PRECISION ON-BOARD ORBIT MODEL FOR ATTITUDE CONTROL OF THE ADVANCED LAND OBSERVING SATELLITE (ALOS)

A star-sensor-based attitude determination system estimates spacecraft attitude with respect to the inertial coordinate system. When a satellite equipped with the star-sensor-based attitude determination system implements geocentric pointing, it requires the satellite's position information relative to the Earth's center. Conventional Earth-pointing satellites carried only low-order on-board orbit models because of their Earth- sensor-based attitude determination systems and moderate attitude accuracy requirements. The Advanced Land Observing Satellite (ALOS), which has stringent attitude control accuracy and attitude stability requirements and therefore a star-sensor-based attitude determination system, carries a high-order precision on-board orbit model that has 15 parameters and accomplishes the required accuracy by frequent updates of those parameters. This paper presents the design of the on-board orbit model and its flight results. In addition, the attitude control errors and attitude stability performance that were induced by the attitude control reference generated by the orbit model are assessed.