Analyzing and Characterizing Scattered Light Noise in aLIGO with ARCHGEM

Non-stationary scattered light creates noise in the Advanced LIGO (Laser Interferometer Gravitational-Wave Observatory) gravitational wave detectors signals, impeding on the

frequency of gravitational wave detections and quality of the data collected. Scattered light produces low frequency noise (20-40 Hz) that couples into the gravitational wave sensitive frequency band (10–100 Hz) through light reflected in mirrors and other surfaces. The scatter noise caused by low frequency motion can be identified as arches in the time-frequency plane of the gravitational wave channel. We investigate the multiple origins of one of them by implementing an algorithm, ARCHGEM that uses a witness channel and scattering event time identified by machine learning tool GravitySpy. The algorithm filters out noise and uses the properties of the arches, to calculate properties of the scattering surfaces. This tool is intended to aid in the noise investigations. Using this algorithm, we investigate the changes in scattered light properties such as the frequency, velocity, and duration for further study of the rate at which they occur during O3b when compared to O4.