Physics Environment Monitoring (PEM)

From I2U2

The LIGO Physics Environment Monitoring (PEM) system draws in about 100 channels of data from seismometers, tiltmeters, magnetometers, electrical-line monitoring equipment, weather stations, radio-frequency monitors and a cosmic-ray-shower detector. PEM data are used to learn how the interferometers are affected by changes in the physical environment, and to check whether environmental parameters were "nominal" when candidate gravitational-wave events were recorded.