Research On Influence Of Antenna Pointing Error Caused By Deformation Of Main Reflector

The large-diameter reflector surface antenna is an important carrier in the fields of radio astronomy and deep space exploration.It is used to receive weak signals in the universe.In order to meet the observation needs of higher frequency bands,the pointing accuracy of radio antennas is usually required to be less than one tenth of the main beam width.For large-aperture antennas with short centimeter-band or millimeter-wave band,the pointing accuracy is required to be as high as several arc seconds.For high-frequency reflective antennas,the pointing problem has become an important focus of antenna performance.During the observation operation of the radio antenna,its main reflector will inevitably be affected by the environmental load,which will cause the actual pointing of the antenna to deviate from the target star source.For many antenna structure subsystem factors that affect the pointing accuracy,little attention has been paid to the error factor of the main reflector deformation.On the other hand,existing mathematical models do not effectively characterize the pointing errors caused by the deformation of the main reflector.In this paper,the actual antenna orientation under the environmental load is called the structural orientation,and the antenna orientation in a perfectly ideal environment is named the reference orientation.The development process of profiling anastomosis theory is elaborated in detail.According to the selection principle of the minimum profiling anastomosis,the system is divided into two categories: the minimum profiling anastomosis of general form and the minimum profiling anastomosis of special form.Based on the above-mentioned profiling method and the space coordinate value of the deformation point on the antenna reflector,the half optical path difference directly related to the antenna gain is selected as the minimum profiling coincidence.Based on the three-degree-of-freedom nonlinear least square calculation principle,a new algorithm for surface fixation and anastomosis is proposed.Based on the profile matching parameters,the pointing error of the antenna structure is predicted under the coordinate system of the reflecting surface,and the pointing error caused by the deformation of the main reflector is spatially characterized.The two spatial distribution characterizations of the pointing error are used to make strict spatial geometric derivations to obtain the precise adjustments of the pitch and azimuth for the correction of the pointing error of the antenna,thereby constructing the indirect relationship between the deformation of the main reflector and the pointing error.Compiling the pointing error correction algorithm based on the mathematical software Matlab.Simultaneously,176 sets of main surface deformation point spatial coordinate values in the main reflector of a 26-meter radio antenna finite element model are used for simulation analysis.The data results show that the root mean square value of the half-optical path difference of the main reflector reflecting the deformation of the structure is generally distributed between 0.5?0.7 mm,which improves the accuracy by50.01% to 63.33% relative to the reference direction.This proves the rationality and accuracy of the pointing error correction mathematical model based on the derivation of the coincidence data.From the analysis of the numerical value,change trend and distribution characteristics of the pitch and azimuth corrections,it is in good agreement with the antenna’s pointing correction rule under the real environmental load.It is of great guiding significance for the large radio antenna to effectively evaluate the loss of pointing accuracy caused by the deformation of the main reflector,and to improve the pointing accuracy.