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The Laser Interferometer Gravitational-Wave Observatory (LIGO) comprises two sites: one in Livingston, Louisiana, and one in Hanford, Washington. Both sites have L-shaped Michelson interferometers, with 4-km arms, that are designed to detect the extremely tiny (10–19 m) differential stretching of space caused by the passage of gravitational waves (GWs) (the Hanford site also has a second interferometer with 2-km arms housed in the same structure). Because the effect is expected to be so small, two geographically separated sites are necessary to eliminate local sources of noise that can mimic a GW signal. Bona fide signals must have common characteristics in all three interferometers and be observed nearly simultaneously at both sites. If successful, LIGO could open a new avenue of astronomy: GW astronomy. Several foreign groups are working on similar, but smaller, observatories. Collaborative data sharing between LIGO and the other groups will allow refinements in the identification of GW signals and enhance the precision with which astrophysical sources can be identified.
Construction began in FY 1992 and was supported by R&RA funds from the NSF Directorate for Mathematical and Physical Sciences (MPS). MREFC funding of construction began in FY 1994. Civil construction was completed in FY 1998. LIGO was commissioned in FY 2001 and began scientific operations in FY 2002.
LIGO is managed by the California Institute of Technology (Caltech) under a cooperative agreement with NSF. A memorandum of understanding with Caltech makes the Massachusetts Institute of Technology