Green Bank Telescope

On November 15, 1988, the original 300-foot (91.5-m) Green Bank radio telescope collapsed due to a sudden failure of a key structural element. This unexpected loss of the National Radio Astronomy Observatory (NRAO)'s major observing facility resulted in the construction of a replacement project, called the Robert C. Byrd Green Bank Telescope (GBT).

NRAO operates the Green Bank Telescope, which is the world's largest fully steerable single aperture antenna. In addition to the GBT, there are several other radio telescopes at the Green Bank site in West Virginia The GBT is generally described as a 328-foot (100-m) telescope, but the actual dimensions of the surface are 328 feet (100 m) by 361 feet (110 m). The overall structure of the GBT is a wheel-and-track design that allows the telescope to view the entire sky above 5 degrees elevation. The track, 210 feet (64 m) in diameter, is level to within a few thousandths of an inch (cm) to provide precise pointing of the structure while bearing 7,300 tons of moving mass. The GBT is of an unusual design. Unlike more conventional radio telescopes, which have a series of supports in the middle of the surface, the GBT's aperture is unblocked so that incoming radio frequency radiation meets the surface directly.

would indicate the presence of an intelligent alien civilization. But after more than 150 hours of monitoring, no evidence of strong radio signals from an intelligent extraterrestrial civilization was obtained. Project Ozma is generally considered as the first serious attempt to listen for interstellar radio signals from an intelligent alien civilization, making Drake's effort the birth of modern SETI.

Project Ozma led to Drake's formulation of a speculative, semiem-pirical mathematical expression, now popularly referred to as the Drake equation. As discussed more fully in a subsequent section, the Drake equation tries to estimate the number of intelligent alien civilizations that might now be capable of communicating with each other in the Milky Way galaxy. Among his many professional accomplishments in radio astronomy, Drake was a professor of astronomy at Cornell University (1964-84), served as the director of the Arecibo Observatory in Puerto Rico, and is currently emeritus professor of astronomy and astrophysics at the University of California at Santa Cruz.

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