The laser interferometer gravitational wave observatory project LIGO

The Laser Interferometer Gravitational Wave Observatory (LIGO) will search for direct evidence of gravitational waves emitted by astrophysical sources in accord with Einstein's General Theory of Relativity. State of the art laser interferometers located in Hanford, Washington and Livingston Parish, Louisiana will unambiguously measure the infinitesimal displacements of isolated test masses which convey the signature of these gravitational waves. The initial implementation of LIGO will consist of three interferometers operating in coincidence to remove spurious terrestrial sources of noise. Construction of the facilities has begun at both sites, while research continues to design and develop the technologies to be utilized in achieving the target sensitivity curve having a minimum sensitivity of ∾ $1 × 10^{-19} meters/√Hz$ at ∾ 150 Hz for the initial phase of LIGO. Advanced LIGO interferometers of the future, having strain sensitivities on the order of $10^{-24}/√Hz$ corresponding to optical phase sensitivities on the order of $10^{-11} radians/√Hz$ over an observing band from 10 Hz to 10 kHz, require a complete understanding of the noise sources limiting detection. These fundamental noise sources will be quantitatively highlighted along with the principles of operation of the initial LIGO detector system and the characteristics of the most promising sources.