Researchers at Kyoto University have developed a new tomographic technique using publicly available orbital data from Starlink satellites to measure and map Earth’s thermospheric density, addressing a critical data gap in upper atmosphere observation, according to recent study findings. As low Earth orbit grows increasingly congested with thousands of operational satellites and pieces of space debris, accurately tracking atmospheric drag has become vital for collision avoidance and spacecraft longevity.
Mapping the Thermosphere Using Starlink Satellites
More than 99 percent of Earth’s upper atmosphere consists of electrically neutral gas known as the thermosphere, stretching between 60 and 620 miles above the surface, according to earth.com reporting. Because this neutral gas does not interact with radio signals the way the ionized ionosphere does, observing it has historically posed significant challenges. To overcome this hurdle, research led by Mamoru Yamamoto at Kyoto University’s Research Institute for Sustainable Humanosphere utilized the orbital decay of roughly 1,200 Starlink satellites operating at an altitude of about 300 miles.
By analyzing public orbital data provided by SpaceX, the research team applied tomography—a technique typically associated with medical imaging scans—to construct a two-dimensional latitude-longitude snapshot of thermospheric density. Yamamoto described the project as a multidisciplinary crossover, noting that deeper dialogue between space science and space engineering is essential for advancing atmospheric research.
Did you know? Unlike the ionosphere, which can be easily monitored because its ionized gas interferes with radio waves, the neutral thermosphere requires indirect methods like tracking satellite drag to measure its density effectively.
Validating Density Data Against Independent Spacecraft
To confirm the accuracy of the new tomographic mapping technique, the Kyoto University team compared their findings against independent density measurements collected by the European Space Agency’s SWARM satellites, according to earth.com. The SWARM spacecraft utilize onboard GPS positioning to log atmospheric changes directly along their orbital tracks, providing a reliable benchmark for comparison.
Across 19 separate analyses of data gathered between September 1 and 7, 2025, the tomographic estimates tracked closely with SWARM’s direct observations. The results showed that the satellite-derived density calculations achieved an average of 95 percent of the values recorded by SWARM, with individual readings spanning a range from 60 to 120 percent. Furthermore, the method accurately located the peak density of the thermosphere within expected geographic bands, matching established atmospheric models.
Enhancing Safety in Congested Low Earth Orbits
The ability to map horizontal variations in thermospheric density across latitude and longitude builds upon an earlier study by the same team, which relied on generalized Two-Line Element data to track changes over time and altitude. By adding a spatial dimension, the updated analysis provides a clearer picture of how atmospheric drag fluctuates globally, which directly impacts satellite operations.
As commercial constellations expand rapidly, unpredictable shifts in atmospheric density can push satellites off course and elevate collision risks. Improved, near-real-time monitoring of the thermosphere can sharpen orbital predictions, strengthen space weather forecasting, and secure safer pathways for future satellite missions operating in crowded orbital bands.
Frequently Asked Questions
What is the thermosphere?
The thermosphere is the layer of Earth’s upper atmosphere extending from roughly 60 to 620 miles above the surface. It is composed of more than 99 percent electrically neutral gas.
Why is measuring thermospheric density so difficult?
Unlike the ionized ionosphere, which readily interacts with radio waves and is simple to observe, the neutral gas of the thermosphere lacks those interactions, requiring indirect measurements like tracking satellite orbital decay.
How did researchers map the atmosphere?
Researchers at Kyoto University applied medical tomography techniques to publicly available orbital and drag data from approximately 1,200 Starlink satellites flying at an altitude of about 300 miles.
How do these findings improve space safety?
By providing precise two-dimensional maps of atmospheric density, the technique helps operators better predict satellite motion and reduce collision risks in crowded low Earth orbits.
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