Thermosphere Mapping: How Starlink Data Revolutionized Density Measurement

Researchers from Kyoto University have developed a method to map the density of Earth's thermosphere using data from commercial satellite constellations. By adapting medical tomography techniques to orbital mechanics, the team created a two-dimensional density map at an altitude of approximately 500 kilometers. The thermosphere, extending from 100 to 1,000 kilometers above the surface, consists predominantly of electrically neutral gas. Unlike the ionized ionosphere, this neutral gas creates atmospheric drag that slows down satellites and alters their trajectories. Because neutral gas does not respond to electromagnetic signals, measuring its density directly is difficult. To overcome this, the scientists used public orbital movement data from approximately 1,200 Starlink satellites. The team expanded traditional Two-Line Element (TLE) analysis by studying horizontal density variations across different latitudes and longitudes. They measured the atmospheric resistance experienced by these satellites as they descended, using these drag patterns to reconstruct the medium's density.