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Study on systematic errors of BDS‑3 broadcast ephemeris and their effects with Helmert transformation

Satellite Navigation 2023年第3期4卷 153-166页

作者： Min Li Jiangnan Zhang Guo Chen Liang Chen Qile Zhao GNSS Research Center Wuhan UniversityNo.129 Luoyu RoadWuhan 430079China School of Geodesy and Geomatics Wuhan UniversityNo.129 Luoyu RoadWuhan 430079China School of Electronic and Information Engineering Beihang UniversityBeijing 100191China

Previous studies have not evaluated the systematic errors implied in the third generation of BeiDou-3 Navigation Satellite System(BDS-3)broadcast *** this paper we evaluate the systematic pattern described by the Helmert transformation parameters,including translations,rotations,and ***-3 broadcast and precise ephemerides from December 2019 to 2022 are collected,and the characteristics of the transformation parameters as well as their effects on the signal in space error are *** annual variation in the z-translation is obtained,and the similar amplitudes of 5.5 cm and phases of approximate 300 days are obtained for different *** the rotation parameters are considered in the orbit comparison,the Root Mean Square(RMS)errors of the along-and cross-track orbital differences decrease from 29.1 to 12.5 cm and from 30.6 to 9.2 cm,respectively,because the three rotation parameters compensate for the majority of the errors in the BDS-3 broadcast ***,the high correlations in the obtained rotation parameters among the three orbital planes suggest that the orientation of the BDS-3 broadcast ephemeris is influenced by common model errors,i.e.,uncertainty of Earth Rotation Parameters(ERPs).Further research is required because an offset of 1.5×10^(–9)for the scale parameter is observed.A degraded User Range Error(URE)for epochs of up to 84%is attained when the systematic pattern is considered,though the impact of the systematic pattern indicated by the z-translation and rotation parameters on the URE is less than 5.0 *** the refinement of the ERPs implemented in the new generation of broadcast ephemeris,we anticipate that the broadcast ephemeris performance of BDS-3 will be improved.

关键词： broadcast ephemeris BDS-3 Helmert transformation Transformation parameters Correlation coefficient URE

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An optimal design of the broadcast ephemeris for LEO navigation augmentation systems

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Geo-Spatial Information Science 2022年第1期25卷 34-46页

作者： Xueli Guo Lei Wang Wenju Fu Yingbo Suo Ruizhi Chen Hongxing Sun State Key Laboratory of Information Engineering in Surveying Mapping and Remote SensingWuhan UniversityWuhanChina Collaborative Innovation Center for Geospatial Technology WuhanChina

As the deployment of large Low Earth Orbiters(LEO)communication constellations,navigation from the LEO satellites becomes an emerging opportunity to enhance the existing satellite navigation *** LEO navigation augmentation(LEO-NA)systems require a centimeter to decimeter accuracy broadcast ephemeris to support high accuracy positioning ***,how to design the broadcast ephemeris becomes the key issue for the LEO-NA *** this paper,the temporal variation characteristics of the LEO orbit elements were analyzed via a spectrum analysis.A non-singular element set for orbit fitting was introduced to overcome the potential singularity problem of the LEO *** on the orbit characteristics,a few new parameters were introduced into the classical 16 parameter ephemeris set to improve the LEO orbit fitting *** order to identify the optimal parameter set,different parameter sets were tested and compared and the 21 parameters data set was recommended to make an optimal balance between the orbit accuracy and the bandwidth *** the real-time broadcast ephemeris generation procedure,the performance of the LEO ephemeris based on the predicted orbit is also *** performance of the proposed ephemeris set was evaluated with four in-orbit LEO satellites and the results indicate the proposed 21 parameter schemes improve the fitting accuracy by 87.4%subject to the 16 parameters *** accuracy for the predicted LEO ephemeris is strongly dependent on the orbit *** these LEO satellites operating higher than 500 km,10 cm signal-in-space ranging error(SISRE)is achievable for over 20 min prediction.

