The Fly's Eye (1981-1993)

"New" Home: Dugway Proving Ground

The new experiment was located in the West Desert of Utah, within the United States Army Dugway Proving Ground (DPG). The detectors sit atop Little Granite Mountain - also known as Five Mile Hill (FMH). Dugway is located 160 km southwest of Salt Lake City. The Proving Ground was chosen because it featured a unique combination of available infra-structure (electricity, communications) and relative isolation. The presence of the military installation also offers excellent security for personnel and equipment.

The West Desert provides an ideal location for fluorescence observations. The floor of the desert lies at an altitude of ~4,500 feet or a vertical depth of ~860 g/cm2, which is well suited for observing cosmic ray air showers in the UHE regime. The nearest population centers are more than 30 miles away, and light pollution is mostly blocked by the surrounding mountains. The average annual rainfall and snowfall are 7.5 and 15.5 inches, respectively. There is a complete absence of surface water within the boundary of DPG, and the average humidity is 48%.

For 347 days per year, the visibility at DPG is better than 10 miles. With an average wind velocity of 6 miles per hour, and its isolation from major urban centers, there is a minimum of aerosol contamination. These conditions allow the greatest number of clear, moonless nights possible for fluorescence observations, and also give the largest possible detection range for air showers to be found anywhere in the world.