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The Sheshan 13 m radio telescope is designed as a new generation of astrometric and geodetic very long baseline interferometry (VLBI) observation system, equipped with 2-14 GHz broadband receiver and X/Ka dual-band receiver. Pointing precision is one of the most important technical specifications of ra- dio telescopes, typically about one tenth of the beam width at the highest observation frequency. For the Sheshan 13 m radio telescope, the required pointing precision is about 18 as at 32 GHz of Ka band. Based on the pointing scan data of the telescope, the method of establishing pointing correction model is dis- cussed, including the curve fitting of the power measurements of extragalactic sources, the tests on the ef- fect of the integration time, and the parameter setting of the pointing correction model. The pointing preci- sion of the telescope is measured and estimated. The resulted pointing correction model can be used as the basis for the system debugging and improvement. It is also the guarantee for the measurement of the sys- tematic technical specifications and precisely tracking of observation target. The data analysis model and analysis process can be used for the daily pointing precision check of the observation system, and can also be used for similar engineering measurement as reference. [ABSTRACT FROM AUTHOR]

The development and necessity of the frequency settings in as trometric and geodetic Very Long Baseline Interferometry (VLBI) observations are analyzed, especially on the advantages and disadvantages of observations at Ka-band. Compared to X-band, the advantages at Ka-band include more compact extragalactic sources, relatively smaller core shift effect, as well as efficiency to improve the precision in the realization of radio celestial reference frame and in the linkage to the quasi-inertia optical frame of Gaia project. Advantages in term s of deep space exploration are high in telemetry data rate, high in VLBI tracking precision, and helpful to mitigate the detrimental effects of ionosphere and solar plasma on the observed time delay. Disadvantages include relatively weak extragalactic sources, high precision requirement of reflector and antenna pointing, and susceptible to atmospheric absorption and emission effects. But the loss in system sensitivity due to these factors could be mostly compensated by the rapid development in high data rate sampling and recording technology. Finally in accordance with the current status of VLBI technique in China some specific recommendations for further development are recommended for criticism by readers. [ABSTRACT FROM AUTHOR]