关键词： LEO broadcast ephemeris orbit fitting leo navigation augmentation orbit prediction

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Improving BDS broadcast ephemeris accuracy using ground-satellite-link observations

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Satellite Navigation 2022年第1期3卷 85-96,I0004页

作者： Junping Chen Jungang Wang Chao Yu Yize Zhang Bin Wang Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Shanghai Key Laboratory of Space Navigation and Positioning Techniques Shanghai Astronomical ObservatoryChinese Academy of SciencesShanghai 200030China

The BeiDou Navigation Satellite System(BDS)employs a hybrid constellation including GEO(Geosynchronous Earth Orbit),IGSO(Inclined Geosynchronous Orbit),and MEO(Medium Earth Orbit)satellites,where the GEO and IGSO satellites are critical to providing continuous and reliable Positioning,Navigation,and Timing(PNT)services in the Asia–Pacifc *** handle the inconsistency between the satellite orbits and clocks in the broadcast ephemeris,which are determined by the Orbit Determination and Time Synchronization(ODTS)and the Two-way Satellite Time Frequency Transfer(TWSTFT)technique,respectively,we present the strategies using ground-satellite-link observations to improve the accuracy of broadcast *** clock diferences between the ODTS and TWSTFT techniques are used for correcting the radial orbit component to derive the refned orbits,which are used to generate the refned broadcast *** test results show the precision of the refned orbits is improved by 50–60%in the 3-h to 12-h predicted arcs for the GEO satellites,and by 40–50%for the IGSO ***,the validation using satellite laser ranging observations shows the mean precision of the refned broadcast ephemeris is improved by 27%compared to the original *** the proposed strategies in the BDS Operational Control Segment(OCS),the time evolution of BDS Single Point Positioning(SPP)in the period from Jan.2016 to April 2021 is *** SPP accuracy is improved from 1.94,2.06 and 3.29 m to 1.39,1.85,and 2.39 m in the north,east,and up components,*** update with the inclusion of BDS-3 satellites improve the corresponding SPP precision to 0.68,0.70 and 1.91 m.

关键词： BDS broadcast ephemeris TWSTFT Orbit determination

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Non-reciprocity correction using broadcast ephemeris in Two-way Satellite Time and Frequency Transfer （TWSTFT）

Non-reciprocity correction using broadcast ephemeris in Two-...

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第四届中国卫星导航学术年会

作者： YANG Wenke GONG Hang ZHU Xiangwei SUN Guangfu School of Electronic Science and Engineering National University of Defense Technology

Two-way satellite time and frequency transfer （TWSTFT） is applied in BeiDou Navigation Satellite System for time synchronization of the ground stations. In fact, the geostationary （GEO） satellites have periodic motions around their planned orbits instead of being stationary to the ground stations, which results in periodic fluctuations of Sagnac correction and signal path geometry correction in TWSTFT. Precise TWSTFT is relaying on the non-reciprocity corrections. An analysis method with broadcast ephemeris of GEO satellite for Sagnac correction and signal path geometry correction is introduced in this paper. With this method, TWSTFT experiment result using BeiDou GEO satellite at 140°E of three links between Beijing and three different sites is analyzed and the periodic fluctuation of Sagnac correction and signal path geometry correction are presented in detail. The fluctuation range of Sagnac correction is from 0.04ns to 0.16ns and that of signal path geometry correction is from 0.01ns to 0.53ns for the three links, which shows that Sagnac correction and signal path geometry correction can not be ignored in time transfer requiring sub-nanosecond precision generally for the three links.

关键词： TWSTFT non-reciprocity corrections Sagnac correction signal path geometry correction broadcast ephemeris

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BDS-2 broadcast ephemeris Orbit Error Compensation Based on ABC-BP Neural Network

BDS-2 Broadcast Ephemeris Orbit Error Compensation Based on ...

