Voyager - Exploration, Space, And The Third Great Age Of Discovery

by Stephen J. Pyne

  Pioneer 10 launched in March 1972, and Pioneer 11 a year later, in April 1973. It was Pioneer 10 that first encountered Jupiter, warned of its lethal radiation, and sent back real-time images of the planet as it approached periapsis. Its instruments sketched a new cartography of the solar system, a geography of magnetism and radiation. But the reports that captivated the public were the pictures that took shape, scan line by scan line, from Pioneer’s Pulsed Image Converter System (PICS). Its spin-stabilization design meant Pioneer did not have a camera, but it could broadcast data from the imaging photopolarimeter’s narrow-angle telescope in strips as it rotated. These were assembled into color images by computer, which added green to the reds and blues that Pioneer sent back, and then projected the result on television.

  By December 2, 1973, the images exceeded those from Earth-based observatories, and as the spacecraft approached periapsis the next day it proclaimed a new perspective on Jupiter, the greatest advance since Galileo had trained his telescope on the planet. Even more, Pioneer changed the process as well as the pictures. While there were no human eyewitnesses, as with the Apollo lunar landings, the public could see what Pioneer could as it swept around Jupiter. The images were grainy—clunky by later standards, and far from the bewitching scenes recorded by Voyager. But they came in real time, and they thrilled, and they helped announce an era of virtual exploration. For its imaging triumph, the Pioneer program even received an Emmy award.63

  The near-death, and ultimate success, of Pioneer 10 warned JPL that Voyager had to harden its electronics and tweak its trajectories. But the Grand Tour required that the mission have similar information regarding Saturn. This task fell to Pioneer 11, which followed a trajectory to Jupiter that would also allow it the option of going to Saturn.

  Pioneer 11 made its closest encounter on December 2, 1974, a third as near to Jupiter as its predecessor, and on a trajectory that gave the first views of Jupiter’s poles (invisible to Earth-based observation), and then slung it to Saturn. By passing through the Jovian radiation ring vertically in this way, it would experience only a short burst of irradiation, which would allow it a nearer encounter. Then it flung around on a trajectory to Saturn in which it trekked across the solar system by passing over the plane of the ecliptic. As it approached Saturn, its controllers and scientists debated between an inside or an outside passage—whether to cross the rings sharply or swing around them altogether. Either route would reveal new knowledge, but NASA determined that the heavy scientific lifting for the planet would come from Voyager, and that Pioneer would test Saturn’s shoals for the explorers to follow. As Pioneer 10 had allowed Pioneer 11 to proceed to Saturn, so Pioneer 11 would be used to allow Voyager 2, if all went well with Voyager 1, to proceed to Uranus. What Voyager required was more precise knowledge about the outside passage.64

  On September 1, 1979, Pioneer successfully navigated through the outer rings, and then passed through them again on the other side on September 3. Along the way it dispatched five images of Titan, another target of Voyager; and through occultation, it discovered a new Saturnian moon, later validated and named Epimetheus.

  That achievement was perhaps not all that Pioneer 11’s most visionary proponents had wished for, but it was all the spacecraft had to do. Among routes over America’s Continental Divide, South Pass is virtually inconspicuous, a rise of land in a broad plateau, rather than a rift through towering mountains like a Khyber Pass; yet it was the way west. So it was with the outside passage at Saturn. The route lay open for the Grand Tour.

  Both Pioneers had yet more to do, this time probing a path that would ultimately take them beyond the solar system. The first, Pioneer 10, crossed the orbit of Uranus on July 1979, and of Pluto in 1990, completing a traverse of the solar system’s hard geography. The soft geography, as defined by the solar wind, was much farther away. Moreover, it was asymmetrical, compressed in the direction of the Sun’s travel and stretched in the opposite direction, leaving a long ionic tail. Pioneer 10 traveled down that tail. Despite its early launch, its slower speed and trajectory thus put it behind in the race to the frontier. Pioneer 11, meanwhile, coasted toward the heliosphere’s bow shock.

