The Modeling,Analysis And Verification Of Error In Short Baseline Interferometry

As one of spacecraft orbit measurement techniques,interferometry has several advantages including high angular sensitivity and passive measurement.Currently,interferometry has become an indispensable orbit measurement for deep spacecraft,which is regarded as one of key techniques supporting deep space navigation.Different from the very long baseline interferometry(VLBI),short baseline interferometry has advantages of flexible meshing and real-time performance.Although error sources of the short baseline interferometry is basically the same as these of the VLBI with non-radio calibration,the main error sources have changed due to the difference of baseline length.Therefore,the traditional error calibration of the VLBI is no longer applicable.And new research on error analysis,modeling and calibration is necessary for the short baseline interferometry.Based on the interferometry theory,the dissertation analyzes error sources which affect the interferometry accuracy,and proposes correction methods of main error sources such as antenna delay,station coordinate,and radio-link delay in a station.First,the error model of station coordinate is established and the verification experiment is carried out.A simulation is conducted to obtain the relationship between the measurement error and the antenna delay error.The calibration method of station coordinate is given,and the influence of measurement error on the antenna center coordinate is analyzed?For a parabolic antenna,regarding a GNSS site in Beijing Aerospace City in Haidian District as the base point,a station site calibration experiment of a parabolic antenna in Huairou District is carried out.For a phase array antenna,a phase center calibration method is proposed and verified by experiment.Second,the antenna delay error is analyzed theoretically,and a simulation experiment is carried out.Considering the structure of an"azimuth-elevation" parabolic antenna,a delay correction mode is established,and the corresponding correction method is given.According to the experiment data,the dissertation calculates the antenna center coordinates and the measurement error.By the result of position relationship between azimuth and pitch axis,and whether the azimuth axis is vertical,the antenna center coordinates are corrected.Finally,the dissertation studies a calibration method of receiving link delay.Based on the Connected Element Interferometry in Beijing Aerospace Control Center,the test and verification experiment of delay about 50m cable and receiving links(including frequency converter,amplifier,RF cable,etc.)is carried out,to evaluate and test the influence of delay variation on the measurement accuracy and radio-link delay in a station within a day.By the calibration method of the DCAL signal,the accuracy of the radio-link delay is calculated and the result reaches 1.4ns.