Noboru Muranaka

Pole and Global Shape of 25143 Itokawa

The locations of the pole and rotation axis of asteroid 25143 Itokawa were derived from Asteroid Multiband Imaging Camera data on the Hayabusa spacecraft. The retrograde pole orientation had a right ascension of 90.53° and a declination of –66.30° (52000 equinox) or equivalently 128.5° and –89.66° in ecliptic coordinates with a 3.9° margin of error. The surface area is 0.393 square kilometers, the volume is 0.018378 cubic kilometers with a 5% margin of error, and the three axis lengths are 535 meters by 294 meters by 209 meters. The global Itokawa revealed a boomerang-shaped appearance composed of two distinct parts with partly faceted regions and a constricted ring structure.

IN-FLIGHT CALIBRATION METHOD OF INSTRUMENT MISALIGNMENT OF AN ASTRONOMY SATELLITE

Abstract A bias error model for the misalignment between mission instrument and optical and inertial attitude sensors is discussed together with a model for drift and scale-factor biases of gyroscopes. An algorithm to estimate these biases from in-orbit calibraiton data is proposed and analysed for an illustrative case of ASTRO-C X-ray Astronomy Satellite. It is shown that some components of the misalignment vectors can be estimated very accurately but others poorly. This is verified by simulation. It is also shown that these knowledges are enough, however, for the attitude control system to eliminate the misalignment-induced pointing error that would be inevitable without in-flight calibration.

In-flight Calibration Method of Instrument Misalignment of an Astronomy Satellite

Abstract A bias error model for the misalignment between mission instrument and optical and inertial attitude sensors is discussed together with a model for drift and scale-factor biases of gyrnscopes. An algorithm to estimate these biases from inorbit calibraiton data is proposed and analysed for an illustrative case of ASTRO-C X-ray Astronomy Satellite. It is shown that some components of the misalignment vectors can be estimated very accurately but others poorly. This is verified by simulation. It is also shown that these know ledges are enough, however, for the attitude control system to eliminate the misslignment-induced pointing error that wouId be inevitable without in-flight calibration.