小卫星编队飞行队形设计与轨道要素确定

用两体相对运动的线性Hill方程进行了小卫星编队飞行队形的初步设计，并给出编队飞行中各绕飞小卫星轨道要素的确定过程，以空间圆形编队为例，在未考虑摄动情况下，通过仿真验证了Hill方程在小卫星编队队形初步设计中的有效性。     

分布式小卫星雷达平台沿航向排列研究

以小卫星群作为平台的天基分布式雷达具有多种用途。沿航向直线排列是分布式小卫星群的一种特殊轨道构形。由于阵列的等锥角线和等多普勒频率线重合，给SAR成像和地面运动目标检测的信号处理带来了极大的便利。受到地球自转的影响，多颗卫星采用同一轨道飞行并不能真正实现沿航向直线分布。为了克服地球自转的影响，现提出满足Hill方程的一种基本不消耗燃料的轨道设计，使多颗卫星飞行在不同的轨道上而实现真正的沿航向直线分布。数学分析表明它可以有效消除地球自转的影响。结合SAR成像的仿真结果证明了该方法的有效性。     

CCSDS Proximity-1及其在编队飞行小卫星群中的应用

讨论近距离空间链路协议 Proximity- 1的层次结构和传输帧 Version- 3构成 ,分析包括 CCSDS标准包和用户自定义数据的数据业务及定时业务。针对编队飞行小卫星群的星间数据交换和自主测控 ,对 Proximity- 1应用于小卫星群星间通信和星间测距作了探讨     

WVD用于SAR运动目标检测和成象的参数估计法

基于联合时间频率两维分布的研究方法，探讨了ＷＶＤ变换用于合成孔径雷达运动目标检测和成象的可行性，给出了能得到运动目标精细成象的参数估计方法，对多点目标和面目标情况下ＷＶＤ存在的问题进行了研究，计算机模拟验证了算法的有效性。     

星间相对测量在三星编队中的应用

以NASA新千年计划中的深空计划3为背景，使用星载类GPS的伪距和载波观测数据，研究利用编队卫星间相对测量，高精度自主确定三星编队星座相对状态的有关问题；研究星间相对测量各种可能的测量方案和可能达到的精度，验证这种星间相对测量技术是否能够满足深空计划3的系统要求．首先建立了三星编队星间相对测量系统的数学模型，然后利用星载高精度伪距和载波观测信息，对各种可能的测量方案进行仿真协方差分析；研究利用卫星姿态机动提供的几何信息，进行单差整周模糊度初始化的问题，讨论了卫星姿态机动方案；最后针对每一种测量方案给出了仿真结果和相关的结论。     

一种基于S-粗集副集的目标编群方法

针对目标编群中的动态要求,提出了一种基于S-粗集副集的目标编群方法.以空间群为对象,用一个双向奇异集合来描述一个空间群,用特征函数来刻画目标迁入迁出群的程度,在此基础上给出了空间群中发现新目标的编群步骤.通过战场态势评估中的一个具体应用实例,证实了该方法的可行性和有效性.     

Large scale structure of the universe

The current situation with the cosmological model and fundamental constants is briefly reviewed. Here, we concentrate on evolutionary effects of large-scale structure formation, in particular, the relationship with the quasar distribution and dynamics is discussed. We argue that groups of bright quasars with few or more than dozen of members within regions l _LS(100–150)h ^–1 Mpc found atz<2 may belong to concentrations of young rich clusters of galaxies, and thus be distant Great Attractors like the local GA or the Shapley concentration. These early large-scale galactic structures (i) provide a natural way to bias the distribution of Abell clusters, and (ii) suggest that the spectrum of primordial density perturbations is nearly flat on scales encompassing both the cluster and GAs,l=k ^–1(10,100)h ^–1 Mpc: _k ² k ³ P(k) k , =1 _–0.4 ^+0.6 , whereP(k) is the power spectrum of density perturbations.     

双星时差频差联合定位系统性能分析

针对基于到达时延(TDOA)/到达频延(FDOA)联合估计定位的双星定位系统,建立了时差频差联合定位的模型并给出了解算过程。对系统定位精度的理论分析和不同参数条件下的定位性能仿真计算结果表明,双星系统可实现对辐射源的高精度定位。频差和时差测量误差对系统性能均有影响,但前者的作用更显著。基线长度越大、卫星轨道高度越低,系统性能就越优。     

Effects of eccentricity of the reference orbit on multi-tethered satellite formations

The paper discusses the relevance of eccentric reference orbits on the dynamics of a tethered formation, when a massive cable model is included in the analysis of a multi-tethered satellite formation. The formations examined in this study are hub-and-spoke (HAS) and closed-hub-and-spoke (CHAS) configurations for in-plane and Earth-facing spin planes. Stability of the formations is studied by means of numerical simulation, together with the evaluation of the effects of eccentricity on tether elongation, agents relative position, and formation orientation and shape.     

Robust stationkeeping and reconfiguration of underactuated spacecraft formations

Feasibility of achieving reliable control for spacecraft formation keeping and reconfiguration without the need for thrust in either the radial or along-track direction is explored in this paper. Analysis of the linearized dynamics without along-track input indicates the presence of an uncontrollable eigenvalue at the origin. A nonlinear controller is designed to indirectly stabilize the uncontrollable modes to a stable manifold around the equilibrium. Conditions for robustness against unmatched uncertainties and disturbances are derived to establish the regions of asymptotic stabilization. The benefits of the proposed control method are also validated via numerical simulations to show that precise formation maintenance can be achieved by dealing with the issues of system nonlinearities, variations in initial conditions, and external disturbances, concurrently.