In October of 2017, Rob Weryk discovered an interstellar object in his hotel room at the Marriott in Provo, Utah. Weryk, an astronomer and postdoctoral fellow at the University of Hawaii, was in town for the forty-ninth meeting of the American Astronomical Society’s Division for Planetary Sciences. One morning, before heading off for a day of presentations, he opened his laptop to go through data he had downloaded from a telescope called Pan-STARRS, which is situated at the Haleakala Observatory, on Maui. The panoramic telescope stares fixedly at vast fields of the night sky, searching for changes over time. Special software flags anything that moves for review.
Weryk noticed that, on October 19th, something new had been detected. Visually, it was uninterpretable—a dot, or maybe noise in the image. Still, once the movement had been spotted, it was possible to go back in time, locating it in the pre-discovery, or “precovery,” data. Weryk used these previous observations to reconstruct the object’s flight path. It behaved oddly: unlike everything else in the solar system, from dust motes to Jupiter, it didn’t seem gravitationally tethered to the sun. As he investigated, an astonishing picture emerged. Long-period comets, which are just barely bound to our solar system, might move at one or two kilometres per second. This object was travelling at twenty-six.
He asked a colleague in Europe to take a look. He also contacted astronomers at the Canada-France-Hawaii Telescope, on the Big Island of Hawaii, who added the object’s coördinates to the list of targets the telescope should view the following night. He wrote to the individual directors of other telescopes, explaining why the object merited observation time. A team and a consensus grew, with scholars around the world using their telescopes to study what was now almost certainly the first interstellar object to be observed entering our solar system. They named it ‘Oumuamua—a Hawaiian word meaning “scout.”
Two years later, at the Jet Propulsion Laboratory, in Pasadena, California, an astronautical engineer named Randii Wessen stood before a wall-sized whiteboard in a room called Left Field. Facing him were eighteen researchers—planetary scientists, astrophysicists, engineers—most in their mid-twenties, all graduate students or postdocs. Bald, bearded, and trim at sixty-one, Wessen worked on the Voyager and Cassini space probes. He is now the lead study architect of J.P.L.’s so-called A-Team—a group in charge of early space-mission concept planning at the lab’s Innovation Foundry. (The team is named both for the discipline of mission architecture and for the nineteen-eighties TV show about a crack team of do-gooding mercenaries.) No two of the hundreds of thousands of identified objects in the solar system are exactly alike; each must be explored according to its own characteristics. Successful missions, therefore, emerge from the spot where the proved and the fantastic intersect. The best way to explore Io, Jupiter’s volcanic moon, could be an orbiter, but it could also be a lava boat. Often, these so-crazy-they-might-work solutions begin on Wessen’s whiteboards.
The young researchers were there as part of the agency’s annual Planetary Science Summer Seminar—a program designed to teach scientists in disparate fields how to work together to plan missions to other worlds. Before arriving in Pasadena, they had attended eleven weekly teleconferences taught by experts on every aspect of mission development. On Slack and over the phone, they had debated different targets of hypothetical exploration. They had settled, finally, on the idea of intercepting and inspecting an ‘Oumuamua-like interstellar object—a mission unlike any NASA had attempted. In Pasadena, during the seminar’s final meetings, they hoped to design a spacecraft capable of determining where such an object came from and whether it contained the basic components of life. They would then present their mission plan and spacecraft design to a review panel of space-exploration veterans charged with tearing it apart.
“So you’re actually going to try to figure out which system this thing came from?” Wessen asked the group. On the board, he wrote out the question: “Which star or star-forming region did the object originate from?” He gawked theatrically at what he had written. “I don’t even know how you would do that,” he said.
“With three different isotope measurements and the trajectory information and the metallicity,” Jesse Tarnas, a doctoral candidate in planetary science from Brown University, said. “I think it is feasible to potentially constrain the core cluster that it might have come from.”
“Four billion years ago?” Wessen asked. “And you think it went in a straight line since then?”
