To the issue of the satellite internal multipath (SIMP) of BeiDou satellites, it proposed and emphasized that the SIMP model should be established as a function of the nadir angle with respect to the observed satellite rather than the elevation of the measurement, so that it can be used for receivers at various altitude. BDS data from global distributed stations operated by the International Monitoring and Assessment System (iGMAS) and the Multi-GNSS Experiment (MGEX) of the International GNSS Service (IGS) are collected and a new SIMP model as a piece-wise linear function of the nadir angle is released for the IGSO-and MEO-satellite groups and for B1, B2 and B3 frequency band individually. The SIMP of GEO,IGSO and MEO satellites is further analyzed with B1/B2 dual-frequency data onboard the FengYun-3 C(FY3C) satellite at an altitude of~830 km, and it showed that, for nadir angles smaller than 7°, the SIMP values for GEO is quite close to the IGSO's, especially for B2, which may suggest that the SIMP model for IGSO satellites possibly also works for GEO satellites. It also demonstrated that, when the nadir angle is smaller than 12°for the MEO and 7°for the IGSO, the estimated SIMP model with data from FY3C is considerable consistent with that estimated with data collected at ground stations. Experiments are carried out to investigate the impacts of the SIMP on wide-lane fractional cycle bias (FCB) estimation for BDS satellites. The result indicates that, with the correction of the estimated SIMP, the repeatability of the FCB series is significantly improved by more than 60% for all satellites. Specifically, for the MEO and IGSO satellites, the repeatability is smaller than 0.05 cycle; the repeatability of 0.023 and 0.068 cycles achieved for GEO satellites C01 and C02 respectively with the estimated SIMP model for IGSO satellites.
[1] 杨元喜, 李金龙, 徐君毅, 等. 中国北斗卫星导航系统对全球PNT用户的贡献[J]. 科学通报, 2011, 56(21):1734-1740. YANG Yuanxi, LI Jinlong, XU Junyi, et al. Contribution of the Compass Satellite Navigation System to Global PNT Users[J]. Chinese Sience Bulletin, 2011, 56(2):2813-2819.
[2] 杨元喜. 北斗卫星导航系统的进展、贡献与挑战[J]. 测绘学报, 2010, 39(1):1-6. YANG Yuanxi. Progress, Contribution and Challenges of Compass/BeiDou Satellite Navigation System[J]. Acta Geodaetica et Cartographica Sinica, 2010, 39(1):1-6.
[3] 陈金平, 胡小工, 唐成盼, 等. 北斗新一代试验卫星星钟及轨道精度初步分析[J]. 中国科学:物理学力学天文学, 2016, 46(11):119502. CHEN Jinping, HU Xiaogong, TANG Chengpan, et al. Orbit Determination and Time Synchronization for New-generation BeiDou Satellites:Preliminary Results[J]. Scientia Sinica:Physica, Mechanica & Astronomica, 2016, 46(11):119502.
[4] SHI Chuang, ZHAO Qile, HU Zhigang, et al. Precise Relative Positioning Using Real Tracking Data from Compass GEO and IGSO Satellites[J]. GPS Solutions, 2013, 17(1):103-119.
[5] MONTENBRUCK O, HAUSCHILD A, STEIGENBERGER P, et al. Initial Assessment of the Compass/BeiDou-2 Regional Navigation Satellite System[J]. GPS Solutions, 2013, 17(2):211-222.
[6] HAUSCHILD A, MONTENBRUCK O, SLEEWAEGEN J M, et al. Characterization of Compass M-1 Signals[J]. GPS Solutions, 2012, 16(1):117-126.
[7] HAUSCHILD A, MONTENBRUCK O, THOELERT S, et al. A Multi-technique Approach for Characterizing the SVN49 Signal Anomaly, Part 1:Receiver Tracking and IQ Constellation[J]. GPS Solutions, 2012, 16(1):19-28.
[8] BLEWITT G, BERTIGER W, WEISS J P. Ambizap3 and GPS Carrier-range:A New Data Type with IGS Applications[M]. Newcastle:IGS Workshop 2010, 2010.
