On the Mitigation of Solar Index Variability for High Precision Orbit Determination in Low Earth Orbit

Abstract

Abstract : Effective satellite mission operations are directly impacted by the ability to generate accurate and precise orbit predictions. High precision orbit determination processes rely on detailed force models to propagate an orbit solution and predict future orbit behavior. While gravity forces are typically well understood, the modeling of non-conservative forces is often more challenging, causing increased difficulty in achieving and maintaining high precision orbit predictions for satellites operating in low Earth orbit. In particular, the atmosphere models used to predict the drag force experienced by a satellite may rely on input parameters such as solar flux and geomagnetic indices, which are often difficult to predict. Multiple methods of selecting the solar flux and geomagnetic index parameters are examined in combination with a number of current and historically recommended atmospheric density models to assess the impact of uncertainty in the predicted index values. Geodetic satellites with high precision satellite laser ranging data are used as test cases for the Naval Research Laboratory's Orbit Covariance Estimation and ANalysis (OCEAN) tool to evaluate solution accuracy and predictive capabilities of each combination. In all test cases examined, using either the Naval Research Laboratory Mass Spectrometer and Incoherent Scatter Radar 2000 or Jacchia-Bowman 2008 atmospheric density model with solar flux and geomagnetic index values held constant, rather than using the predicted index values, provided the most accurate orbit predictions. Surprisingly, the exponential atmospheric density model, which does not take into account atmospheric parameters, yielded more accurate orbit predictions than any model using predicted solar flux and geomagnetic indices.