TC-1和Cluster对向阳侧磁层顶通量传输事件的联合观测研究

2004年2至4月期间,探测一号(TC-1)卫星和Cluster卫星有25次同时处在向阳侧磁层顶附近的磁鞘内,TC-1卫星在低纬区,Cluster卫星在中高纬区.利用这一期间两卫星探测到的27个通量传输事件(FTE),分析行星际磁场(IMF)横向分量BT={By,Bz}对磁层顶重联发生位置的影响,以及分量重联的观测事实,得到如下主要结果.(1)当IMF南向分量Bz占优势(|Bz|＞|By|)时,FTE大多(约占87.5%)能在低纬观测到,而当IMF By分量占优势(|Bz|＜|By|)时,则FTE大部分能在中高纬观测到(占84.2%);(2)很少观测到相关联的事件(关联事件指在低纬生成的FTE,向高纬运动中先后被TC-1卫星和Cluster卫星探测到的事件),表明在低纬形成的FTE可能大多沿磁层顶两侧滑向磁尾,只有少数可能运动到高纬地区;(3)中纬地区探测到的FTE大多是以分量重联方式产生于该区,而非来自磁赤道附近成对形成的FTE.      

Galileo系统与GPS卫星定位系统相位组合观测值的模型研究

在介绍Galileo系统空间信号的基础上,以模糊度保持整数为前提,给出了Galileo系统的4个频率载波与GPS L2载波的组合相位观测值的定义,并对有关误差影响加以分析,最后根据一定的组合标准论述了具有相应特性的组合观测值,并给出一些典型的组合.      

Android智能手机双频GNSS伪距差分动态定位性能分析

随着智能手机全球导航卫星系统(GNSS)天线和芯片从单频单模向多频多模快速发展,基于其所衍生出来的位置服务(LBS)应用极大地便利了大众用户的日常生活.然而受限于低成本、低功耗的信号接收与处理单元,手机在无增强信息的情况下仅依赖伪距单点定位难以为用户提供稳定、高精度的导航服务.因此,基于小米8手机(Mi8)的GNSS双频原始数据,采用非组合的双频伪距观测值、载波历元差分观测值和多普勒观测值构建了滤波定位模型,并引入伪距差分数据,以提升手机定位的连续性和精度.在较复杂环境下开展了行人和车载实验,实测结果表明:双频定位精度与单频相比提升了15％～30％,伪距差分定位精度和单点定位相比提升了5％～20％,行人和车载双频伪距差分定位的平面位置误差分别为0.65m和1.03m,基本满足手机用户在城市复杂环境下的高精度定位服务需求.     

BeiDou-3 orbit and clock quality of the IGS Multi-GNSS Pilot Project

Within the Multi-GNSS Pilot Project (MGEX) of the International GNSS Service (IGS), precise orbit and clock products for the BeiDou-3 global navigation satellite system (BDS-3) are routinely generated by a total of five analysis centers. The processing standards and specific properties of the individual products are reviewed and the BDS-3 orbit and clock product performance is assessed through direct inter-comparison, satellite laser ranging (SLR) residuals, clock stability analysis, and precise point positioning solutions. The orbit consistency evaluated by the signal-in-space range error is on the level of 4–8 cm for the medium Earth orbit satellites whereas SLR residuals have RMS values between 3 and 9 cm. The clock analysis reveals sytematic effects related to the elevation of the Sun above the orbital plane for all ACs pointing to deficiencies in solar radiation pressure modeling. Nevertheless, precise point positioning with the BDS-3 MGEX orbit and clock products results in 3D RMS values between 7 and 8 mm.     

灵巧型大孔径四反星敏感器镜头设计

星敏感器镜头是星敏感器姿态轨道控制系统的重要组成部分，具有相对孔径大、工作谱段宽、绝对畸变低的特点，针对这些特点，在四反射镜初始结构的基础上，分析了镜头探测能力和相对孔径的关系，明确了镜头设计指标，利用非球面反射镜强大的像差校正能力，优化设计得到了全反射4反星敏感器镜头。镜头焦距170mm，轴向长度50mm，镜头F数2，等效入瞳直径51.2mm，圆视场±2.25°。镜头工作波段可由膜系决定，无色差，空间频率35lp/mm处传递函数优于0.6，畸变优于0.01%，弥散斑直径优于13μm，系统15μm范围内能量集中度优于80%，渐晕系数小于0.95，该镜头可用于亚像素精度的飞船姿态轨道控制系统，为星敏感器导航光学系统设计提供了参考。     

