Near Real-Time Thermospheric Density Monitoring from Public Satellite Tracking and Space Weather Data

We present a framework to achieve near real-time (NRT) monitoring of the Low Earth Orbit (LEO) environment using publicly available data. We first assimilate Two-Line-Elements (TLEs) from thousands of ballistically stable LEO objects to parameterize the shape and scale of the global atmosphere from the past ~24 hours. When compared to available reference data from 2014 to 2026, our estimates are shown to have an accuracy of ~10-20% for altitudes between 200km and 600km during even the most extreme geomagnetic storms. We then parameterize variations in mass density using solar and geomagnetic activity indices, enabling extension of the TLE-derived solution through short-term forecasts. Our approach enables actionable nowcasts and forecasts of the upper atmosphere for the broader LEO community.