In-Flight Attitude Perturbation Estimation for Earth-Orbiting Spacecraft

This paper presents four innovative techniques, three Kalman-based and one observer-based, to estimate environmental perturbation torques acting on an Earth-orbiting spacecraft. The Kalman-based techniques all use simple generic models for the state dependence of the perturbation, and for estimating the unknown coefficients included in these generic mathematical formulations. The observer-based technique is developed with the nonlinear disturbance observer theory. The proposed strategies are validated in numerical simulations and are traded-off in terms of estimation accuracy and computational load requirement. Then, the most suitable estimation technique is combined with a batch least square filter algorithm to yield a perturbation estimation system with low computational load, which can be implemented onboard a spacecraft. Finally, the proposed estimation strategy is applied to a realistic gyroless Earth-orbiting spacecraft mission: the European Space Agency’s Project for Onboard Autonomy (PROBA)-2 mission. Ultimately, the selected estimation strategy will be implemented onboard the PROBA-2 spacecraft for in-flight validation. All strategies proposed in this article are general and are applicable to any Earth-orbiting spacecraft.