This grant will support continued operation of the Fly's Eye (FE I and FE II) detectors by the University of Utah. The research addressed concerns the fundamental questions surrounding the very highest energy cosmic rays which enter Earth's atmosphere from space. The nature, source and energy of these rays are examined by FE I and FE II situated at Dugway, Utah approximately 90 miles from Salt Lake City, by measuring the minute amounts of light emitted by nitrogen in the air as cosmic ray fragments pass through. Nitrogen fluorescence produced in cosmic ray showers is focussed by two arrays of mirrors (FE I and FE II, respectively) onto photomultiplier tubes. Data are recorded electronically, and shower track directions are reconstructed from position and timing information by off line computer analysis. Shower shape, direction and size are used to determine the nature, origin and energy of the primary cosmic radiation.
