| Most of the new generation meteorological satellites are designed as three-axis-stabilized. The scan mirror with stepping motion and scanning motion is usually an important equipment on such kinds of satellite. Its motions are coupled with the satellite's attitude motions, which in turn exert significant effects on the motion of scan mirror. Without adequate compensation, the deviation of scanning track will be introduced, and the quality of scanned image will be seriously affected.In this paper, the scan mirror was considered as a rigid body which was connected by stepping axle and scanning axle. As the motion of scan mirror is governed by a specific control law, so the scan mirror can be treated as a momentum component on the satellite. Based on the theorem of moment of momentum, the coupled satellite/scan mirror dynamic motion equations were established at first, and the motion stability was analyzed for the coupled system. Then the scanning track deviation caused by the satellite attitude motions was simulated. The results show that there is an accumulation effect of scanning deviation in stepping component and the maximum value of azimuth deviation exceeded the limitation set for American GOES I-M series satellite. The effects of inertia ratio between satellite and scan mirror on scanning track deviation were also analyzed.The motion compensation scheme for scan-mirror was then proposed in the thesis. In this scheme, the governing equations of scan-mirror motions were modified according to moment of momentum conservation assumption. Compensated scanning tracks and azimuth of scan-mirror optical axes were obtained and comparisons of scan deviations before and after compensation was also made. The results show that the accumulation of scan deviation can be minimized and the maximum value of azimuth deviation is much lower than 2.8urad. This compensation scheme is simple with high efficiency and can beapplied to the design of Mirror Motion Compensation (MMC) system of new generation of meteorological satellites.The effects of initial attitude of the satellite on the scanning deviation were also studied in this thesis, and the results show that the scanning deviations caused by initial attitude is very small. For the case that there exist two scan mirrors on one satellite, an compensation scheme was also proposed.Several conclusions such as the motions of scan mirror does not influence the stability of satellite/scan mirror dynamics system, scanning deviation is irrelative to the scanning speed were obtained in this thesis . |
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