Carried on MetOp, the SEM-2 (Space Environment Monitor) is a spectrometer that provides measurements to determine the intensity of the Earth's radiation belts and the flux of charged particles at the satellite altitude. It provides knowledge of solar terrestrial phenomena and also provides warnings of solar wind occurrences that may impair long-range communication, high-altitude operations, damage satellite circuits and solar panels, or cause changes in drag and magnetic torque on satellites.