The project started with three students Dr. Horanyi had recruited from his own faculty. Soon, word spread around campus that a professor was looking for students to work on a NASA-led mission to Pluto. “In a matter of months, we had 20 or so students on the team,” Dr. Horanyi said. Though it was an academic project, the Student Dust Counter had to adhere to the same NASA standards as the other instruments on New Horizons, which meant regular reviews in front of panels of visiting NASA engineers. (Dr. Horanyi remembers it more as an “interrogation.”) In the two years it took to build the dust counter, many students graduated and moved on, replaced by a new batch of undergraduates. Of the original team, four students are still at the University of Colorado, Boulder, in some capacity; two graduated, but eventually returned to work on the Student Dust Counter.

Tiffany Finley came onboard as the project manager in 2002, while she was a graduate student. She was responsible for seeing the instrument all the way through, from design to construction to calibration. “I’d just been looking for something cool to work on, and suddenly it was like, wait, you guys are going to Pluto? Sign me up,” she said. After graduating, Ms. Finley worked as an aerospace engineer before landing a job at the Southwest Research Institute, first with the NASA Juno mission to Jupiter and then with New Horizons. She is now responsible for command sequencing on the Student Dust Counter — creating a series of orders that tell the instrument what to do and when to do it. (Dr. Horanyi joked that Ms. Finley started out as his student and is now his boss.)

Similarly, David James began work on the dust counter in 2003 for his physics Ph.D., with Dr. Horanyi as his adviser. His work looked at the polyvinylidene fluoride detectors that make up the dust counter, which generate a charge when hit with a dust particle. The detectors are composed of a plastic film and coated with a thin layer of metal; when a dust particle hits the detectors, the charges rearrange themselves, creating an electronic signal. The Student Dust Counter measures this signal and sends the information back to Earth for analysis.

Dr. James, too, left the university for a few years after graduating, but returned after realizing that the dust counter was a unique opportunity. “New Horizons is one of the greatest missions in space history,” Dr. James said. “To continue to be part of that, especially on a project you started working on as a student, is too exciting to pass up.” Dr. James is now overseeing the latest batch of Colorado students recruited to work with the instrument as New Horizons gears up for its flyby of Pluto in July.

Dr. James and Ms. Finley have fond memories of summers spent in the lab working on the dust counter, despite the sleepless nights spent worrying about the NASA review panels. Dr. James recalls one long week testing the instrument in various temperatures to make sure it could survive the journey to Pluto. The students worked in 24-hour shifts, juggling classes and other obligations, to document the procedure.