- Joe Atkinson
- Posted On
Space News: Air quality satellite constellation begins taking shape
On Feb. 18 a new era began in an international effort to improve air quality science and forecasting around the world to help reduce the impact of air pollution on human health and the environment.
The first of three instruments in a pioneering new space-based constellation launched from French Guiana toward an orbit where it will make hourly daytime measurements of several air pollutants.
South Korea's Geostationary Environment Monitoring Spectrometer, or GEMS, instrument rocketed into space on the Korean Aerospace Research Institute GEO-KOMPSAT-2B satellite.
From a geostationary, or fixed, orbital location, GEMS will make measurements over Asia. NASA's Tropospheric Emissions: Monitoring of Pollution, or TEMPO, scheduled to launch in 2022 as a payload on Intelsat 40e, will make measurements over North America.
To complete the constellation the European Space Agency, or ESA, Sentinel-4 satellite, expected to launch in 2023, will make measurements over Europe and North Africa.
Once complete, this air quality satellite “virtual constellation” will measure pollutants – including ozone, nitrogen dioxide, formaldehyde and tiny atmospheric particles called aerosols – in unprecedented detail and frequency.
Air pollution can be damaging to the human respiratory and cardiovascular system and to the environment. Near-real-time data products from the constellation will significantly improve air quality forecasting around the most densely populated areas of the Northern Hemisphere. That data can also help inform decisions by policymakers to improve air quality.
"The GEMS launch was a key step in building an integrated global observing system for air quality, which will give us an unprecedented view of air pollution around the world at higher temporal and spatial scales," said Barry Lefer, tropospheric composition program manager in the Earth Science Division of NASA's Science Mission Directorate.
Current satellite instruments that monitor air quality – such as NASA's Ozone Monitoring Instrument (OMI) on Aura and ESA's TROPOspheric Monitoring Instrument, or TROPOMI, on the Sentinel-5 Precursor, or Sentinel-5P – circle the Earth in sun-synchronous polar orbits that only allow them to make once-daily measurements over any given part of the planet.
First in Orbit: GEMS
That changes now with the launch of GEMS. Nearly identical to TEMPO – both were built by Ball Aerospace in Boulder, Colorado – GEMS will make detailed hourly daytime measurements that, among other things, will help address concerns around aerosols in South Korea.
Despite decreasing long-term trends in those aerosols, levels are still high. The South Korean public has been concerned about their sources, whether they are produced locally or transported from neighboring countries.
Also of concern in South Korea are increasing levels of ozone. While ozone in the stratosphere filters out harmful ultraviolet radiation, ozone in the layer of the atmosphere closest to Earth's surface, the troposphere, is a significant pollutant.
GEMS will help scientists better monitor ozone and pinpoint the sources of the chemical precursors that give rise to it. The principal investigator for GEMS is Jhoon Kim of the Department of Atmospheric Sciences at Yonsei University in Seoul.
The GEMS field of view extends well beyond South Korea. It will give researchers better measurements of major pollution hotspots and transport in countries such as India, China and Japan.
Continental U.S., Wall to Wall: TEMPO
Currently in storage at Ball Aerospace awaiting satellite integration, TEMPO will zero in on North America, from Puerto Rico to northern Canada, from the Atlantic to the Pacific, encompassing the entire continental United States.
Some of the specific issues TEMPO will help address include rush-hour pollution in urban and suburban areas; transport of pollution from biomass burning and ozone production; air pollution from oil and gas fields; and ship pollution tracks and drilling platform plumes. These measurements will have implications for air quality forecasting and public health and will improve national pollution inventories.
TEMPO measurements will also have unique research applications. The instrument could be used to measure the extent to which the evaporation of water from corn crops, also known as corn sweat, worsens heat waves and air pollution in the U.S. Midwest. It could also help measure nitrogen dioxide released by farm soil that occurs when it rains soon after the application of fertilizer. Kelly Chance, of the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, is the principal investigator for TEMPO.
Scientific possibilities for TEMPO have been explored by some 40 members of the scientific community, as detailed in the TEMPO Green Paper. Several dozen studies and experiments are presented there, including those that use the hourly TEMPO measurements and those that require higher time resolution, as short as 10 minutes.
Air Quality Forecasting for Europe: Sentinel-4
The basic air quality challenges European countries face are much the same as those faced by North American and Asian countries, in particular, high levels of aerosols, nitrogen dioxide and ozone. According to a recent analysis published in the European Heart Journal, air pollution in Europe reduces European average life expectancy in Europe by about two years.
Sentinel 4 is part of Copernicus, the European Union's Earth observation program, and its main purpose will be to provide measurement data on a long-term basis to the Copernicus Atmosphere Monitoring Service.
This service provides daily forecasts, analyses of past air quality episodes, and trends of atmospheric composition by combining data from satellites and ground-based networks using numerical modeling techniques.
Ben Veihelmann, of the Atmospheric Section of ESA's Earth and Mission Science Division, is the mission scientist for Sentinel-4 and Sentinel-5.
ESA is responsible for building the Sentinel-4 instrument, which will be operated by the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT). Two Sentinel-4 instruments will be flown one after the other on the geostationary Meteosat Third Generation Sounder satellites, to cover a total lifetime of 15 years. The launch of the first Sentinel-4 is planned for 2023.
TROPOMI on Sentinel-5P, in orbit since 2017, complements the geostationary constellation by providing atmospheric composition data over regions not covered by those instruments and will help assess and improve the consistency between the data products of GEMS, TEMPO and Sentinel-4.
Data products from all the "virtual constellation" satellite instruments will be freely available to scientists working to better understand air quality, long-range transport of air pollutants, emission source distributions and chemical processes.
Joe Atkinson works for the NASA Langley Research Center.