When meteorologist John Haynes moved to Washington, DC, 20 years ago, he could stand on the rooftop of NASA headquarters and see airborne traces of the nearby interstate highway—there was that much pollution. “There was a cloud of smog that just followed the freeway,” he says, “all the way out into Virginia.”
A decade later, NASA started planting the seeds of a global effort to monitor urban air quality and its effects on health. Those seeds are now beginning to sprout: Just after midnight, the agency launched its first instrument capable of hovering over North America to spy on urban pollution. This summer, the team will enhance that data with measurements taken by aircraft. NASA also just announced its first satellite mission that will be done in partnership with health experts to reveal the relationship between specific health conditions and the toxic airborne particles lingering above some of the world’s largest cities.
Overall, they want to create a granular portrait of what exactly is in the sky, and how it got there—one that can’t be detailed with ground-based pollution monitors alone. Seventy-nine percent of US counties lack an Environmental Protection Agency monitor on the ground, so the EPA’s information isn’t representative of the air most Americans are breathing. Data from other parts of the world is even more sparse.
This is not NASA’s first foray into environmental surveillance. The agency has been measuring the ozone layer—the topmost part of the atmosphere—for decades, and monitoring closer to the Earth since the 1990s by flying small aircraft over the ocean, rainforests, and parts of Asia and Africa. “That was sort of what we call the exploratory days,” says Earth scientist Barry Lefer, manager of NASA’s Tropospheric Composition Program, which focuses on the chemical makeup of pollutants inhabiting the atmosphere underneath the ozone layer. “But,” he continues, “the transition to urban air quality is relatively new.”
Let’s face it: There are challenges to monitoring emissions over anything as small as a city—much less a neighborhood—from a space as gigantic as the sky. The agency’s first satellite dedicated to studying atmospheric carbon dioxide, the Orbiting Carbon Observatory-2, launched in 2014 and is still active. Its successor, OCO-3, is now mounted on the International Space Station. The two have produced detailed area maps of carbon emissions over the Los Angeles basin and from Europe’s largest power plant. But while OCO-3 passes over nearly every city on Earth, its information is still limited because it lacks continuous monitoring of any location over long periods.
Enter Tempo, short for Tropospheric Emissions: Monitoring of Pollution, the NASA air quality mission that launched early this morning. Unlike previous Earth-observing satellites, it will be the first instrument locked in a geostationary orbit—meaning it’ll rotate at the same speed and direction as the planet so it can loiter over a single part of the globe. For the first time, NASA will be able to make hourly daytime observations of nitrogen dioxide, ozone, formaldehyde, and more across North America, including the continental United States, the Caribbean islands, and most of Canada and Mexico. “We’re going to get from sunrise to sunset,” Lefer says, with data taken frequently enough to see spikes during rush hour traffic.