Beidou Navigation Enhancement Simulation Research Based On LEO Constellation

Low Earth Orbit(LEO)satellites rely on their own advantages such as fast movement speed,rapid geometric configuration changes,and strong ground station receiving signals,which can be combined with the Global Positioning System(GPS)and Bei Dou satellite navigation system(BDS)and other existing Global Navigation Satellite Systems(GNSS)complement each other's advantages,and have great significance in enhancing GNSS Precise Point Positioning(PPP)and precise orbit determination.LEO satellites has been widely concerned and researched.At the same time,the LEO constellation can also realize navigation and positioning without GNSS.This paper makes research on LEO constellations enhance BDS Precise Point Positioning.Using System Tool Kit(STK)which developed by Analytical Graphics design LEO constellations of different configurations.Combining with self-programmed simulation precision orbit files,this paper builds GNSS /LEO observation link simulation platform,which simulates the observation data of different links.This paper exploring the enhancement effect of the LEO constellations on Precise Point Positioning of the Beidou satellite navigation system in satellites numbers and satellites orbit height.The main contents and conclusions of the paper are as follows:(1)This paper simulates the constellations of Beidou satellite navigation system,Iridium constellation,"Hongyan" constellation,and introducing their constellation configuration.According to the needs of subsequent experiments,this paper designs LEO constellations with different orbital altitudes and satellite numbers,this paper preliminarily analyzes the enhancement effect of adding LEO constellation to BDS PPP process in the following aspects: the trajectory of the sub-satellite point,the global DOP value distribution,the global average satellite visibility distribution,and the global navigation accuracy distribution.The results show that with the addition of the LEO constellation,the average number of visible satellites in the world,especially in the polar regions has been greatly improved.After joining the LEO constellation,the global PDOP value is reduced,and the reduction is more obvious with the increase of the number of LEO satellites,and the PDOP value of the polar region has decreased especially.The addition of the LEO constellation effectively improves the satellite configuration in high latitude areas and enhance navigation accuracy.(2)Based on the report function of STK software and self-editing software,GNSS/LEO precision orbit files are generated by simulation.Based on the ground-based GNSS observation equations,the spaceborne GNSS observation equations,and the intersatellite link observation equations,GNSS/LEO observation link simulation platform is constructed,and the simulation generation includes various corrections such as ionospheric delay correction,tropospheric delay correction,and satellite clock offset correction.Observation data with higher confidence of the term.(3)This paper explores the enhancement effect of the LEO constellation on the BDS PPP from the number of satellites in the LEO constellations,the altitude of the satellite orbit,the sampling rate of the station observation and the distribution latitude of the ground station during the observation process.The results show that the enhancement effect of the LEO constellation on BDS PPP increases with the number of LEO satellites.When the number of LEO satellites is selected as 100,144,196 and 256,the degree of improvement of the convergence speed of BDS PPP raise as 65.67%,70.15%,77.16% and 91.05%.Experiments have proved that under the same configuration and the number of satellites of LEO constellation,the higher satellite orbit,the better the enhancement effect on the BDS PPP.The higher LEO satellite orbit allows more LEOs to be observed and participate in the positioning calculation,and accelerate the convergence speed of BDS PPP.The experiments show that in the three sets of experiments designed,the LEO constellation with an orbit height of 2000 km has better enhancement effect than LEO constellation with an orbital altitude of 1000 km.The simulation observation data with sampling rates of 1s,5s,10 s,15s,20 s,and 30 s are used to perform positioning calculations.The experiments show that the observation sampling rate of LEO satellites improves the performance of BDS PPP by about 90%.There is no significant difference.(4)This paper also simulates the LEO constellation with navigation and positioning capabilities,and performs Precise Point Positioning and Single Point Positioning(SPP)performance analysis on the LEO constellation,which proves that when the LEO constellation meets the navigation and positioning requirements,can provide navigation and positioning services.