by Alan Stern
But there was opposition within the Hubble project to conducting such a large search on short notice. Despite that, the New Horizons team proposed the time it needed, with John leading the effort. Their proposal was turned down. They were incredulous. The Decadal Survey had directed New Horizons to study Kuiper Belt Objects.
Only Hubble could enable the New Horizons mission to undertake this study. Would NASA allow them to fail to have a Kuiper Belt mission after Pluto for want of a couple of weeks of Hubble time, 2 percent of Hubble’s efforts that year? After all, there was no other credible way to explore KBOs anytime in the next several decades, except with New Horizons—and if they didn’t get Hubble time, their mission was not going to have a Kuiper Belt flyby target.
Alan appealed to NASA Headquarters, and after a second John Spencer proposal to the Hubble project in the spring of 2014 and some high-stakes backroom maneuvering, the Hubble project announced that the KBO observing time for New Horizons had been approved.
Observations began the same week, under the pressure of time because the star fields that needed to be searched would be out of position as the Sun neared them in the sky by the fall. As the Hubble data began to rain down, several weeks of round-the-clock work to analyze the images, make candidate detections, and schedule follow-up confirmation observations began. John, Marc, and a cadre of postdocs and collaborators crammed months of search work into weeks, knowing that, because the Pluto flyby was looming and they would soon have to quit work on this, time was running out. One afternoon, Marc—who led the data-analysis effort—said to Alan and John, “You’d better come down to my office and look at this.” He had found a KBO that New Horizons could reach!
Soon, Marc and his team found a second reachable KBO in the Hubble data, and then a possible third, along with several others that were close to, but not quite, reachable within their fuel supply. Follow-up observations confirmed that two of the three objects were indeed reachable.
The Hubble effort had succeeded; New Horizons now had a choice of two KBO targets to intercept for a flyby after Pluto! Both were just the kind of planet-building-block size they wanted, and both could be reached by early 2019, about three and a half years after the Pluto flyby.
ENTERING PLUTO SPACE
Occasionally, as New Horizons flew across the solar system, Alan would arrange for events or announcements designed to help engage the public, and to remind people of a spacecraft racing toward an unseen world beyond the explored planets.
One of these events took place in 2008, as New Horizons was speeding away from Jupiter and beginning its long journey across the vast middle solar system toward Pluto. That October, a full-size replica of the New Horizons spacecraft was “inducted” into the National Air and Space Museum near Dulles, Virginia, outside Washington, DC, and put on display. It was a rare privilege—fewer than 1 percent of all spacecraft are honored this way. At a public lecture commemorating the event, Alan announced that New Horizons was carrying nine mementos on its flight to Pluto and beyond. Each was symbolic.
1. A container holding a small portion of Clyde Tombaugh’s ashes and the inscription Alan wrote about him.
2. A CD-ROM with more than 434,000 names of people who had participated in a “Send Your Name to Pluto” activity organized by the Planetary Society and NASA.
3. Another CD-ROM with pictures and notes from people on all the various teams who had designed, built, and launched New Horizons.
4. A Florida state quarter, for the state where New Horizons was launched.
5. A Maryland state quarter, for the state where New Horizons was built.
6. A small piece of carbon fiber from SpaceShipOne, which in 2004 became the first privately built piloted spaceship to reach space.
7. A small U.S. flag on the port side of the spacecraft.
8. A second small U.S. flag on the starboard side of the spacecraft.
9. That 1991 U.S. stamp proclaiming, PLUTO NOT YET EXPLORED, something New Horizons audaciously expected to make obsolete in 2015.
Alan ended that speech by saying that it was a privilege for the New Horizons team to carry each of these nine mementos, and he promised that once the first reconnaissance of Pluto was completed, the team planned to petition the U.S. Postal Service to issue a new stamp for Pluto, commemorating its exploration.
