基于GLONASS星历的预报轨道的误差分析

推导了协议地球坐标系下的卫星运动方程.通过分析由GLONASS(Global Navigation Satellite System)广播星历参数确定的卫星预报轨道的拟合精度,指出了摄动力模型的简化、积分器的选择,以及忽略了极移影响等因素是引起拟合误差的主要因素,其中摄动力模型的简化起最主要的作用.通过对卫星轨道运动方程积分30?min,可知由摄动力模型的简化、积分器和忽略极移影响等因素引起的拟合误差分别为0.827?m,0.224?m和0.025?m.要提高预报轨道拟合的精度,关键是要对摄动力简化特别是地球引力摄动高阶项的截断以及日月引力场简化造成的轨道预报精度损失加以控制.     

Earth–Moon low energy trajectory optimization in the real system

The problem of the Earth–Moon low energy trajectory optimization in the real system (the model defined by the JPL ephemeris DE405) is considered in this paper. First, this problem is investigated in the model of circular restricted three-body problem, since the fuel consumption is closely related to the Jacobi integral of the transfer trajectory, a method based on Jacobi integral is proposed and eight optimal trajectories are obtained. These optimal trajectories provide initial information (the flight time and the braking velocity impulse) to search the optimal low energy trajectories in the real system through optimization techniques. Considering the merit and drawback of particle swarm optimization and differential evolution algorithm in solving the space trajectory problem, an improved cooperative evolutionary algorithm is put forward. Result shows that the low energy trajectories in the real system are more fuel-efficient than the corresponding ones under the circular restricted three-body problem.     

GEO卫星广播星历的拟合参数设计

基于第一类无奇点要素的拟合参数和5°倾角旋转法,可以实现GEO发播电文与MEO和IGSO的电文一致性,但是没有完全避免数学奇异性.文章从无奇点要素的选取和主要摄动力的影响分析两方面出发,提出了一套16参数的GEO星历表示法.首先,利用同步要素描述卫星的星下点运动轨迹;其次,摄动参数中顾及了地球引力位田谐项引起的定点漂移.拟合试验表明,2h星历拟合的用户距离误差的均方根优于0.01m.     

一种大椭圆轨道卫星星历预报方法

针对大偏心率轨道长时间星历预报,稠密输出星历的低效率问题,提出了一种新的星历预报方法。该方法通过建立卫星摄动力模型,对卫星运动方程进行数值积分来获取卫星星历。该方法的轨道积分器以标准的8阶Adams-Cowell多步法为基础,针对大偏心率轨道的特性,在一个轨道周期的不同时段内采用不同的积分步长,同时引入了用于生成小间隔等间距卫星星历的插值公式。该方法降低了卫星运动方程右函数的计算次数,尤其适用于需要稠密输出卫星星历的情况。以STK(Satellite Tool Kit,卫星工具包)的HPOP(High Precision Orbit Propagator,高精度轨道预报)模型为验证基准,通过数学仿真校验了该方法的有效性和精度。算例表明,该方法在预报精度损失很小的情况下,计算时间远小于标准的多步法和HPOP模型。     

一种高精度实时GPS卫星钟差预测算法

为获得高精度实时GPS卫星钟差,文章提出一种基于多项式和最小二乘支持向量机(Least Squares Support Vector Machines,LS-SVM)相结合的钟差预报方法.该方法采用国际GNSS服务发布的超快速观测星历建模进行短期预报,首先根据卫星钟的物理特性用附有周期项的多项式模型进行拟合以提取趋势项和周期项,然后用LS-SVM对多项式拟合残差进行建模预报,最后将预报结果加上趋势项和周期项,得到最终的钟差预报值.试验结果表明,所提算法能够实时有效地对GPS卫星钟差进行预报,且精度优于超快速预报星历.     

