Owens Valley Radio Observatory Big Pine, CA
The Owens Valley Radio Observatory (OVRO) is the largest university-operated radio observatory in the world. The observatory is located near Bishop, California, approximately 250 miles north of Los Angeles on the east side of the Sierra Nevada. For reference, its coordinates are 37°14'02" latitude, 118°16'56" longitude at 1222 meters above sea level. The major instruments at the observatory are:
The newly completed millimeter-wavelength array consists of six high-accuracy radio telescopes, each 10.4 meters (34 feet) in diameter. The individual telescopes can be moved to observing stations along a T-shaped railroad track and pointed toward the same object in space. By combining the detected signals through a process called interferometry, extremely high-definition pictures can be produced. As in all interferometry, the degree of detail achieved depends upon the distance between the telescopes; for example, a single dish with a diameter of 300 meters (about one fifth of a mile) would be required to match the resolution that can be obtained with these new instruments.
An intensive program of microwave background observations is currently underway at OVRO using the 40-meter (130-foot) telescope. According to the Big Bang theory, the universe began some 15 billion years ago with an enormous explosion of primeval matter, and has been expanding and cooling ever since. The remnant heat radiation of this explosion can now be detected as very weak radio noise coming from all directions in space. A fundamental problem is how the once homogeneous, expanding gas gave rise to the current, lumpy distribution of stars and galaxies. Observations of this "microwave background" provide information about the conditions of the early universe and help determine how the original expanding ball of gas condensed into the celestial bodies we see today.
New receivers and signal processing equipment have transformed the 27-meter (90-foot) telescopes into a powerful interferometer for studying the Sun. Solar temperatures range from about 5,500 degrees Celsius at the solar surface to two million degrees at a higher level known as the corona. In the corona, strong magnetic fields guide and constrain ionized gas. Solar flares occur when the energy stored in the tangled magnetic fields explosively releases. Electrons in these fields generate radio emission at wavelengths dependent on the strength of the field. The solar interferometer can be tuned rapidly to many different wavelengths so magnetic fields of different intensities can be seen almost simultaneously. Scientists can then determine the way in which these fields emerge, strengthen, entangle themselves, perhaps fire, and then decay.
Graduate student research with the instruments at Owens Valley has been extensive. Long-term commitments of observing time have been available to students enabling more innovative and comprehensive projects than would have been possible at a national observatory. Typically 5-7 graduate students are supported with fellowships and have done a significant fraction of their Ph.D. research with the observatory instruments. Projects have ranged from purely observational research with the existing instrumentation to the design, development, and use of new instrumentation.