[en] In September 2015 the Advanced LIGO detectors inaugurated the era of gravitational-wave astrophysics with the observation of GW150914. In this proceeding, I will describe the upgrade that made the detection possible, review the binary black hole observations of the first a LIGO observing run, and discuss plans for the future.

[en] Interferometric gravitational-wave detectors are complex instruments comprised of a Michelson interferometer enhanced by multiple coupled cavities. Active feedback control is required to operate these instruments and keep the cavities locked on resonance. The optical response is highly nonlinear until a good operating point is reached. The linear operating range is between 0.01% and 1% of a fringe for each degree of freedom. The resonance lock has to be achieved in all five degrees of freedom simultaneously, making the acquisition difficult. Furthermore, the cavity linewidth seen by the laser is only ∼1 Hz, which is four orders of magnitude smaller than the linewidth of the free running laser. The arm length stabilization system is a new technique used for arm cavity locking in Advanced LIGO. Together with a modulation technique utilizing third harmonics to lock the central Michelson interferometer, the Advanced LIGO detector has been successfully locked and brought to an operating point where detecting gravitational-waves becomes feasible. (paper)

[en] The LIGO Scientific Collaboration (LSC) glitch group is part of the LIGO detector characterization effort. It consists of data analysts and detector experts who, during and after science runs, collaborate for a better understanding of noise transients in the detectors. Goals of the glitch group during the fifth LIGO science run (S5) included (1) offline assessment of the detector data quality, with focus on noise transients, (2) veto recommendations for astrophysical analysis and (3) feedback to the commissioning team on anomalies seen in gravitational wave and auxiliary data channels. Other activities included the study of auto-correlation of triggers from burst searches, stationarity of the detector noise and veto studies. The group identified causes for several noise transients that triggered false alarms in the gravitational wave searches; the times of such transients were identified and vetoed from the data generating the LSC astrophysical results