Calibration Method Of Double-CCD Star Sensor

Accurate navigation information is the foundation for completing a variety of space missions,including image observation and signal transmission.As the core information for the navigation,the attitude of spacecraft is mainly determined by the attitude sensors.Star sensors have been widely used in a variety of fields,including satellite communication,remote sensing and navigation for spacecraft for its highest measurement accuracy and the ability to work independently.In reality,there is a bias between the designed parameters and the real parameters of star sensors because of the error brought by manufacture and assembling process,so it is necessary to calibrate the internal parameters of star sensors.The main contents of this thesis are as follows:1.The structures and the basic principle of star sensors have been studied,followed by the description of main technical parameters of star sensors.This thesis focuses on the various errors in star sensors and introduces some calibration parameters of star sensors,such as principal points,focal length and optical distortion.At last,three different methods for calibrating the internal parameters of star sensors,namely undetermined coefficient method,internal parameter method and two-step method about cosine are introduced in this thesis.The comparison among them shows that two-step method about cosine outperforms the other methods in measuring high accuracy.2.According to the existing multi-parameter distortion model,some new calibration distortion models based on ignoring the influence of thin-prism distortion are introduced in this thesis.According to the two-step method about cosine and the principle of least-square,various high-order lens distortion models are proposed and compared under different noise levels of star locations.The results show that 6-parameter third order radial distortion model together with the second order tangential distortion model is better than other lens distortion models in terms of stability.The calibration accuracy obtained by the actual data is better than the original distortion model.3.According to the attitude measurement principle of star sensors and the invariance principle in the angular distance between stars,three different methods are put forward to calibrate the installation matrix between double-CCD.Then the simulation and experiment based on these methods are conducted.The results show that the method that getting the attitude matrix of the respective field of view with Quest algorithm firstly and then getting the installation matrix between double-CCD based on the relations of coordinate transformation can achieve the most stable results.The method based on the invariance principle in the angular distance between stars also has some merits.