“No,” Tarnas said. “But, look, you characterize three different isotopic compositions. . . .” He outlined a strategy: use telescopes to deduce, from the light reflecting off and absorbed by the object, which metals it was made from; match those observations with stars along its trajectory; make an educated guess about its system of origin.
From the back of the room, another member of the A-Team—one of a dozen observers—voiced her skepticism. “It’s really going to be hard to do that,” she said. “And if you go to NASA and say that, and there’s anybody in the exoplanet community there, they’re going to tell you that objective is not going to work.” Since the beginning of the seminar, experts at J.P.L. had been explaining to the researchers just how difficult their mission would be. Finding a target was the first challenge: even assuming, optimistically, the discovery of one interstellar object per year, the team might have to wait twenty years for a candidate with the right speed and trajectory. It would be impossible, moreover, to know in advance what the object was or how it might behave. It could be an inert husk speeding through space; alternatively, frozen and comet-like, it might awaken with heat of the sun, spewing gas, dust, ice, and grains fatal to any approaching probe. After discovering the object, mission planners would have just a few weeks to decide whether to launch.
In Left Field, Wessen and the researchers worked their way through these complexities and others. Eight hours later, the big whiteboard—fifty feet wide, and stretching from ceiling to floor—was filled with dry-erase marker. The next day, six rolling whiteboards were covered, too.
The Planetary Science Summer Seminar exists because NASA’s budget is small relative to the costs of space exploration. As a result, the agency makes no exploration decisions unilaterally; it crowd-sources its ideas from the planetary-science community. When funding permits, it issues “announcements of opportunity” to American laboratories, universities, and corporations, asking for their ideas. Submitting institutions launch their own internal competitions; the best proposals, which arrive at NASA headquarters by the dozens, are then “competed” against each other, “downselected” to a handful for further development, and narrowed to a final duo for a head-to-head competition. If a spacecraft and mission are selected, hundreds of millions of dollars will flow to the winning team, and careers and lives will be transformed. Many planetary scientists spend decades trying to get something off the ground, and most fail to do so.
Actual mission proposals run thousands of pages; developing one requires years of work and significant research funding. Students at the seminar experience the process in miniature. They create a “science traceability matrix”—a document showing how a mission’s objectives, hypotheses, instruments, and trajectory fit together as a seamless whole. In designing their spacecraft, they use the same software and methodologies that are employed in real multibillion-dollar flight projects. In the end, they deliver their presentation to some of the same decision-makers who evaluate full-scale proposals. While summer-seminar missions don’t take flight, they contribute to the slow refinement of concepts across decades. The work regularly yields papers published in peer-reviewed journals, and the instructors are often developing missions themselves. (Karl Mitchell, who teaches at the summer school, is also the project scientist on Trident, a Triton mission currently in competition for NASA selection.)
When participants arrive at J.P.L.’s campus, they find that it consists of about a hundred buildings, great and small, clustered along the San Gabriel mountains. In the cavernous high bays, spacecraft are built; in the outdoor Mars Yard, rovers are tested on simulated Martian terrain. The Space Flight Operations Facility is the mission control center for spacecraft across the solar system; it receives trajectory and science data from far-off probes and sends instructions back. Engineers call it the Center of the Universe.