More opportunities for public engagement came during key milestones in the succeeding flight years, and these, along with popular articles, blogs, social media, and public talks, kept New Horizons in the public eye across the many years it took to reach Pluto’s doorstep.
Then, in late summer 2014, a special occasion offered an opportunity to remind the public that the long journey was coming to an end and the exploration of Pluto was now less than a year away. New Horizons was crossing the orbit of Neptune. It was a powerfully symbolic moment with a clear message—“Next stop, Pluto!”
The emotional power of the Neptune crossing was heightened by a coincidence of dates that could not have been imagined when that small band of Plutophiles first began agitating for a mission to explore Pluto during the summer of 1989 as Voyager 2 explored Neptune: the New Horizons crossing of Neptune’s orbit on August 25, 2014, came exactly twenty-five years to the very day after Voyager had swept past Neptune!
To Alan, the symbolism of that anniversary was too incredible to be ignored. So, working with NASA, the team created a public event both to commemorate Voyager and to build anticipation for the Pluto flyby, just over ten months away. As a part of the event, a panel discussion was held at NASA Headquarters in Washington, DC, and was streamed live on NASA TV for space fans all around the world. Moderated by this book’s coauthor David Grinspoon, himself a veteran of Voyager from student and post-doc days, the panel featured New Horizons scientists Fran Bagenal, John Spencer, Jeff Moore, and Bonnie Burratti, each of whom had worked at the Voyager Neptune encounter. Each reminisced about the excitement and inspiration of Voyager at Neptune and how that exploration early in their careers had affected each of them. Now, in middle age, they were part of a team about to explore the next, even more distant planet for the first time.1
The panel’s conversation eventually turned to careers and mentorship and how, just as their mentors had done for them in the 1980s, they were now themselves mentoring a new generation of young scientists who would be learning the ropes on New Horizons, and who would then, hopefully, be leading new missions of their own in the 2030s and 2040s.
This made for a perfect segue. Alan called a group of young New Horizons scientists, many born during the Voyager era, to the stage. Like many in the public, they had never witnessed the intensity and excitement of a first planetary exploration, but they were soon going to learn firsthand just what it was like.
Next, Caltech’s Ed Stone, the celebrated scientist who had led Voyager’s scientific team since it launched, gave Alan an American flag that had hung in Voyager mission control, to now hang in New Horizons mission control. Within the New Horizons team, the poignancy of that event was further heightened by the fact that Tom Coughlin, the original New Horizons project manager, had passed away just two weeks before.
That day, as New Horizons crossed beyond the orbit of Neptune, a figurative baton had been passed: the banner of exploration of the solar system had been transferred from Voyager to New Horizons, and from one generation of scientists to another. Once it was beyond Neptune, New Horizons was now considered in “Pluto space,” because it had reached the solar system’s third zone, and was ready to soon explore it.
It was time for New Horizons to shine.
WAKING THE BIRD
The crossing of Neptune’s orbit had been a milestone on Earth, but New Horizons slept right through it, gliding onward at its incredible speed in silent hibernation. Across the rest of 2014 too, New Horizons flew on in deep sleep, covering over 100 million more miles beyond Neptune’s orbit by the time that December had come.
Back on Earth though, its tea
m wasn’t hibernating. Those months were a blur of final flyby simulations, planning for the expected onslaught of press and public attention, creating dozens of software tools to analyze soon-to-be-collected Pluto-system data, and the coding and testing of the early flyby approach sequences that would kick off almost as soon as 2015 did.
On December 6, 2014, right on schedule, New Horizons commanded itself out of hibernation for the final time on its long cruise out to Pluto. The spacecraft was now barely six months from its flyby. Alan recalls:
Exiting hibernation for that last time meant showtime at Pluto was finally approaching. When we started hibernating back in 2007 after passing Jupiter, we found being in hibernation was pretty weird, because we’d been actively operating the spacecraft every day during the eighteen months since launch. It took us about a year to get comfortable and make hibernation routine. But by the time we got to 2014, we were so used to hibernation that it was like a warm blanket, and conversely the thought of living without it seemed weird.
