“嫦娥二号”平动点和小行星探测试验中的轨道计算

曹建峰

(中国科学院上海天文台上海200030)

“嫦娥二号”平动点和小行星探测试验中的轨道计算

曹建峰†

(中国科学院上海天文台上海200030)

论文以CE-2(嫦娥二号)平动点飞行试验、小行星探测试验以及YH-1火星探测任务为背景,对深空探测测定轨技术开展研究.相关研究成果直接为小行星图塔蒂斯探测试验的拍照成像提供了高精度的轨道支持.针对YH-1火星探测开展了先期的测定轨研究,研究成果虽未能直接应用于火星探测任务,但积累的理论知识可服务于我国后续深空探测.论文的研究可以概括为以下几个方面：

(1)回顾统计定轨理论,简单介绍了时空参考系、动力学模型、估值方法及考察协方差理论.

(2)开展深空探测的观测建模研究.基于理论分析,推导建立测距、多普勒以及VLBI(Very Long Baseline Interferometry)等观测类型的测量模型.在观测模型建立过程中对算法进行优化,在保证计算精度的同时,提高了计算效率.此外,针对嫦娥卫星巡航飞行阶段自旋稳定的特点,建立了测量数据的自旋修正模型,既满足了数据修正的需求,亦可实现天线安装位置的估算.

(3)对CE-2平动点飞行试验期间积分中心选取的问题进行了研究,基于理论推导,得出选取地球作为积分中心开展轨道计算更适合的结论.针对平动点飞行试验期间的轨道计算,建立了真实力模型下空固坐标系与会合坐标系的转换关系;构建了对流层延迟修正的平均效应模型,实现了CE-2在平动点飞行阶段全程2–10 km、在平稳飞行阶段优于5 km的定轨精度,为CE-2平动点飞行试验提供了精确轨道支持.

(4)对CE-2小行星探测试验的轨道计算开展了研究,为探测试验小行星清晰成像提供精确轨道支持.交会前两次轨道修正仅有13 d间隔,而小行星清晰成像要求轨道精度优于15 km.针对控后弧段有限的特点,建立了融合轨控前后测轨数据进行轨道计算的策略,实现了控后12 d优于10 km的定轨精度.

(5)针对早期YH-1火星探测任务开展了仿真计算,分析了影响定轨精度的主要误差源和当前测控条件下YH-1可能的定轨计算能力,先期的研究工作可为后续的自主火星探测提供支持.对上海天文台跟踪的MEX(Mars Express)测轨数据进行处理分析,解算的轨道与ESA(European Space Agency)精密轨道偏差百米量级,验证了深空探测观测模型、动力学模型的准确性以及定轨软件的能力.

Setting within the context of the flight trial of CE-2(Chang’e 2)around the Sunterrestrial libration point,the asteroid exploration as well as the YH-1 Mars explorationmission,this paper conducted various related studies on orbit determination techniques for deep space exploration.The research results provided high-precision orbit support for the successful photographing of the Toutatis.This paper also carried out preliminary orbit determination studies on YH-1 mission.Although the study findings can not be used directly in the Mars exploration mission,they can still be useful for the future explorations.This thesis is composed of the following five aspects.

(1)Reviewed the statistical orbit determination theory,and gave a description of the spatiotemporal frame of reference,dynamical model issues,methods of estimation,perturbation analysis theory,as well as the algorithms for considering covariance analysis.

(2)Developed the observational model for the deep space exploration.Based on theoretical analysis,the models of ranging,ranging rate,and VLBI(Very Long Baseline Interferometry)are derived.During the modeling process,the algorithm is optimized to improve the computational efficiency without deteriorating the accuracy.In addition,with the spin-stabilized characteristic of CE-2 in its cruise phase taken into consideration,a spin stabilization correction model of the tracking data is constructed,which not only meets the requirement of data correction,but also can estimate the alignment of antenna.

(3)Carried out a study on the selection of integration center for CE-2 libration flight trial.The result shows that the Earth is most suitable for orbital prediction.A precise satellite ephemeris for CE-2’s flight trial is provided.The transformation relation between the spatial- fixed coordinate system and the rotation coordinate system is constructed.An orbital accuracy of 2–10 km in the whole flight process and 5 km for the stable flight phase are achieved based on an overlap comparison.

(4)Provided orbit support for CE-2’s asteroid exploration.Under the circumstances that only 13 days are left between the last two orbit maneuvers before the encounter,and an accuracy of better than 15 km is required for the target photographing,an orbit determination strategy incorporating pre-and post-maneuver tracking data is developed,which achieved an orbit determination accuracy of 10 km,and presented a calibration basis for velocity increment during the maneuver.

(5)Performed YH-1 Mars exploration simulation,and analyzed the major error sources a ff ecting the orbit determination accuracy.The YH-1’s possible orbit determination ability under the current tracking capacity is also studied.These researches can provide support for the subsequent Mars exploration.In addition,the Mars Express tracking data from Shanghai Astronomical Observatory are processed and calculated,and the position discrepancy between the orbit thus obtained and European Space Agency’s orbit is of the order of several hundred meters.This trial tested the accuracy of the observation model,dynamical model,and the ability of orbit determination software for deep space exploration.

Orbit Determination for CE-2 Libration Flight and Asteroid Exploration Trial

CAO Jian-feng
(Shanghai Astronomical Observatory,Chinese Academy of Sciences,Shanghai 200030)

10.15940/j.cnki.0001-5245.2016.01.012 博士学位论文摘要选登

†2013-07-07获得博士学位,导师:上海天文台胡小工研究员;jfcao@foxmail.com