Research On Two-dimensional Image Motion Compensation Of Space-borne Staring Imager Based On Scanning Control

Compared with scanning imaging and push-broom imaging, staring imaging couldoffer longer residence time which is good for raising SNR, besides, staring imagingcould observe the phenomenon in the field of view, thus has higher time resolution, andcombined with two-dimensional pointing instrument, the observe range could be muchlarger. The detector’s integrate time of staring imager loaded on earth synchronous orbitcould not effected by speed-height-radio and resolution, but for those loaded on loworbit, the satellite’s flight is faster than the the detected aim, thus the image on thedetector is moved, the earth rotation and satellite’s movement could also make theimage move on the detector. Image movement makes the image blur and the resolutiondecreasing, effecting the image quality badly, and the high the resolution is, the worstimage motion’s affect is. Thus the image motion compensation is necessary.There are many ways to compensate the image motion, the compensation based onpointing mirror could have more field of view and observe dynamic aim, thus offerlonger residence time. So this paper uses pointing mirror as the compensation method.Based on analysis on image motion speed and different image motion quantity, thispaper propose the image motion compensation demand according to the imager’sparameters, and the principle of the pointing mirror’s motion compensation, and decidesthe achievement goal; make a research of the compensation servo system, includinghow to choose the important component, the design analysis and the controlling strategy,make sure of the pointing mirror and its two-dimensional servo machine’s quality,inertia, surface and supporting method, and permanent magnet synchronous motor asservo motor, grating coder as angle sensor, DSP as motor controller. Besides, simulateand analyze the performance of three-closed-loop of servo system byMATLAB/SIMULINK, and decides the parameters of the PID controller. Finally, builtthe experiment platform to test the servo system’s current loop’s following performance,the speed loop’s step response and speed, the position loop’s pointing function,repeating pointing precision, dynamic response time and dynamic precision, andanalyze the actual servo system’s error source, based on those, do the imagecompensation experiment using resolution board and LCD screen as aim, and use grads,dot acutance and MTF to estimate the compensation affect, and calculate the imagecompensation error. The experiment results show that the compensation servo system could achieve7’’pointing precision, returning time less than4s,32ms dynamic response time, and thepitching axis’s dynamic precision less than30’’, the azimuth axis’s dynamic precisionless than20’’. And the imager has the function of along-track compensation andcross-track scanning, and the image compensation based on pointing mirror is feasible.