Fault Diagnosis of Microscope Satellite Thrusters Using H-infinity/H_ Filters

Microscope is a satellite due to be launched in March 2008 (Microscope is undertaken jointly by the Centre National d'Etudes Spatiales, France, the ESA, the Office National d'Etude et de Recherche en Aerospatial, France, and the Cote d'Azur Observatory, France). It has the mission of testing the equivalence principle, which postulates the equality between gravitational mass and inertial mass. This paper addresses the fault diagnosis task of the Microscope thrusters. The faulty situations correspond to thrusters blocking themselves and/or closing when in operation. Two model-based diagnosis schemes based on H ∞ /H_ filters are proposed and compared with each other in terms of performances and complexity. Nonlinear simulations show that both schemes are able to detect and isolate faults, despite the presence of measurement noises, measurement delays, sensor misalignment phenomena, and disturbances (i. e. , third-body disturbances, J 2 disturbances, atmospheric drag, and solar radiation pressure).