A Survey of Current Operations-Ready Thermospheric Density Models for Drag Modeling in LEO Operations

Abstract

In Low Earth Orbit (LEO), atmospheric drag is the largest contributor to trajectory prediction error. The current thermospheric density model used by the Combined Space Operations Center (CSpOC) in operations is the High Accuracy Satellite Drag Model (HASDM). Since HASDM is not available for use outside of the US Government, satellite operators are left to determine what publicly available, open-source density model they should integrate into their internal operational software. This decision is nontrivial due to the number of available density models, each having variable performance dependent on several factors including space weather conditions and orbit altitude. To compound matters, the rapid rise of this solar cycle suggests that the predicted solar maximum between 2024-2027 could be higher than the previous solar maximum, thus causing larger perturbations due to drag from atmospheric density on LEO satellites. Given the evermore challenging nature of operations in LEO, it is imperative for satellite operators to update legacy density models to a state-of-the-art density model to provide improved trajectory predictions for collision risk assessment and vital day-to-day operational decisions. This paper outlines several operations-ready thermospheric density models, describing their performance, computation time, required operational space weather input parameters, and notes for implementation. We define an operations-ready density model as a model that is well-documented, has verified and quantified model performance, and provides publicly available model code for implementation on a user’s own system. Operations-ready models include the Drag Temperature Model (DTM), the Jacchia-Bowman 2008 (JB2008) model, the US Naval Research Laboratory Mass Spectrometer and Incoherent Scatter radar 2.0 (NRLMSIS 2.0) model, and the Thermosphere– Ionosphere–Electrodynamics General Circulation Model (TIE-GCM). US Government operational density models, HASDM and the Whole Atmosphere Model and Ionosphere Plasmasphere Electrodynamics (WAM-IPE) model, are included for comparison in the Analysis section. Models are evaluated against global HASDM density and local Gravity Recovery And Climate Experiment Follow-On (GRACE-FO) satellite accelerometer density data. A propagation analysis is also included in which model performance is compared during quiet and storm conditions and resulting LEO object trajectory prediction errors are quantified at various orbit altitudes. The analysis shows that any of the named operations-ready density models (DTM2020, JB2008, NRLMSIS 2.0, TIE-GCM) are a viable option for satellite operations. In addition to LEO satellite operators, the results from this paper are also informative for the transition of civilian space traffic coordination efforts out of CSpOC and into the Department of Commerce.