Geostationary Environment Monitoring Spectrometer (GEMS)

Geostationary Environment Monitoring Spectrometer (GEMS) is an operational geostationary UV-visible hyperspectrometer on GEO-KOMPSAT-2B, launched in February 2020.^[1][2] It measures sulfur dioxide, nitrogen dioxide, ozone, formaldehyde, and aerosols over East and Southeast Asia from geostationary orbit.^[1] Its documented instrument class is a UV/VIS grating imaging spectrometer with a 300-500 nm range, spectral resolution below 0.6 nm, hourly daylight coverage over 5 S to 45 N and 75 E to 145 E, and 5 km resolution over Korea.^[2]

Tropospheric nitrogen dioxide and sulfur dioxide column retrieval is demonstrated on GEO-KOMPSAT-2B.^[1] Peer-reviewed validation work documents GEMS polarization characteristics and a correction algorithm, which matters for users evaluating radiometric stability and trace-gas retrieval quality in the UV-visible range.^[3] GEMS supports regional air-quality and atmospheric-composition monitoring that needs frequent daylight geostationary refresh over Asia rather than global polar-orbit coverage.^[1][2]