BDS实时卫星钟差质量控制及钟差基准研究

At present there is not public and available real-time satellite clock offset product which belongs to the second BeiDou satellite navigation system (BDS). The real-time Navigation, Positioning and Timing (PNT) service capabilities of BDS are limited seriously. Therefore three core technologies will be researched which include BDS real-time satellite clock offset determination, BDS clock offset reference model and BDS clock offset product quality control. First a real-time classified detecting method for multiple abnormal conditions will be proposed to detect the cycle slips, blunders and clock jumps in real-time data stream. The optimal BDS real-time satellite clock offset model and the multithreading parameter separation algorithm will be constructed to improve the precision and efficient of traditional real-time clock offset processing. Some methods will be studied and proposed which use other GNSS data to enhance BDS real-time clock product performance. Meanwhile, the real-time adaptive clock offset prediction algorithm which considers clock jumps and atomic clock characteristics will be proposed to describe rules of BDS satellite clocks and phase jumps. In view of no unified reference model of BDS/GNSS clock offset products, some improved optimal reference algorithm and transformation model will be proposed. Further reference compatibility of multi-GNSS receivers clock offset products will be designed. In order to estimate precision and reliability of BDS satellite clock offset products, a new real-time system of clock offset product quality control and performance evaluation will be studied and built. In addition, the precise data processing program will be developed, several experiment based on real-time satellite clock offset products will be carried out. In a conclusion, the prospective researches in this project are able to support to enhance the service performance of BDS real-time satellite clock offset and promote clock offset products compatibility of BDS and other GNSS.

北斗二代卫星导航系统（BDS）目前无公开可用的卫星钟差实时流产品，严重限制其实时导航定位授时服务能力。课题针对北斗实时卫星钟差确定、钟差产品基准和钟差产品质量控制三大核心技术进行攻关。首先针对实时周跳、粗差和钟跳等混合异常探测难题，提出多异常分类实时探测方法；针对传统实时钟差解算低效率低精度问题，构建实时优化钟差模型和多线程参数分离算法，并融合多GNSS数据提升BDS实时钟差产品性能；针对BDS卫星钟分群及相位跳变特性，提出顾及钟跳和原子钟特性的实时自适应钟差预报算法；针对BDS/GNSS钟差产品统一基准的研究空白，攻关BDS/GNSS基准优选策略和转换模型，提出多模接收机钟差多基准兼容方案；针对BDS钟差产品精度和可靠性评估难题，研究建立钟差实时质量控制及性能评估体系；最后，研制处理软件并开展实验验证，为提升BDS实时钟差服务性能以及促进BDS与其他GNSS钟差产品兼容性提供技术支撑。

卫星与地面站之间的距离测量实际上是精确的时间测量，其中1纳秒的时间测量误差将导致0.3米的距离测量误差。卫星钟差是指卫星钟的时间与某一基准时间的差值。卫星钟差是否准确在导航系统服务中起到关键作用。本项目主要针对卫星钟差估计较慢，钟差估计时的粗差，钟差基准影响钟差估计等问题，对卫星钟差、卫星轨道、大气延迟和精密定位等方面展开了大量研究。在卫星钟差方面：提出了GNSS多系统卫星钟差快速估计与质量控制方法，显著提升了钟差估计的精度与可靠性。研究比较了不同钟差基准对钟差估计的影响，建立了一种顾及钟差基准切换补偿的北斗实时卫星钟差估计算法。提出了一种附加周期和神经网络补偿的北斗超快速钟差预报模型，钟差预报精度达到了国际领先水平。详细评估了GNSS五个系统的星载原子钟特性，为卫星钟监测提供了参考。在卫星定轨方面，精化了北斗二代与北斗三代卫星的天线模型，解决了北斗三代卫星轨道的系统性偏差问题。提出了北斗卫星轨道机动探测与机动期间的精密定轨方法，提升了精密产品的数据利用率。在大气延迟方面：分析了GNSS四个系统PPP 技术反演水汽的精度差异以及组合反演对性能提升幅度。提出了一种顾及边界入射信号的多模组合层析方法，多模组合信号和边界入射信号的引入均能增加有效观测数据的数目。在定位方面：从理论公式和实验结果两方面验证了不同PPP模型估计FCB产品的等价性。揭示了不同PPP 模型进行相位偏差FCB 估计的理论等价性；建立了三频GNSS 观测数据非组合PPP 和FCB 估计模型。建立基于双频精密卫星轨道钟差产品的三频非组合PPP 模型，构建了相应的三频FCB的估计方法，验证了三频FCB的估计精度以及三频PPP 模糊度固定解的精度。构建了顾及系统间偏差的多系统组合PPP 定位数学模型，验证了多系统组合PPP模型的模糊度固定性能。提出了顾及接收机码偏差的非组合PPP 模型，构建了相应模糊度固定算法。提出了利用非组合PPP 模糊度固定解估计电离层延迟的方法。