Earth's upper atmosphere at around 500 kilometers altitude is notoriously difficult to observe directly. But researchers at Kyoto University have found an ingenious workaround: using SpaceX's own Starlink satellite constellation as a giant atmospheric scanner.
The team used publicly available orbital data from roughly 1,200 Starlink satellites and applied tomography — a technique commonly associated with medical CT scans — to map the thermosphere, the layer of electrically neutral gas that makes up more than 99 percent of the upper atmosphere.
How It Works
As satellites orbit Earth, traces of the upper atmosphere exert drag that gradually decays their orbits. By tracking these subtle orbital changes across 1,200 satellites simultaneously, the researchers could estimate atmospheric density at different locations.
The result was the first two-dimensional latitude-longitude snapshot of thermospheric density at roughly 500 kilometers altitude — a tomographic analysis of its kind.
Why It Matters
The thermosphere is far harder to study than the ionosphere (the electrically charged gas that makes up less than 1 percent of the upper atmosphere). While the ionosphere affects radio waves and is therefore relatively easy to observe, the neutral gas of the thermosphere has remained largely invisible to remote sensing.
Better measurements of thermospheric density could advance atmospheric research while also providing critical information for space engineering. As thousands of satellites and pieces of space debris crowd low Earth orbit, accurately predicting atmospheric drag is essential for forecasting satellite motion and reducing collision risk.
Validated Against ESA Data
The resulting density patterns showed strong consistency with observations from the European Space Agency's SWARM satellites, which measure atmospheric density along their own orbital paths — validating the Starlink-based approach.
"This is a multidisciplinary study between space science and space engineering," said corresponding author Mamoru Yamamoto. "Reading papers from both research fields, we realized that deeper dialogue between researchers from both fields is necessary."
The technique could eventually support near-real-time atmospheric density monitoring, improving space weather forecasting and contributing to safer satellite operations.
The study was published in Earth, Planets and Space (DOI: 10.1186/s40623-026-02509-5).
