HASDM

The High Accuracy Satellite Drag Model (HASDM) is a data-assimilative thermospheric neutral-density system originally developed by the U.S. Air Force to improve satellite orbit determination and prediction in low-Earth orbit. Unlike conventional empirical atmosphere models that determine density primarily from solar and geomagnetic activity indices, HASDM incorporates observed atmospheric-drag effects from a set of calibration satellites to estimate time-dependent corrections to a background thermospheric density model.

At the core of HASDM is the Dynamic Calibration Atmosphere (DCA) technique. DCA simultaneously processes satellite tracking observations and estimates corrections to the global thermospheric density field. The corrections represent spatial and temporal variations in density as functions of latitude, local solar time, and altitude, allowing HASDM to capture thermospheric variability that is not represented adequately by climatological empirical models.

The original implementation used a modified Jacchia thermosphere model as its background atmosphere. Later versions of HASDM use a version of the Jacchia-Bowman 2008 (JB2008) empirical model as the background state, with observations from multiple calibration satellites assimilated to correct the modeled density field. The assimilation of satellite-drag information enables HASDM to represent dynamically evolving thermospheric density, including responses to solar and geomagnetic forcing, more accurately than an empirical background model alone.

For CCMC Runs-on-Request, the available HASDM product is based on the SET HASDM Density Database, a historical archive of HASDM neutral mass-density fields covering 2000 to 2025. The archive provides global density fields at 3-hour cadence, on a 10° latitude × 15° longitude grid, with 25-km altitude spacing from 175 to 825 km. The database spans solar cycles 23 and 24 and is suitable for thermospheric-density validation and space-weather studies.

HASDM is provided through CCMC as a historical database rather than as an executable physics-based or empirical model. The available SET HASDM Density Database covers January 1, 2000 through December 31, 2025, with density fields provided every 3 hours on a fixed 10° latitude × 15° longitude grid and 25-km altitude spacing from 175 to 825 km. Requests are therefore limited to the temporal and spatial coverage of the archived database; values between available grid points or time steps require interpolation.

mass density

For publications or conference papers using the SET HASDM Density Database, please include the following acknowledgement:

“The SET HASDM density data are provided for scientific use courtesy of Space Environment Technologies.”