Using New Balloon-Borne Technology to Probe Deeper Into our Dark Universe

How can we better understand vital questions about the unseeable dark matter that seems to constitute much of the vast universe around us? And how can we capture the faintest yet most information-rich signals from distant astrophysical explosions in our cosmos?

At least in part by launching a helium balloon into the Earth’s outer atmosphere.

That’s the gambit of the Gamma-Ray and AntiMatter Survey (GRAMS). GRAMS is a mission led by an international team of scientists, including key partners at Columbia, who plan to launch powerful particle imaging technology, which has until now largely been used deep underground, far above the Earth’s surface. The project will enable unprecedented observations of our cosmic sky.

The GRAMS team today announced that it has won a highly competitive $5.5 million NASA award to demonstrate a proof-of-concept prototype for this ambitious mission, called “pGRAMS.”

The pGRAMS project will place a cutting-edge particle detector called a liquid argon time projection chamber (or LArTPC) onto a helium balloon to demonstrate its ability to capture astroparticle signals during flight. LArTPCs are already used as particle imagers on the Earth’s surface, and as dark matter imagers deep underground. The GRAMS project will mark the first time that this imaging technology has been used in the sky, where it can be more sensitive to gamma rays and antimatter particles from deep space. The balloon is expected to reach as high as 120,000 feet in altitude.

The project will use novel imaging technology that can ultimately be used to probe the hidden reaches of the universe through sensitive measurements of medium-energy (“MeV”) gamma rays. Such gamma rays are notoriously difficult to measure but carry priceless information about their astrophysical birthplaces. The technology will also be sensitive to excess antimatter particles that may be the imprints of dark matter—a mysterious type of matter that scientists have shown makes up the majority of our matter-dominated universe, but that they have yet to observe directly.

The GRAMS team is led by Northeastern University, with Columbia University and NASA’s Goddard Space Flight Center as key partners. A total of 73 collaborators from 21 global institutions are part of GRAMS, which also includes collaborators at Barnard College, Howard University, and several institutions in Japan. The project was founded by a team of collaborators including Columbia physics professor Georgia Karagiorgi in 2018.

The team aims to launch pGRAMS as a balloon flight sometime in 2025 or 2026, before expanding use of the technology on a bigger scale. “We will use this first flight opportunity to demonstrate the LArTPC performance in flight,” said Karagiorgi. “This pathfinder flight is an important first step for the success of the future GRAMS mission. It will demonstrate the capabilities of such instruments, and give guidance on how to overcome technological challenges with operating this technology in the sky.”

Karagiorgi is leading the effort to construct the electronic readout system of the pGRAMS LArTPC. This effort leverages nearly two decades of Columbia’s leading contributions to LArTPC technology.

The Columbia team, led by Karagiorgi, will also closely collaborate with Barnard College Physics Professor and GRAMS Deputy Science Coordinator Reshmi Mukherjee, and her team, on simulations and data analysis from the pGRAMS flight. “Future possibilities for this technology as cosmic gamma-ray detectors are immense,” Mukherjee said.

“The GRAMS collaboration aims to break through existing technological barriers,” said Northeastern Physics Professor and pGRAMS Principal Investigator Tsuguo Aramaki. “After this upcoming prototype flight in the U.S., we will move forward with science balloon flights as a precursor of the GRAMS satellite mission. We are very excited to share this moment with the whole GRAMS team.”