NASA approves a $20 million multi-institution balloon project conducted by University of Chicago scientists

Abby Vieregg, a physicist at the University of Chicago, is heading an international project that effectively utilizes Antarctica’s ice as a gigantic detector to locate incredibly energetic particles from space. The $20 million project, which was just approved by NASA, will create an equipment that will be launched above the Antarctic in a balloon in December 2024.

“We’re looking for the universe’s highest-energy neutrinos,” said Vieregg, an associate professor in the Physics Department. “Neutrinos are created at the most intense and extreme regions in the universe, and they provide a unique window into these places.” Finding one or more of them might lead to the discovery of whole new knowledge about the cosmos.”

The multinational partnership of 12 institutions will create a radio detector that will be mounted to a NASA-launched high-altitude balloon that will hunt for neutrino signals at 120,000 feet over Antarctica. The project is known as PUEO, which stands for Payload for Ultrahigh Energy Observations. (It shares its name with the only live owl native to Hawaii, where the PUEO experiment’s forerunner was born.)

The pueo (Asio flammeus), Hawaii’s sole live owl, is named after the new NASA-approved project.

‘It’s a lovely way of looking at the cosmos.’

Because neutrinos seldom interact with matter, they are commonly referred to as “ghost” particles. Every second, trillions of trillions of trillions of trillions of trillions of trillions of trillions of trillions of trillions of trillion

Neutrinos can serve as unique hints about what’s going on elsewhere in the universe, including the cosmic collisions, galaxies, and black holes where they are generated, because they can travel great distances without becoming distorted or derailed.

“Neutrinos are a lovely way to look at the cosmos since they flow across space unfettered,” Vieregg remarked. “They can come from a long distance away and aren’t jumbled along the way, so they point back to their origin.”

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Scientists have discovered a handful of these neutrinos entering the Earth’s atmosphere from space. They believe, however, that there are even more neutrinos out there with extremely high energies—multiple orders of magnitude greater than the particles being accelerated at Europe’s Large Hadron Collider—that have yet to be observed. These neutrinos may reveal information about the universe’s most dramatic events.

That is, assuming you are successful in catching them.

Vieregg would have to build a country-sized detector to catch these neutrinos since they interact with other types of matter so seldom. She may also utilize one that already exists: the ice sheet that covers Antarctica.

“The ice cap is excellent,” Vieregg remarked, “a homogenous, massive, radiotransparent block spanning millions of square kilometers.” “It’s almost as though we created it.”

There’s a risk that one of these very powerful neutrinos will collide with one of the atoms inside the Antarctic ice sheet if it passes through the Earth. Radio waves are created as a result of the impact, and they travel through the ice. As it hovers above Antarctica, PUEO will pick up this radio broadcast.

It will require some quite specialized equipment to do so.

Neutrinos can provide unique insights into what's going on in the cosmos

The next generation

PUEO is the next generation of ANITA, a mission headed by the University of Hawaii that flew four times over the Antarctic aboard NASA balloons between 2006 and 2016 in search of comparable neutrinos. PUEO, on the other hand, will be equipped with a considerably more powerful detector.

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The new detector makes use of an ancient astronomy method known as interferometry, which mixes data from several telescopes. PUEO is covered with radio antennae, which will be merged and analyzed by a central data collecting system to create a stronger signal.

A stronger signal would be a huge step forward since it would allow scientists to distinguish vital signals from the background noise. “There are terabytes of data pouring into the detector every minute, and we predict just a few neutrino occurrences out of billions,” said Cosmin Deaconu, a UChicago research scientist who is working on the PUEO software. “Because you can’t store all of that data to disk, we need to create a software that can swiftly pick which signals to preserve and which to reject.”

PUEO will take off from Antarctica, much like its predecessor, ANITA, did in 2016. (above). Cosmin Deaconu, Eric Oberla, and Andrew Ludwig, PhD’19, from left to right. UChicago is the source of this image.

Many frequent signals resemble neutrinos but are not neutrinos. These might range from satellite broadcasts to a cigarette lighter being flicked. “There are just a few areas in Antarctica where people would be creating these, so it’s simpler to rule those out,” Deaconu said. “However, things like static electricity created by wind must be taken into consideration.”

Vieregg and his colleagues put the interferometric phased array concept to the test on the ground in two experiments: ARA at the South Pole in 2018 and RNO-G in Greenland in the summer of 2021. Both exhibited a considerable improvement in performance over earlier designs, which bodes well for PUEO’s aerial detector. “PUEO will have ten times the sensitivity of all prior ANITA flights combined,” Vieregg stated.

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The team will create PUEO prototypes and complete the design in the next months. Small teams from institutions around the country will create sections of the instrument when the plan is finalized, which will then be assembled and tested at UChicago. “For example, we want to make sure it can tolerate near-space vacuum,” said Eric Oberla, a UChicago research scientist who is constructing PUEO’s hardware. “We’ll do testing in a vacuum chamber here on campus and later in a massive NASA room during the instrument integration campaign because it’s harder to disperse heat when there’s no air to transport it away, which may be an issue for electronics.”

"Finding one or more of these neutrinos might lead to the discovery of whole new knowledge about the cosmos."

PUEO will next be transported to a NASA facility in Palestine, Texas, for final testing before being flown to the Antarctica launch site.

The detector might fly for a month or more, gathering data and relaying it back to Earth, where scientists would search through it for signs of the first-ever high-energy neutrino detection, depending on weather conditions.

“We are thrilled to have the PUEO stratospheric balloon mission included in the initial batch of Pioneers missions, and we look forward to the outstanding research it will return,” said Michael Garcia, the Pioneers in Astrophysics Program’s head at NASA/HQ.

According to Vieregg, the Pioneers initiative allowed the scientists to “dream large.” “We might say, ‘What could we do if we could build anything we wanted?'”

“It’s a discovery experiment,” she noted, “so nothing is assured.” “However, all signs point to there being something out there for us to uncover—and even a few neutrinos would be a fantastic scientific find.”

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