Coordinates: 40°12′N112°48′W / 40.2°N 112.8°W / 40.2; -112.8 The Chicago Air Shower Array (CASA) was a very large array of scintillation counters located in Utah, fifty miles (80 kilometers) southwest of Salt Lake City in Dugway Proving Grounds. CASA began operating in 1992 in conjunction with a second instrument, the Michigan Anti Array (MIA), under the name CASA-MIA. The MIA was made of 2500 square meters of buried muon detectors. At the time of its completion, the CASA was the most sensitive experiment built to date in the study of gamma ray and cosmic ray interactions at energies above 100 TeV (1014electronvolts or 16 microjoules). Research topics on data from this experiment covered a wide variety of physics issues, including the search for gamma-rays from extragalactic sources (quasars and gamma-ray bursts), the study of diffuse gamma-ray emission from the Galactic plane, and a measurement of the cosmic ray composition in the poorly understood region from 100 to 100,000 TeV. The project was decommissioned sometime before the summer of 2001.