This story has been updated to reflect a new scheduled launch time, Weds., Sept. 24.

Princeton astrophysicists David McComas and Jamie Rankin are two of the leaders of NASA’s Interstellar Mapping and Acceleration Probe (IMAP), a mission to map our solar neighborhood and learn about the cosmic shield protecting our solar system from harmful cosmic radiation. 

McComas, a professor of astrophysical sciences and associated faculty in mechanical and aerospace engineering, is IMAP’s principal investigator. Rankin, a research scholar and lecturer in astrophysical sciences, is the instrument lead for one of the mission’s highly sophisticated space instruments, which was built on the Princeton campus. 

Neither originally imagined their career path leading to the launchpad at Cape Canaveral: McComas has dyslexia and was very slow to read as a child, but quick to learn anything mechanical. Rankin, a talented musician, originally planned to be a classical music composer.

An unexpected path to the stars

McComas has spoken publicly about the challenges and advantages of his dyslexic brain. Whether it’s due to coping strategies or neurology, he is a very visual thinker and unusually good with his hands. 

In high school, he designed and sold jewelry so successfully that he considered skipping college — and when he did go, his deft fingers and skill with precision mechanical work made him a valuable addition to the space science program, first at MIT, and then at Los Alamos National Laboratory. (It didn’t hurt that he had an intuitive grasp of physics and a knack for visualizing complex problems.) 

While at Los Alamos, he worked on space instruments for NASA, the European Space Agency and the U.S. Air Force. After a few years, Los Alamos paid for him to get a Ph.D. from the University of California-Los Angeles.

Working through the challenges of dyslexia was foundational to McComas’ work ethic and laid the groundwork for him to be a good leader.

“I don’t think I’d be where I was if it was easy for me to read,” he said. “I think I got here to a large extent because there were a bunch of things that were hard, and I had to adjust and find ways to be successful anyway.” 

He also incorporated the lessons he learned into his vision for how to build teams that are greater than the sum of their parts — and successfully win NASA contracts. The IMAP team is his biggest yet, including 82 U.S. partner organizations in 35 states, plus institutions in the United Kingdom, Poland, Switzerland, Germany and Japan.

“Everybody has different strengths and weaknesses,” he said. “Teams that win are teams that put together everybody’s strengths and have people do what they’re good at, with good leaders who can effectively manage them as a team and get the best out of everybody.”

From classical music to space missions

Still in her mid-30s, Rankin is young to be an instrument lead on such a major NASA mission. As instrument lead, she is responsible for the design and construction of IMAP’s Solar Wind and Pickup Ion (SWAPI) instrument, which will gather particles flowing out from the sun and others coming into our solar system from beyond the heliosphere. She supervises the instrument from a technical perspective, and is also the leader of the team analyzing and interpreting the data it collects. 

She earned a B.A. in music composition from the University of Utah, as well as a B.S. in physics. As she considered her career trajectory, mentors there helped her connect with professional musicians, academics and physicists working in industry.  “It was fun to interview them all and figure out if I could see myself in those positions,” she said. 

After conversations with musicians, she decided that a day job as a scientist would provide her the “freedom to explore and pursue musical endeavors as I wish, without the concerns for trying to make ends meet.”

On the science side, she recalled one physicist who “was trying to push me to come into industry. I asked, ‘So when would I be able to do cutting-edge research on the mysteries of the universe?’” He and other mentors encouraged her to follow that dream.

She chose to go to Caltech for graduate school, where she calibrated and helped build EPI-Hi, which is now flying through the sun’s corona aboard the Parker Solar Probe. SWAPI “isn’t the first instrument I’ve touched that’s going in space,” she noted.

At Caltech, she met Ed Stone, the project scientist on Voyager, who hadn’t taken a graduate student in about 25 years before bringing Rankin into his lab. When he retired from Voyager, his longtime deputy stepped into his shoes and Rankin was named the deputy project scientist for Voyager — one of the youngest at NASA ever to have such a prestigious role.

McComas and Rankin first crossed paths at Caltech, when he was checking in on EPI-Hi, one of the two components of the IS☉IS instrument for which McComas was (and is) PI. (The Integrated Science Investigation of the Sun added the symbol for the sun in the middle of its name when the acronym ISIS became problematic.) McComas saw her potential and soon invited her to join his research team at Princeton. 

Mentoring the next generation

Originally, McComas had taken on the role of mission PI and SWAPI instrument lead, with Rankin as his SWAPI deputy, but it didn’t take long before he swapped their positions, demoting himself to deputy instrument lead and passing SWAPI into her hands. 

“My plan is that Jamie and others like her will be the ones who lead the field forward. I would like my legacy to be that I helped make that possible,” McComas said.

