基于星载GPS的资源三号卫星精密定轨

资源三号卫星是我国首颗民用立体测图卫星,于2012年1月9日发射。卫星上配备有国产双频GPS接收机。利用非差双频GPS数据,基于卫星动力学原理和事后批处理定轨模式,采用30小时弧段（重叠弧长为 6小时） 对资源三号卫星进行了精密定轨,卫星位置重叠弧段精度平均为4.95cm。利用卫星激光测距（SLR）观测数据对星载GPS定轨结果进行了检核,检核精度优于4cm,无明显系统偏差。结果表明,该定轨精度完全能够满足资源三号卫星任务的要求。     

基于全球网和区域网SLR数据的低轨卫星定轨精度分析

卫星激光测距(SLR)是目前低轨卫星常用的定轨手段之一.文章以贾森-1(Jason-1)和"环境卫星"(EN VISAT)实测数据为例,讨论了不同弧段长度(1天、3天和7天)的全球网SLR数据对低轨卫星定轨精度的影响,分析了基于美国网、欧洲网和亚洲网等区域网SLR数据的低轨卫星精密定轨精度.检验定轨精度的参考轨道来自美...     

Jason-2 DORIS/SLR精密定轨

Jason-2卫星搭载了第三代DORIS接收机DGXX,与前两代接收机相比,DGXX在时效性和数据量上都有显著提高。本文研究了DGXX接收机输出的相位观测数据与传统的Doppler数据之间的转换,并通过内符精度比较、轨道重叠检验、独立轨道比较及卫星激光测距(SLR)检验分析了DORIS数据独立定轨和SLR+DORIS数据联合定轨精度及SLR在联合定轨中的贡献。另外,考虑到部分DORIS地面信标站气象数据可能不够精确或缺失会影响DORIS数据中对流层延迟模型改正精度,本文通过和实测气象数据比较分析了最新的气象参数模型GPT在DORIS定轨中的应用及其对定轨精度的影响。计算结果表明:GPT模型和DORIS地面信标站实测气象数据的定轨精度相当,在无实测气象数据情况下可利用GPT模型替代;DORIS数据独立定轨和SLR+DORIS联合定轨径向均能达到1cm精度,SLR+DORIS联合定轨精度略优于DORIS独立定轨精度,联合定轨中SLR的主要贡献是能降低解算参数中的湿天顶延迟和DORIS频率漂移的相关性、保持轨道精度的长期稳定性。     

低轨道卫星GPS精密定轨动力学方法的研究

结合低轨卫星简化动力学定轨算法,以及不同几何信息精度条件下的纯几何定轨和动力定轨精度比较,定量分析星载双频GPS实现精密定轨过程中的主要因素,得到星载GPS接收机性能设计所需的关键技术指标,为卫星精密定轨系统的顶层设计提供了科学合理的参考依据。     

利用GPS非差观测值的GRACE卫星精密定轨

参照GPS精密单点定位（PPP，Precise Point Positioning）模型设计了一种新的卫星定轨方法一组合星载加速度计测量数据和IGS提供的GPS精密星历及精密钟差数据进行低轨卫星的精密定轨。利用星载加速度计提高卫星受力模型准确性，使动力法定轨精度和可靠性都得到提升。同时，采用多种改正技术提高GPS非差观测值测量精度，保证最终高精度卫星定轨。本文建立了卫星定轨的轨道滤波模型，得出了有益的结论，即采用星载加速度计测量卫星非保守力可提高卫星定轨精度，在ITRF2000参考系下三轴精度优于18cm。这种方法不需要在全球建市基准观测站．定轨设备简单．费用低廉．     

基于星历拟合的短弧运动学定轨

当导航卫星在姿轨控和轨道恢复期间,传统的统计定轨理论难以实现精密定轨。首次提出 了基于10参数星历拟合的短弧运动学定轨方法,建立和推导了相应的理论模型和定轨解算方 法。其优点在于不仅能够反映卫星运动的物理学特征,提高了速度和轨道预报精度,而且不 需要累积数据,实现近实时快速计算,克服了动力学法定轨发散和单点定位无法获得速度信 息的不足。对COMPASS M-01导航卫星实测数据的处理表明,10分钟短弧运动学定轨的位置精 度优于10 m,速度精度为2 cm／s,预报5分钟轨道精度为15.02 m,满足了短弧跟踪条件下R DSS对轨道精度的要求,实现了卫星精密定轨。
     