Application of an evolution strategy in planetary ephemeris modeling

Classical planetary ephemeris construction comprises three major steps which are to be performed iteratively: numerical integration of coupled equations of motion of a multi-body system (propagator step), reduction of observations (reduction step), and optimization of model parameters (adjustment step). In future, this approach may become challenged by further refinements in force modeling (e.g. inclusion of much more significant minor bodies than in the past), an ever-growing number of planetary observations (e.g. the vast amount of spacecraft tracking data), and big data issues in general. In order to circumvent the need for both the inversion of normal equation matrices and the determination of partial derivatives, and to prepare the ephemeris for applications apart from stand-alone solar-system planetary orbit calculations, here we propose an alternative ephemeris construction method. The main idea is to solve it as an optimization problem by straightforward direct evaluation of the whole set of mathematical formulas, rather than to solve it as an inverse problem with all its tacit mathematical assumptions and potential numerical difficulties. The usual gradient search is replaced by a stochastic search, namely an evolution strategy, the latter of which is perfect for the exploitation of parallel computing capabilities. Furthermore, this new approach allows for multi-criteria optimization and time-varying optima. These issues will become important in future once ephemeris construction is just one part of even larger optimization problems, e.g. the combined and consistent determination of a generalized physical state (orbit, size, shape, rotation, gravity, $\dots$) of celestial bodies (planets, satellites, asteroids, or comets), and/or if one seeks near real-time solutions. Here, we outline the general idea and exemplarily optimize high-correlated asteroidal ring model parameters (total mass and heliocentric radius), and individual asteroid masses, based on simulated observations.     

基于自适应滤波的编队卫星实时相对定轨

提出基于自适应滤波的编队卫星实时相对定轨算法,利用2005-12-09—10两颗GRACE（Gravity Recovery and Climate Experiment）卫星的GPS（Global Positioning System）实测数据进行实时相对定轨试验计算,采用JPL（Jet Propulsion Laboratory）轨道对试验结果外部检核,结果表明:①自适应滤波相对定轨通过自适应因子,可以较好地平衡编队卫星的观测信息和相对动力学信息,其相对定轨结果精度优于Kalman滤波相对定轨结果;②自适应滤波相对定轨结果随着星间基线缩短而精度提高;③两颗GRACE卫星采用单频伪距和广播星历进行自适应滤波相对定轨,可以得到精度优于6cm的星间基线。     

一种24参数GPS广播星历方案研究

针对进一步降低广播星历拟合误差,文章提出了一种改进的GPS 24参数广播星历,并给出了广播星历的改进算法。实验结果表明:对于4h拟合长度,GPS全星座所有卫星、所有弧段的三维位置拟合性能均有显著提升,三维位置拟合误差的均方根值和最大值分别降低87%和47%,以三维位置拟合误差的均方根值作为评价指标,改进的GPS 24参数广播星历拟合精度达到毫米级。     

利用星载GPS数据进行海洋2A卫星快速精密定轨

针对海洋2A(HY2A)卫星快速精密定轨的需求,本文基于非差动力学方法,利用国际GNSS服务组织(IGS)和上海天文台GNSS数据处理中心（SHA）提供的超快速星历产品IGU和SHU,对HY2A卫星进行快速精密定轨研究。计算结果表明,以法国国家空间研究中心(CNES)提供的精密轨道作为参考轨道,联合超快速星历SHU和IGU的预报星历,可以确定径向厘米级精度的快速轨道。同时利用卫星激光测距（SLR）数据检核快速精密轨道,得到 SHU和IGU预报星历确定的快速精密轨道站星距方向残差的RMS分别为2.9和4.8cm。可见,利用SHU和IGU预报星历组合可以得到厘米级的快速精密轨道,对HY2A卫星的海洋环境监测和海洋灾害预警具有一定应用价值。     

两种GPS广播星历参数算法的比较

介绍了新GPS广播星历参数,分析了新旧GPS广播星历参数及其用户算法的区别,导出了卫星位置矢量对新GPS广播星历参数的偏导数,并与旧GPS广播星历参数偏导数进行了简要的比较分析.计算结果表明,两种GPS广播星历参数算法都能很好地描述MEO卫星的轨道特性,且广播星历参数拟合算法的精度损失仅为数厘米.