Atmospheric Composition Observations from Geostationary Orbit: Evolution of the Geostationary Environment Monitoring Spectrometer (GEMS) and the Tropospheric Emissions: Monitoring of Pollution (TEMPO), to NOAA’s Atmospheric Composition (ACX) Mission

The TEMPO instrument launched on April 7, 2023 and achieved first light through the aperture on August 2, 2023. On-orbit performance verification and early environmental products have been produced and shared. The Geostationary Environment Monitoring Spectrometer (GEMS) was launched in February 2020 and began its operational mission in September 2020. These UV/Vis instruments are designed to make hourly measurements of atmospheric trace gases and aerosols critical to the understanding of atmospheric composition and air quality. The high spatial and temporal resolution of these instruments allows for measurement and analysis of the complex diurnal cycle of pollution driven by the combination of photochemistry, chemical composition, and the dynamic nature of the atmosphere. These two instruments were developed and manufactured in parallel and share much of a common design, capabilities, and calibration.

NOAA’s Geostationary Extended Observations (GeoXO) mission extends and expands Earth observations provided by the GOES-R system. The GeoXO constellation contains a GEO-Central observatory with an Atmospheric Composition Spectrometer (ACX) instrument. The ACX mission provides the same high spatial and temporal resolution observations as TEMPO, but with more operational mission requirements. Mission observables are aligned with many NOAA application forecasting and monitoring areas such as air quality, hazards, weather & climate, fire weather, and greenhouse gas and stratospheric ozone. The launch of the ACX mission is planned for no earlier than 2035.

Overviews of the GEMS and TEMPO instrument designs and performance and commonalities between these heritage instruments, and the ACX requirements will be discussed, as well as options for mission and data continuity between TEMPO and ACX.