基于导航星座空间VLBI的航天器轨道稀疏测量与估计

Space very long baseline interferometry (SVLBI) can get rid of the diameter of the earth, which holds the characters such as lone baseline, quick change and small influence by the earth atmosphere. Due to the improved angular resolution of quasar, the improvement of the image quality for the radio source and the interconnection between different reference systems, SVLBI has been focused on in recent years. The research focus on the application of SVLBI in the global navigation constellation space extended task. Two notable characters, the huge data scale and the strong dynamic baseline composition, are studied in detail. First, according to the system characteristics, the compressive sampling theory is introduced to design a sparse measurement for the navigation signal. Then, how to use the navigation constellation to build interferometry baseline for spacecraft orbit determination is pursued, including the establishment of measurement models of different interferometry strategy, optimization of dynamic baseline and the development of robust, high precision orbit determination algorithm. This exploration may reduce the data size. In the project, a new way to solve the problems such as high cost and few available baseline will be given, which lay the theoretical and technical foundation for SVLBI based spacecraft orbit determination.

空间甚长基线干涉测量技术（VLBI）可以摆脱地球直径的限制，其干涉基线长、变化迅速和受地球大气影响小等特点，具有提高天体测量角分辨率、改善射电源成图质量和实现多参考系互联等优势，因而近年来备受青睐。课题以空间VLBI技术应用于全球导航星座任务扩展为背景，重点针对系统大数据量和高动态基线构型两个显著特点展开研究。首先根据导航星座空间VLBI系统特点，探索基于压缩采样原理的空间VLBI导航信号稀疏测量方法，以降低系统数据规模。然后研究如何利用导航星座构造干涉测量基线实现航天器的轨道确定，包括建立各种干涉模式的测量模型，分析动态基线优选策略和开发稳健、高精度轨道确定算法。项目研究将给空间VLBI基线构建成本高和可用空间基线少这一瓶颈问题提供一条崭新的解决思路，为实现基于导航星座等空间VLBI系统的测量和定轨工作奠定理论和技术基础。

鉴于北斗导航星座轨道精度高、地面监测系统覆盖广和能够在长时间、大范围空域内形成多基线的优势，本项目研究如何利用导航星座构建SVLBI系统，实现航天器（特别是深空探测器）的轨道高精度测量和估计。利用导航信号具有稀疏性的先验特征，研究了基于压缩采样原理探索SVLBI稀疏测量方法。针对导航星座基线数量多、时变性强的特点，研究了导航星座SVLBI的测量模型和时延计算方法，建立了含误差校准的轨道测量模型，进而设计系统性能评价指标，根据不同导航任务需求研究了基线优化选取策略。适应新系统强非线性估计结构、高动态测量数据、基线接力与组合测量的复杂误差等特点，从运动建模、机动检测与辨识、系统误差检测与校准、自适应高精度滤波算法等方面研究了航天器轨道实时确定方法。还利用连线干涉测量系统和“嫦娥”系列月球探测任务，开展了误差标校和导航算法等的验证工作。通过项目研究，给北斗导航系统拓展应用提供了潜在的方向，也为SVLBI构建成本高和可用基线少的瓶颈问题提供了新的解决思路，并且为大范围、高动态空间目标实时轨道确定提供了一系列实用的理论与方法。