Checking In With Columbia’s Astroparticle Physics Balloon Experimenters in Antarctica
Doctoral candidate Gabriel Bridges and postdoc Kaliroë Pappas filled Columbia News in on their work hunting for dark matter.
For the past two months, the scientists at the helm of a new, Columbia-led balloon experiment have been working tirelessly to launch that mission in Antarctica. The experiment, called the General Antiparticle Spectrometer, or GAPS, is on the hunt for low energy anti-nuclei. If it observes them (and if it doesn’t), it will help clarify the nature of dark matter, the mysterious matter that dominates the universe, but which scientists cannot observe with existing instruments. Due to weather conditions, the project was not able to launch this past month as planned. But the team will stow their work away with the aim of launching it this coming December.
The experiment is led by professors Chuck Hailey and Kerstin Perez, along with collaborators at other institutions. Working alongside them are Columbia PhD candidate Gabriel Lewis Bridges and Columbia postdoctoral researcher Kaliroë M.W. Pappas, who arrived in Antarctica in November.
Columbia News caught up with Bridges and Pappas to ask them about their work on the project, and daily life on the southern continent.
How did you get involved in GAPS?
Kaliroë M.W. Pappas: I worked down the hall from Professor Kerstin Perez for the first few years of my PhD, back when she worked at MIT. I worked on axion dark matter direct-detection, which is in the same field of physics as GAPS but using completely different experimental methods. I was always fascinated by the science of the GAPS experiment and I had been interested in balloon physics since my time as an undergraduate at University of Illinois Urbana-Champaign where I briefly worked on the SPIDER balloon-borne cosmic microwave background telescope. When I heard Kerstin needed a postdoc around the time I was due to graduate I connected with her and we decided to work together.

Gabriel Lewis Bridges: I was introduced to Professor Chuck Hailey as an undergraduate when I was hunting for research opportunities. Professor Hailey runs a very successful undergrad research group in high energy astrophysics and my skills were a good fit for the group. I started with some observational astrophysics, using data from NuSTAR, an X-Ray space telescope. That summer, Chuck hired me to passivate detectors for GAPS. GAPS needs more than 1,000 of these detectors and each one needed to be coated in a plastic polymer to prevent it from degrading when exposed to humidity in the air. He also presented a lecture series on the science behind the experiment—everything from the solid state physics of our silicon detectors to the cutting edge of dark matter detection. I was hooked on GAPS and wanted to continue my studies in instrumentation, working on the experiment through grad school. Chuck had an opening in his lab and soon I was traveling the country building the experiment.
What are you primarily tasked with while you’re on-site in Antarctica?
Pappas: My primary task here is working on the integration of the payload, which is everything that gets connected to the balloon, including the detector, cooling system and solar panels. I do everything from mounting time-of-flight panels to routing and plugging in all sorts of cables. The detector panels range in size depending on their position on the payload. The panels are constructed to surround the tracker in layers and in an “umbrella” that covers the top of the payload. The smallest panel is composed of one paddle about a meter tall and a few inches wide, taking two people to install.
The largest panel has 12 of those paddles mounted on a carbon-fiber backing, requiring almost the whole team (about 10 people) to complete the mounting. All these panels (and many other parts of the experiment) require multiple cables for power, readout, and triggering, this results in the GAPS payload having thousands of cables that must all individually be plugged in and checked to ensure they are in working order!
Bridges: I do a little bit of everything. As the deputy payload manager, I organize and participate in most of the day-to-day integration tasks. Usually this means (after some planning meetings) I’m installing a detector system, routing cables to and from electronics boxes, or strategizing the best way to install the next piece of equipment. I’m also the primary operator of our silicon tracker (one major component of the experiment) so I spend a lot of my time making sure that this particular system is operational and performing as expected.
What does a typical day look like?
Pappas: We have to be on the transport by 7:30 every morning, and it takes anywhere from 30 to 50 minutes to get from McMurdo Station, the research station where we live while here, to the work site (depending on the weather and who is driving). The work we do each day varies based on which portion of the payload we are integrating that day. At 11:30 we have lunch on-site in the galley then return to work for the afternoon. At 5:30 the transport leaves the work site to return to McMurdo Station at which point we get dinner at the cafeteria before retiring for the night.

Bridges: I live in a double-room with a midrat (someone who works a “night” schedule, which I guess I should say is indistinguishable from normal hours in this land of 24-hour sun). It’s great for having the room to myself after work. I usually wake-up around 6 in the morning with breakfast before the 7:30 bus (an Antarctic rated vehicle w/ 6’ diameter tires) takes us to the Long-Duration Balloon Facility (LDB), a half hour drive from McMurdo. After a brief morning meeting, we work on GAPS in the high bay, (“high” bay because the ceilings are 40 feet tall to accommodate our payload and lifting equipment!), until lunch (prepared by our own mess hall which is a real improvement over the larger base kitchen!). We end our work at 5:30 when the bus returns us to McMurdo. There is a camp-like atmosphere so sometimes a hike will happen and after dinner, trivia nights, movie nights, etc. There is also a lounge. We crash pretty early to get ready for the next day.
How long did it take you to get to Antarctica and what was your route?
Pappas: It took me about 22 hours to get to Christchurch, New Zealand, from JFK airport, with a layover in Auckland, New Zealand. After staying in Christchurch for a few days we took a C-17 American military plane to the ice (about a 5-hour flight) then drove from the runway to McMurdo, which took another hour or so.

Bridges: I had basically the same experience but I left from Los Angeles instead of New York. I arrived about a week earlier than Kaliroë with some parts of our experiment. On my C-17 flight we were confined to the sides of the aircraft since they had to fit 2 of our 20-foot shipping containers in the middle!
What surprised you about Antarctica?
Pappas: As Gabriel noted, the food was better than I thought it would be, especially the on-site lunch, and McMurdo Station really feels like an adult sleep-away camp, from the dorms to the hiking and even the generally friendly environment.
Bridges: Most of my day is spent inside a high bay, a large building facility that operates, more or less, indistinguishably from the five other high bays I’ve worked in on this project. Everything has been set up and organized by humans to make our work and living here possible, yet there is an ever-present physical reminder when you step outside and glimpse the erupting Mt. Erebus and an endless landscape of snow and ice, that beyond the base, village, and high bay, this land is primarily untouched, unaltered by humans. That’s pretty amazing to get to experience firsthand.