STABILITY ANALYSIS ON EARTH OBSERVING SYSTEM AM-1 SPACECRAFT EARTH ACQUISITION

The design and analysis of the Earth Observing System AM-1 spacecraft Earth acquisition mode are presented. In addition to addressing the pr actical design of the spacecraft attitude control system, some mathema tical proofs of the system stability based on the spacecraft nonlinear dynamics and kinematics are demonstrated. Tile main approach of the a nalysis is to identify all of the equilibrium points of the closed-loo p system and then to investigate the stability of each of the equilibr ium points. Since it is not restricted to near the nominal operating p oint, this work extends the previous linear analysis results to certai n cases where large attitude errors are possible. All three control co nfigurations in the Earth acquisition mode are investigated. The syste m convergence from any yaw attitude to the nominal Earth pointing atti tude Is proven. The results developed in the paper provide a deeper un derstanding of the system dynamics and are especially useful in analyz ing off-nominal launch-vehicle/spacecraft separations and in determini ng submode transition thresholds. The design and analysis are supporte d by high fidelity spacecraft simulation.