Development and Ground Evaluation of Ground-Target Tracking Control of Microsatellite RISESAT

Abstract

Space Robotics Laboratory (SRL) of Tohoku University is currently developing a 50-kg-class Earth observation satellite "RISESAT". In this paper, we propose a new ground-target tracking control algorithm and attitude control system for RISESAT. The primal mission of RISESAT is multi-spectral observation of the Earth surface using a 5 m GSD High-Precision-Telescope (HPT) with liquid crystal tunable filters. During an observation, the HPT takes a dozen images of a ground target by changing observation bands. General Earth observation satellites using push-broom cameras require high attitude stability to obtain continuous images. However, RISESAT has to track a ground target with an accuracy of 0.1° and 0.008°/s attitude stability because imaging and wavelength switching take few seconds in total. Therefore, we propose a new ground-target tracking algorithm which can keep orientation of ground-target image to a constant direction which satellite operator requires. Evaluations of the algorithms were carried out by hardware-in-the-loop simulator "MEVIμS" which is a satellite system verification environment developed by SRL. We confirm that the algorithm satisfies the mission requirements under the influence of sensor noise and computation time limits.