Carl Sagan in 1986: ‘Voyager has become a new kind of intelligent being—part robot, part human’

Carl Sagan in 1986: ‘Voyager has become a new kind of intelligent being—part robot, part human’

The notorious scientist reflected on the lesser-identified triumphs and lofty ambitions of Voyager in Popular Science’s October 1986 challenge.


Bill Gourgey


Revealed Mar 25, 2024 9:02 AM EDT

Bettmann/Getty / Popular Science

One of the troubles that saved legendary astronomer Carl Sagan up at evening was whether or now not aliens would understand us. In the mid-Nineteen Seventies, Sagan led a committee shaped by NASA to assemble a series of images, recorded greetings, and music to characterize Earth. The montage was pressed onto golden albums and dispatched across the cosmos on the backs of Voyagers 1 and 2.

In a 1986 narrative Sagan wrote for Popular Science, he famed that “hypothetical aliens are certain to be very varied from us—independently advanced on another world,” which meant they seemingly wouldn’t be able to decipher the golden discs. But he took assurance from an underappreciated dimension of Voyagers’ message: the designs of the vessels themselves.

“We are software makers,” Sagan wrote. “That is a fundamental aspect, and perhaps the essence, of being human.” What better way to declare alien civilizations that Earthlings are toolmakers than by sending a living room-sized, aluminum-framed probe clear across the Milky Way. 

Although both spacecraft have been completely designed to swing by Jupiter and Saturn, Voyager 2’s trajectory also hurled it past Uranus and Neptune. Despite a lot of mishaps along the way—and because of the elite toolmaker abilities of NASA engineers—the probe was in moral enough shape to send back shut-americaof these distant worlds. In 2012, Voyager 1 became the first interstellar spacecraft, adopted rapidly thereafter by Voyager 2. “Once out of the solar system,” Sagan wrote, “the surfaces of the spacecraft will remain intact for a billion years or more,” so resilient is their draw.

Today, the probes are 12–15 billion miles from Earth, quiet operable (despite experiencing contemporary communication difficulties), and sailing thru the relative calm of interstellar space. They are anticipated to continue to transmit data back to Earth for another year or so, or unless their plutonium batteries quit. 

It was early Twentieth century wi-fi inventor Guglielmo Marconi who urged that radio signals never die, they completely diminish as they travel across space and time. Even after communications from the Voyager spacecraft cease, perhaps the tiny voices of Earth’s first emissaries, animated by NASA’s master toolmakers nearly half a century ago, will continue to crawl thru the cosmos for all time, accessible to far-flung civilizations outfitted with delicate enough receivers to hear.

“Voyager’s Triumph” (Carl Sagan, October 1986)

A famed scientist tells the little-identified narrative of the remarkable feats of the Voyager engineers, a dedicated band who repeatedly overcame technical adversity to be certain that the success of these historical expeditions to the outer solar system.

Carl Sagan is Director, Laboratory for Planetary Reports, Cornell College, and, since 1970, a member of the Voy­ager Imaging Science Team. His Cosmos: A Special Model is televised this fall. 

