Autonomous Guidance for Minimum-Time Transfers to Geostationary Orbits Using Solar Electric Propulsion
- Paper number
IAC-07-C1.6.04
- Author
Dr. Yang Gao, Academy of Opto-Electronics, China
- Year
2007
- Abstract
Satellites in geostationary orbits (GEO) are usually placed in geostationary transfer orbits (GTO) or low Earth orbits (LEO) by launch vehicles and then use the onboard propulsion to perform appropriate orbital transfers. Encouraged by the most recent successful use of solar electric propulsion for SMART-1 mission, the transfer to GEO is one of the most possible near-Earth missions orbit maneuvers using low-thrust solar electric propulsion. Due to the relatively long transfer time that is usually on the order of months, a practical autonomous guidance scheme for GEO transfers is very necessary. The most common way to guide the spacecraft is to uplink optimal control and trajectories at a certain time interval (e.g. every a few days). However, this method requires many-time offline trajectory optimizations and also increases communication burdens between satellite and ground. Based on lessons learnt from SMART-1, Rathsmane etc. pointed out that a possible solution for future electric propulsion missions would therefore be to have onboard an autonomous guidance and navigation system. [1] In this paper, an autonomous guidance scheme for minimum-time GEO transfers is proposed. The spacecraft is to track the mean orbital elements of optimal transfer trajectories. The guidance scheme employs a novel control strategy [2, 3] that is a combination of tangential steering, inertial steering, and piecewise yaw steering. These three control laws are applied over different arcs within each transfer revolution such that semi-major axis, eccentricity, and inclination can be changed simultaneously to track the desired corresponding mean orbital elements. In order to reduce the onboard guidance computation burden, the analytic time rates of mean orbital elements using the proposed control laws are employed. The concept of model predictive control [4] is used to form online optimization problems to track mean elements of optimally designed transfer trajectories over a series of finite time horizons. A few number of parameters related to the control laws are optimized to remove the orbital elements errors by a method (Rosenbrock’s method) without calculating derivatives. The Rosenbrock’s method ensures the robustness of the optimum searching, which is the key to the stability of the proposed guidance scheme. The extension of this guidance approach is to guide the spacecraft without tracking nominal trajectories. More important, the guidance scheme is capable to include the Earth shadow and oblateness J2 effects. The numerical results of GEO transfers from GTO and LEO demonstrate the satisfactory tracking performance. The guidance scheme can also be used for other types of Earth-orbit transfers. References [1] Rathsman, P., Kugelberg, J, Bodin,P., Racca,G.D., Foing,B., and Stagnaro, L., “SMART-1: Development and lessons learnt,” Acta Astronautica, Vol. 57, 2005, pp. 455 – 468. [2] Gao, Y., and Kluever, C. A., “An Algorithm for Computing Near Optimal, Many-Revolution Earth-Orbit Transfers,” AAS 05-371, 2005 AAS/AIAA Astrodynamics Specialist Conference, August 7-11, 2005. [3] Gao, Y., “Near-Optimal Very Low-Thrust Earth-Orbit Transfers and Guidance Schemes,” Journal of Guidance, Control, and Dynamics, Vol.30, No.2, 2007, pp.529-539. [4] Arrieta-Camacho, J.J. and Biegler, L. T., “Real Time Optimal Guidance of Low-Thrust Spacecraft: An Application of Nonlinear Model Predictive Control,” Annals of the New York Academy of Sciences, Vol. 1065, 2005, pp.174-188.
- Abstract document