Building 301, where the Innovation Foundry is situated, is more nondescript. It contains cubicles, conference rooms, water coolers, and offices for the planning-focussed A-Team and another group, Team X, which specializes in spacecraft design. In Wessen’s office, a globe of the moon sits near a plastic alien skull; a copy of “The Ten Special Commandments for a Would-Be Planet Hunter,” signed by its author, Clyde Tombaugh, the discoverer of Pluto, hangs on the wall, near a signed scientific paper by Jan Oort, who hypothesized the existence of a cloud of comets and other space debris surrounding the solar system. From behind his desk, Wessen explained that winning mission approval is not a purely scientific endeavor. Many of those charged with judging mission proposals lack any scientific background; they are political appointees, accountants, managers, and engineers. Planners can’t justify the inclusion of a thermal infrared spectrometer on the basis of its noteworthy wavelength range alone; they must also explain to an accountant why the device is cost-effective. Ultimately, Wessen said, the only way to sell a highly technical mission to stakeholders with diverse, often non-technical backgrounds is to tell a story. At the summer seminar, he cites the storytelling model used by the film studio Pixar, whose tales are conceptualized through a six-step process:
At the seminar, Wessen helps the researchers refine their stories. Spacecraft design is next. Kelley Case, the head of the Innovation Foundry’s Concept Office, led me down the hall and into the Team X project design center. Blond and bespectacled, Case, who is almost entirely unknown outside of J.P.L., is one of the most influential leaders in American space exploration. As the lab’s “concept design methods chief,” her job is to help refine and improve proposed spacecraft designs. Her team has worked on “cubesats” (car-sized satellites that are miniaturized into briefcases), rovers built to explore lunar tunnels, and probes tasked with searching for life within the plumes of Enceladus, the Saturnian moon that is blasting its interior ocean into space. In 2019, NASA’s Mars Cube One cubesats, conceived in the Innovation Foundry, proved revolutionary when, during a series of high-precision Martian flybys, they relayed data back to Earth while the InSight lander was touching down on the planet. The project’s advances in miniaturization could make future deep-space missions an order of magnitude less expensive. In 2022, the Innovation Foundry will launch its next major spacecraft, which will explore the metal asteroid Psyche, believed to be the core of an ancient, obliterated protoplanet.
Such designs come together in what looks like a high-school computer-science classroom. Whiteboards are mounted above crowded rows of computer workstations; a small sign atop each monitor designates a particular mission element—“command and data systems,” “thermal,” “mechanical,” “power,” “cost,” “telecom,” “propulsion,” and so on. At the front of the room, a small sign outlines Elisabeth Kübler-Ross’s five stages of grief. Designing a spacecraft subsystem, Case explained, also involves denial, anger, bargaining, depression, and acceptance. The trade-offs are painful. Carry too many scientific instruments, and you drain power; add too much thermal protection, and you limit launch capacity; collect too much data, and you’ll have no way to store it or return it to Earth. Money is a limit, too: ambition must be weighed against thrift. “You don’t want to be the flat squirrel,” Case said. “That’s the squirrel that couldn’t make a decision.” Trade-offs must be made thoughtfully, decisively, and coherently.
In a conference room at the Marriott Courtyard, in downtown Pasadena, the seminar participants were confronting these complexities. After two days of meetings with Wessen and the A-Team, Kimberly Moore, a Ph.D. candidate in planetary science at Harvard and the leader of the mission, had begun asking herself whether a rendezvous with an interstellar object was even possible. It was 10:45 P.M. Moore and the other researchers, gathered around conjoined tables littered with surge protectors, beer bottles, and coffee cups, were at their laptops, pulling up papers on long-period comets, which swing near to Earth once every several centuries. Almost certainly, such a comet would be slower and more predictable than an interstellar object, or I.S.O. Would it be better to go after one of those? Was it really possible to adequately answer the question of whether an I.S.O. contained organic compounds?
“It’s not clear to me that we could propose a mission to an interstellar object and get worthy science with the technological status that we have now,” Moore said. “Even though I.S.O.s are flashy, I don’t want to go ahead with a mission that has a half-baked and a weak proposal.”
Perhaps proving the implausibility of an I.S.O. interception was valuable in itself. “A null result is still important,” Alexander Thelen, a curly-haired atmospheric chemist, pointed out. “It makes it so people don’t have to reinvent the wheel.”
Wringing success out of failure is something of a tradition in space exploration. In 1989, just after the Galileo space probe had left Earth and started its trip to Jupiter, the high-gain antenna on its side failed to open to its full, sixteen-foot diameter. Without it, no data could be sent back. Engineers at J.P.L. found a way to use its coffee-can-sized low-gain antenna instead; over the next thirteen years, Galileo discovered a magnetic field within Ganymede—the only moon known to possess one—confirmed the existence of a saltwater ocean inside Europa, and watched a comet, Shoemaker-Levy 9, plunge into the Jovian atmosphere.
