Introducing the geostationary environment monitoring spectrometer

To consistently observe deteriorating air quality over East Asia, the National Institute of Environmental Research, Republic of Korea, is planning to launch an environmental observation sensor, the Geostationary Environment Monitoring Spectrometer (GEMS), onboard the GK-2B satellite (a successor to the GeoKOMPSAT-1) in late 2019. GEMS is a hyperspectral spectrometer that covers the ultraviolet-visible range (300 to 500 nm) with full-width at half-maximum of 0.6 nm. It has been designed for the observation of air pollutants and short-lived climate pollutants. GEMS captures images at hourly intervals in the daytime, alternating with the Geostationary Ocean Color Imager-II every 30 min. Over the Seoul Special Metropolitan area, South Korea, the spatial sampling resolution of GEMS is 3.5 x 8 km (north-south and east-west, respectively). There are 16 baseline products, including aerosol optical depth and the vertical column density of trace gases such as nitrogen dioxide, sulfur dioxide, formaldehyde, and ozone. Research continues into additional applications (e.g., ground-level concentrations and emissions). (C) The Authors.