Tatsuaki Hashimoto

Autonomous guidance is required for spacecrafts to explore unknown asteroids in deep space. A method to estimate 3D position of a spacecraft with respect to the asteroid is descibed. When the terrein can be approximated to a plane, one feature is used to estmate the position of the spacecraft with the help of the attitude and altitude information of the spacecraft. Nextly, a methold to navigate a spacecraft is presented based on the solution of the perspective-four-point problem. And then, this paper also proposes a scheme to estimate the positions and attitudes of a spacecraft and the structure of features from two views of five features. The validity of the one-feature method is shown by computer simulations on asteroid rendezvous.

A method of autonomously imaging a celestial body,such as one of Martian satellites or asteroids,from a spacecraft during a flyby is presented.Since direct support from the Earth is difficult,a camera onboard which is used for the imaging must track the target autonomouly.For this purpose,the target orbit is estimated based on an extended Kalman filter by utilizing image data obtained successively from an onboard camera ever since the camera finds the target from far away.The observation error,which is found to be ascribed mostly to image processing(centroid calculation)error, is mesured through an experiment on an scaled artificial model of a target body,and an effective method to reduce the error is proposed.

″ASCA″ is a Japan′s fourth X-ray astronomy satellite which was launched on 20th February 1993 from Kagoshima Space Center.″ASCA″ is equipped with a high-resolution X-ray telescopes,and is expected to perform tight observation schedule. From these reason,rapid maneuver capability and fine attitude pointing performance are required on the attitude control system. The key technology to satisfy these requirements is precise attitude determination system on-board. In this paper,this attitude determination system is introduced and the evaluation results in-orbit are also described.