Owens Valley Radio Observatory (OVRO) is the radio astronomy observatory of the California Institute of Technology, located near Bishop, California, about 400 kilometers north of Los Angeles on the east side of the Sierra Nevada, at an altitude of 1,220 meters. Its main instruments are: the Millimeter-Wavelength Array, a new interferometer array of six high-accuracy radio telescopes, each 10.4 meters in diameter and moveable along a T-shaped railroad track to give the equivalent resolution of a single 300-meter dish; the 40-Meter Telescope, a single dish built in 1965; and the Solar Array, consisting of two 27-meter telescopes, dating from 1960, that is now used as an interferometer for studying magnetic field variations on the Sun.