From 22,000 Miles Up, This Satellite Tracks Airborne Health Threats Almost in Real Time

In early August, the skies above Portland, Oregon, took on an increasingly familiar sepia tint as easterly winds wafted plumes of gas and smoke from wildfires into the air over the city. At one point Portland’s air quality was ranked worst in the world, leading to the closure of summer camps and public pools and the cancellation of outdoor concerts. In a summer of intense heat and wildfires, similar scenarios played out in cities across North America—New York, Denver, Chicago, Toledo.

Above it all, a satellite recorded the dynamic swirl of gases and particulates fueling these air quality crises. From a vantage point 22,000 miles above the equator, the Tropospheric Emissions: Monitoring of Pollution (TEMPO) satellite, a joint effort by NASA and the Smithsonian Astrophysical Observatory, has provided near-real-time hourly snapshots of pollutants originating, migrating and dissipating in the daytime atmosphere over North America since September 2025. Whereas previous pollution-monitoring satellites offered only one or two daily snapshots of air quality, this ongoing, continent-scale picture has helped researchers and regulators better understand and respond to some of the most unpredictable and uncontrollable pollutants in the atmosphere.

TEMPO reveals how pollution—like the weather—is not stagnant. But progress in reducing two pollutants in particular—ozone and particulates smaller than 2.5 micrometers in diameter, or PM2.5—has stalled over the past 15 years or so. Both are secondary pollutants, formed through chemical reactions in the atmosphere that are influenced by sunlight, heat and other variables.

With their complex chemistry and the fact that their precursors come from diffuse sources such as airports, agriculture and wildfires, secondary pollutants have been especially difficult to understand and control. They remain major contributors to the estimated 100,000 premature deaths, 10,000 premature births and 200,000 cases of child-onset asthma that are still caused each year by air pollution in the U.S. And as a 2023 paper in the Annual Review of Pharmacology and Toxicology concluded, there is growing evidence that air pollution may contribute to neurodevelopmental diseases such as schizophrenia as well as neurodegenerative diseases such as Alzheimer’s and Parkinson’s.

TEMPO’s ability to track how secondary pollutants form over the course of a day has wide-ranging potential to help reduce those figures. State and local governments can use TEMPO to identify and mitigate precursors, which helps them better comply with federal air quality standards. Scientists can create forecast models for secondary pollutants and issue timelier warnings of dangerous air quality.

And public health researchers can inform pollution control measures with more precise information about where and when secondary pollutants affect human health. TEMPO gathers data with a spectrometer that measures UV and visible light absorption patterns in the atmosphere, which can then be used to derive estimated concentrations of nitrogen dioxide (NO2), formaldehyde, aerosols and ground-level ozone down to a resolution of about four square miles. The satellite fills in the gaps left by the U.S.