State Estimation and Parameter Identification of Freely Spinning Flexible Spacecraft

The attitude estimation of a flexible spacecraft using the noise-corrupted measurements provided by sensors is studied. The flexibility of the system is expressed in terms of internal deformation modes, and only a limited number of the latter are kept in view of simplifying the model. The estimation method is based on the extended Kalman filter algorithm, using an augmented state vector which includes the unknown parameters of the system. The filter thus provides an estimation of these parameters along with that of the original state-variables of the system. The method is implemented using a simulated model, thereby permitting an appraisal of the results, and reference is made to results obtained for a practical case where a somewhat different approach was taken as regards the way in which the flexibility is expressed.