  Each carried two messages. One was a plaque attached to the chassis of the spacecraft that, overtly, stood as a communiqué to any future finder of the hulk. It was a kind of calling card that identified who sent the machine and from where; in this, again, it tried out what the Voyagers would elaborate. The plaques became the lasting logo of Pioneer. The second message was its radio signal to Earth. Both spacecraft continued to broadcast—Pioneer 11 up to 1995, and Pioneer 10 into 2003; and the Deep Space Network continued to tease out their ever-feebler transmissions. In this, again, Pioneer assisted Voyager by prodding and refining the DSN. As one observer remarked, the total energy from Pioneer’s radio signal at the edge of the planets “would have to be collected for several million years to light a single 7.5-watt nightlight for a millionth of a second.” To extract that signal from the cosmic background buzz was a daunting achievement. If the two Voyagers were to succeed—Voyager 1 blitzing to the heliopause, and Voyager 2 completing the Grand Tour—they would need extraordinary communications. Those technologies were first devised to listen to Pioneer.65

  In June 1983, while Voyager 2 was halfway between Saturn and Uranus, Pioneer 10 slid beyond the orbit of Neptune. In 1995 Pioneer 11 suffered a broken Sun sensor, and despite some slight reserves of power, it could no longer direct its wispy transmissions to Earth, and fell silent, still heading toward the constellation Aquila. Pioneer 10 continued to broadcast, but so painfully and weakly that its scientific value was nil. It sank into a virtual coma, and on March 30, 1997, at 11:45 a.m., life support ended, as the last signals were downlinked to the DSN station in Madrid. Still, hope lingered, and Pioneer 10, oblivious to Earth, sent a signal captured by the radio telescope at Arecibo. But like a Newcomen engine in an age of diesels, the equipment required to track and interpret Pioneer was beyond obsolescence. Even heroic measures could barely sense the messages sent across 7.5 billion miles and 20 hours. On March 2, 2002, Pioneer exchanged greetings with Earth on its thirtieth birthday. On February 7, 2003, across 8 billion miles, it finally fell silent, and Pioneer 10 joined its sibling as a machine corpse hurtling through the cosmos.66

  The tragedy of pioneering is to create conditions that eliminate the pioneers—and that was the fate of Pioneers 10 and 11. Compared with the Voyagers, the Pioneers were slow and kludgy, and despite an impressive early lead and first contacts with Jupiter and Saturn, the Voyagers overwhelmed their scientific results and their capacity to evoke wonder, and then overtook them physically in 1998 to become the most distant objects to leave Earth. Unlike the Pioneers, the Voyagers have enough power and working instruments to function until perhaps 2020. They would likely survive to pierce the veil of the heliosphere and to report that event.

  The frontier belonged to Voyager.

  BEYOND THE BARRIER

  The hard geography proved less formidable than feared, and for mission planners, surprisingly less daunting than the solar system’s soft geography.

  Pioneer 10 found (and Pioneer 11 confirmed) that most of the interplanetary realm’s perilous particles clustered around Earth or at the center of the asteroid belt, where they thickened to almost three times the density apparent in interplanetary space. High-velocity micrometeorites and dust particles were fewer than anticipated. Both spacecraft whisked through with hardly a scratch. Likewise, the planetary rings proved porous or thinned to the point where they could be skirted. There was only one near-collision. At Saturn, Pioneer 11 found, by occultation, a new inner moon on its approach, and then nearly collided with it upon its departure.67

  The Voyagers threaded through the asteroids, slid around and through the rings, and avoided undetected satellites.

