Simulation Analysis of Positioning Reduction of Spacecraft as per the Chinese VLBI Network

According to the current status of the Chinese VLBI network and through data simulation,the effect of the orbit prediction error,the white noise and systematic errors in VLBI delays and ranging errors on the positioning reduction of spacecraft is analyzed.Results show that it is preferable to suppress the dispersion of positioning data points by applying constraint of geocentric distance of spacecraft when there is only VLBI tracking data.The positioning solution with observations of three VLBI stations is a biased estimate.For the case of four tracking stations the uncertainty of the constraint should be in accordance with the orbit prediction error.If the uncertainty is too large then the effect of suppression on the dispersion of positioning points would be limited.If it is too small then some systematic offset would be led into the positioning results.White noises in delay and ranging mainly result in dispersion of positioning data points.While systematic errors in observations result in systematic offsets in the positioning results,and there are trend asymptotic line jumps in the sequence of positioning points,which could also be taken as a criterion for the existence of systematic errors in observations.In addition,at the moment when VLBI stations change from three to four or vice versa,there may exist the trend jump in the sequence of positioning points.The analysis in this paper could provide a reference for the positioning reduction of spacecraft in the follow-on lunar exploration and the Yinghuo project.