muon shower size distributions (determined from CASA and MIA, respectively) were used to measure the cosmic ray energy spectrum between 100 and 10,000 TeV. The CASA-MIA results showed a smooth steepening of the spectrum, in contrast with some earlier experiments that reported a sharper feature (known as the "knee"). CASA-MIA measurements of the cosmic ray composition were made from a combined fit to the surface and muon detector data and indicated a mixed composition at lower energies (below 1,000 TeV) that evolved smoothly to a heavier composition at energies approaching 10,000 TeV. A separate, and complementary, measurement of the cosmic ray composition was made by the BLANCA instrument that operated in conjunction with CASA-MIA and used the lateral distribution of the Cherenkov radiation in air showers. Scientific collaborations The CASA project was conceived by James W. Cronin and the design and construction were carried out by a team of scientists, engineers and technicians in the Enrico Fermi Institute of the University of Chicago (see for more details). The initial core group of scientists consisted of Cronin, postdoctoral fellows Kenneth Gibbs, Brian Newport, Rene Ong, and Leslie Rosenberg, and graduate students Nicholas Mascarenhas, Hans Krimm and Timothy McKay. During the operational phase of CASA, the Chicago group included postdoctoral fellows Mark Chantell, Corbin Covault, Brian Fick and Lucy Fortson, and graduate students Alexander Borione, Joseph Fowler and Scott Oser. The Michigan Muon Array was constructed by a team of researchers from the University of Michigan, including James Matthews, David Nitz, Daniel Sinclair, and John van der Velde. See also Large High Altitude Air Shower Observatory References High energy particle telescopes Cosmic-ray experiments Gamma-ray telescopes Astronomical observatories in Utah