  What did threaten Pioneer was interplanetary space’s soft geography. An immense solar storm, the largest ever recorded, shook Pioneer 10 on August 2, 1972. Pioneers 6 t
hrough 9, already deployed around the inner planets to measure solar activity, had sensed and then tracked a solar wind of unprecedented power and velocity (3.6 million kilometers per hour) that exploded outward. By the time this ionic tsunami struck Pioneer 10 some three days later, it had shed half its velocity, although by transforming that energy into higher temperature, and its wind had become so diffuse that Pioneer 10 sensed its passing only through the traces it left on a battery of delicate instruments.68

  What did nearly cripple the spunky spacecraft was its scrape with the radiation belts of Jupiter, a blast completely unanticipated by designers. As it approached closest encounter, each half-hourly data dump notched up radiation to levels that would saturate and then overwhelm its onboard instruments—more than a thousand times what theory had predicted. Then, just as unexpectedly as rates had risen, they fell. The radiation belts of Jupiter, it was soon realized, were not only far more potent than those of Earth-like planets but also more unstable, and wobbled around the gaseous giant at an eleven-degree tilt. The gusty ionic wind had veered, as it were, just enough to permit Pioneer to pass through without foundering on the magnetic reefs. Two cosmic ray telescopes became temporarily infirm, and the blast of irradiation gave fatal cataracts to the optics of the Sisyphus instrument.69

  The Voyagers’ designers hurriedly reworked the still-abuilding spacecraft to shield its sensitive instruments. Thanks to Pioneer, the hazards of space had become sufficiently well known to build protection into the Voyagers’ apparatus before launch. But the Voyagers had one other enormous advantage over Pioneer: their programmable computers. They could self-analyze, receive new instructions, and operate with a degree of autonomy. Pioneer 10’s flyby of Jupiter required 16,000 commands from Earth, and a flaw in any one could prove fatal. On Voyager an error could, within limits, be repaired or circumvented. Just as the Voyager Grand Tour could incorporate the lessons of Pioneer, so new lessons could become encoded into practice as the spacecraft sped across the solar system.

  The asteroid belt does not track a simple orbit but those of a slushy cluster of planetoids and debris scattered across a wide swath. It took the spacecraft most of a year to traverse the full field. Voyager 1 and 2 exited the realm unscathed in August and September 1978, respectively.

  DAY 413 - 6 02

  11. Cruise

  The Voyagers sailed on, and on. Week passed week, month passed month. Between the asteroid belt and Jupiter lay 370 million kilometers of interplanetary space. Mars was half again as far from the Sun as Earth was, the asteroid belt almost three times as distant, and Jupiter was twice that. The journey could seem endless.

  The euphoria of launch had long passed, and the frenzied elation of encounter lay far in the distance. Other planetary projects beckoned, and JPL siphoned off engineers to work on those. Attention wandered. The Voyagers passed through a void of concentration, filled, when possible, by anticipation and analogy. Since there was a lot of interplanetary space, and a lot of earthly time to pass before the first, defining encounter, the Voyagers spent a great deal of time measuring and weighing analogies, and were in turn measured and weighed by them.

  SPACE FOR ANALOGY

  What did space mean? In practical terms the choices were those represented by von Braun, Van Allen, and Pickering as they hoisted Explorer 1 over their collective heads. It meant colonization, science, and journey as exploration, and the American space program found it hard to hold them all together. But for some partisans, the space program overall meant more. It stood for—promised to catalyze—an immense social reformation destined to transform the American commonwealth on a scale with few precedents. In the words of one techno-prophet, “the thrust into space will change the ideas and lives of people more drastically than the Industrial Revolution.”70

  As early as 1962, NASA commissioned the American Academy of Arts and Sciences to explore the “secondary” impacts of the rapidly metastasizing national investment in space, anticipating that the vaunted spin-offs would extend far beyond simple economic stimulus. Good academics, the group devoted most of its exegetical energies arguing the limitations of historical analogy in principle. In the end they opted to examine the advent of the railroad as a possible model, and again, good scholars, they so hedged their analysis with qualifiers and caveats that the analogy virtually fizzled out on the launchpad. By then, too, political realities were quelling the rush of spending; by the end of Apollo, the NASA claim on the federal budget had reached a very modest steady state. The space program would not become the transcontinental railroad of the twentieth century. Partisans for utopian revolution would have to look elsewhere .71

  What the exercise did emphasize was the complexity of novelty amid a thriving culture. A new machine, program, or idea derived its power from the richness and intensity of its interactions with the rest of society—and the space program was an interaction. Had the AAAS Committee on Space shifted its attention from the startling monies funneled into NASA and the promise of endless spin-offs, a kind of political perpetual-motion machine, and turned to exploration history, it would have probed and poked at very different data sets but come to a similar conclusion. Voyages of discovery derived their power from the fullness of their cultural engagements. A new machine or idea may reform society but only after it first fits in. An enterprise such as Voyager could not inspire or remake what did not already exist.

