How to Plan a Space Mission

By David W. Brown is the author of “The Mission,” a forthcoming book about the exploration of Europa.

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.)