A Whale Ecology Observation Satellite (WEOS) was successfully launched on December 14th, 2002. We adopted a single-axis magnetic torquer damping control and gravity gradient attitude stabilization for WEOS. It is the first trial in Japan for pointing communications antennas towards Earth, and the GPS antenna towards zenith. The damping control and attitude stabilization system of WEOS consists of a three-axis magnetometer, a magnetic torquer coil, a deployable mast with a fixed mass at the tip, and attitude control software. This system carried out rate damping control of the principal axis of the maximum moment of inertia and earth pointing attitude stabilization. Immediately after separation from the H-IIA-4 launch vehicle, WEOS tumbled due to the imbalance force of the three separation springs. The tumbling was reduced by the closed-loop damping control and then the mast was deployed. After 1 week, we confirmed the establishment of the gravity gradient attitude stabilization. This paper describes the attitude control system, operation procedure, and control results.
A Whale Ecology Observation Satellite (WEOS) was successfully launched on Dec. 14th 2002 as one of the piggyback payloads of H-IIA-4 launch vehicle. The functions of the attitude control system for the WEOS are detumbling and libration control by single axis magnetic torquer, and the earth pointing control by utilizing of gravity gradient torque.According to the resources limitation, the WEOS adopted the gravity gradient attitude stabilization system instead of the three axis attitude control system, as the first trial in Japan. The gravity gradient attitude stabilization system is working well as planned. This paper describes the attitude control system of WEOS and its control results.
: 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.
SUMMARYWe optimized orbital elements to minimize the squared deviation of the satellite position intermittently measured by an on-board GPS receiver from the satellite position measured from orbital elements using the SGP orbit model, and then reentered the results into the SGP orbital model to attempt an interpolation calculation of the satellite position and velocity at any given point in time. As a result of applying this system to data from a GPS receiver on board the Whale Ecology Observation Satellite (WEOS), we found that by using positions measured at several minute intervals over a period of about 2 hours, we could calculate the position of WEOS with an error of about 50 m at any given instant within the time frame, among other conclusions.
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