“Oh, shit,” somebody said, from down the table. A bottle of water had been knocked over and was emptying itself into the keyboard of Moore’s laptop. Moore picked it up and tilted it, so that water flowed from the side. She turned to Kristie Llera, a researcher at the Southwest Research Institute, and asked her about the Large Synoptic Survey Telescope, in Chile, and how it might enable the mission they were trying to get off the ground.
By morning, the team had decided to stick with the interstellar-object plan. Even robotic missions are human enterprises; the researchers wanted to do something exciting, and no one had intercepted an I.S.O. before. They arrived at the Team X design center at around nine. Moore and Samuel Courville, the geophysicist who would be leading the design phase, sat at a table at the front of the room; the other researchers sat at their designated workstations, each next to a Team X engineer.
Moore stood and, using PowerPoint, walked the group through the mission, which they called Bridge to the Stars. Their goal was to intercept a fast-moving interstellar object and probe it. By doing so, they hoped to determine whether the building blocks of life were dispersed among different star systems, whether other systems were chemically similar to our own, and whether they had formed in the same way as ours. After detecting an interstellar visitor, they’d evaluate it quickly, then launch within six months, making contact somewhere between the asteroid belt and the sun. Their spacecraft, in turn, would then launch an “impactor”—a specially designed projectile—tasked with smashing into the object and blasting tiny fragments of it into space. (The team members had agreed on this aspect of the plan only after a lengthy discussion.) The spacecraft would point its instruments at the ejecta, studying its composition, searching for the ingredients necessary for life. Considering the speeds involved, the uncertain nature of the object itself, and the danger posed by debris to a spacecraft, the plan was ambitious. But, Moore concluded, the science was sound. The weak point was the impactor. “We talked about this last night,” Moore said. “The only way to make this work is with an impact. We’re open to anything. We just want to hit the target.”
Alfred Nash, the lead engineer of Team X, looked on from behind glasses and a horseshoe mustache. He began leading the team through a discussion of the technical difficulties. “Why is there a better-than-even chance it won’t work?” he asked.
“The targeting positions,” Charles Budney, an experimental-spacecraft engineer, and one of the seminar’s two permanent instructors, replied. “It’s hard enough for us to maneuver into position without—”
“Sorry,” Nash said, interrupting. “I just had an amazing thought. Why don’t we just do what they do in the Air Force and paint it with a laser and utilize targeting technology?” In 2005, a mission called Deep Impact, also designed by J.P.L., had used such a system to launch a similar impactor at an asteroid.
“But the Deep Impact object was ten times bigger and ten times slower,” Moore said.
Nash nodded, unfazed. “We have three hundred and fifty-five quality minutes,” he said. “I know you’re all up to the task.”
In the project design center, decisions flow outward from the front of the room. A choice made by the principal investigator—Moore, in this case, with Courville as the project management and “capture lead”—travels first to the “cost” station, then to the stations representing all the other components of the spacecraft. Over time, all the stations interact. Propulsion talks to power; thermal negotiates with instruments, and guidance with cost. The cost team finds the money it needs by arranging trades with and among the other stations. The room was sweltering; the air-conditioning wasn’t working. As cost and mass fluctuated, the design center acquired the noisy, stressed-out atmosphere of a trading floor.
In an adjacent room, Noah Hammond, a graduate student in planetary science, stood with Stephen Krach, a Team X engineer. They had been working on a computer model of the spacecraft and had encountered a thorny problem. Because of the risk that a piece of ejecta could obliterate their probe, the team had decided to operate it in what they called “bent pipe” mode: rather than store data and return it all at once, after the rendezvous, information would be streamed back to Earth as it came in. For this to work, the spacecraft’s antenna would need to be fixed on Earth at all times. Meanwhile, the instruments would have to face the object, and the solar panels would have to face the sun. The antenna, therefore, would need to be able to turn in any direction, rotating through three hundred and sixty degrees of freedom on one axis, with added maneuverability on a gimbal.