[9] WANNINGER L, BEER S. BeiDou Satellite-induced Code Pseudorange Variations:Diagnosis and Therapy[J]. GPS Solutions, 2015, 19(4):639-648.
[10] LOU Yidong, GONG Xiaopeng, GU Shengfeng, et al. Assessment of Code Bias Variations of BDS Triple-Frequency Signals and Their Impacts on Ambiguity Resolution for Long Baselines[J]. GPS Solutions, 2017, 21(1):177-186.
[11] ZHANG Xiaohong, HE Xiyang, LIU Wanke. Characteristics of Systematic Errors in the BDS Hatch-Melbourne-Wübbena Combination and Its Influence on Wide-lane Ambiguity Resolution[J]. GPS Solutions, 2017, 21(1):265-277.
[12] YANG Wenke, TONG Haibo, PAN Lei, et al. Analysis and Correction of BDS Code Multipath Bias[C]//SUN Jiadong, LIU Jingnan, FAN Shiwei, et al. Proceedings of the China Satellite Navigation Conference (CSNC) 2016:Volume Ⅲ.[S.l.]:Springer, 2016.
[13] WANG Shuzhi, ZHU Guangwu, BAI Weihua, et al. For the First Time FengYun3 C Satellite-global Navigation Satellite System Occultation Sounder Achieved Spaceborne BeiDou System Radio Occultation[J]. Acta Physica Sinica, 2015, 64(8):089301.
[14] KLEUSBERG A, TEUNISSEN P J G. GPS for Geodesy[M]. Berlin:Springer-Verlag, 1996:407.
[15] MONTENBRUCK O, HAUSCHILD A, STEIGENBERGER P, et al. Three's the Challenge:A Close Look at GPS SVN62 Triple-frequency Signal Combinations Finds Carrier-phase Variations on the New L5[J]. GPS World, 2010, 21(8):8-19.
[16] CHEN Hua, JIANG Weiping, GE Maorong, et al. An Enhanced Strategy for GNSS Data Processing of Massive Networks[J]. Journal of Geodesy, 2014, 88(9):857-867.
[17] 李振海, 焦文海, 黄晓瑞, 等. GNSS服务空域空间信号可用性比较与分析[J]. 宇航学报, 2013, 34(12):1605-1613. LI Zhenhai, JIAO Wenhai, HUANG Xiaorui, et al. Comparison and Analysis of Signal Availability in the GNSS Service Volume[J]. Journal of Astronautics, 2013, 34(12):1605-1613.
[18] GE M, GENDT G, SHI M, et al. Resolution of GPS Carrier-Phase Ambiguity in Precise Point Positioning[M]. Vienna:EGU Assembly, 2007.
[19] LAURICHESSE D, MERCIER F, BERTHIAS J P, et al. Integer Ambiguity Resolution on Undifferenced GPS Phase Measurements and Its Application to PPP and Satellite Precise Orbit Determination[J]. Navigation, 2009, 56(2):135-149.
[20] COLLINS P, LAHAYE F, HEROUX P, et al. Precise Point Positioning with Ambiguity Resolution Using the Decoupled Clock Model[M]//Proceedings of ION GNSS 2008. Savannah, Georgia:Institute of Navigation, 2008.
[21] LIU Yanyan, YE Shirong, SONG Weiwei, et al. Integrating GPS and BDS to Shorten the Initialization Time for Ambiguity-Fixed PPP[J]. GPS Solutions, 2017, 21(2):333-343.
[22] LI Xingxing, ZHANG Xiaohong. Improving the Estimation of Uncalibrated Fractional Phase Offsets for PPP Ambiguity Resolution[J]. The Journal of Navigation, 2012, 65(3):513-529.
[23] WANG Min, CAI Hongzhou, PAN Zongpeng. BDS/GPS Relative Positioning for Long Baseline with Undifferenced Observations[J]. Advances in Space Research, 2015, 55(1):113-124.
