Abstract
The High Accuracy Satellite Drag Model (HASDM) is the operational
thermospheric density model used by the US Space Force (USSF) Combined
Space Operations Center (CSpOC). By using real-time data assimilation,
HASDM can provide density estimates with increased accuracy over
empirical models. With historical HASDM density data being released
publicly for the first time, we can analyze the data to identify
dominant modes of variations in the upper atmosphere. As HASDM is a
close relative to the Jacchia-Bowman 2008 Empirical Thermospheric
Density Model (JB2008), we look at time-matched density data to better
understand the models’ characteristics. This model comparison is
conducted through the use of Principal Component Analysis (PCA). We then
compare both datasets to the CHAllenging Minisatellie Payload (CHAMP)
and Gravity Recovery and Climate Experiment (GRACE)
accelerometer-derived density estimates. By looking at the principal
components and PCA scores from the two models, we confirm the increased
complexity of the HASDM dataset while the CHAMP and GRACE comparisons
show that HASDM more closely matches the accelerometer-derived densities
with mean absolute differences of 23.81% and 30.84% compared to CHAMP
and GRACE-A, respectively.