  Similarly, there was no lack of analogies to exploration history. Space travel was imagined as a stage in earthly evolution, a metamorphosis in humanity’s maturation, and manifest destiny gone to Mars. The planetary program was Leif Ericson, Columbus, and Magellan. What such allusions all shared was dissociation from particular sustaining societies; they were universal. Yet what boosters and designers needed was a closer look at just how those predecessors interacted with their cultures, and for that, since the Third Age was still aborning, they might profitably have examined the founders of the Great Voyages. They might have looked, especially, at the Portuguese paradigm.

  The Portuguese ignited the First Age, traveled the widest, contributed the greatest number of pilots and mariners, and established a framework of trade, conquest, and discovery that the other nations subsequently emulated or seized outright. Portugal’s overseas empire was an astonishing commitment that drained perhaps a tenth of the population out of Portugal and compelled the country to defend what it quickly appreciated it could not. The flush of early wealth it acquired it soon destroyed with foreign wars. Others, notably the Dutch, picked off its best Indies holdings. But while the interlopers poached pieces, a remarkably robust imperium endured. Portugal’s saga told not of an endless quest that, once launched, became unstoppable, but of a life cycle, one that expanded and then contracted.

  The Portuguese experience established the default setting for exploration’s software. The degree of interpenetration between geographic discovery and Portuguese society was astonishing, of which the suite of exploring ships was only a down payment. Consider the founding explorers, all of whom combined exploration with some other enterprise: affairs of state, commerce and conquest, proselytizing and poetry. Henry the Navigator, late-medieval prince, blurry-eyed speculator, who began the fusion of discovery with state policy. Vasco da Gama, merchant and administrator, representing the bonding of commerce with exploration. Afonso de Albuquerque, soldier and strategist, seizing at gunpoint the critical nodes of traffic through the Indian and South China seas. Saint Francis Xavier, tempering the sword with the cross, missionizing in India, the East Indies, and especially Japan, with plans to proselytize in China. Luiz Vaz de Camões, adventurer turned litterateur, author of Os Lusíadas, which cast contemporary explorers into the mode of classical heroes and which became the national epic. “Had there been more of the world,” Camões wrote, his bold mariners “would have discovered it.” Revealingly, the founders of the Enterprise of the Indies all died overseas.

  Enthusiasm there was for expansion, but the questions of where and how and to what end kindl
ed a furious debate amid competing claims. Nine years passed after Bartholomeu Dias rounded the Cape before da Gama headed to India, and exploring energies in the Indies were soon dissipated in Morocco. The whole enterprise began winding down within sixty years after its founding. That astonishing outrush had lasted less than two generations, exhausted by overreach and especially by heedless military adventures. The colonies took on lives of their own, populated not by fresh émigrés from Portugal but by mixed-blood societies whose ties to the metropole were largely language and faith, and ever-more-tenuous memories. And even as Camões penned his epic amalgam of triumph and tragedy, Fernão Mendes Pinto was recording a parallel, equally fabulous tale of adventure, mishap, and squandered opportunities that makes his Peregrinicão read as though it were an early draft of Gulliver’s Travels. In brief, Portugal did it all, and its Great Voyages transformed it as little else could. They also destroyed it as few national undertakings might. The outcome depended on what else exploration bonded to.

  Did the program that launched Voyager resemble the Portuguese paradigm? Not in its particulars; not even by analogy. What they shared was that both Voyager and its Portuguese antecedents rallied and merged many complex enthusiasms within their sustaining societies. Those exploration analogies work best that are older and more diffuse and less subject to empirical qualifications. The more remote the historical sources behind an allusion, the more nebulous are its details and the more susceptible it becomes to multiple meanings. Columbus could mean anything. Lewis and Clark could mean everything.