HY-2卫星DORIS厘米级精密定轨

"海洋二号"(HY-2)卫星搭载了新一代DORIS接收机,可提供双频相位和伪距测量数据。针对HY-2卫星的RINEX 3.0格式的相位测量数据,研究了一种区别于传统相位观测数据处理的历元间差分处理方法,将相位观测数据转换为距离变化率观测数据,并进行相关误差修正,建立了HY-2卫星的宏表面力和经验力等摄动模型,基于动力学定轨原理实现了基于DORIS相位观测数据的精密定轨。利用HY-2卫星的DORIS实测数据进行定轨,初步计算结果表明,径向轨道误差优于2cm、三维位置误差约10cm,满足HY-2卫星应用的厘米级轨道精度需求。     

一种新的亚米级星载GPS伪距实时定轨方法

提出了一种新的星载GPS实时定轨方法,该方法以伪距作为主要观测值,通过在卡尔曼滤波模型中设置参数来吸收广播星历中的轨道误差与钟误差,从而实现亚米级精度的实时定轨。采用自主研制的实时定轨软件SATODS对GRACE-A卫星的实测数据模拟实时处理,结果表明:采用本文方法后,实时定轨的位置精度和速度精度(3DRMS)分别可达0.4~0.6 m与0.4~0.6 mm/s;相比于传统的伪距实时定轨精度可提高40%。     

北斗在轨卫星广播星历精度分析

为分析北斗广播星历的精度，采用激光测距资料和精密星历作为参考进行分析。由于没有提供BDS-3试验卫星精密星历，本文设计了3天弧段的DBS-3试验卫星精密定轨试验，解算的轨道精度约为50 cm，钟差精度约为2 ns。之后联合国际GNSS监测评估系统iGMAS发布的事后BDS-2精密星历，对BDS-3/BDS-2广播星历轨道、钟差精度进行分析。为准确评估广播星历轨道精度，还采用SLR观测数据作为外部检核手段分析北斗在轨卫星广播星历轨道精度。统计了广播星历轨道误差的1D RMS和钟差误差的STD，结果表明：多数钟差精度优于 10 ns ，轨道精度优于5 m。另外为分析广播星历卫星钟的时频性能，计算了在轨卫星钟差的频率稳定度、漂移率和准确度，试验结果表明：BDS-3试验卫星各项性能指标普遍优于BDS-2，频率准确度、频率漂移率和频率稳定性指标计算结果显示BDS-3卫星相对于BDS-2卫星分别提升了42.8%,22.5%,9.5%。     

单颗MEO卫星定轨中的二阶钟差模型

分析使用简化动力学和观测模型对单颗MEO卫星进行定轨时星地钟差参数化建模问题,建立了一个基于全弧段二阶钟差模型的定轨方案,分析了该钟差模型的精度,及其对定轨精度和卫星钟差预报精度的影响.结合对实测数据处理的结果说明,基于二阶钟差模型的定轨方案的定轨精度好于10m,相对于以往研究中对钟差分段建模的定轨方案精度明显较高,并且其对错误数据有着更好的抗差性.分析同时表明,使用二阶模型作钟差预报的精度好于20ns.     

Optimal low-thrust transfers between close near-circular coplanar orbits

Four types of optimal solutions are demonstrated to exist for transfers (time of flight is not fixed) between close near-circular coplanar orbits. One solution is realized with the help of fixed orientation of the propulsion system (PS) along a transversal in the orbital coordinate system. Another is reached at fixed orientation of the PS in the inertial coordinate system. The third and fourth types of solutions change the PS orientation in the process of executing the maneuver. Regions of existence are established for all types of solutions, and algorithms for determination of parameters of these maneuvers are suggested. The algorithms were used to calculate parameters of the maneuvers of transfer from a launching orbit to a working Sun-synchronous orbit, and to calculate the maneuvers of supporting the parameters of such an orbit in a specified range.     