Rankin sees it as her role to play that mentorship forward.

“I am at Princeton because I had so many amazing professors and mentors that believed in me along the way and gave me opportunities,” she said. “I could hardly believe it when Ed took me on, and now I have an amazing mentor in Dave.”

Rankin teaches students in the Space Physics Lab course, a two-semester deep dive into the hands-on realities of space hardware. Each year, undergraduates build a sophisticated space instrument of their own design working in Princeton's cleanroom alongside the scientists and engineers from the IMAP team.

Photo by Bill Baker

She loves teaching students, she said, “because I know the importance of that critical role, the mentor role. I love giving them opportunities because I’m so thankful for the opportunities I’ve been given.” 

When she met McComas, he was (and still is) the mission PI for IBEX, the Interstellar Boundary Explorer, as well as the instrument PI for IS☉IS. IBEX was asking many of the same questions as IMAP, but at a much smaller scale and with only two instruments. 

Rankin’s work with IS☉IS and Voyager meant that she had a uniquely broad perspective on the heliosphere, which starts from the sun and pushes out roughly 10 billion miles into space. ISʘIS is in a tight orbit around the sun, IBEX and IMAP are studying the outermost boundary of the heliosphere, and the twin Voyager spacecraft have passed beyond the heliosphere into interstellar space.

Empowering the next generation

McComas is taking the long view as a mentor. “I intend to teach and research for as long as I’m humanly able to do that,” he said. He also wants to help transition the field into younger hands as PIs and instrument leaders. 

“I want the next generation to step forward and do what I was doing when I was in my 30s,” he said. “And I want to be right behind them, helping them. I’m still going to be running my group, but they should be taking their turns at the wheel.”

In addition to Rankin, McComas has nurtured many other junior scientists into leadership roles, including two at Princeton who are working on IMAP instruments. Mitchell Shen, an associate research scholar at Princeton, is the deputy instrument lead on IMAP-Lo, which gathers energetic neutral atoms (ENAs) at the low end of their energy range. Leng Ying Khoo, a postdoctoral research associate, is in the process of becoming an instrument scientist on CoDICE, the Compact Dual Ion Composition Experiment. 

“At Princeton, at any university, that should be the goal: encouraging and mentoring not just the students but the postdocs, the researchers, everybody,” he said.

From a preschool basement to the edge of the solar system — and beyond

When McComas invited Rankin to join his Princeton research team, he told her that she’d be his right hand in building a NASA-grade space physics laboratory. 

Construction on the new facility began in February 2020 in the basement of a former preschool, but quickly stopped when the campus closed to in-person activities. By July, Rankin and McComas and a very few others were allowed back on campus to continue meticulously assembling the lab.

The result is spectacular, McComas said. “It is the best in the world for the sort of instruments that we design and develop,” he said. “And now, we’ve run the entire process: we’ve built and calibrated and delivered the SWAPI instrument,” along with fully calibrating the IMAP-Lo instrument and cross-calibrating SWAPI with CoDICE.

After years of design and planning IMAP, McComas, Rankin and the other thousand or so people on the IMAP team across the U.S. and the world are now in their final week, counting down to launch, which is scheduled for 7:30 a.m. Wednesday. Princeton’s Department of Astrophysical Sciences and Center on Science and Technology are hosting a watch party in Peyton Hall, and NASA's live broadcast will run from 6:40 a.m. till about 9:15.

Dozens of industry and academic partners have contributed to IMAP, from 35 of the 50 U.S. states plus the United Kingdom, Poland, Switzerland, Germany and Japan.

Image courtesy of NASA/Johns Hopkins APL

While launch is dramatic, McComas says that for him the most exciting part of a mission comes a few months later, when the spacecraft arrives at its designated orbit and the instruments are sending back their observations, recording phenomena that could never have been detected before.

“As an experimental physicist, this is what I live for. You measure things that nobody’s seen before. Nobody’s even thought about it. Nobody’s even wondered whether such a thing was possible. That’s real discovery science.” 

IMAP’s anticipated “first light,” when the data begins streaming in, will come over the fall and the mission will be in full science mode by the end of January 2026. 

Because the life cycle of a space mission is so long — typically around a decade — very few people have led a mission more than once. “I’ve been very fortunate,” McComas said, to lead IBEX, IS☉IS, and now IMAP, as well as many other instruments and missions.

Rankin is looking forward to integrating IMAP data with data from the Parker Solar Probe —and even with the data still being sent back from the Voyager spacecraft, which first launched in 1977.

“At Princeton, we have a lot of exciting research focused on seeing how these pictures merge,” she said. While their instrumentation is different, they’re all looking at the heliosphere — the same part of space. “So what do they tell us,” she wonders, “about our place amongst the stars?”