The Interstellar Age

by Jim Bell

  It seemed obvious to Pythagoras. It would take more than 250 years, however, for another famous Greek mathematician and astronomer, Eratosthenes, to prove it and to accurately estimate our planet’s size. He performed one of the most simple and famous scientific experiments of all time, and one that is easy for schoolkids to reproduce today, using just two sticks and a sunny day. One stick was in the southern Egyptian city of Syene (modern-day Aswan), on a day when, at noon, the sun was directly overhead and that stick did not cast a shadow. The other stick was in his own northern Egyptian city of Alexandria (Eratosthenes was the head of the Library of Alexandria, an amazing collection of all of the then-known books of the world—the equivalent of the Internet on Planet Earth in the third century BCE), where, on the same day, a stick would indeed cast a short shadow at noon. He knew that the angle between the sticks was the result of being at different places on a sphere, so he had an assistant (a graduate student, no doubt) walk off and measure the distance between Alexandria and Syene.

  His predecessors Plato and Archimedes, not mathematical slouches, to be sure, used their best reasoning to estimate the diameter of the Earth as 14,000 and 11,000 miles, respectively. Eratosthenes, armed with data from his simple measurements, came up with around 9,000 miles, or within about 15 percent of the correct modern answer (7,918 miles). Not bad for sticks and shadows.

  Fast-forward almost 2,200 years and we’ve entered an era when we can, in fact, just leave our planet, turn around, and take a look. The first time this was actually done was in the late 1940s, with cameras on suborbital German V-2 rockets that had been captured by the US Army after World War II and transported to the White Sands Missile Range in New Mexico. From altitudes of around 100 miles, the grainy V-2 photos showed the graceful curvature of part of the Earth’s limb. However, the first truly “global-scale” photo of the Earth from space wasn’t taken until nine years after the first Earth-orbiting satellites were launched. That photo, taken on August 23, 1966, by the NASA Lunar Orbiter I spacecraft, shows a beautiful, black-and-white crescent Earth appearing to rise behind the horizon of the moon.

  Most people haven’t heard of the Lunar Orbiter missions—a series of five robotic spacecraft sent to orbit the moon between 1966 and 1967 in order to scout for landing sites for the Apollo astronauts. They used a one-of-a-kind photo lab, born of the resourcefulness that has come to exemplify the space program. A set of Kodak film cameras was configured to take 70mm film pictures, to automatically develop the film inside a little chemical lab onboard the spacecraft, and then to digitize the developed negatives and transmit the digital data back to Earth. Essentially, the Lunar Orbiters used a scanner and a fax to send their pictures back, and they succeeded in mapping more than 99 percent of the moon that way. When the opportunity to take a photo of the Earth was recognized by Lunar Orbiter I mission controllers, they had to seek permission to take the risky step of using the spacecraft’s onboard thrusters to tilt the camera’s view toward the lunar horizon, where the Earth would be. It was risky because the Boeing spacecraft engineers pointed out that if it didn’t tilt back to its original orientation, that would have effectively ended the mission, only shortly after it had begun. NASA did approve the maneuver, and the resulting photo is indeed spectacular. I think that officials at NASA headquarters and Langley Research Center (which managed the mission) were compelled to approve the request, given the potential public relations value of what would be another first for America’s space program, against the backdrop of important Soviet advances in lunar exploration and the looming deadline of landing astronauts on the moon “before this decade was out,” established by a bold vision of the late President Kennedy.

  The Lunar Orbiter I photo of “Earthrise” was indeed a huge public relations hit. It became an instant poster handed out by NASA to members of Congress and visiting dignitaries as an example of tangible progress toward the Apollo landing goal, as well as the prowess of NASA’s young robotic exploration program in general. Just a few weeks later, LIFE magazine ran the photo in a two-page spread. Eight months later, NASA’s Surveyor 3 lunar lander one-upped the feat by taking the first color photo of the whole Earth from space—another beautiful crescent view. The public relations potential and raw visceral motivational power of viewing the Earth from space was apparent in these first early efforts.

  The next big leap in viewing our planet from space came from the crew of the Apollo 8 mission—the first full-up test of most of the components needed for a successful landing on the moon, and the farthest trip away from their home planet that any humans had ever taken. Apollo 8 launched on December 21, 1968, and the crew and mission-support staff back in Houston successfully navigated the two-and-a-half-day cruise to the moon, and then fired the Command and Service Module’s main engine to brake into lunar orbit. Commander Frank Borman, Command Module Pilot Jim Lovell, and Lunar Module (LM) Pilot William Anders then spent the next twenty hours orbiting the moon ten times, becoming the first humans ever to do so. Bill Anders was technically the LM pilot on the mission, but since Apollo 8 didn’t carry an actual LM for landing on the moon, and since he was a scientist by training, his job was mainly focused on acquiring photographs of the moon that could help in the study of its geology and in the analysis of potential landing sites for future Apollo missions. According to the NASA recordings and transcripts, on their fourth orbit around the moon, on December 24, 1968, Anders, Borman, and Lovell had the following exchange:

  ANDERS: Oh my God! Look at that picture over there! There’s the Earth coming up. Wow, is that pretty.

