北斗首颗备份卫星性能初步分析

摘要

主要从卫星钟差预报、轨道测定精度、伪距波动情况等角度分析了I6卫星与北斗卫星导航系统(BDS)其他现役倾斜地球同步轨道(IGSO)卫星的异同,并从位置精度因子(PDOP)和格网可用性评估了I6卫星入网对BDS的贡献.利用星地双向时频传递设备观测的星地钟差数据,评估了I6卫星星载原子钟的预报性能,结果表明,I6卫星发播的卫星钟参数外推5 h预报误差的均方根误差(RMS)为2.32 ns,外推1 h预报误差的RMS为0.73 ns,与现役IGSO卫星钟差预报水平相当;对多星联合精密定轨结果分析表明,与北斗现役I3卫星相比,姿态控制方式优化后的I6卫星在地影期间的轨道精度并未发生明显衰减,克服了现有北斗二号卫星在地影期间轨道精度下降,从而影响北斗服务的连续性、可用性问题;利用大口径抛物面天线采集到的数据对I6卫星的伪距波动进行了分析,结果表明I6卫星单个观测弧段内其伪距波动峰峰差约为1 m,与其他IGSO卫星一致;进行PDOP仿真计算,结果表明I6卫星的加入使得喀什地区的PDOP最大值由12.82下降为7.26,PDOP大于6的时段所占百分比由29.11%下降为17.21%;对格网电离层产品实施解算,结果表明I6卫星的加入使得6个电离层格网点的可用度提升至95%以上.%To further enhance the capability of BeiDou Navigation Satellite System (BDS) to provide continuous and efficient service , the first backup satellite I6 was launched in March 2016 .The differences and similarities between I6 and other IGSO satellites were analyzed , from the perspective of satellite clock prediction , orbit determination accuracy and pseudorange variation .The contribution of I6 to BDS was evaluated by PDOP values and grid availability .The satellite clock measurements obtained by two-way satellite time frequency transfer (TWSTFT ) system were used to evaluate clock prediction error of I6 .The results show that for 5-hour prediction , clock error of I6 is 2. 32 ns in terms of root-mean-square (RMS) and the extrapolated one-hour prediction error is 0. 73 ns(RMS) .Compared with other IGSO satellites clock ,the error forecast level of I6 is equivalent . The orbit determination accuracy of I6 optimized by the attitude control method is not degraded obviously compared with the I3 of BDS when the Sun is close to the I6′s orbit plane , which overcomes the decrease of the orbit accuracy of the existing BDS satellites during the shadow . The pseudorange variation of the I6 satellite was analyzed using the data collected by the large aperture parabolic antenna .The results show that the peak-to-peak difference of the pseudorange variation is about 1m in the single observation arc of I6 satellite .It is consistent with other IGSO satellites .I6 is in the hot standby mode of operation , providing services with the original BeiDou satellites after May 2016 , changing the BDS constellation composition . The results of PDOP simulation show that the maximum PDOP of KaShi is decreased from 12. 82 to 7. 26 ,and the percentage of PDOP greater than 6 is decreased from 29. 11% to 17. 21% .The results show that I6 increases the availability of six ionospheric grid points .