On Jan. 25, 1986, the Voyager 2 robot probe entered the Uranus system and reported a procession of wonders. The encounter lasted completely a few hours, however the data faithfully relayed back to Earth have revolu­tionized our information of the aquamarine planet, its more than 15 moons, its pitch black rings, and its belt of trapped excessive-energy charged particles. Voyager 2 and its compan­ion, Voyager 1, have accomplished this earlier than. At Jupiter, in 1979, they braved a dose of trapped charged particles 1,000 times what it takes to raze a human being[PSJuly’seventynine);andinallthatradiationtheycameacrosstheringsofthelargestplanetthefirstactivevolcanoesoutsideEarthandapos­sibleundergroundoceanonanairlessworld—amongafewhundredothermajorfindingsAtSaturnin1980and1981the2spacecraftsurvivedapummelingbytinycoolparticlesastheyplummetedthrubeforehandun­identifiedrings;andtheretheycameacrossnownotafewhoweverthou­sandsofSaturnianringscoolmoonshonestlatelymeltedthruunknowncausesandalargeworldwithanoceanofliquidhydrocarbonssurmountedbycloudsoforganicmatterIPSMarch’81lThesespacecrafthavereturnedtoEarthfourtrillionbitsofinformationtheequivalentofabout100000encyclopediavolumes [PSJuly’79);andinallthatradiationtheydiscoveredtheringsofthelargestplanetthefirstactivevolcanoesoutsideEarthandapos­sibleundergroundoceanonanairlessworld—amongafewhundredothermajorfindingsAtSaturnin1980and1981thetwospacecraftsurvivedapummelingbytinyicyparticlesastheyplummetedthroughpreviouslyun­knownrings;andtheretheydiscoverednotafewbutthou­sandsofSaturnianringsicymoonsrecentlymeltedthroughunknowncausesandalargeworldwithanoceanofliquidhydrocarbonssurmountedbycloudsoforganicmatterIPSMarch’81lThesespacecrafthavereturnedtoEarthfourtrillionbitsofinformationtheequivalentofabout100000encyclopediavolumes 

Because we are caught on Earth, we are forced to search for at distant worlds thru an ocean of distorting air. It’s miles easy to search for why our spacecraft have revolutionized the glance of the solar system: We ascend to the stark clarity of the vacuum of space, and there approach our aims, flying past them or orbiting them or landing on their surfaces. These nearby worlds have noteworthy to teach us about our contain, and they’re going to be—unless we are so silly as to murder ourselves—as familiar to our descendents as the neighboring states are to these who reside in America today. 

Voyager and its brethren are prodigies of human inven­tiveness. Apt earlier than Voyager 2 was to come across the Uranus system, the mission draw had scheduled a final direction correction, a brief firing of the on-board propul­sion system to dwelling Voyager appropriately as it flew among the moving moons. But the direction correction proved un­ necessary. The spacecraft was already within 200 kilome­ters of its designed trajectory after a voyage along an arcing path 5 billion kilometers in length. That is roughly the equivalent of throwing a pin thru the search for of a needle 50 kilometers away, or firing your target pistol in New York and hitting the bull’s search for in Dallas.

The lodes of planetary treasure have been transmitted back to Earth by the radio antenna aboard Voyager; however Earth is so far away that by the time the signal was gathered in by radiotelescopes on our planet, the got vitality was completely 10-16 watts (fifteen zeros after the decimal point). Comparing this weak signal with the vitality emitted by an ordinary reading lamp is care for comparing the width of an atom with the distance between Earth and the moon. (Incidentally, the first photograph ever taken of Earth and the moon together in space was acquired by one of the Voyager spacecraft.)

We tend to hear noteworthy about the splendors returned, and very little about the ships that brought them, or the shipwrights. It has always been that way. Our history books compose now not declare us noteworthy about the builders of the Nina, Pinta, and Santa Maria, and even the principle of the caravel. De­spite ample precedent, it’s miles a clear injustice: The Voyager engineering team and its accomplishments need to be rather more broadly identified.

The Voyager spacecraft have been designed and assembled, and are operated by the Jet Propulsion Laboratory (JPL) of the National Aeronautics and Space Administration in Pasadena, Calif. The mission was conceived during the late 1960s, first funded in 1972, however was now not approved in its contemporary fabricate (which includes encounters at Uranus and Neptune) unless after the 1979 Jupiter flyby. The two spacecraft have been launched in late summer and early fall 1977 by a non-reusable Titan/Centaur booster configuration at Cape Canaveral, Fla. Weighing about a ton, a Voyager would contain a moral-sized living room. Each spacecraft draws about 400 watts of vitality—considerably less than an average American dwelling—from a generator that converts radioactive plutonium into electrical energy. The instrument that measures interplanetary magnetic fields is so delicate that the circulation of electrical energy thru the innards of the spacecraft would generate untrue signals. As a result, this instrument is placed at the finish of a lengthy assert stretching out from the spacecraft. With other projections, it affords Voyager a moderately porcupine appearance. Two cameras, infrared and ultraviolet spectrometers, and an instrument called the photopolarimeter are on a scan platform; the platform swivels so these instruments can point toward a target world. The spacecraft antenna must know where Earth is that if the transmitted data are to be got back dwelling. The spacecraft also wishes to understand where the sun is and at least one shining star, so it can orient itself in three dimensions and point neatly toward any passing world. It does no moral to be able to approach back photographs over billions of miles in the event you can’t point the camera.