After all, we really hadn’t operated the spacecraft day in and day out for more than a couple of months at a time in any given year since 2007. So the prospect of going back to that for all of the 2015 and 2016 flyby activities and the long downlink of data afterwards was a little daunting.
But most of all, exiting hibernation for the final time in 2014 felt momentous, because it meant that the only thing in front of us now was the flyby itself. No more years to go. It was a turning of a page: we had crossed the entire solar system. We really were on Pluto’s doorstep. 2014 was ending, and that surreal never-never year of 2015, which had been in our future for so long, was about to begin.
There was a gathering at the APL MOC to receive the signal from New Horizons, letting mission control know their bird had awakened for the flyby. NASA executives were there, along with a gaggle of reporters and camera crews. At the expected time, when the signal reached Earth—having traveled four hours at the speed of light from Pluto 3 billion miles away—Alice Bowman beamed and gave a thumbs-up. New Horizons was reporting in, ready for duty at Pluto! The room erupted in cheers; champagne, cake, and music ensued.
There is a long tradition in space missions to mark milestone occasions with a “wake-up song.” That started all the way back in 1965 when the astronauts of Gemini 6 were woken up in flight with “Hello, Dolly!” and it continued across all the human spaceflights ever since. Somewhere in the 1990s, robotic missions began using music for milestone occasions, too. For the occasion of New Horizons emerging from its last hibernation en route to Pluto, Alan chose a piece called “Faith of the Heart,” an emotional theme song from the TV series Star Trek: Enterprise. Its lyrics seemed so appropriate to the journey of New Horizons. In fact, when Alan heard this song, to him it seemed to be telling the whole story of the mission.2
The song begins “It’s been a long road, getting from there to here.” The poignant lyrics then tell a story about undertaking a long journey, overcoming adversity, and triumphing over opponents trying to hold you back, over many years, through having the perseverance to see your dream come true. But just how appropriate these lyrics were, the team members would not know until the following summer when they would discover the expansive heart-shaped feature that dominates the surface of Pluto. The song concludes with the lines “I can reach any star, I’ve got faith, faith of the heart.”
ON PLUTO’S DOORSTEP
The flyby of Pluto formally began barely a month after hibernation ended, on January 15, 2015, when the spacecraft started to execute the first of its dozen or so distant-approach command loads, which ran until the beginning of April. Pluto was still just a dot in the distance—about 150 million miles away—and most of the scientific instruments aboard New Horizons could still not even detect it. But the flyby science was beginning with nearly round-the-clock measurements of the environment out near Pluto’s orbit using the onboard plasma and dust instruments SWAP, PEPSSI, and SDC.
With the LORRI telescopic imager, New Horizons could begin to resolve Pluto and Charon as bright dots. A week’s worth of LORRI images captured slightly more than one full mutual orbit of the pair around one another, and were looped together into movies. In them, Pluto doesn’t stay put in the center of the frame with Charon merely circling around it. Instead, both are circling one another around an invisible balance point close to Pluto but between them. That back and forth yo-yo motion of Pluto and Charon was starkly different from movies of moons orbiting giant planets like Jupiter or Saturn, where the planet in the center remains fixed as if in bedrock—immovable.
There was something charming and engaging about seeing Pluto and Charon yo-yoing back and forth under one another’s gravitational pull. No one had ever seen anything like it in all the decades of planetary exploration: a double planet doing a swing dance, with the larger dancer being pulled to and fro by its somewhat smaller partner. When NASA released a video of this mesmerizing orbital dance, it became a viral internet hit, its charm heightened even more so by its pixelated imperfections and the jumpy frames that were captioned “Not a simulation!”
