基于语义相似度计算的航天标准关联度评价

随着航天领域各级各类标准编制数量的逐年递增，相关标准之间的交叉重复制定问题随之而来。为解决该问题，文中通过计算语义相似度的方法开展航天领域标准名称、标准范围及主要内容的关联度评价。算例分析结果表明，该方法可以有效评估标准间的关联程度。     

RTK model and positioning performance analysis using Galileo four-frequency observations

This paper proposes a real-time kinematic (RTK) model that uses one common reference satellite for the Galileo system with four frequency observations. In the proposed model, the double-differenced (DD) pseudorange and carrier phase biases among the different frequencies are estimated as unknown parameters to recover the integer features of the DD ambiguities among the different frequencies for ambiguity resolution and precise positioning. Analysis results show that the E5a, E5b, and E5 frequencies have virtually the same performance in terms of the positioning accuracy, observation residuals, and ratio values of ambiguity resolution. However, the E1 frequency performs worse than the E5a, E5b, and E5 frequencies. The RTK results for the combination of multiple frequencies are much better than those for a single-frequency observation, the coordinates’ standard deviation is improved about 20–30%, and the ambiguity fix time is improved about 10%.     

新型宽带宽波束圆极化卫星导航终端天线的设计与实现

卫星通信与卫星定位系统的应用发展，对终端设备天线的性能提出了更高的应用需求。为实现宽频带宽波束圆极化天线的设计，采用正交移相馈电网络对含有背腔的交叉偶极子天线馈电，实现了宽带圆极化单向辐射特性，同时利用磁电偶极子对交叉偶极子进行加载，展宽了天线的波束宽度，促使天线在50.7%的相对带宽内S11＜-10dB，在1.3~1.75GHz的频带内轴比小于3dB，轴比小于3dB的圆极化波束宽度可达180°，增益不小于6.6dB。经实测验证，所设计的天线具有宽频带宽波束特性，同时具有结构紧凑、性能稳定的优点，适用于卫星通信与导航终端系统。     

首颗自主地月转移微卫星“龙江二号”

本文对世界首颗独立完成地月转移、近月制动、环月飞行的微卫星“龙江二号”进行了介绍。首先阐述了龙江二号的任务目标和总体方案；然后重点分析了轨道设计与控制、复杂电磁干扰的标定与抑制、宽视场三维基线干涉测量等关键技术难点；接着回顾了任务的实施过程；最后详细介绍了低频射电探测仪、沙特光学相机和VHF/UHF通信模块与学生微型CMOS相机等有效载荷，并展示了上述载荷获取的初步成果。     

基于有限Fourier级数的航天器转移轨迹设计

针对航天器小推力转移轨迹的初始设计问题，利用基于三阶Fourier级数的设计方法实现了航天器小推力的多圈转移。同时，基于有限Fourier级数的形状法，对具有多个约束条件的小推力多圈转移轨迹进行了优化设计。选取了共面同轴同偏心率的初始和末端轨道位置，对所提出的方法进行了仿真验证。结果表明：与改进逆五阶多项式形状法相比，所提出的方法虽然增加了转移时间，但当转移圈数为5圈、有限Fourier级数的项数为10时，可减少将近75%的转移速度增量，同时大大减小了所需的最大推力加速度的值。     

直线模拟加载系统的研究进展与发展趋势

直线模拟加载系统是一种用于在实验室条件下模拟承载对象工作时所受直线负载力的半实物仿真系统，可用于模拟各类飞行器关键部件在工作过程中所受的气体阻力载荷。针对目前常用的机械式、电液式和电动式直线模拟加载系统，分析其基本加载原理和研究进展，结合自行研制的电动式直线模拟加载系统进行了深入探讨。针对多余力抑制方法的关键问题，详细论述了直线负载模拟器的结构补偿方法和控制策略。最后，展望了直线模拟加载系统的发展趋势，归纳了电动式直线模拟加载系统的高精度、大载荷发展方向。     

A New D-GCL for Unidirectional Motion with Large Displacement

Numerical simulations of unsteady flow problems with moving boundaries commonly require the use of geometric conservation law(GCL).However,in cases of unidirectional large mesh deformation,the cumulative error caused by the discrete procedure in GCL can significantly increase,and a direct consequence is that the calculated cell volume may become negative.To control the cumulative error,a new discrete GCL(D-GCL)is proposed.Unlike the original D-GCL,the proposed method uses the control volume analytically evaluated according to the grid motion at the time level n,instead of using the calculated value from the D-GCL itself.Error analysis indicates that the truncation error of the numerical scheme is guaranteed to be the same order as that obtained from the original D-GCL,while the accumulated error is greatly reduced.For validation,two challenging large deformation cases including a rotating circular cylinder case and a descending GAW-(1)two-element airfoil case are selected to be investigated.Good agreements are found between the calculated results and some other literature data,demonstrating the feasibility of the proposed D-GCL for unidirectional motions with large displacements.     

载人航天器体装太阳电池阵有效发电面积计算方法

航天器的发电能力与太阳电池阵有效发电面积成正比。针对圆柱形载人航天器，提出了一种体装太阳电池阵有效发电面积计算方法。首先，将太阳电池阵沿圆周方向划分为多个子阵，通过坐标变换，计算太阳矢量与每个子阵法线的夹角（即太阳入射角）；然后，将每个子阵面积与对应太阳入射角的余弦相乘并求和，得到体装太阳电池阵的有效发电面积。对不同轨道日照角、不同飞行姿态下体装太阳电池阵有效发电面积进行仿真分析，仿真结果表明:三轴对地姿态下平均有效发电面积为安装面积的25%~32%，通过固定角度偏航可将有效发电面积提高至安装面积的30%~44%。