Design Of Satellite Autonomous Attitude Determination And Its Experimental System Based On Star Identification

The determination of satellite attitude as the basis of that the autonomous acquisition of the satellite, instructions receives, attitude control changes and send data to ground, and that is a key role in the field of celestial navigation, remote location and so on. The second generation CCD star sensor has the characteristics of high precision, no attitude accumulation error, and fast fault recovery capability. It has become a more popular research object in the field of aerospace, aviation and military.In order to improve the performance of CCD star sensor acquisition of satellite attitude information in real time and reduce the cost of experiment research in space. Paper use two PC machines and a cradle head that is equipped with CCD camera and controlled by SC300 series of shift control box, and establish a star image simulation, data process, and autonomous satellite attitude determination system. In general, The process of satellite attitude determination can be divided into two modes, namely, the initial attitude acquisition mode and the attitude output tracking mode. Detailed analysis of initial attitude capture mode, choose a star whose magnitude less than 6.5 from Tyco II standard star table, make standard navigation star database, simulate star images use these data in one of PC machines. And preprocess star images, include analysis of image noise in space environment, simulate the quality of star images in the environment, add Gaussian noise. And denoise images by the weighted average smoothing method and split image background threshold method. Star images are displayed by CCD camera in the other PC, within the field of view of the star centroid extraction. Respectively, use the classic centroid extraction algorithm, weighted centroid extraction algorithm, as well as with threshold centroid extraction algorithm. Analysis of the accuracy of each algorithm, and that provide an improved centroid extraction algorithm based on these. Compared with experiments, it is concluded that the algorithm accuracy is higher than the first three. A triangle star pattern recognition algorithm and a grid star identification algorithm are used to analyze the advantages and disadvantages of the algorithm, and a new algorithm is proposed. To make the experimental comparison, it is conclude that the sensitivity of the algorithm to the star position is better than the ordinary grid algorithm.The initial attitude of the satellite is calculated by the star that is identified by star images and conversion between coordinate system and simulation this results. After getting the original attitude of the satellite into the mode of outputting and tracking attitude, this pattern of the gesture matching the use of estimated ideas. According to the change of position of previous frame of the stars, the star images position is estimated at the next frame field. Record label star position, calculate the relative displacement of sight axis change. Through the PC software control issued serial instructions to the cradle head, pointing to change. Realize the simulation of star images tracking. Take estimated sight axis as the reference star images and these star data known, take the star image of CCD camera observation as the observation star image. To reference the fast tracking algorithm of multi frame star images, the final output satellite attitude.