面向空间站的大型航天器精密定轨及预报关键技术研究

In order to fully carry out large-scale space science experiments and applied technology research, China will complete the on-orbit construction of the manned space station around 2022. The precise orbit determination of the space station is a key content for conducting space science research and is an important prerequisite for the analysis of various types of scientific detection data. However, the large mass and volume of the space station, complex configuration, and varied operation modes of the assembly bring new challenges to precise orbit determination for such large spacecraft. The traditional ground tracking method is difficult to meet the requirements of the current task on the accuracy of the orbit determination. According to the overall design of the mission, each compartment of China’s future space station will be equipped with high-performance multi-GNSS receivers, providing a more accurate measurement basis for precise orbit determination. This project will mainly study the key technologies of in-orbit center-of-mass estimation using onboard GNSS measurements, fine-scale modeling of the spacecraft surface stress, continuous small-thrust maneuver modeling and calibration, multi-GNSS data fusion for orbit determination, as well as long-term orbit forecast for low-Earth spacecraft. This project will also develop a set of spaceborne GNSS data processing software to verify the correctness and effectiveness of technologies mentioned above, and then, to solve the problems of precise orbit determination and forecast for the future space station.

为全面开展大规模的空间科学实验和应用技术研究，我国将于2022年前后完成载人空间站的在轨建造。空间站的精密轨道确定是开展空间科学研究的关键内容，是各类科学探测数据分析的重要前提。但是，空间站质量体积大、空间构型复杂、组合体运行模式多变等特点对精密轨道确定提出了新的挑战，传统的地面跟踪测量手段难以满足当前任务对定轨精度指标的要求。根据任务总体方案设计，我国未来空间站的各舱段均将搭载高性能的多模GNSS接收机，为精密轨道确定提供更高精度的测量基础。本项目将主要研究基于星载GNSS测量的大型航天器在轨质心估计、航天器表面力精细化建模、持续小推力机动建模及校准、多GNSS系统数据融合定轨、低轨航天器中长期轨道预报等关键技术。同时，开发一套具有自主知识产权的星载GNSS数据处理软件，验证核心技术的正确性和有效性，解决空间站精密定轨和预报中的关键问题。

本项目针对空间站结构复杂、构型多变、支持多GNSS系统观测等特点，开展了一系列星载GNSS精密定轨关键技术研究，为我国空间站高精度科学轨道确定提供了必要技术支撑。针对大型复杂结构航天器表面力精细化建模问题，开展了迎风面积和光照面积计算的宏模型研究，提高了航天器轨道动力学模型表示精度，实现了天宫二号厘米级精密轨道确定。针对三轴稳定对地定向和对日定向两种姿态模式，分析了基于星载GNSS数据同步开展航天器定轨和质心偏差估计的可行性，并利用GRACE和天琴一号卫星开展了实测数据验证。在星载多模GNSS融合定轨方面，开展了星载GNSS系统间偏差特性分析与建模研究，突破了星载GPS和BDS融合定轨技术，实现了低轨航天器厘米级绝对定轨和亚毫米级相对定轨。在小推力机动处理方面，通过常值加速度建模和机动附近单步、多步混合积分器设计，有效消除了机动对精密定轨的影响，根据机动估计结果还可进一步评估当前轨控效果，为后续轨控计划制定和剩余燃料估计提供可靠依据。在大型航天器中长期轨道预报方面，分析了不同经验大气密度模型对空间站轨道预报的影响，给出了大气密度模型优选策略；提出了一种基于TLE的弹道系数估计方法，实现了非合作目标中长期轨道预报，并在天宫一号陨落预报中发挥了重要作用。