  BORMAN: (joking) Hey, don’t take that, it’s not scheduled.

  ANDERS: (laughs) You got a color film, Jim? Hand me that roll of color quick, would you . . .

  LOVELL: Oh man, that’s great!

  The three men were the first people to observe an “Earthrise” from another world. Anders and Borman took a number of color and black-and-white photos over the next few minutes, but once the crew returned and the film was developed, the photo that Anders took first has turned out to garner the most press and public interest, partly because it is in color, and partly because it is so well composed, benefiting from the lucky timing of the event compared to their busy flight plan. The crew had also captured the world’s attention just a few hours after the Earthrise photo was taken, with their Christmas Eve reading of part of the Bible’s Genesis creation story to an enormous worldwide television audience.

  Some commentators credit the Apollo 8 Earthrise photo with helping inspire the first Earth Day in 1970, and even with providing the impetus to propel much of the modern environmental movement into the mainstream. After all, standing on the surface of the Earth, it is easy to feel the vast and seemingly infinite nature of our natural world. But seeing the Earth as an isolated sphere floating in the emptiness of space really drives home just how limited our resources truly are. In LIFE magazine’s 2003 compendium “100 Photographs That Changed the World,” wilderness photographer Galen Rowell named Earthrise, which featured prominently on the cover of the magazine, as “the most influential environmental photograph ever taken.” Despite perhaps being eclipsed in the media and pop culture a few years later by the now-iconic December 1972 Blue Marble photo of the full Earth taken by the crew of Apollo 17 (arguably the widest-distributed photo in the history of photography), to me the astonishing nature of these first views of our planet from space has had a compounding effect. They demonstrate, graphically, the frailty and isolation of our planet, the vulnerability of our home world compared to the vastness of space, and the dawning of a new global consciousness—one that is still struggling to achieve critical mass—that recognizes the special responsibility that our species bears for the stewardship of this precious cocoon of life called Earth.

  THE LITTLE SELFIE

  The Voyager 1 imaging team was responsible for what I think of as the next advance in planetary selfies, taking the first photograph of the Earth and moon together just a
few weeks after launch. Mission and imaging team planners like the late Andy Collins of JPL realized that as the spacecraft was departing from Earth, once it got to a distance of over 7 million miles away or so, it would be possible to photograph both the Earth and the moon together in the same field of view. The imaging sequence was partly justified as an initial test of the cameras after the rigors of launch. Had the intense shocks and vibrations caused any damage or change in performance relative to prelaunch expectations? Did the various rocket stages and thruster firings generate any contamination that might be fogging up the lenses? Did someone leave the lens caps on? Indeed, imaging team instrument scientist Candy Hansen, who had just started working on the Voyager project in the summer of 1977, recalls that the sequence also had an important spacecraft systems function. Voyager’s scan platform was stowed for launch and had to be deployed to its correct position once the vehicle was out in space. However, after the deploy command was sent, the sensor that could confirm that the scan platform had deployed and latched properly into place failed, so there was no way to know for sure whether it had happened. Well, Candy recalls Andy Collins and others thinking, if they commanded an Earth-Moon photo assuming that the platform was properly deployed and the positions of the Earth and the moon in the photo were as expected, that should prove it. And indeed, it did.

  I would work with Andy many years later on the development of the cameras for the Mars rovers Spirit and Opportunity, and Candy’s story about that clever work-around is typical of the ingenuity and creativity that he brought to solving many other problems in robotic space exploration systems. Importantly, though, Andy and the rest of the Voyager imaging team knew back in the summer of 1977 that they had a chance to take the first photograph (in a long series of historic “firsts” bestowed upon us by Voyager) of the Earth and moon dancing together in space. Indeed, there was wide public interest in seeing, through the eyes of Voyager, our home planet and its nearest celestial neighbor from a completely new and different perspective than ever before. “A pretty pair,” remarked Carl Sagan, showing off the historic Voyager photo in one of the episodes of his 1980 television series, Cosmos.

  Three years later, as Voyager 1 sailed past Saturn and was slingshot up and out of the ecliptic—the racetrack-like plane that the planets orbit within—its mission of photographic exploration was coming to an end. As planned, the spacecraft would keep traveling on an upward path, rising higher and higher above the rest of the planets. The cameras would be turned off, and the fields and particles experiments would take over as the primary science of the mission shifted to the exploration of the limits of the sun’s influence on our solar system. The cameras were working fine; it was just that they used a large fraction of the slowly dwindling plutonium power supply’s electricity, and besides, there just wasn’t anything for Voyager 1 to photograph after Saturn and Titan.

  Carl Sagan thought differently. In his mind, perhaps in his dreams, there was at least one more historic “first” that the Voyager 1 cameras could achieve, at least one more new perspective that we could—and he strongly felt should—embrace. Voyager 1 was rising out of the ecliptic plane like an airplane rising off a runway, slowly revealing things that could not be seen so clearly, or at all, from the ground. Sagan and Voyager imaging team planners like Candy Hansen realized that it would be possible from Voyager’s new perspective to take a portrait of not only the Earth, but also almost the entire family of the sun’s planets. It would be the first solar-system selfie, a name that I think would have made Sagan smile.

