Precise orbit determination for TH02-02 satellites based on BDS3 and GPS observations

The Tianhui-202(TH02-02)satellite formation,as a supplement to the microwave mapping satellite system Tianhui-201(TH02-01),is the first Interferometric Synthetic Aperture Radar(InSAR)satellite formation-flying system that supports the tracking of BeiDou global navigation Satellite system(BDS3)new B1C and B2a signals.Meanwhile,the twin TH02-02 satellites also support the tracking of Global Positioning System(GPS)L1&L2 and BDS B1I&B3I signals.As the spaceborne receiver employs two independent boards to track the Global Navigation Satellite System(GNSS)satellites,we design an orbit determination strategy by estimating independent receiver clock offsets epoch by epoch for each GNSS to realize the multi-GNSS data fusion from different boards.The performance of the spaceborne receiver is evaluated and the contribution of BDS3 to the kinematic and reduced-dynamic Precise Orbit Determination(POD)of TH02-02 satellites is investigated.The tracking data onboard shows that the average number of available BDS3 and GPS satellites are 8.7 and 9.1,respectively.The carrier-to-noise ratio and carrier phase noise of BDS3 B1C and B2a signals are comparable to those of GPS.However,strong azimuth-related systematic biases are recognized in the pseudorange multipath errors of B1C and B3I.The pseudorange noise of BDS3 signals is better than that of GPS after eliminating the multipath errors from specific signals.Taking the GPS-based reduced-dynamic orbit with single-receiver ambiguity fixing technique as a reference,the results of BDS3-only and BDS3+GPS combined POD are assessed.The Root Mean Square(RMS)of orbit comparison of BDS3-based kinematic and reduced-dynamic POD with reference orbit are better than 7 cm and 3 cm in three-Dimensional direction(3D).The POD performance based on B1C&B2a data is comparable to that based on B1I&B3I.The precision of BDS3+GPS combined kinematic orbit can reach up to 3 cm(3D RMS),which has a more than 25%improvement relative to the GPS-only solution.In addition,the consistency between the BDS3+GPS combined reduced-dynamic orbit and the GPS-based ambiguity-fixed orbit is better than 1.5 cm(3D RMS).

北斗全球最简系统空间信号精度分析

本文利用2018年5月1日-5月27目的数据，开展了北斗全球最简系统空间信号精度评估，并对卫星钟在轨性能进行了初步的分析。结果表明：广播星历轨道R、T、N三个方向误差分别为0．71m、1．81m、2．51m（95％），广播星历钟差误差为3．43ns（95％），空间信号用户测距误差为1．30m（95％）；卫星钟天稳定度为10^-14量级；频率准确度大多数为10^-12量级，部分为10^-10量级；频率漂移率接近10^-14量级。

北斗三号最简系统伪距单点定位精度分析

本文利用CANB和DWIN等7个站在2018年年积日141~144期间的观测数据,进行北斗三号卫星单频(B1C)伪距单点定位试验.结果表明:北斗三号卫星单频(B1C)伪距单点定位的平均PDOP在3.75-4.35之间,可见卫星数4~6颗,基本满足伪距单点定位要求。北斗三号单频伪距单点定位精度在东(E)水平方向优于6.5mJt(N)方向优于4m,天顶(U)方向优于&5m,三维(P)方向优于11.5m。

北斗三号最简系统卫星信号质量分析

截至2018年5月,中国共发射了8颗北斗三号(BDS-3)中圆地球轨道(medium Earth orbit,MEO)卫星,组成北斗三号最简系统,播发了B1C、B2a和B2b新卫星信号,仅有17个国际全球导航卫星系统监测评估系统(international global navigation satellite system monitoring and assessment system,iGMAS)跟踪站能够接收到BDS-3卫星信号。选用17个iGMAS观测站10 d的观测数据,从数据完整率、信噪比、多路径效应、电离层延迟和周跳方面进行质量分析,并与GPS L1/L5和Galileo E1/E5a重叠频率对比,评价当前BDS-3卫星信号性能以及iGMAS测站的接收能力。结果表明,装有GNSS_GGR接收机的iGMAS测站的伪距观测值含有较大的粗差,个别装有CETC-54-GMR-4011接收机的跟踪站的周跳现象较严重。通过分析多路径效应可知,BDS-3卫星各个信号中不存在与高度角有关的系统偏差。BDS-3最简系统卫星观测数据质量与GPS L1/L5和Galileo E1/E5a相当,能够满足北斗卫星导航系统正常的工作需求。