大气环境监测卫星方案设计与技术特点

大气环境监测卫星(DQ-1)是国家民用空间基础设施中长期发展规划中的科研卫星，其运行于705 km高度的太阳同步轨道，装载大气探测激光雷达(ACDL)、高精度偏振扫描仪(POSP)、多角度偏振成像仪(DPC)、紫外高光谱大气成分探测仪(EMI)及宽幅成像光谱仪(WSI)等5台遥感仪器，通过主动激光与被动高光谱、多光谱、多角度、偏振等手段结合，实现对大气CO2、细颗粒物、污染气体、云和气溶胶等要素，以及对大气环境、水环境和生态环境等进行大范围、连续、动态、全天时的综合监测;卫星CO2柱浓度探测精度优于1 ppm，为国际最高。卫星入轨后各分系统工作正常，在轨测试结果均满足要求，能够进一步提升我国大气环境综合监测、全球气候变化和农作物估产、农业灾害等应对能力，推动生态环境、气象、农业农村等领域遥感应用。本文概述了DQ-1卫星的总体设计方案，总结了卫星的主要技术特点及创新点，介绍了卫星系统在轨测试情况，并对卫星的应用前景进行了展望。     

Refined modeling and experimental verification of a torque motor for an electro-hydraulic servo valve

The Permanent Magnet Torque Motor (PMTM) is the key electro-mechanical conversion device in an Electro-Hydraulic Servo Valve (EHSV). In this work, a refined model of a PMTM is developed, considering the non-working air-gaps between the upper or lower yoke and the armature, the fringing effect at the limiting holes, and the nonlinear permeability of soft magnetic material. Based on the refined model, the influences of various factors on the calculation accuracy of the magnetic flux at the pole surfaces of the armature and the output torque are investigated. For verifying the validity of the refined model, a Finite Element Analysis (FEA) of the PMTM is conducted, and a test platform is constructed. Compared with existing models, the refined model can better reveal the intrinsic mechanism of the PMTM, and its calculations are more consistent with the FEA results. The experimental results of the armature deflection displacement show that the refined model can accurately describe the output characteristics of the PMTM.     

芯片级光钟技术综述

芯片级光钟是一种基于热原子中光频跃迁的新型光钟,近年来随着光子集成技术、激光技术和微机电技术的发展,该类光钟可以实现较小的体积和较高的精度,有望广泛应用于对体积、质量、功耗和精度敏感的各种国防装备中.介绍了国内外芯片级光钟技术的进展情况,阐述了芯片级光钟的相关技术,包括基于双光子跃迁的光频标技术、微制造气室技术和微腔光频梳技术等,分析了影响频率稳定度和准确度的主要因素,最后对芯片级光钟面临的机遇和挑战进行了简要的展望.     

挠性空间机械臂伪速率增量反馈控制

针对空间机械臂平台中挠性机械臂与平台的耦合情况,采用伪速率反馈控制方法对机械臂平台的姿态控制系统进行设计和分析,使机械臂平台的姿态控制系统满足稳定性、控制精度等性能,并采用描述函数法对所设计线性控制系统的方法中,描述函数法是较为有效的方.η率脉冲调制喷气控制方案。本文在原有的伪速率脉.η的姿态控制系统进行稳定性分析。     

Comprehensive performance review of BDS-3 after one-year official operation

On July 31, 2020, the third generation BeiDou Global Satellite Navigation System (BDS-3) was officially put into service. Here we first reviewed the development history of BDS-3, and described the status of BDS-3 constellation, satellite signals, and ground tracking network. Then we expounded the 10 innovations in which BDS-3 differs from the other global satellite navigation systems. In addition, the latest service performance status of BDS-3 was displayed from a comprehensive perspective. The performance of BDS-3 was analyzed and evaluated from five aspects: constellation performance, observation data quality, spatial signal performance, PNT (Positioning, Navigation, and Timing) service performance, and precision positioning application. We used 14 indices to conduct comprehensive assessment of the BDS-3 service performance. Finally, the main direction of the next development of BDS was prospected.