Technical Article

Thermospheric mass density derived in near real time from space debris

Swedish Defence Research Agency, Stockholm, Sweden

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 5 November 2025
Accepted: 13 February 2026

Abstract

Near-Earth space is becoming increasingly congested. A rapid increase in the number of orbiting objects around Earth underscores the need for accurate tracking and prediction of space objects. Space weather constitutes the most important source of uncertainty in low-Earth orbit, where solar and geomagnetic activity can cause abrupt changes in the neutral mass density and satellite drag. In this study, we present a computationally efficient and operationally feasible approach to estimating the globally averaged thermospheric mass density in near real time using publicly available Two-Line Element (TLE) data from space debris objects. The method constitutes a potential basis of a TLE-based density estimation for continuous monitoring of low-Earth orbit, providing a complement to existing modeling efforts in support of space situational awareness. By implementing the method, while simulating real-time limitations, we estimate the thermospheric density during 2018–2024 using 2348 debris objects between 200 and 800 km altitude. Validation against satellite-derived densities shows an excellent result that exceeds that of commonly used empirical models, even during geomagnetic storms. Finally, we demonstrate the utility of the method to nowcast the decay rate of a fictional satellite during the May 2024 Gannon geomagnetic storm.