Yoshiyuki Ishijima

Design and development of the first Quasi-Zenith Satellite attitude and orbit control system

The Quasi-zenith Satellite (QZS-1) is the first Japanese first navigation satellite to demonstrate the technology for providing GPS interoperable and augmentation services around Japan and Oceania. The attitude and orbit control system (AOCS) of the QZS-1 has several features that improve the mission availability. The use of a star tracker in a GEO altitude orbit and yaw steering function for high inclination are important features. In addition, robust software can maintain nominal operation, even in cases where one failure would occur in attitude sensors, actuators, or the main computer. Furthermore, the intervals of reaction wheel momentum unloading and orbital maneuvers are maximized by optimizing the system design and considering disturbances, such as solar radiation pressure, orbital perturbations, and thrust variations. As described herein, we present an overview and the design results of the QZS-1 attitude and orbit control system.

A Satellite Simulator and Model Based Operations in Quasi-Zenith Satellite System

This paper introduces a system engineering methodology using a model-based operational concept and satellite simulator as key tools for design, development, and operation processes. The spacecraft model is derived from its required functions. The satellite operational procedures are organized in accordance with operational mode transitions so the operations crew can understand and identify the procedure easily. The model is developed, maintained and used throughout the life cycle of the system. An example of the application of this method is introduced in the development of the Quasi-Zenith Satellite System, which is a Japanese regional satellite based navigation system.

Sensor architecture for the robotic control of large flexible space structures

The future construction and maintenance of very large space structures such as orbital solar power stations and telescopes will require teams of free-flying space robots. For robots to effectively perform these tasks, they will require knowledge of the structures vibrations. Here, a robotic based sensor architecture for the vibration estimation of very large structures is presented. It is shown that this information can be effectively estimated by combining data provided by free-flying remote robot “observers” equipped with range sensors with structure-mounted acceleration sensors. A modified Kalman filter fuses low-bandwidth vision data from the remote sensing robots with the high bandwidth, but spatially sparse structure-mounted acceleration sensors. Results from experimental studies are presented that confirm the effectiveness of this approach. 2007 Wiley Periodicals, Inc.

Development of a New Generation Spaceborne GPS Receiver

We are investigating a New Generation Spaceborne GPS Receiver that can determine a position more precisely, but which is smaller, with lower cost and lower power consumption than a conventional receiver. This new type of spaceborne receiver includes a CMOS Silicon on Insulator (SOI) chip and adopts a direct

Flight Data Analysis of ADEOS-II GPS Receivers

Abstract Flight data analysis ofGPS receivers (GPSR) installed on the Advanced Earth Observing Satellite-II (ADEOS-II) is summarized in this paper. On orbit navigation accuracy, satellite selection, signal acquisition and tracking, satellite visibility, multi-path interference, and signal level are summarized by flight data evaluation.