Research On Satellite Autonomous Orbit Determination Using Synthetic Aperture Radar

Autonomous orbit determination of satellite means that orbit determination is solely finished on board, independent of the observation of ground system. In this way, it can improve the autonomy and security of satellites, and it can decrease the cost of navigation task efficiently. Synthetic Aperture Radar (SAR) is a kind of remote sensing radar. Besides the routine function of velocity measuring and distance measuring as the normal radar, it allows the generation of high resolution images, independently of weather condition and sun illumination. SAR observed quantity always have high accuracy, and most of them are scalar quantities. Hence, these methods adapt to high-accuracy autonomous orbit determination, and it can improve the checking of application as well. Satellite autonomous orbit determination using synthetic aperture radar is a new direction. From the angle of engineering implementation, this paper proceeds as follows:Firstly, the orbit determination theory is analyzed in this paper. Landmarks have been set previously, and the location information is memorized in space-borne computer. SAR generaties image of ground and recognizes the landmarks. Then the orbit determination is implemented by using the distance of landmarks and Doppler frequency.Target rang equation and Doppler frequency equation have been established based on the theory of orbit determination , and the type of orbit for this technology of orbit determination as well as other design tasks need to be analyzed from the point of view of engineering implementation.By the analysis above, the system parameters of SAR have been analyzed based on the operation principle of SAR. Referring to the satellite's task parameters, the design example has been presented according to the design flow for the purpose of later analysis of orbit determination. SAR system parameters have been designed; additionally, landmarks parameters have been designed. Imaging features of SAR and optical imaging system are widely divergent. The layout of landmarks are restricted by the condition of geography. Based on the features mentioned above, the material,shape and layout of the landmarks are analyzed. The simulation has been done by simulation software called Satellite Tool Kit(STK). The simulation results meet the observation requirement of orbit determination.Finally, the accuracy analysis of orbit determination have been researched in combination with the design above. The cause of SAR measuring error, landmarks locating error and asynchrony ground echo of landmarks have been analyzed. The error mentioned above have been combined. By the simulation experiment based on Monte Carlo , the influence by error sources has been analyzed. Moreover, the numerical solution of orbit determination error have been researched. According to the simulation results, this technology of orbit determination can be satisfied to satellite atutonomous orbit determination with high accuracy.