40 Years Ago NASA Launched Voyagers 1 and 2. It’s Been a Stunning Ride.

Launch of Voyager 2

There has never been an expedition like the Voyager mission, and likely there will never be another to rival it. Now as we celebrate the 40th anniversary of its launch - August 20 for Voyager 2, September 5 for Voyager 1 – it might be a good occasion to place the enterprise in its historical context. In truth, triangulating between past and future has been one of Voyager's triumphs.

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The mission. The prod was a planetary alignment that occurs every 176 years. The outer planets - Jupiter to Neptune - arrange themselves in such a way that a spacecraft can in principle swing from one to the other in sequence, each fling adding critical velocity, in what was quickly dubbed the Grand Tour. It would next happen in 1977. The last time it occurred Thomas Jefferson was president, three years away from sending Lewis and Clark across the continent. This time NASA proposed to send two robotic spacecraft across the solar system.

Still, the politics was a close-run thing. It was the heroic age of planetary exploration, and NASA had just sent two Viking spacecraft to Mars to coincide with the American bicentennial. Voyager would carry the flame to the outer planets. But NASA's glory years were rapidly winding down. The Apollo program ended. The space shuttle stumbled in its place, a white elephant that would become a black hole in the budget. And there were technical concerns. Spacecraft had barely made it to Mars, and a trek to the edge of the solar system (20 times further out) was a gamble. The available computing power was less than that in a digital watch today. The Grand Tour was cancelled.

Then it was resurrected as a mission to Jupiter and Saturn, with the prospect, buried in its hardware and calculations, of perhaps, if the spacecraft completed their tasks at Saturn, of sending Voyager 2 to Uranus. Only five months before launch did the mission rebirth its lame "Mariner Jupiter-Saturn '77" title to "Voyager." At launch Voyager 1 came within seconds of failing to reach its required orbit. During its early cruise phase, Voyager 2 lost its primary antenna, and completed its trek across the solar system with a backup.

Voyager 1 succeeded spectacularly at Jupiter and Saturn. That freed Voyager 2 to tweak its trajectory around Saturn in such a way that it could chase Uranus. At Uranus it wheeled its path toward Neptune. Voyager 1's flight over Titan's pole took it out of the plane of the ecliptic and toward the stars. Voyager 2's flight over Triton did likewise. In March, 2013 Voyager 1 crossed the outer sheath of the heliosphere and entered interstellar space. Voyager 2 will follow in the next few years. They are now moving at 38,000 mph and 34,000 mph, respectively, at a distance of 139 and 115 astronomical units from Earth. They continue to transmit information. By shutting down all but the most essential functions, they have enough power to last another decade.

The returns have been magnificent. The Voyagers truly saw with fresh eyes of discovery.

The Voyagers were the second spacecraft to survey Jupiter and Saturn, but they were the first to do so with a full panoply of instruments and to survey the giant planets’ moons, and the first (and only) to visit Uranus and Neptune. They are the first to enter the heliopause and Voyager 1 was the first to exit and pass into interstellar space. They took the first photos of the Earth and Moon together. They discovered 26 unknown moons. They found volcanoes on Io, the inner moon of Jupiter, which were warmed by the gravitational tides of the planet, and they unveiled geysers on Triton, among the coldest object in the solar system. They revealed that the outer planets hold a menagerie of worlds far more active and varied than anyone had imagined. They are defining the blustery border of bow shock, where the solar and interstellar winds churn in filmy swirls against each other. “You only explore the solar system for the first time once,” Larry Soderblom, one of the mission’s two geologists noted. “Voyager did that.”

Equally defining is the sheer longevity of the mission. The Voyagers launched 20 years after Sputnik. They continue 40 years later. They span 67% of the entire space age, a proportion that will continue as they pass, still mechanically sentient, through interstellar space. There is nothing else comparable in exploration history. It’s as though Vasco daGama had embarked from Lisbon in 1498 and was still at sea 25 years after Magellan’s Victoria had completed its circumnavigation. Moreover, after the space shuttle Challenger blew up (during Voyager 2's departure from Uranus), the Voyager mission remained the only show in space. For a decade it was the American space program.

The Voyagers' instrumental array was matched by a cultural payload. Their most famous package was a golden record with greetings, songs, and images from Earth - a space-borne Family of Man. They were headed to the stars; they needed calling cards. The odds that an alien Other might decode its message were astronomically tiny, but their real point was that they were read by millions of Earthlings.

The Voyager twins began as machines crafted to do science. As they pass through the veil of the heliosphere, however, they are assuming the quality of a vision quest because more than data, more than images, more than stories of broken hardware and software glitches and ingenious workarounds, more than sheer endurance, the Voyagers have been a journey. Their cultural payload is what distinguishes the mission from adventuring; their trek is what distinguishes it from space science. The Hubble space telescope has, through relentless imaging and clever software, discovered more moons than the Voyagers; but it has no narrative. It sings no saga.

The Voyagers tap into a deep psyche of questing. Yet in one critical way they differ from the classic hero’s journey. They won’t return. Instead, they carry their home with them in the form of the golden records. Narrative closure for this Voyagers' tale acquires a self-referential loop. The Voyagers are explorers of modernism.

One of its many alluring peculiarities - what should make it especially enticing for historians - is that the Voyager mission has looked back as much as it has looked forward. Two weeks after its 1977 launch Voyager 1 turned back to shoot the first image of the Earth and its Moon. On Valentine’s Day, 1990 it looked back on the solar system and took a family portrait of six planets, including the famous “pale blue dot” that was Earth. When it turned its cameras back on Io, it captured a volcano in eruption. Its most radiant images of Saturn’s rings came when it looked back over its shoulder, the rings backlit by the Sun.

