An Algorithm for Estimating Thermospheric Density Using LEO Dual-Frequency GNSS Receivers: Design, Uncertainty Analysis, and Validation

Jian Yao, Stefan M. Codrescu, Faisal Wahabu, Mihail V. Codrescu, and Stephen Leroy

Peer Reviewed

Abstract:	Low-Earth orbit (LEO) satellites typically reside in the thermosphere. Although the thermosphere surrounding LEO satellites is very thin, its drag force accumulates, significantly influencing satellite orbits. With the rapid growth of the satellite industry, there is a growing need to monitor thermospheric density at various altitudes and locations. In this context, we report an algorithm for estimating thermospheric density using dual-frequency GNSS receivers on LEO satellites. Notably, our algorithm performs well even in the presence of rotating satellite solar panels. We note that a very preliminary method showed some promising results but also raised concerning issues, such as distorted thermospheric density values (Yao et al., 2023). Our new algorithm framework consists of four key parts. First, we extract along-track total acceleration (and velocity) from standard LEO precise-orbit-determination processing. Second, by subtracting the acceleration due to solar radiation pressure (SRP), we can compute the air-drag acceleration. Third, we introduce drag coefficients for the satellite’s main body and solar panels, respectively. These parameters are estimated by fitting several days of observed drag acceleration into the model-derived acceleration. Finally, with information about the projected satellite surface area and the satellite velocity relative to the Earthcorotating thermosphere, we estimate the thermospheric density based on the air-drag acceleration. We have conducted the uncertainty analysis through the chain rule of our equations. Our results exemplified by six COSMIC-2 satellites demonstrate reasonable agreement with the Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) model (Codrescu et al., 2012) during the geomagnetic storm around February 3-5, 2022, which validates our methodology.
Published in:	Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025) September 8 - 12, 2025 Hilton Baltimore Inner Harbor Baltimore, Maryland
Pages:	3281 - 3292
Cite this article:	Yao, Jian, Codrescu, Stefan M., Wahabu, Faisal, Codrescu, Mihail V., Leroy, Stephen, "An Algorithm for Estimating Thermospheric Density Using LEO Dual-Frequency GNSS Receivers: Design, Uncertainty Analysis, and Validation," Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 3281-3292. https://doi.org/10.33012/2025.20349
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