A smooth and robust Harris-Priester atmospheric density model for low Earth orbit applications

The modified Harris-Priester model is a computationally inexpensive method for approximating atmospheric density in the thermosphere and lower exosphere - a vital step in low Earth orbit trajectory propagation. This work introduces a revision, dubbed cubic Harris-Priester, which ensures continuous first derivatives, eliminates singularities, and adds a mechanism for introducing smooth functional dependencies on environmental conditions. These changes increase the accuracy, robustness, and utility of the model, particularly for preliminary orbit propagation, estimation, and optimization applications in which fast, reasonably accurate force models and sensitivities are desirable. Density results and computational efficiency are compared to other density models. The Fortran code used to implement the model is provided as an electronic supplement.