¶ Scattered Light
Scattered Light is low-frequency, long-duration, humpy glitches that usually have several lines stacked on top of each other. This glitch type is caused by light scattering off of dust or other particles in the LIGO vacuum system. The scattered light can produce a bright, narrow peak in the detector output that can be mistaken for a gravitational wave signal. (Source: LIGO Scientific Collaboration, "Observation of Gravitational Waves from Two Neutron Star - Black Hole Coalescences")
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