Posted on | October 29, 2010 | Comments Off
NASA has awarded Mānoa and five U.S. institutions a $4.6 million grant for the Antarctic Impulsive Transient Antenna experiment. Mānoa, the lead institution, will receive $1.4 million. Mānoa Professor Peter Gorham, who serves as principal investigator, is one of approximately 45 researchers who has been working on the ANITA experiment since 2003.
The ANITA project is designed to view the Antarctic ice sheet over a wide area using a sophisticated array of antennas. Researchers “listen” for sharp bursts of radio waves emitted by cosmic high energy neutrinos as they interact deep within the ice sheet, producing what amounts to a mini-bolt of lightning within the ice sheet. The payload of 40 antennas is carried around the Antarctic ice sheet by a stadium-sized balloon circling the continent at an altitude of 120,000 feet—four times as high as a passenger airplane travels. Radio bursts from within the ice can travel through the radio-transparent ice, emerging to be seen from above by ANITA.
In a previous flight in 2007, the team detected a handful of radio bursts that didn’t fit the profile for neutrinos, but could not be tied to any other source either. Later searches through that data yielded a total of 16 such events. The team members then realized that they were observing radio signals from ultra-high-energy cosmic-rays—protons or atomic nuclei rather than neutrinos. These cosmic-rays were making radio bursts in the Earth’s atmosphere, which then reflected off the ice surface, to be seen by ANITA.
“These cosmic-ray events were a real surprise for us,” says Gorham. “It is a completely new way to detect these rare particles, and it may turn out that observations by a balloon or spacecraft payload are the most powerful way to see the highest energy particles in the universe.” The paper describing this discovery was chosen as the cover article in the October 8 edition of Physical Review Letters.
The next planned flight of ANITA will focus on gaining much more knowledge about both high energy neutrinos, which have yet to be conclusively detected, and the newly detected cosmic rays. “We saw two possible neutrinos in a previous flight,” says Gorham. “In our next flight, we hope to see a more convincing set of neutrinos, and several hundred cosmic-ray events.” The next ANITA flight is expected to take place about three years from now.