Abstract
A Whale Ecology Observation Satellite (WEOS) was successfully launched on 14th December 2002. We adopted gravity gradient attitude control technique for the attitude stabilization of the WEOS as the first trial in Japan for pointing the communications antennas toward the earth, and the GPS antenna toward the zenith. The attitude control system of the WEOS consists of a three axis magnetometer, a magnetic torquer coil, and a deployable mast with a mass fixed at the tip, and attitude control software. This system carries out rate damping control of the principal axis of maximum moment of inertia and earth pointing attitude control. Immediately after the separation from the H2A-4 rocket, WEOS tumbled due to the imbalance force of three separation springs. The tumbling was reduced by the closed loop damping control and then the mast was extended. After one week, we confirmed the establishment of the gravity gradient attitude stabilization. This paper describes the attitude control system, operation procedure, and control results.
