Robust Prediction and Estimation of Time Varying Ballistic Coefficients

ABSTRACT: Recent improvements in atmospheric density modeling now provide more confidence in spacecraft ballistic coefficient (BC) estimations, which were previously corrupted by large errors in density. Without attitude knowledge, forecasting the true BC for accurate future state and uncertainty predictions (for non-spherical satellites) remains elusive. In this project, our objective is to improve this predictive capability for ballistic coefficients, thus improving the existing drag models and associated accuracy of the U.S. Space Object Catalog. To work towards this goal we propose a strategy that includes elements of both estimation and prediction. The two primary innovations that we offer are 1) Time Series Fits via Periodic Basis Functions and Physics-Based Simulated Data, and 2) Embedding the BC Function Fit in the Filter Estimation. In the first, we intend to leverage our experience in computational orbit mechanics to bring a physics-based realism to the data for the time series algorithm testing and tuning. In the second, we will examine the filter problem in a simulated environment with a broad scope of initial conditions and system parameters. In this bottom-up design perspective we seek to gain critical insight to the underlying dynamics, common error sources and signatures, and improved estimation strategies. BENEFIT: Results of this STTR could be used to improve the accuracy of the U.S. Space Catalog, a critical component for space situational awareness. The algorithms that produce realistic and consistent estimates and predictions of ballistic coefficients developed during Phase II will be developed into a software product targeted for operational use in the Joint Space Operations Center (JSpOC) Mission System (JMS). By exploring the system under Phase I, and prototyping it under Phase II, we can market the JMS program for funding to develop and deploy it operationally under Phase III. The algorithms developed in this STTR may also be developed into a commercial software product such as Orbit Determination Tool Kit from Analytical Graphics, Inc.