On-orbit repairs

Each spacecraft expenses about as noteworthy as a single up to date strategic bomber. But unlike bombers, Voyager cannot, as soon as launched, be returned to the hangar for repairs.

As a result, the spacecraft’s computers and electronics are designed redundantly. And when Voyager finds itself in pains, the computers employ branched contingency tree common sense to work out the appropriate direction of action. As the spacecraft journeys increasingly far from Earth, the spherical-day out gentle (and radio) travel time also increases, approaching six hours by the time Voyager is at the distance of Uranus.

Thus, in case of an emergency, the spacecraft wishes to understand easy assign itself in a safe standby mode while awaiting instructions from Earth. As the spacecraft ages, more and more failures are anticipated, both in its mechanical parts and its computer system, although there may be as yet no signal of a critical reminiscence deterioration, some robot Alzheimer’s disease. When an surprising failure happens, special teams of engineers—some of whom have been with the Voyager program since its inception—are assigned to “work” the jam. They are going to glance the underlying basic science and draw upon their old journey with the failed subsystems. They may compose experiments with identical Voyager spacecraft equipment that was never launched and even manufacture a large quantity of parts of the kind that failed in repeat to gain some statistical understanding of the failure mode.

In April 1978, almost eight months after launch, an overlooked flooring command caused Voyager 2’s on-board computer to change from the high radio receiver to its backup.

During the following flooring transmission to the spacecraft, the receiver refused to lock onto the signal from Earth. A ingredient called a tracking loop capacitor had failed. After seven days in which Voyager 2 was out of contact, its fault protection software commanded the backup receiver to be switched off and the high receiver to be switched back on. But, mysteriously, the high receiver failed moments later: It never recovered. Voyager 2 was now fundamentally imperiled. Although the primary receiver had failed, the on-board computer commanded the spacecraft to make employ of it. There was no way for the controllers on Earth to command Voyager to revert to the backup receiver. Even worse, the backup receiver may be unable to receive the commands from Earth because of the failed capacitor. Finally, after a week of command silence, the computer was programmed to change automatically between receivers.

And during that week’s time the JPL engineers designed an innovative command frequency regulate direction of to make a few essential commands comprehensible to the damaged backup receiver.

This meant the engineers have been able to communicate, at least a little bit, with the spacecraft. Unfortunately the backup receiver now grew to become giddy, becoming extraordinarily delicate to the stray heat dumped when various parts of the spacecraft have been powered up or down. Over the following months the JPL engineers designed and performed a series of assessments that allow them to totally understand the thermal penalties of most operational modes of the spacecraft on its ability to receive commands from Earth. The backup-receiver jam was fully circumvented. It was this backup receiver that acquired all the commands from Earth on easy gather data in the Jupiter, Saturn, and Uranus systems. The engineers had saved the mission. But to be on the safe facet, during most of Voyager’s subsequent flight there may be in station in the onboard computers a nominal data-taking sequence for the following planet to be encountered.)