The complex design had grown hard to visualize and manipulate on a computer screen, and so Hammond and Krach had retreated to the Lego stash in the next room. Hammond plunged his hands into a clear plastic bin, scooping up blocks, which he began snapping together. Slowly, out of blue, red, white, and yellow blocks, he built the antenna; the boom assembly; and the square-shaped main body, with its solar panels, boosters, and camera. For a while, he flew the spacecraft around, to see how the antenna might adjust to various trajectories. Then he carried it back into the main room and held it up.
“This is our spacecraft!” he announced. Sweltering at their desks, the engineers and researchers applauded.
Another group had been wrestling with a different challenge. The mission was being developed to meet the requirements of a NASA program called New Frontiers—an exploratory initiative in which the agency launches robotic spacecraft costing between five hundred million and a billion dollars each. The rules for a New Frontiers mission proposal are rigidly defined; one of them is that its designers must be completely certain that its scientific objectives will be met. This posed a problem. Could the team truly guarantee that their impactor wouldn’t miss? The possibility of failure would count against them when the mission was evaluated.
Nash had been considering the issue for a while. Finally, an idea came to him. “Bwahahaha!” he said. He walked over to Moore and Courville. The rules of New Frontiers, he explained, contained a “science enhancement option” clause. In addition to key science objectives, proposals could describe extra data that might happen to be obtained during a mission, as a kind of opportunistic bonus.
“So,” he said, “if you can justify the existence of the impactor without it having to impact—i.e., it takes a high-resolution photo, or something else—then you can have a ‘science enhancement option’ to analyze the data that come in, in case it hits.” Under this new scheme, the impactor would not, officially, be an impactor; instead, it would be a mission-essential camera. “It’s a close-proximity reconnaissance vehicle that might become an impactor,” Nash went on. “They can’t score points against that. You are using the rules of the game to your advantage! You’re taking your least defensible thing and moving it into your most defensible space.”
The goal of the Team X process is to “close” the design of a mission. Over lunch, Nash explained that any design could be considered closed when it is self-consistent: “A works with B works with C works with D.” He held up his water bottle for consideration, pointing to its various elements. “It’s got four or five parts. Not all of them interact with each other, but some of them do. This little tube fits in the cap. . . .” Not every spacecraft that crosses the threshold of Team X project design center closes; the room has seen a lot of flat squirrels. But, by noon the next day, the I.S.O. spacecraft had closed, its components in tune with its goals, its goals in line with the rules, its design under mass and under budget.
On the last day of the seminar, Moore stood in Room C of the Team X secured area, presenting the mission to the seven-person review board. Three minutes into her talk, she was explaining how astronomers might expect to detect one interstellar object each year using current telescopes. “With future technology, that number might rise to two per year,” she said.
“So, we’ve only detected one?” asked Louise Prockter, the director of the Lunar and Planetary Institute—one of the nation’s premier research centers devoted to planetary science.
“We’ve only detected one that we can definitely prove was on a trajectory from outside our solar system,” Moore said.
“So why do you assume that we are going to detect more?”
Moore directed the question to Peter Buhler, a postdoc from J.P.L.. “There are a lot of theoretical models,” Buhler said. “The detection cadence that we expect to see from these models is about one every three to five years.”
Curt Niebur, the program scientist of New Frontiers, interjected. “You say it’s one every three to five years, but Kimberly said a couple per year.” Every New Frontiers proposal lands on Niebur’s desk at NASA; one of his jobs is to separate science from science fiction. “My concern about this is you must have an observation campaign to find your target,” he said. “Money does not buy your way onto Hubble.”
