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Smog in Shanghai, China

New Satellites Tracking Air Pollution

New Observing Capabilities

Several new satellite instruments, that were recently launched or are nearing launch, promise to provide much better data on air pollutants than can be obtained from current satellites.

  • Higher Spatial Resolution: The European Space Agency’s TROPOspheric Monitoring Instrument (TROPOMI; launched in 2017) collects data on NO2, sulfur dioxide (SO2), carbon monoxide (CO), and methane (CH4) at sub-urban spatial resolutions (e.g., a few kilometers) and at resolutions much finer than current instruments.
  • Higher Temporal Resolution: A fleet of satellites in geosynchronous orbit covering major polluted regions of the world will provide much needed information on how air pollutant concentrations and emissions vary throughout the day. (A satellite in geosynchronous orbit will appear to remain in a fixed location in the sky relative to an observer on the ground.) Currently, there are several satellites (e.g., National Oceanic and Atmospheric Administration GOES-R; Japan Space Agency Himawari-8/9) in geosynchronous orbits that provide information on aerosols. Three satellites in geosynchronous orbits are planned to observe NO2, SO2, CO, and CH4 over East Asia (Korean Space Agency Geostationary Environment Monitoring Spectrometer (GEMS)), North America (NASA Tropospheric Emissions: Monitoring Pollution (TEMPO)), and Europe (European Space Agency Sentinel-4). Given the potential of air pollution to increase in the growing world megacities, geosynchronous satellites with similar capabilities are needed over tropical and subtropical land masses as well.
  • An Upcoming NASA Health Mission: The NASA Multi-Angle Imager for Aerosols (MAIA) mission, which has a focus to provide data useful to health researchers, will collect high-resolution data on the properties of aerosols, which may be used to infer surface PM2.5, in several of the world’s megacities.

These new capabilities will improve our ability to infer surface concentrations of air pollutants from satellite data. While it is not currently feasible to infer surface concentrations of O3 from satellite data, surface concentrations of a number of pollutants, such as PM2.5, SO2, and NO2, are inferred using atmospheric models. For example, PM2.5 may be inferred from a quantity observed from space called aerosol optical depth (AOD), which is a measure of the extinction of sunlight by small airborne particles (aerosols). However, there are often large uncertainties associated with these estimates (Duncan et al., 2014 and references therein). Nevertheless, these estimates are proving useful for air quality managers and health researchers as demonstrated on this website. For example, Science writer, Emily Underwood, interviewed a number of HAQAST scientists and describes how they are using satellite data for health applications in her article, entitled "Measuring Air Pollution's Health Impacts from Space"