Another heart-wrenching failure happened moral after Voyager 2 emerged from behind Saturn after its closest approach to the planet in August 1981. The scan platform had been moving rapidly in the azimuth route—hasty pointing here and there among the rings, moons, and the planet itself during the time of closest approach. All at as soon as, the platform jammed. A caught scan platform obviously implies a extreme reduction in future photographs and other key data. The scan platform is pushed by gear trains called actuators, so first the JPL engineers ran an identical replica of the flight actuator in a simulated mission. The flooring actuator failed after 348 revolutions: the actuator on the spacecraft had failed after 352 revolutions. The jam grew to become out to be a lubrication failure. Plainly, it may be very probably now not to overtake Voyager with an oil can. The engineers puzzled whether or now not it may be imaginable to restart the failed actuator by alternately heating and cooling it, so that the thermal stresses would cause the parts of the actuator to expand and contract at varied rates and un-jam the system. After gaining journey with specially manufactured actuators on the flooring, the engineers jubilantly came across that they have been able to make employ of this direction of to start the scan platform up again in space. More than this, they devised tactics to diagnose any imminent actuator failure early enough to work around the jam. Voyager 2’s scan platform worked perfectly in the Uranus system. The engineers had saved the day again.

Ingenious solutions

Voyager 1 and 2 have been designed to explore the Jupiter and Saturn systems completely. It’s miles fair that their trajectories would carry them to Uranus and Neptune, however officially these planets have been never contemplated as targets for Voyager exploration: The spacecraft was now not supposed to last that lengthy. Because of trajectory requirements in the Saturn system, Voyager 1 was flung on a path that will never encounter any other identified world; however Voyager 2 flew to Uranus with brilliant success, and is now on its way to an August 1989 encounter with the Neptune system.

At these expansive distances, daylight is getting steadily dimmer, and the spacecraft’s transmitted radio signals to Earth are getting steadily fainter. These have been predictable however quiet very critical concerns that the JPL engineers and scientists also had to cure earlier than the encounter with Uranus.

Because of the low gentle stages at Uranus, the Voyager television cameras have been obliged to take longer time exposures. But the spacecraft was hurtling thru the Uranus system so fast (about 35,000 miles per hour) that the image would have been smeared or blurred—an journey shared by many amateur photographers. To conquer this, all the spacecraft had to be moved during the time exposures to compensate for the circulate, care for panning in the route opposite yours while taking a photograph of a boulevard scene from a moving car. This may sound easier than it’s miles: You have to compensate for probably the most casual of motions. At zero gravity, the mere start and quit of the on-board tape recorder that’s registering the image can jiggle the spacecraft enough to smear the image. This jam was solved by commanding the spacecraft thrusters, instruments of heavenly sensitivity, to compensate for the tape-recorder jiggle at the start and quit of each sequence by turning all the spacecraft moral a little. To compensate for the low got radio vitality at Earth, a new and more efficient digital encoding algorithm was designed for the cameras, and the radiotelescopes on Earth have been joined in conjunction with oth ers to increase their sensitivity. Overall, the imaging system worked, by many criteria, better at Uranus than it did at Saturn and even at Jupiter.

Voyager has become a new kind of intelligent being—part robot, part human. It extends the human senses to far-off worlds.

The ingenuity of the JPL engineers is growing faster than the spacecraft is deteriorating. And Voyager may now not be accomplished exploring after its Neptune encounter.

There is, of direction, a chance that some vital subsystem will fail day after today, however in terms of the radioactive decay of the plutonium vitality supply, the 2 Voyager spacecraft will be able to approach back data to Earth unless roughly the year 2015. By then they’re going to have traveled more than a hundred times Earth’s distance from the sun, and may have penetrated the heliopause, the place where the interplanetary magnetic area and charged particles are replaced by their interstellar counterparts; the heliopause is one definition of the frontier of the solar system.

Robotic-human partnerships

These engineers are heroes of our time. And yet almost no one knows their names. I have attached a table giving the names of a few of the JPL engineers who played central roles in the success of the Voyager missions.

In a society actually concerned for its future, Don Gray, Charlie Kohlhase, or Howard Marderness, may be as effectively identified for his or her extraordinary abilities and accomplishments as Dwight Gooden, Wayne Gretzky, or Kareem Abdul Jabbar are for theirs.