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第十三届中国卫星导航年会

作者： Hanlin Chen Xing Su Fei Niu Qiang Li Zhimin Liu College of Geodesy and Geomatics Shandong University of Science and Technology Key Laboratory of Geomatics and Digital Technology of Shandong Province Shandong University of Science and Technology Beijing Satellite Navigation Center

With the completion of BeiDou Navigation Satellite System（BDS） constellation deployment, the research on improving the service performance of BDS has become the focus. broadcast ephemeris is a prerequisite for normal navigation in real time navigation and positioning. The real-time performance of broadcast ephemeris results in bad orbit accuracy, and its error variation cannot be accurately described by mathematical model, which has a unignorable impact in positioning and navigation. Based on this research background, we take Multi-GNSS Experiment（MGEX） precision ephemeris as reference and use Back Propagation（BP） Neural Network（NN） and Artificial Bee Colony Algorithm（ABC） optimized BP NN to model the orbit error of broadcast ephemeris to improve the its orbit accuracy. The experimental results show that the two NN models have good modeling effect on broadcast ephemeris orbit error, and the orbit accuracy of broadcast ephemeris of different satellites is improved by 20%-80%.ABC-BP NN has higher accuracy than BP NN, and the results of 3 and 5 days of different orbit types show that it has better ability to control error accumulation, and has better error compensation results for broadcast ephemeris in short and medium term.

关键词： broadcast ephemeris Satellite orbit error Neural network Error model AODE

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SIS accuracy and service performance of the BDS-3 basic system

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Science China(Physics,Mechanics & Astronomy) 2020年第6期63卷 105-116页

作者： JinPing Chen XiaoGong Hu ChengPan Tang ShanShi Zhou YuFei Yang JunYang Pan Hui Ren YueXin Ma QiuNing Tian Bin Wu Yang Yu Beijing Satellite Navigation Center Beijing 100094China Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China Shanghai Key Laboratory for Space Positioning and Navigation Shanghai 200030China

On December 27,2018,the basic system of the third-generation BeiDou navigation satellite system(BDS-3)completed the deployment of its constellation of 18 MEO networking satellites as well as the construction of the operation control system(OCS)and began to provide basic navigation services to users *** with BDS-2,BDS-3 aims to offer users better navigation signals and higher precision with a series of new *** example,the spaceborne atomic clock of BDS-3 is upgraded for higher performance,the Ka-band inter-satellite link is adopted for inter-satellite ranging and communication,and new B1C and B2a signals are broadcast in addition to B1I and B3I signals(compatible with BDS-2).In addition,a 9-parameter model based on a spherical harmonic function is employed for ionospheric delay *** the observation data from 18 satellites of the basic system,this paper conducts a comprehensive evaluation of the pseudorange measurement characteristics,signal-in-space(SIS)accuracy of navigation messages and global service capability of *** results indicate that the pseudorange measurement multipath effect and observation noise of BDS-3 satellites are better than those of BDS-2;additionally,with the support of inter-satellite links,the user range error(URE)of the BDS-3 satellite broadcast ephemeris is better than 10 cm,the precision of the broadcast clock parameter is better than 1.5 ns,and the SIS accuracy is better than 0.6 m *** from the traditional Klobuchar model,the BeiDou global broadcast ionospheric delay correction model(BDGIM)can provide ionospheric delay corrections better than 70%for worldwide single-frequency *** service capability evaluation of the basic system consists mainly of the accuracy improvement of the B1I and B3I signals according to BDS-2 as well as the global positioning accuracy of the new *** results prove that the BDS-3 basic system has achieved the design goal;that is,both the hori

关键词： BDS-3 SIS URE multipath effect broadcast ephemeris broadcast clock ionospheric model positioning accuracy

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Orbital Elements Ephemerides and Interfaces Design of LEO Satellites

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Journal of Geodesy and Geoinformation Science 2019年第4期2卷 44-52页

