The High Resolution Fly's Eye or HiRes detector was an ultra-high-energy cosmic ray observatory that operated in the West Desert of Utah from 1981 until April 2006.
The sites were located on hilltops in Dugway Proving Grounds, a U.S. Army test facility in the West Desert of Utah.
HiRes-I was instrumented with sample and hold electronics which took a "snapshot" of the extensive air shower generated when the incident cosmic ray interacted with the atmosphere.
HiRes-II was instrumented with a flash analog to digital converter (FADC) so that it essentially made movies of the cosmic ray events.
Dr. Pierre Sokolsky and Dr. George Cassidy, both of the University of Utah, received the 2007 Panofsky Prize for their work on the HiRes experiment.