Research Objective
Understand and mitigate the effects of navigation errors on spacecraft formation flying missions.
- Analysis of the impact of the velocity errors on spacecraft formation flying missions (general orbit configurations)
- Investigate the fundamental performance limits of CDGPS estimators, and identify estimator changes that might improve upon the accuracy of the current velocity estimates
- Identify augmentation approaches that might be efficiently added to the spacecraft to improve velocity estimates (onboard and/or ground based)
- Extend current control techniques to further enhance their ability to achieve fuel efficient performance even with sensing errors, differential drag disturbances, and gravity perturbations.
Focus on
- Navigation filter parameters and their effect on semimajor axis knowledge
- Analysis of the effects of spacecraft relative navigation errors on closed loop control in widely spaced, highly elliptical orbits
- Improving optimized control algorithms by incorporating precise
knowledge of expected noise characteristics
Results in Phase 1
Examined effects of navigation filter properties on semimajor axis estimation and formation flying control
- Linearized analysis of velocity noise with position measurements.
- Extended linearized analysis to include velocity measurements.
- Examined discrete and nonlinear effects.
- Developed linearized dynamics based on GVEs and embedded those dynamics in a model predictive controller.
- Development of GVE-based dynamics; demonstration of large baseline formation flying.
- Extended GVE-based dynamics to include the effects of differential J2 disturbances.
- Demonstrated analytic performance prediction for formation flying mission using a model predictive control algorithm. Showed benefits by conducting trade studies of control parameters.
Results in Phase 2
- Developed optimized approach to finding J2 invariant relative orbits. The method balances fuel use minimization, drift minimization, and template matching.
- Verified and implemented a new approach for creating J2-modified discrete input matrices.
Related Publications
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Mitchell, M., Breger, L., How, J. P., and Alfriend, K. T., “Effects of navigation filter properties on formation flying control,” AIAA Guidance, Navigation, and Control Conference (GNC), Providence, RI: 2004.
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Breger, L., and How, J. P., “J_2-Modified GVE-Based MPC for Formation Flying Spacecraft,” AIAA Guidance, Navigation, and Control Conference (GNC), San Francisco, CA: 2005.
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Breger, L., and How, J. P., “Gauss’s variational equation-based dynamics and control for formation flying spacecraft,” AIAA Journal on Guidance, Control, and Dynamics, vol. 30, 2007, pp. 437–448.
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Breger, L., How, J. P., and Richards, A., “Model Predictive Control of Spacecraft Formations with Sensing Noise,” American Control Conference (ACC), Portland, OR: 2005, pp. 2385–2390.