By early April 2015, with New Horizons just over 100 million miles from the first binary planet ever explored, the planet was bright enough as seen from New Horizons that its Ralph color camera could detect Pluto and Charon for the first time. NASA released this first color image. It wasn’t much—just two little smudges of light near one another. Pluto appeared distinctly larger and brighter and reddish, while Charon was smaller, darker, and obviously grayer in color. Again, not much—but the public reaction again went viral. Something about the novelty and authenticity of these images, the awareness that they were taken by a machine that humans had built and sent so far away, was exciting people across the world. Few in NASA or the New Horizons team realized, even then, that the growing wave of public excitement they were seeing would become full-blown Plutomania by July.
BACKSTAGE BEFORE THE MAIN EVENT
To the outside world, besides the occasional image releases, not much was seen happening aboard New Horizons or in the project, but behind the scenes the mission team buzzed with activity during the early months of 2015. It was like being at a fine restaurant just ahead of a big banquet. If you stepped inside in the afternoon, the dining room would look quiet and peaceful, as if nothing was happening. But back in the kitchen you’d see something completely different—a blur of frenzied activity as the chefs and staff rushed to be ready for the main event.
One key effort taking place backstage on New Horizons involved navigating the spacecraft to home in on Pluto. Those LORRI images of Pluto and Charon orbiting one another that went viral hadn’t been shot just for PR purposes. They were part of the critical early approach “OpNav” campaigns. OpNav is space geek–speak for “optical navigation,” imaging Pluto against star fields to very precisely determine what engine burns were needed to reach the exact aim point around which the team had designed the Core flyby sequence.
Because New Horizons could only point and shoot its close-approach images based on advance calculations of where it would be relative to Pluto and each of Pluto’s moons, mission designers calculated that the spacecraft could be no more than sixty miles off target for the flyby of Pluto; in addition, it had to arrive within less than nine minutes of its appointed time. If New Horizons didn’t navigate well enough to meet both of these criteria, its closest images would be blank or partial frames, and the flyby and the mission—the whole, crazy quarter-century of effort to explore Pluto—would devolve into failure.
During approach, the mission navigation teams (there were two) needed to measure how closely Pluto’s actual position against the stars compared to carefully calculated predictions. Analysis of these navigation images allowed the nav teams to determine how much correction was needed through engine burns to thread the eye of the needle. The two different nav teams, making independent calculations, served as a check on one another; the stakes were too high to do anything less.
Each week, as New
Horizons rushed onward toward Pluto, the two teams sat down with Alan and Glen and encounter mission manager Mark Holdridge to present their latest calculations. By early mid-February, it was clear that a first, small engine burn was needed to correct their course to the intended aim point. So Alice Bowman and her team designed, tested, and then sent the engine-firing commands up to New Horizons. On March 10 the spacecraft burned its thrusters for 93 seconds to tweak its approach speed by just 2.5 miles per hour. Not much, but that correction would eliminate the 7,000-plus mile error that the LORRI images indicated that New Horizons had been off course. The correction maneuver went off flawlessly—New Horizons was now aimed precisely at its intended bull’s-eye!
IT BEGINS
In late May of 2015, Alan moved out to APL in Maryland for the flyby. This was it. He would not be back at home in Boulder for more than a few days until the flyby operations were complete at the end of July. By then, the decades-long goal of exploring Pluto would have either succeeded or failed. The moment of truth had arrived.
A few days later Alan’s executive assistant, Cindy Conrad, also arrived at APL to begin getting the logistics in order for the onslaught of science, nav, instrument engineering, and public engagement teams soon to take up working residence there for the flyby. By the end of June, the on-site New Horizons team at APL had swelled to over 200 flight controllers, engineers, scientists, and others, working seven days a week, virtually around the clock. They took over a large building at APL’s space department, with dozens of offices, team meeting rooms, break rooms, conference rooms, and even places for people to sleep. The sleeping rooms and cots were key because the workload was simply nonstop, day and night.