作者： Shanchuan FANG Lan DU Yunpeng GAO Peiyuan ZHOU Zejun LIU Technical Department of Taiyuan Satellite Launch Center Taiyuan 030027China Information Engineering University Zhengzhou 450001China

Low earth orbit satellites,with unique advantages,are prosperous types of navigation augmentation satellites for the GNSS satellites *** broadcast ephemeris element needs to be designed as an important index of the augmented *** GPS ephemerides of 16/18 elements cannot be directly applied to the LEOs because of the poor fitting accuracies in along-track positional ***,the ill-conditioned problem of the normal-matrix exists in fitting algorithm due to the small eccentricity of the LEO *** on the nonsingular orbital elements,5 sets of ephemerides with element numbers from 16 to 19 were designed respectively by adding or modifying orbital elements magnifying the along-track and radial positional *** fitting experiments based on the LEO of 300 to 1500 km altitudes show that the fitting UREs of the proposed 16/17/18/18*/19-element ephemerides are better than 10/6/4/5/2.5 cm,*** to the dynamical range of the fitting elements,the interfaces were designed for the 5 sets of *** effects of data truncation on fitting UREs are at millimeter *** total bits are 329/343/376/379/396,respectively.29/15 bits are saved for the 16/17-element ephemerides compared with the GPS16 ephemeris,while 64/61/41 bits can be saved for the 18/18*/19-element ephemerides compared with the GPS18 elements ephemeris.

关键词： LEO satellites broadcast ephemeris nonsingular orbital elements of the first kind quantization unit

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Comparison of Short-term Stability Estimation Methods of GNSS On-board Clock

Comparison of Short-term Stability Estimation Methods of GNS...

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第三届中国卫星导航学术年会

作者： GONG Hang* 1 ,YANG Wenke 1 ,WANG Yong 1 ,ZHU Xiangwei 1 ,WANG Feixue 1 1.Satellite Navigation R&D Center,School of Electronic Science and Engineering,National University of Defense Technology,Changsha,Hunan 410073,China

The short-term frequency stability of satellite on-board clock is of great significance for GNSS applications,such as satellite clock modeling,simulation and clock offset *** this paper,four short-term frequency stability esti-mation methods are analyzed,which need observation data from only one station in contrast with ODTS needing continuous observation of large ground monitoring *** and accuracy of all these four methods is analyzed and compared using GPS and COMPASS observation data,and their advantage and disadvantage are discussed *** COMPASS and Galileo systems which are currently in the early stage of construction,this paper proposes some meaningful suggestions of on-board clock short-term frequency stability estima-tion.

关键词： GNSS On-board Clock Short-term Stability Estimation Precise ephemeris broadcast ephemeris Smoothed Carrier Phase COMPASS ODTS (Orbit Determination and Time Synchronization)

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A centimeter-level continuous measurement method after the differential data of RTK interruption

A centimeter-level continuous measurement method after the d...

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第十三届中国卫星导航年会

作者： Qi Yu Hongyu Shan Guofu Pan Yanhui Li Zhongrong Yang Hi-Target Surveying Instrument Co. Ltd.

Aiming at the problem that the positioning accuracy of the rover station will decrease rapidly with the increase of the differential period when the differential data is interrupted in RTK measurement technology, and the centimeter-level position service cannot be provided. A continuation method of breakpoint based on single station is proposed. When the differential data of the rover is interrupted, the data of the rover will be processed through the double-difference model between epochs and satellites based on the broadcast ephemeris. In order to calculate the high-precision time baseline and then get the centimeter-level position of the rover station, the ionospheric error, tropospheric error, satellite clock error and orbit error are all corrected or estimated. In this paper, the method is verified by the static data and dynamic data. The experimental result shows that the positioning accuracy at plane can maintain at centimeter level within 10 minutes, which can effectively improve the reliability and continuity of RTK results in the scenarios of unstable differential data.

关键词： rover station RTK differential interrupt accuracymaintain broadcast ephemeris

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