The impact of unknown attitude perturbations on payload pointing performance of Earth-orbiting satellites is well known. The real-time three-axis estimation of those perturbations in order to improve the pointing accuracy is therefore critical, especially for high accuracy observation missions, such as Sun observation experiments. Current solutions to this problem consist in either increasing the bandwidth of the main attitude filter or to use an optimal estimation algorithm. Whereas the first solution reduces the stability margin of the overall guidance, navigation and control system, the second solution is computationally intense and is therefore not suitable for real-time space operations. In this paper, a novel solution to the in-flight estimation of perturbation torques problem is presented. The novel algorithm, NDO (nonlinear disturbance observer), is computationally efficient and is suitable for any Earth-orbiting spacecraft. The results presented in this paper show that the proposed strategy is a promising perturbation estimation technology even for small satellites equipped only with low-cost attitude sensors and without a gyroscope. Copyright

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Conference 61st International Astronautical Congress 2010, IAC 2010
Ulrich, S, & Côté, J. (2010). Onboard attitude perturbation estimation for gyroless spacecraft. Presented at the 61st International Astronautical Congress 2010, IAC 2010.