  But not everyone was a fan of the idea. For many years, spacecraft engineers and Voyager imaging team members had fastidiously avoided inadvertently pointing the sensitive Imaging Science Subsystem cameras at the sun. Their reasoning: the cameras used telescope optics to focus their images; sunlight accidentally piped down through those magnifying optics could heat up the photodetectors and fry the system. Pointing at the sun is bad. And so now Dr. Sagan wants to do what? Point at the sun? Who is this guy?

  “But there’s nothing else to look at,” retorted proponents of Sagan’s idea. “If we burn out the cameras in the effort, so what?” However, while Voyager 1 had nothing else to take pictures of after the Saturn flyby in late 1980, her twin Voyager 2 was steadily speeding on to a flyby of Uranus in 1986 and then, the team hoped, of Neptune in 1989. The camera systems on the spacecraft were identical, and so for calibration or diagnosis of certain potential kinds of problems, the cameras on Voyager 1 could theoretically still be used to diagnose any software or hardware problems that might occur on Voyager 2. That backup functionality, even if unlikely to ever be needed, would not be available at all if Voyager 1’s cameras were fried in the attempt to take a solar-system family portrait.

  Plus, the imaging team was dwindling in size due to post-Saturn budget cuts, and the people still working on the project were fully occupied preparing for the Uranus encounter. Sagan and others knew that they couldn’t defend the solar-system portrait request on scientific grounds. “The point of such a picture would not be mainly scientific,” wrote Sagan. “I knew that, even from Saturn, the Earth would appear too small for Voyager’s cameras to make out any detail. Our planet would be just a point of light, not even filling a single pixel, hardly distinguishable from the other points of light it could image from nearby planets and far-off suns. But I thought that—like the famous frame-filling Apollo photographs of the whole Earth—such a picture might be useful nevertheless as a perspective on our place in the Cosmos.” What a perspective, indeed. But the need for the team to focus their efforts on Voyager 2 meant that the “pretty picture” work would have to wait. And so Sagan and others waited, for a decade, while Voyager 2 made spectacular discoveries at Uranus and Neptune and Voyager 1 climbed steadily higher above the ecliptic. . . .

  Finally, after the successful August 1989 flyby of Neptune and the completion of the playback of all the imaging data taken during approach, flyby, and departure, Sagan and others once again raised the issue of trying for the solar-system portrait. While Voyager 2 had been diverted southward after gracefully arcing over the north pole of Neptune, it was still relatively close to the ecliptic. Voyager 1, now more than 30 degrees above the plane of the solar system and still climbing, had the superior view. In late 1989 the idea was pitched again, but once again it was put off while additional calibrations were performed on the cameras to make sure that the Neptune images, especially, could be properly analyzed. It seemed a prudent precaution, and so Sagan and the other advocates waited some more.

  The possibility came to a head after the Neptune flyby, though, when it was revealed that because of impending budget cuts to the Voyager program, many of the technicians who were responsible for the commanding of the cameras and the pointing of the spacecraft were to be laid off or transferred to other jobs almost immediately. These people’s skills would be needed to plan, acquire, and process the portrait—which had to happen soon if it were going to happen at all. An internal debate began within NASA over whether the cash-strapped Voyager project could afford to spend time and effort on what some people apparently regarded as a superfluous stunt. In the minds of some of the leaders of the planetary exploration program at JPL and NASA headquarters at the time, not only was there no science value in these images, the attempt would be yet another distraction as the project was winding down its staffing and preparing for the long interstellar phase of the mission.

  This kind of attitude was far from uncommon in the leadership of NASA at the time. So-called education and public outreach activities like Sagan’s solar-system portrait were not regarded as worthy of inclusion on planetary-exploration mission budgets. The attitude was pervasive across much of science in the ’70s and ’80s and was part of the reason that Carl Sagan had been denied membership in the National Academy of Sciences. Much of his work was regarded by his peers, especially members of the Academy, as “soft” science—communications and education-related or even (as I can ima
gine in the minds of some of his more jealous peers) grandstanding.

  Times have changed. NASA and National Science Foundation proposals for funding the research programs of individual scientists now must demonstrate how we will communicate and disseminate our results to the general public, and in what specific ways our work has general relevance and importance to our society.

  Fortunately, after the Neptune encounter, top NASA officials such as Associate Administrator for Science Len Fisk and Administrator Richard Truly shared Carl Sagan’s vision of the historic, aesthetic value of the solar-system family portrait. Ed Stone was also a strong supporter of the idea. He recalls a dinner at Caltech organized by Sagan and The Planetary Society just before the Voyager Neptune flyby in 1989, during which he, Sagan, Fisk, and Voyager Project Manager Norm Haynes talked about what it would take to make “the picture of the century” happen. By this point in time it was essentially a budgetary issue, as Voyager’s funding was set to ramp down steeply right after Neptune. Happily, Fisk and Truly interceded to make sure the people and resources were made available for this one last Voyager mosaic, which was taken on February 14, Valentine’s Day, 1990.