Written by Ben Houser
When launched in 2022, the Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument will revolutionize the way scientists observe air pollution and atmospheric chemistry. Hovering 22,000 miles above the equator in geostationary orbit, TEMPO will measure air pollutants over North America every daylight hour; these hourly measurements set TEMPO apart from current air pollution satellites, which are limited in both observation frequency and spatial resolution. TEMPO’s high-resolution hourly measurements will support an array of potential applications, some of which were impossible before TEMPO. For example, public health studies examining the impact of air pollution on health will be possible on shorter timescales than ever before and short-term emissions tracking will give scientists new insight into air pollution.
The TEMPO instrument is a grating spectrometer, which sweeps a mirror over North America and collects both ultraviolet and visible light that has been scattered by particles in the atmosphere. Based on these measurements, the TEMPO Science Team, led by Principal Investigator Dr. Kelly Chance at the Smithsonian Astrophysical Observatory, are developing science algorithms to extract key information on trace gases, aerosols, and clouds present in the atmosphere. At the center of the field of regard, TEMPO’s spatial resolution of 2.1 kilometers per pixel in the north-south direction and 4.5 kilometers per pixel in the east-west direction. Such high resolution allows TEMPO to monitor pollution at sub-urban scales, tracking air quality within the borders of urban areas and surrounding suburbs.
SPoRT scientist Dr. Aaron Naeger is the TEMPO mission Deputy Program Applications Lead, who is responsible for engaging potential TEMPO end-users, coordinating the pre-launch activities of TEMPO end-users, and leading the TEMPO Early Adopter team. Dr. Naeger does extensive research on air pollution and aerosols, and anticipates the impact that TEMPO will have on his work. “Currently I use low-earth orbit satellite data from the NASA Ozone Monitoring Instrument (OMI) and European Space Agency’s (ESA) Tropospheric Monitoring Instrument (TROPOMI) to track and study air pollution across the globe, which are limited to one or two observations per day over the same area,” Dr. Naeger said. “TEMPO will significantly expand the breadth of my research activities by providing hourly observations of air pollutants from morning to evening across Greater North America.” TEMPO’s capabilities will offer new opportunities to scientists like Dr. Naeger, who are currently unable to track air pollution with such high observation frequency. “These new research activities can include studying the complex chemical evolution of pollutant events throughout the day, source contributions from natural and anthropogenic emissions, and impact of different air pollutants on human health,” said Dr. Naeger.
As TEMPO end-users await the instrument’s launch in 2022, the TEMPO early adopter program is helping to ensure that their operations and systems are ready for the new data. The program began in 2019 to provide a means of communication between the TEMPO Science Team and end-users, and to ensure end-users are ready to go when the satellite hosting TEMPO reaches orbit (Figures 1 and 2). To accomplish this, NASA SPoRT is distributing several synthetic TEMPO products, including ozone, nitrogen dioxide, sulfur dioxide, formaldehyde, water vapor, and aerosols. These synthetic products mimic future TEMPO data, allowing end-users to configure and troubleshoot their systems pre-launch. On 18-19 May 2020, a joint virtual Early Adopter workshop was held for TEMPO and MAIA, a second air quality instrument launching in 2022. Dr. Naeger led the TEMPO workshop, which included several presentations on TEMPO’s status, applications, and synthetic data.
Due to TEMPO’s frequent and detailed observations of several air pollutants, there is a wide range of potential applications. One such application is the study of thunderstorms; Dr. Naeger said, “there are a lot of interesting applications but perhaps the most interesting application is focused on the use of nitrogen dioxide observations from TEMPO to monitor and track lightning-produced nitrous oxide in the upper troposphere which can lead to substantial ozone production.” TEMPO may also help researchers understand the relationship between aerosols and tropical cyclones; combining data from TEMPO and other weather tracking satellites will enable researchers to understand how different trace gas and aerosol environments influence the intensity and behavior of tropical cyclones. Researchers plan to use TEMPO for numerous other applications, such as understanding the complex chemistry of smoke plumes from fires, tracking variations in nitrogen oxide emissions from soils in agricultural areas, and monitoring the daily evolution of pollution in areas of complex terrain.
TEMPO’s capability for detailed air quality measurements makes it especially interesting to public health researchers, who study the impact of air quality on human health. “Air quality and epidemiology research studies will be significantly improved through incorporation of TEMPO data,” said Dr. Naeger. “We will be able to understand how different air pollutants impact health by analyzing the hourly TEMPO trace gas products along with health data and records.” Using TEMPO data in air quality models will also lead to more realistic forecasts, and there is a plan to combine TEMPO data with models to improve Environmental Protection Agency’s air quality indices.
In the future, TEMPO will be an important tool in advancing climate change research. “TEMPO can help researchers understand the impact of climate change on air pollution due to wildfires since the hourly observations will effectively monitor the evolution of smoke throughout the day,” said Dr. Naeger. “The longer the TEMPO mission lifetime, the more impact the unprecedented observations will have on climate change research.” A long lifespan means that TEMPO will be able to track changes in the atmosphere over long periods of time, which will reveal even more insight into the role of climate change on air pollution. TEMPO’s climate change research capabilities will be assisted by other satellites around the word: Geostationary Environment Monitoring Spectrometer (GEMS), a similar instrument to TEMPO, was launched over Asia in February 2020. By 2023, a similar air-pollution tracking satellite will also be operational in Europe. This geostationary trio will monitor air pollution and atmospheric chemistry on a global scale. “Utilizing this suite of geostationary observations will be key for global climate change research,” said Dr. Naeger.