Voyager has become a new kind of intelligent being-part robot, part human. It extends the human senses to far-off worlds. For easy tasks and temporary concerns, it relies on its contain intelligence; however for more complex tasks and longer term concerns, it turns to another, considerably larger brain—the collective intelligence and journey of the JPL engineers. This pattern is sure to develop. The Voyagers embody the skills of the early Nineteen Seventies; if such spacecraft have been to be designed in the near future, they would incorporate stunning enhancements in artificial intelligence, in data-processing pace, in the ability to self-diagnose and repair, and in the capacity for the spacecraft to learn from journey. In the many environments too dangerous for folk, the lengthy sprint belongs to robot-human partnerships that will acknowledge Voyager as antecedent and pioneer.

No longer like what appears to be the norm in the so-called defense industry, the Voyager spacecraft came in at assign, on time, and vastly exceeding both their draw specifications and the fondest dreams of their builders. These machines compose now not search for to manipulate, threaten, wound, or murder; they characterize the exploratory part of our nature, state free to roam the solar system and beyond.

Once out of the solar system, the surfaces of the spacecraft will main intact for a billion years or more, as the Voyagers circumnavigate the middle of the Milky Way galaxy.

This kind of skills, its findings freely revealed to all humans in every single place, is one of the few activities of the United States admired as noteworthy by these who find our policies uncongenial as by these who agree with us on every challenge. Unfortunately, the tragedy of the space shuttle Challenger implies agonizing delays in the launch of Voyager’s successor missions, such as the Galileo Jupiter orbiter and entry probe. With out real toughen from Congress and the White Home, and a clear lengthy-term NASA goal, NASA scientists and engineers will be forced to find other work, and the historical American triumphs in solar-system exploration—symbolized by Voyager—will become a thing of the past. Missions to the planets are one of these things—and I mean this for all the human species—that we compose completely. We are software makers—here’s a fundamental aspect, and perhaps the essence, of being human.

Greeting the aliens

Each Voyager spacecraft are on escape trajectories from the solar system. The gravitational fields of Jupiter, Saturn, and Uranus have flung them at such excessive velocities that they are destined ultimately to leave the solar system altogether and wander for ages in the calm, cool blackness of interstellar space—where, it turns out, there may be essentially no erosion.

Once out of the solar system, the surfaces of the spacecraft will main intact for a billion years or more, as the Voyagers circumnavigate the middle of the Milky Way galaxy. We compose now not know whether or now not there are other space-faring civilizations in the Milky Way. And in the event that they compose exist, we compose now not understand how abundant they are.

But there may be at least a chance that some time in the far flung future one of the Voyagers will be intercepted by an alien craft. Voyagers 1 and 2 are the fastest spacecraft ever launched by humans; moreover, they are traveling so slowly that this can be tens of thousands of years earlier than they swagger the distance to the nearest star. And they are now not headed toward any of the nearby stars. As a result there will be no danger of Voyager attracting “antagonistic” aliens to Earth, at least now not any time rapidly.

So, it appeared appropriate to include some message of greeting from Earth At NASA’s ask, a committee I chaired designed a phonograph file that was affixed to the exterior of each of the Voyager spacecraft. The data contain 116 photographs in digital fabricate, describing our science and skills, our institutions, and ourselves; what will certainly be unintelligible greetings in many languages; a sound essay on the evolution of our planet; and an hour and a half of the sector’s greatest music. But the hypothetical aliens are certain to be very varied from us—independently advanced on another world. Are we really sure they may understand our message? Every time I bear these concerns stirring, though, I reassure myself: Whatever the incomprehensibilities of the Voyager file, any extraterrestrial that finds this can have another standard by which to resolve us. Each Voyager is itself a message. In its exploratory intent, in the lofty ambition of its aims, and in the brilliance of its draw and performance, it speaks eloquently for us.

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