the foresight of the engineers and scientists that built them. They are pioneering scientific instruments that revolutionised our understanding of the outer planets and their moons, time capsules and timeless interstellar messengers.
After making several important discoveries about the properties of Jupiter and Saturn and their moons, and capturing the beautiful Pale Blue Dot image, Voyager 2 continued on to Neptune and Uranus whilst Voyager 1 was set on an interstellar escape trajectory and is currently approaching the edge of our solar system. At 118 astronomical units (AU) it is the furthest man-made object from Earth and is likely to pass through the heliosheath into the interstellar medium sometime between 2012 and 2015, at which point humanity will officially become an interstellar species.
The Voyagers remain in working order, albeit with many of their instruments offline, an impressive 34 years after launch. They still remain in radio contact with Earth and commands transmitted at light speed take approximately 16 hours to reach the probes. These weak tracking signals are 20 billion times more feeble than the electrical current passing through a standard digital watch. If Voyager 1 avoids collision (with micrometeorites and space debris) it will continue to wander through interstellar space forever and it is unlikely to be overtaken by any other conventional human spacecraft or probe. It will be 40,000 years before the lonely Voyager passes near another star when it comes within 1.6 light years of the enigmatic M-type star AC+79 3888 in the constellation Camelopardalis.
In around 5 and a half billion years from now the Sun will have ballooned into an enormous red giant and possibly consumed all of the inner planets, including the Earth. Humans will either have gone extinct or left the ageing Solar System long before our decaying Sun enters its final death throes. Even then, it is possible that somewhere in deep space the lonely Voyagers will continue to obediently sail through the depths of space and time on a mission lasting an eternity; a mission with no end and no more formal objectives. The probes will not decay in the vacuum of space and their form and technology will be preserved indefinitely, long after their instruments have stopped working.
It is also possible that in the very distant future the Voyager probe may be intercepted by an advanced alien civilisation, or even future humans or our descendants. It is with this remote eventuality in mind that the scientific team behind the probes, lead by Carl Sagan, attached the Voyager Golden Record (VGR) to the spacecraft. The VGR contains sounds and images designed to depict the diversity of life on Earth as well as the location the origin of the probes. The significance of the VGR as a message from humanity to the Universe was not underestimated by the scientific team or the leaders of the world at that time. An image included in the VGR is a message from the then U.S. President Jimmy Carter:
“This is a present from a small, distant world, a token of our sounds, our science, our images, our music, our thoughts and our feelings. We are attempting to survive our time so we may live into yours…”
Voyager 1 is therefore much more than just a spacecraft, it is an interstellar time-capsule and a messenger to the stars. Perhaps someday it will be the oldest surviving relic of a lost civilisation with great aspirations and a demonstrable foresight able to appreciate the scale of the Universe. The Voyager probes are as close to art as science can get. They are truly wonderful, eternal symbols of the best intentions of our species and the universalist philosophy of science.
Fly on Voyagers, fly on.
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