Less well appreciated may be the way the Voyager twins have looked back on the history of exploration. Their long trajectory is a triangulation between future and past. Mechanically, the twin spacecraft launched on a three-stage Titan Centaur rocket. Historically, what carried them to escape velocity were three great ages of discovery that began 600 years earlier. They were how Western civilization learned about a wider world.

There were several false dawns. Exploration became continuous - acquired an institutional identity - when Europe put to sea in the 15th century. But that long voyage of discovery has not been constant. It shows crests and troughs. It began explosively, unfurled with the Renaissance, driven primarily by the rivalry between Spain and Portugal. Then it stalled as discovery settled into trade; by the early 18th century exploring was banal, ignored, or satirized. It renewed as northern Europe took up imperialism and valenced the voyage of discovery to the Enlightenment. Naturalists displaced missionaries; new genera of flora and fauna replaced cinnamon and pepper as precious cargos. A global rivalry between Britain and France sprawled out to include Russia, the United States, and others expanding beyond their homelands.

Then, on the polar ice sheets, exploration ran out of continents and ran out of luck; science looked to atoms and genes; and modernism, like a software virus, began rewriting high culture. Intellectuals preferred to follow Freud into the unconscious rather than Stanley into the Congo. Modernist art had little kinship with geographic discovery. Europe convulsed with war, turning its energies against itself rather than projecting them outward. The fusion of geopolitics, science, art, technology, literature, and expansionism that had sparked earlier ages of exploration broke apart. Discovery stalled, once again languishing in a cultural doldrums.

Exploring revived in the postwar era, pivoting on Antarctica, while submersibles and rockets opened the deep oceans and the solar system to another great age of discovery. This time the critical rivalry was the Cold War between the U.S. and the USSR. This new age, the third, ours, is yet young. Its hardware and software are often out of sync, as we struggle to find ways to mesh our extraordinary technology with the culture of Greater Modernism. The robot has assumed the mantle of explorer; in the absence of an Other, the encounter becomes an exercise in self-discovery or immersion in the robots. Project teams speak, for example, of “inhabiting” the Mars Exploring Robots, Spirit and Opportunity. Such novelties are innovations in the long chronicle of geographic discovery, yet they are lineal descendents, or reincarnated avatars, of Pedro Cabral, Charles Sturt, and John Wesley Powell, who also had to adapt voyaging to transport the baggage of their day and navigate by the cultural constellations of their times.

The great outbursts involved more than geopolitics and commerce. They also narrated an evolving moral drama, a profound encounter between peoples that addressed questions of identity and a people's place in the Great Scheme of Things. They complemented a sense of where we are with a sense of who we are. The first age was dominated by the encounter of Europeans with people far removed from Biblical tribes and the geographies of the Ancients. The second age added a vision of explorers as Moses figures, as founders of new settler societies.

The third age lost such perspectives in a cultural whiteout. These were lands not only uninhabited but uninhabitable. There were no indigenes to convert, fight, study, or trade with. There were no enduring societies, or even families; outposts had no churches, schools, or social order beyond the most elemental. Remote sensing devices mapped the ocean floors. Robot spacecraft mapped the planets. An encounter meant a flyby with instruments and cameras.

In the past someone had to meet the newly encountered someones. Now they don't. There are no new languages to learn, no political and social norms to negotiate, no alternative worldviews to ponder. If there are no longer the ugly encounters that had burdened earlier exploration, there was no human drama of the old sort to challenge, inspire, or extend the frontiers of moral meaning. It all occurred through machine avatars. An encounter was an event, not an engagement.

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Come, my friends,

'tis not too late to seek a newer world.

- Alfred Tennyson, "Ulysses"

Each age has its grand gesture, an expedition that captured the character and domains of discovery peculiar to its circumstances. For the Great Voyages of the Renaissance it was surely the circumnavigation of the world ocean by the Victoria, captained by Ferdinand Magellan until, in the spirit of the age, he died in a senseless fit of militaristic hubris. For the renewed exploration of the Enlightenment, it was the traverse of a continent, a cross-section of natural history of the sort pioneered by Alexander von Humboldt before the baton passed to Lewis & Clark, Burke and Wills, Alexander Mackenzie, Henry Stanley, even Ernest Shackleton.

What the equivalent for the third age will be is unclear – we’re still in the early days. Viewed as exploration, most of the activity will occur in Earth’s deep oceans, and it may be that historians will consider the cumulative adventures of the submersible Alvin as the most representative emblem of the era. But the story of Alvin is a biography rather than the narrative of a quest. What the age begs for is the equivalent of a circumnavigation of the world-circling oceanic abyss or a traverse of the solar system, an expedition outfitted not just to adventure and survive but to inquire beyond the veil of the possible and to inspire as well as inform.

Which is why my vote goes to Voyager. More munificently than any other mission Voyager speaks to what exploration can mean in our times, and why it matters, and how we might understand our age’s awkward alloy of innovation and historical inheritance. Nor has anything else matched its appeal to the idealism of discovery, the oft-utopian yearning that has launched explorers to search for newer worlds, not least in the hope that Earth might be among them.

The Grand Tour: a composite of the outer planets and select moons encountered by the Voyagers.  Painting by Don Davis for NASA-JPL.