Kyoto University Researchers Develop New Technique to Measure Thermospheric Density

The atmosphere surrounding Earth is becoming increasingly congested, populated by thousands of satellites and pieces of space debris in low Earth orbit. To better predict satellite movement and mitigate the risk of collisions, accurate measurement of atmospheric density is crucial at altitudes several hundred kilometers above the planet, where remnants of the upper atmosphere can affect satellite trajectories.

Researchers at Kyoto University have introduced a new method for visualizing the thermosphere, the region of the upper atmosphere that consists of more than 99 percent electrically neutral gas. “This is a multidisciplinary study between space science and space engineering,” said corresponding author Mamoru Yamamoto. He emphasized the need for greater collaboration between the two fields.

Employing publicly available orbital data from Starlink satellites, the researchers implemented tomography—a technique commonly used in medical imaging—to estimate thermospheric density. By analyzing atmospheric drag through the gradual decline of satellite orbits, they focused on around 1,200 satellites operating at an altitude of approximately 482 kilometers.

Creating a Two-Dimensional Map of Atmospheric Density

With these measurements, the team produced a two-dimensional latitude-longitude mapping of thermospheric density at an altitude of about 500 kilometers. This analysis marks the first tomographic assessment of its type, revealing density patterns that aligned closely with data from the European Space Agency’s SWARM satellites, which track changes in atmospheric density along their orbital paths.

This investigation builds upon prior research by the same team, which analyzed how thermospheric density fluctuated over time and altitude utilizing Two-Line Element (TLE) data from the Starlink satellites. The recent study adds a horizontal dimension, examining variations across latitude and longitude and enhancing the understanding of the thermosphere’s geographical structure.

Enhancing Satellite Operations and Safety

The implications of this research are significant as the number of objects in Earth’s orbit continues to rise. More accurate atmospheric density information can enhance predictions regarding satellite movements, thereby decreasing the likelihood of collisions between satellites and space debris. Moreover, this technique could eventually enable near-real-time measurements of atmospheric density around active satellites, aiding space weather forecasting and contributing to more reliable satellite operations.