On Dec. 17, 2014, Martin Israel, PhD, professor of physics at Washington University in St. Louis, emailed to say that the stratospheric balloon carrying ANITA III, a high-energy astrophysics experiment, was about to be released into the polar vortex above Antarctica.
Israel and W. Robert Binns, PhD, research professor of physics at Washington University, had been anxiously monitoring the launch site from St. Louis. Both are co-investigators on the ANITA project, a multi-university consortium led by Peter Gorham of the University of Hawaii-Manoa.
The Columbia Scientific Balloon Facility (CSBF) team that releases stratospheric balloons in Antarctica waits to launch until conditions are nearly perfect. Before ANITA finally flew, five launch attempts had to be scrubbed because of wind.
Antarctica is the coldest, but also the windiest, continent on the planet. “To launch a balloon the surface winds have to be below about 8 knots, which is about 9 miles an hour,” said Binns, the veteran of many balloon campaigns.
Why is ANITA listening for radio bursts?
When an ultra-high-energy neutrino interacts with the ice, it produces a giant shower of electrons and positrons, Binns said. The shower in turn creates a radio burst that refracts up through the ice to the air and travels through the air to ANITA’s receivers.
“Because neutrinos don’t interact with much of anything, they let us see far, far away,” Israel said. “Any other type of radiation is limited by one thing or another, but with neutrinos we could probe the whole universe.”
Ultra-high-energy cosmic rays also produce radio bursts, but they interact with Earth’s atmosphere rather than the ice, producing radio bursts that reflect off the ice and up to ANITA.
Radio bursts are generated because the particle showers are traveling faster than the speed of light in the ice or the air.
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