OUR BILLION MILES FROM EARTH,
a massive region of planetesimal bodies called the Kuiper Belt circumscribes our solar system. Home to dwarf planets like Pluto, the belt also boasts thousands of small, planet-like objects which may date back to the beginnings of our own planetary system. On Jan. 1, 2019, NASA’s New Horizons space probe completed a flyby of one of these objects— (486958) 2014 MU69, informally known as either MU69 or Ultima Thule. More than three years earlier, New Horizons had become the first spacecraft to investigate Pluto. Back home on Earth, six Harvey Mudd alumni who had made a small contribution to this historic moment in space exploration looked on.
New Frontiers Nearly a decade before New Horizons reached Ultima Thule, Steven Berry ’11 Austin Lee ’10, Cullen McMahon ’11, Claire Robinson ’11, Chris Sauro ’10 and Florian Scheulen ’10 were recruited for a Clinic Program project with the Southwest Research Institute (SwRI), a science, engineering and technology nonprofit that helped engineer the New Horizons spacecraft alongside the Johns Hopkins University Applied Physics Laboratory. In 2009, the students were charged by SwRI staff scientist and clinic liaison Marc Buie with improving an optimal image subtraction (OIS) algorithm. This algorithm would be used to detect and track Kuiper Belt objects, with the goal of selecting one for New Horizons to study in the future. “Those folks—they were really, really clever, crafty students. They dug in and tackled the project and did everything that I asked them to do and more. It was fantastic,” says Buie, for whom space exploration has always been a calling. “At an age when most kids would say they wanted to be a doctor or a fireman or something like that, I would actually say I want to be a nuclear physicist, not really knowing what that meant,” he recalls. “I got really turned on to the space program, watching the astronauts go to the moon, and that set me on a course for where I’ve ended up today.” As for his planet of choice: “I distinctly remember Pluto picking me,” he adds. In fall 1982, Buie was about to embark on his doctoral dissertation in planetary sciences at the University of Arizona. After reading a paper his adviser had written about methane on Pluto, he
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HARVEY MUDD COLLEGE
T he most detailed images of Ultima Thule obtained just minutes before New Horizons’ closest approach at 12:33 a.m. EST on Jan. 1.
became hooked on all things Plutonian. Buie’s dissertation went on to prove that methane was on the planet’s surface rather than in its atmosphere—a big change in how scientists viewed Pluto at the time. Even then, a mission to the edge of the solar system beckoned. “I remember thinking: We’ve not gone to Pluto with a spacecraft, but this is something that could happen in my lifetime, during my career, and I want to be a part of that,” Buie says. From then on, he and other Pluto enthusiasts devoted their energies to lobbying for a funded mission. Finally, in 2006, New Horizons launched from Cape Canaveral. Its destination: Pluto and beyond.
In the Stars Pluto looms large in Buie’s life. But for the six Mudders, it was new territory. According to Lee, who has since gone on to work for Apple as a silicon engineer, “our biggest challenge at first was just getting up to speed; we had a lot to learn.” After setting up the project, Buie travelled to campus to meet with Lee and his classmates. “Marc was fantastic,” says McMahon, now CEO
of Bay Area simulation infrastructure company Simr. “He brought a clear focus to the work he wanted out of us and demonstrated with his hustle and engagement what he expected of us on the project.” His expectations were high: the group was asked to speed up the OIS algorithm by a factor of at least a thousand. Originally written in C, the algorithm had been converted to IDL (interactive data language, a programming language commonly used by planetary scientists) by someone who was not well-versed in IDL. As a result, it was glacially slow. “While it worked, it took hours to do one image subtraction, and only on a small test image at that,” Buie remembers. “I knew that there was a useful tool here, but I needed help in just turning the crank and turning it into a tool that I could actually use.” The New Horizons team planned to use OIS to search images from ground- and space-based telescopes for a Kuiper Belt object that would become the spacecraft’s post-Pluto target. How? Imagine using a powerful telescope to take multiple images of the star-filled Milky Way. Using OIS, you can “overlay” those images on top of one another and “subtract” all the stationary objects. This is how you find “objects marching across the field. That’s how you discover planets. That’s how Pluto was discovered,” explains Buie.
