Modeling and correction of pointing error of space-borne optical imager

Pointing error is one of the most critical performance indices of space-borne optical imager and is of great significance for optical imaging and target tracking. In order to correct the pointing error of an optical imager and make it meet the design requirement, first of all, the mathematical model of the relation of pointing error and assembly errors of mechanical components is established, acquiring the analytical expressions of pitch angle and azimuth angle of the 2-DOFs pointing mechanism. Then, the mathematical model of transformation matrix calibration of coordinate systems is set up and the calculation formulas of transformation matrix and angular deviation are provided. Moreover, the simulation model of pointing error is built based on Monte-Carlo method given that the distribution of each assembly error satisfies normal assumption, together with the distribution of pointing error before and after assembly error correction. Finally, the correction test of pointing error is accomplished and test results before and after correction are compared, demonstrating that the maximum of compensated value is 26 '' and the minimum is 6 '' and the pointing accuracy has increased by 64% in average. After correction, the total pointing error of imager is no more than 20 '' which meets the system performance requirement.