This paper studies on-orbit system idntification experiment on Engineering Test Satellite-VIII (ETS-VIII), which will be launched in 2006 by H-IIA type 204 rocket. This will become the largest three-axis stabilized geoshncronous satellite in Japan. In the experiment, flexible parameters of large deployable antenna and large solar panels will be estimated by the downlinked telemetry data of stellite attitude and solar panel mounted accelerometers during the satellite check-out phase. We developed "ACFS Tool" for estimating onboard satellite attitude states using dwell data in the telemetry. In this paper, we show the the validity of the tool by numerical simulation.
