EUSO-SPB2 cannot detect these particles directly, but it can look for telltale signs in the atmosphere when neutrinos and cosmic rays collide with molecules in the ground and atmosphere. Its two instruments search for traces of these collisions. UV light produced by cosmic rays striking atmospheric molecules and producing a shower of particles is detected. The other looks for a special type of light called Cherenkov radiation that is produced after a neutrino hits an Earth molecule; the collision sends a tau particle flying away, which then decays and produces a shower of billions of secondary particles that create the telltale Cherenkov light.
Most previous experiments to find these particles have sat on the ground looking at the atmosphere. EUSO-SPB2 is fairly fair above the atmosphere looking down. This gives the instruments a much broader potential view of the traces of these collisions.
“The more atmosphere you can observe, the better, because ultra-high-energy cosmic rays are extremely rare,” said UChicago physicist Rebecca Diesing, who is helping build one of the instruments that will come aboard. of the ball. “A one square kilometer patch of Earth will only be hit by one of these particles about once a century.”
EUSO-SPB2 will also be launched while several gravitational wave detectors are in operation. These observatories are designed to pick up the ripples in spacetime that occur when black holes or neutron stars collide. If gravitational wave detectors pick up such a collision, EUSO-SPB2 may swing to try to search for neutrinos in the aftermath.
Assemble the pieces
Even getting this far has been a journey, the scientists said. Because nothing like this has been done before, dozens of scientists and engineers have worked to ensure that the instruments and the balloon will work together.
“For example, we had to choose materials that were light enough to fit within the weight limit of what the balloon could carry, but also strong enough to withstand the shock of launch – when the parachute deploys, the pod experiences up to eight to 10 G’s,” explained Johannes Eser, a UChicago scientist who has worked on EUSO-SPB2 since its inception.
Different parts of EUSO-SPB2 have been built in institutions around the world; for example, Georgia Tech builds the Cherenkov camera, and institutions in France and Italy have built the UV fluorescence camera. Meanwhile, the University of Chicago is building several parts, including a device to measure the cloud cover around the balloon and the innovative pod that carries the instruments, as well as simulations and supervision of the entire project.
The entire cargo is assembled at the Colorado School of Mines this summer and fall, then shipped to NASA facilities in Palestine, Texas, for a “suspension test” – to ensure that the entire the device holds together and works well when hanging from the ball. Finally, it will make its way to New Zealand for an expected spring 2023 launch.