Moore was still on slide one of forty-five, but Prockter and Neibur had already identified a central weakness in the mission concept. The mission assumed that other institutions would maintain an indefinite, ground-based campaign to find interstellar objects. But NASA doesn’t control the world’s telescopes; even getting the NASA-owned Hubble Space Telescope to help in the search would require approval from a panel of scientists and a directive from the head of the agency’s science division. “That’s a tall order, but, then, it gets worse,” Niebur said. “Because NASA doesn’t control Pan-STARRS and Gemini—those are National Science Foundation-funded. The lesson I want you all to get here is that there’s a lot of inertia to overcome.” Niebur continued, “You have to work very hard to get other people invested in what you are trying to do. In a competitive environment, if you go ahead with a proposal with the statement that ‘They already do this science, so we don’t need to worry about it,’ you’re going to get shredded. . . . Pulling together large collaborations like this, that cross divisions at NASA, that cross agencies as well, it’s a challenge, and you’ve got to reflect that challenge in your plan.”
The presentation, which was scheduled to take ninety minutes, concluded after a hundred and sixty-two. The students were released, and the panelists met alone to discuss what they’d seen.
“I’ve been involved in a lot of these,” Kim Rey, the deputy manager of the J.P.L. solar system mission exploration office, said. “They answered every question, and they had one or two layers below what they were talking about to provide a rationale. And they worked as a team.” Still, he concluded, “I’m not sure they answered the question, Why this mission and why now?”
Julie Castillo, a research scientist at the lab, was troubled by the assumed prevalence of interstellar objects in the solar system. “I think there are a lot of issues with their estimates,” she said.
“I think it would be absolutely kind of groundbreaking for them to be ready to launch in six months,” Prockter said. “There’s no feasible way to make that happen.” The panelists laughed. (Prockter, who is the principal investigator of the Trident mission proposal, is a Planetary Science Summer Seminar graduate herself.)
“Let’s say, ‘The detection, launch, and mission appears ambitious in its timeline and assumptions,’ ” another panelist said.
“That’s a much nicer way of phrasing it,” Prockter said.
When the students returned, the panelists began with the mission’s strengths, especially given the constraints of time. Out of three months of teleconferences, and with only four in-person days together, they had built a serious proposal. (The task will be even harder this year: amid the coronavirus pandemic, the seminar is meeting entirely over video conference.) Castillo called the mission “brave”; Prockter described it as “truly interdisciplinary.” The presentation had been professional, the team cohesive.
Randy Herrera, J.P.L.’s deputy manager of project-systems engineering and formulation, was first to deliver the bad news. “The thing that I was struggling with when I first sat down was, What, exactly, was their mission going to do?” he said. “If I would have summarized it, it would have been like: detect an I.S.O.; pull the spacecraft out of storage; launch the spacecraft; get to a point that you can launch the impactor; view the impact; and take measurements.” But what was it all about? The team needed an initial grounding—a story, a raison d’être—to make sense of their extraordinary plan.
That night, the group went out for drinks to celebrate the week, the presentation, the mission, and one other. Planetary science is a niche field, and only a few schools in the country have departments devoted to it; gatherings are special. Moore couldn’t stay long—she had packed that morning to fly to a wedding across the country. Still, in the months afterward, the researchers remained in touch, writing papers and giving talks about their work. One team member, Sierra Ferguson, a doctoral student in the School of Earth and Space Exploration at Arizona State University, happened to be going over her notes when she found an answer to Herrera’s remark about the mission’s missing story. She had written a version of it on the first day of the seminar, when Randii Wessen had explained the Pixar method. It followed the formula. “Once upon a time,” it began,
It was rough, but there would be plenty of time for refinement.
"how" - Google News
July 12, 2020 at 05:02PM
https://ift.tt/2OjDH89
How to Plan a Space Mission - The New Yorker
"how" - Google News
https://ift.tt/2MfXd3I
Bagikan Berita Ini
0 Response to "How to Plan a Space Mission - The New Yorker"
Post a Comment