The Laser Interferometer Gravitational-Wave Observatory (LIGO) project

The Laser Interferometer Gravitational Wave Observatory (LIGO), a USA National Science Foundation sponsored project being performed jointly by the California Institute of Technology and the Massachusetts Institute of Technology, is one of a new class of astronomical instruments designed to probe the Universe by detecting gravitational waves. Signal characteristics and expected event rates for these sources are discussed. A brief history of interferometric gravitational wave detectors and reference to ongoing and collaborative international projects is also provided. LIGO will consist of two widely separated sites at which L-shaped vacuum systems, each with two 4 km long arms, will house interferometers for coincident detection of gravitational waves. The initial LIGO detector consists of 3 interferometers, two at one site and one at the other. Each interferometer measures the motion of freely suspended and seismically isolated masses induced by a GW. Correlations among the three interferometers will be used to eliminate events due to terrestrial noise. The LIGO facilities are designed to be extensible with the intent to add and upgrade interferometers in the future.