CE5T拓展试验轨道精度分析

针对嫦娥5T服务舱(CE5T)拓展试验中的绕地大椭圆轨道，分析了轨道动力学演化趋势，通过测轨数据类型组合策略分析了统一S频段测量(USB)和甚长基线干涉测量(VLBI)在定轨中的贡献，得到了百米级的精密定轨精度；针对地月第二平动点(L2)绕飞轨道，分析了地心和月心积分的轨道动力学差异，制定了精密定轨的参数求解策略，得到了百米级的精密定轨精度；针对月球交会对接轨道的特点，选取三种不同的重力场模型定轨，比较了三者在轨道预报和数据拟合的差异，并与嫦娥3号(CE3)环月轨道的定轨精度进行比对，验证了不同重力场的适用范围，从计算精度和效率两方面制定了优化的定轨策略。     

Assessing the Risk of Orbital Debris Impact

A Space Debris Impact Risk Analysis Tool (SDIRAT) was developed and implemented to assess the orbital debris impact risk on a specified target in Earth orbit, in terms of flux, relative velocity, impact velocity, direction of the incoming particles, debris mass and diameter. Based on a deterministic approach, SDIRAT uses a realistic orbital debris population where each representative particle is identified by its rectangular coordinates (position and velocity) at a reference epoch. Using this information, some geometrical algorithms were developed and implemented to evaluate the contribution of each particle to the incoming flux. The position of the particle with respect to a specified target drives the selection criteria to reject, or select, it as a possible projectile. On the other hand, the relative velocity vector can be used to estimate the impact direction of the incoming flux. SDIRAT was conceived as a general tool for a variety of scenarios, such as low circular and elliptical orbits, up to the geosynchronous ring. This paper presents some examples of possible applications, including the computation of the incoming debris flux on SAX (low Earth orbit), SIRIO (geosynchronous orbit) and the IRIS upper stage (elliptical orbit). Other applications assess the impact risk for the Soviet Radar Ocean Reconnaissance Satellites Cosmos 1900 and Cosmos 1932.     

自由返回轨道的P平面参数快速设计方法

针对自由返回轨道求解过程中地心轨道类型变化造成的B平面参数方法计算失败问题,提出一种基于P平面参数的自由返回轨道快速设计方法。首先,基于轨道半通径参数的普适性,给出了不同轨道类型的P平面参数定义,建立了以P平面参数为求解目标量的自由返回轨道求解模型。其次,给出了基于P平面参数的自由返回轨道快速设计方法,在构建的瞬时地月惯性系下,以平面双二体自由返回轨道作为初值,实现了高精度力模型下的自由返回轨道快速求解。对8种构型自由返回轨道的设计结果表明,P平面参数具有类似于B平面参数的大收敛域,且有效解决了轨道类型变化对计算的影响,可直接应用于中国后续月球探测任务轨道设计。     

Low-energy Earth–Moon transfers involving manifolds through isomorphic mapping

Analysis and design of low-energy transfers to the Moon has been a subject of great interest for decades. Exterior and interior transfers, based on the transit through the regions where the collinear libration points are located, have been studied for a long time and some space missions have already taken advantage of the results of these studies. This paper is concerned with a geometrical approach for low-energy Earth-to-Moon mission analysis, based on isomorphic mapping. The isomorphic mapping of trajectories allows a visual, intuitive representation of periodic orbits and of the related invariant manifolds, which correspond to tubes that emanate from the curve associated with the periodic orbit. Two types of Earth-to-Moon missions are considered. The first mission is composed of the following arcs: (i) transfer trajectory from a circular low Earth orbit to the stable invariant manifold associated with the Lyapunov orbit at L₁ (corresponding to a specified energy level) and (ii) transfer trajectory along the unstable manifold associated with the Lyapunov orbit at L₁, with final injection in a periodic orbit around the Moon. The second mission is composed of the following arcs: (i) transfer trajectory from a circular low Earth orbit to the stable invariant manifold associated with the Lyapunov orbit at L₁ (corresponding to a specified energy level) and (ii) transfer trajectory along the unstable manifold associated with the Lyapunov orbit at L₁, with final injection in a capture (non-periodic) orbit around the Moon. In both cases three velocity impulses are needed to perform the transfer: the first at an unknown initial point along the low Earth orbit, the second at injection on the stable manifold, the third at injection in the final (periodic or capture) orbit. The final goal is in finding the optimization parameters, which are represented by the locations, directions, and magnitudes of the velocity impulses such that the overall delta-v of the transfer is minimized. This work proves how isomorphic mapping (in two distinct forms) can be profitably employed to optimize such transfers, by determining in a geometrical fashion the desired optimization parameters that minimize the delta-v budget required to perform the transfer.     

