Use of Drag Measurements to Improve Short-Term Orbit Prediction.
AEROSPACE CORP EL SEGUNDO CALIF IVAN A GETTING LABS
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The improvement in short-term orbit prediction that results from the use of real-time drag measurements to determine the initial vehicle vector has been studied using orbit simulation calculations. Realistic time-dependent behavior of the drag force was provided by the use of calorimeter data from an actual flight. The study was limited to a specific class of low-altitude orbits and to average conditions of magnetic activity. In five samples of calorimeter data, RMS errors in a 3-rev predict span were reduced by factors or 2 and or 3 in the radial and intrack components, respectively, caused solely by the improvement in the initial vector of the predict span. Errors that remain despite the utilization of a near-perfect starting vector could only be caused by improperly modeled drag effects. Because such effects are likely to be the limiting factor in prediction accuracy, improved capability of density prediction will be necessary to meet stringent mission requirements. Until reliable density forecasting capability becomes a reality, the persistence feature of the atmosphere can be exploited to improve short-term prediction. In four out of five cases studied, prediction based on the last orbit of drag data in the fit span reduced errors significantly in the predict span. Author
- Unmanned Spacecraft