Satellite Interferometric Data Processing Method And Its Experimental Research

As an important radio interferometric technique,the very Long Baseline Interferometry is widely used in the fields of astrometry,geodecy,and deep space exploration.In recent years,VLBI has been used in the tracking and observation of navigation satellites and other medium and high earth orbital satellites.Correlations and post correlated data reductions are important steps that produces interferometric data and extract observables,i.e.,baseline delays.Presently,there is still no public and free use correlation and post-processing software for satellite VLBI observations.For this reason,we developed a satellite interferometric data processing software package based on astronomical software i.e.,Di FX,AIPS,and Parsel Tongue,which is used for reducing satellites tracking data of the ZFS-VLBI 2010 system.Aiming at VLBI observing medium and high orbit satallites,the satellite interferometer data processing software is designed and developed.Based on this software packge,using the satellite observation data of the ZFS-VLBI 2010 system,the research on system error correction method of the interferometric data has been carried out.The main results of the paper are:(1)The development of VLBI technology at home and abroad is summarized,and various satellite interferometry modes and their system errors are analyzed.The history and current development of VLBI technique is reviewed,current correlation and data processing softwares are introduced.The theory of VLBI satellite tracking,the principle of differential VLBI,techniques of the VLBI signal receiving and data processing method and the fringe search method are presented.The ZFS-VLBI 2010 system is introduced in detail,a variety of satellite interferometric measurement modes are analyzed,various observational errors of the system are studied.Based on the above basis,satellite interferometry experiments and data processing analysis are carried out.(2)In order to realize automated process of satellite interferometric data,a set of satellite interferometric data processing system was established based on three astronomical software i.e.,Di FX,AIPS,and Parsel Tongue.With these software,we developed satellite interferometric data correlation,neutral atmosphere,ionosphere,clock model and instrument hardware delay compensations functions,and perform fringe search to generate baseline delay and delay rate sequences.Focused on the analysis of the added system error calibration function modules and the total delay calculation method,and the data processing system framework and operation flow were designed.We use such system to reduce the experimental data of the ZFS-VLBI 2010 system,after calibration,the phases of cross power spectra can be leveled,and calibrated from 0 to 360 degrees to 0±5 degrees.(3)In the satellite interferometry system,the correction methods of tropospheric delay,ionospheric delay,inter-sation clock error and hardware equipment delay have been studied,and the measured data processing has been carried out.The developed satellite interferometric data processing system is used to correct various system errors,and the correction results and accuracy of each link are analyzed.Results of several tracking experiments are presented,including ZFS-VLBI 2010 system experiments to observe Beidou GEO satellites and 5×3.7-meter system experiments to observe Z10 GEO satellite.The neutral atmospheric delays calibrated accuracy can reach 0.07 ns;the global single-layer ionospheric forecast model can be used for real-time tasks to achieve ionospheric correction with an accuracy level of 0.5～1 ns in the S-band;the time delay part of the hardware equipment can be corrected with an accuracy level of about 0.3 ns.Finally,satellite baseline delay sequences with an accuracy of 1-2 ns can be obtained.