空间多目标拦截交会平台停泊轨道设计优化

针对空间多目标交会(拦截)平台停泊轨道设计问题,定义有效交会(拦截)区作为衡量平台交会(拦截)目标能力的指标,提出并建立了该类空间平台停泊轨道设计优化和分析模型,采用多岛遗传算法(MGA),以有效交会(拦截)区的最大化作为优化目标,以可交会(拦截)目标的数目和子飞行器轨道转移所需要的脉冲速度增量等为约束条件,对该类平台停泊轨道要素和子飞行器变轨时机进行综合设计优化。将上述模型和算法用于两空间平台设计中,一个是针对低轨2目标的交会平台,另一个是针对中轨3目标的拦截平台,得到合理的结果,表明所提出的设计优化模型以及选择的寻优算法是有效的。     

木星探测器轨道计算中的动力学

针对木星探测任务中轨道计算所面临的轨道动力学问题进行研究。首先，对木星探测轨道计算中涉及的时空参考系进行概述，比较了木星动力学时(TDJ)与质心动力学时(TDB)的差异；其次，对木星的定向参数模型及转换关系进行描述，给出了木星天球参考系与固联参考系的转换关系；再次，对木星探测器定轨计算中所需考虑的动力学模型进行讨论，提供了各类摄动加速度计算所需的公式；最后，对木星探测器JUNO的星历数据进行动力学拟合，检验了动力学模型的正确性。     

一种适用于椭圆轨道的新型偏航导引规律

多普勒特性是星载合成孔径雷达(SAR)数据处理中关键参数之一,对方位向性能以及成像精度都有着非常重要的影响。基于轨道动力学理论,该文简要论述了传统偏航导引方法和全零多普勒方法,并分别分析了它们应用于椭圆轨道时的不足之处,提出了一种新的适用于椭圆轨道的偏航导引方法。利用TerraSAR\|X卫星轨道参数,分别使用这三种方法进行了数值仿真,仿真结果表明,使用新的偏航导引方法后,多普勒中心频率被减小到不超过5Hz,比传统的偏航导引方法缩小了约一百倍,比基于瞬时圆轨道的全零多普勒方法缩小了超过5倍,表明了该方法的优势及有效性。     

A deterministic computational model for the two dimensional electron and photon transport

A deterministic (non-statistical) two dimensional (2D) computational model describing the transport of electron and photon typical of space radiation environment in various shield media is described. The 2D formalism is casted into a code which is an extension of a previously developed one dimensional (1D) deterministic electron and photon transport code. The goal of both 1D and 2D codes is to satisfy engineering design applications (i.e. rapid analysis) while maintaining an accurate physics based representation of electron and photon transport in space environment. Both 1D and 2D transport codes have utilized established theoretical representations to describe the relevant collisional and radiative interactions and transport processes. In the 2D version, the shield material specifications are made more general as having the pertinent cross sections. In the 2D model, the specification of the computational field is in terms of a distance of traverse z along an axial direction as well as a variable distribution of deflection (i.e. polar) angles θ where −π/2<θ<π/2, and corresponding symmetry is assumed for the range of azimuth angles (0<φ<2π). In the transport formalism, a combined mean-free-path and average trajectory approach is used. For candidate shielding materials, using the trapped electron radiation environments at low Earth orbit (LEO), geosynchronous orbit (GEO) and Jupiter moon Europa, verification of the 2D formalism vs. 1D and an existing Monte Carlo code are presented.     

卫星星座整网轨道确定分析与仿真

编队飞行的卫星或卫星星座对轨道确定自主性和精度提出了较高要求。针对这个问题,通过建立星座的轨道动力学模型和星间观测的测量模型,将星座中的星间观测数据和地面观测数据融合起来,将待估的卫星轨道参数和部分动力学参数进行适当的分类,研究卫星星座整网轨道确定的新方法,并在理论上分析了整网定轨方法能提高定轨精度的原因;最后采用自主开发的卫星星座整网轨道确定软件进行了仿真计算。计算表明,该方法能有效地减少对地面站的依赖,并较大幅度提高定轨时卫星绝对位置和相对位置精度。