Research On Modeling Analysis And Design Of Pointing Errors For Large Radio Telescope

Large radio telescope is one of the most important equipments for space-objects observation. The precision of its shafting orientation measuring data is the guarantee of carring out high precise orbit determination of sapce objects. As an important means of improving its positioning precision, analysis and correction of pointing errors are the significant issue of the current study and also the need of development of space science, deep space exploration and raising the level of aerospace science and technology in China. Modeling analysis and design of pointing errors for large radio telescope is the aim of the paper. Based on the principles of pointing measurement of altazimuth radio telescope, various errors which influence the pointing precision of observation device are detailedly analyzed. Several models of pointing errors analysis and correction are developed and improved. Along with these have been applied in the practice , expectative results have been gained.The main work in the paper is as follows:All kinds of errors affecting the measurement precision are classified into static errors and dynamic errors. According to different errors, hardware calibration and software correction are studied. Based on the software correction principles of pointing errors, the two static correction models of pointing errors are proposed. Comparative analysis of the advantages and drawbacks between two models are also made.Quaternion is an effective way of studying space geometry. By using the methods of spatial orientation and quaternion rotation transform, analytical models and calculating method of various accuracy affected components are established. By mapping the relationship between telescope performance and geometric errors, a new pointing error correction model with physical errors is presented. Simulation results using experimental pointing data show that the proposed model improves the pointing precision effectively.Aiming at the limitation of linear correction model, a new pointing error correction technology based on semi-parametric estimation methods is proposed. The linear parts of correction model are described by some parameters, while non-linear factors or disturbance factors are treated as non-parametric components. According to the difference of calibration experimental conditions and sampling data types, three correction models are proposed. Their solutions and precision analysis on statistical significance are also inferred and presented. Using measuring data and simulated data, the results show that the semi-parametric model is more ideal than linear one, which is because the data are made full use of.Due to the inherent uncertainty of factors influencing pointing precision of large radio telescope, the forecasting results with uncertainties are produced by system forecasting model. To give exact expression of the uncertainty in system, a generalized extended forecasting model with fuzzy parameters is proposed. Based on the mechanism of generalized extended approach, the update a priori data are treated as interpolative constraints in the generalized extended forecasting model, as well as that with fuzzy parameters. Parameters in the model are solved using the method of fuzzy least-square fitting. By the comparison of system simulations , the results of proposed forecasting model are effective.Based on the summarization of error analysis and processing, problems about error are penetrated and investigated with the notion of modern design. New idea of treating error problems, namely error design, is proposed systemically, which comprises error correction design, error matching design, error canceling design, error prevention design and error permission design. Error design changes the idea of treating error problems from traditional passive processing into active design, which offers new theory and methodology for modeling analysis and design of pointing errors for large radio telescopes.