Real Time Operational Thermospheric Density Monitoring from the Air Force HASDM Satellite Program

The Air Force has a real time High Accuracy Satellite Drag Model (HASDM) program operationally monitoring global thermospheric density variations at altitudes of 200 km to 800 km. Approximately 80 inactive satellites and debris are being tracked every orbit revolution by numerous high accuracy Space Surveillance Network (SSN) radars and optical sensors. A set of global spherical harmonic thermospheric density corrections covering the 200 km to 800 km altitude regime are obtained on a 3-hour time grid using all the SSN observations. These corrections are then used to obtain accurate differential orbit corrections on the entire population of low earth satellites and debris in the atmospheric drag regime. The density corrections have been obtain from year 2000 to present time and have been used extensively for different thermospheric research projects. The CHAMP, GRACE, and GOCE satellite accelerometer data have been used in many of these projects to determine very accurate thermospheric density variations over a multitude of major solar storms, and the HASDM density data has been used as the main density calibration tool for obtaining these very accurate density variations. Other projects have used the global HASDM density computations for validation and data assimilation in physics-based thermospheric models for understanding the physical processes involved in the coupling of the thermosphere, ionosphere, and magnetosphere of the earth. This presentation describes the HASDM modeling, accuracy, and use of these density corrections, along with how to obtain HASDM global density values for current and future thermospheric research projects.