Pointing Calibration Of 13-meter Radio Telescope Of The National Time Service Center

National Time Service Center(NTSC),Chinese Academy of Sciences(CAS)built the 3×13m VLBI network referenced to the VLBI2010 standard.The telescopes are located at Jilin,Sanya and Kashi.The network undertakes the VLBI navigation satellite measurement orbit mission and conducts the world time UT1 measurement study.The pointing accuracy of antenna is one of the important specifications of the telescope,that affects the observational performance of the VLBI system.When the deviation occurs,the signal intensity received by the radio telescope decreases,the observation integration time increases,and the target source signal may not be received.Thus,it is of importance to build a correct pointing model for the telescopes.In this thesis,we present works related on pointing models of the NTSC 3×13m VLBI system,including,(1)Background information,including telescopes,coordinate system,principle and methods on pointing of telescopes.According to the characteristics of the NTSC-13 meter radio telescope,the physical causes of the pointing accuracy of the 13-meter radio telescope are studied from the aspects of system factors and environmental factors.The law of the influence of each error source is analyzed,and the corresponding error correction method is studied.(2)Measured the beam pattern of the telescope using the cross-scan method;investigated pointing errors by both Gaussian fitting and Fourier fitting methods;determined the pointing errors with the Fourier method.(3)Established the sub-term correction model by analyzing error sources for the pointing model,and according to the actual situation of 13-meter radio telescope,based on the commonly used 8-parameter correction model,proposed an improved 18-parameter pointing error correction model.Compared with the 8-parameter correction model and the 12-parameter correction model,found the 18-parameter pointing model is a feasible model for the 13 m antennas.(4)By measuring bright extragalactic radio sources with known accurate coordinates,the pointing errors of 13 m telescopes were determined,then the 18-parameter pointing model were determined by least square fitting.(5)Designed and written the pointing correction software,completed the single point error fitting of the cross scan data,and the 18 parameter pointing model fitting,which significantly improved the automation level of the pointing correction work.In summary,this thesis started from introduction of the 13-meter radio telescope system,analyzed and compared the pointing error correction method,and applied the established 18-parameter correction model to the 13-meter radio telescope pointing correction.After pointing calibration,finally,we achieved a pointing accuracy of 46.64 arcsec,that are lower than 10% of the beam size of the telescope.