Parameter Identification of Large Spacecraft Systems Based on Frequency Characteristics

In this paper we describe parameter identification for an in-orbit satellite. Actual experimental results are described for the Low Atmospheric Control Experiment (LACE) spacecraft. This is a low earth orbit satellite that was launched into a circular orbit. Its structure consists of a central rigid body or bus with three deployable booms. We accomplished the identification of the structural modes and damping factors of the spacecraft in orbit utilizing the frequency characteristics of the Hankel operator. Frequency domain error bounds and time domain error bounds were considered. The experiment utilized ground based laser illumination and identified three of the lowest vibration modes. The accuracy of the methods was extremely good.