精量穴直播晚稻的产量形成特性研究

采用2种水稻密度的精量穴直播种植方式与人工移栽种植方式,对比研究了精量穴直播晚稻的产量形成特性.结果表明,2种密度的精量穴直播的实际产量比人工移栽的实际产量显著增加,分别增产2.75%～10.48%.精量穴直播较人工移栽的有效穗数多、结实率高.在孕穗期和齐穗期,精量穴直播的水稻叶片叶绿素含量显著高于人工移栽的,同时其光合速率也较高.     

城市环境下北斗B-CNAV1电文RS-LDPC 级联编码方法

针对城市环境下卫星导航系统用户接收终端对电文编译码算法的低复杂度和抗衰落性能需求，以北斗导航系统B-CNAV1电文为改进对象提出了一种外码采用RS码、内码采用二进制LDPC码的电文级联编码方法。通过RS码提高电文对抗突发错误的能力，同时利用二进制LDPC码保证电文对抗随机错误的能力。采用LMS信道对城市接收环境建模，仿真结果验证了本文提出的RS-LDPC级联码与B-CNAV1电文64进制LDPC码具有相近的性能，同时大幅降低了算法复杂度，较好地实现了电文纠错性能和实现复杂度的平衡，提供了一种适用于城市环境的高性能、低复杂度电文编码方法。     

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.     

导航通信融合定义、方式与典型系统

随着人们对定位安全和定位准确性要求的提升，仅仅依赖卫星导航系统已经不能满足用户在各种复杂环境下的个性化定位需求，在此背景下，通信导航一体化技术应运而生。移动通信网络具有覆盖广、用户数量大和安全保密性好等优点，将通信系统作为卫星导航系统的有效补充，可以有效提升导航系统的性能。导航通信融合技术已经成为导航领域未来发展的重要技术热点，但目前缺乏清晰的导通融合架构和导通融合方式。从导通融合的技术层面进行划分，提出了波形融合、信息融合、硬件融合三种导通融合方式，分析了通信系统的辅助信息对导航系统精度和抗干扰能力的影响，以及两种典型的导通融合系统的优缺点，并对其未来的发展进行了展望，补充了导航通信融合技术的基础理论，对导通融合技术的发展具有重大意义。     

导航卫星时频系统发展综述

全球各大卫星导航系统近年来发展迅速,性能持续提升,其中卫星时频系统的高性能、稳定可靠和保持星间时频同步是系统实现高精度测量的基础.介绍了目前应用于各卫星导航系统的铷钟、氢钟、铯钟等星载原子钟和时频生成与保持技术的特点、发展概况及在轨应用情况.面向精度提升和自主运行能力提升的需求,分析了可能应用于下一代导航卫星的星载原子钟技术、星上时频生成与保持单元性能提升方法以及星间高精度激光时频同步技术,以支撑未来时频基准的天基化和我国综合PNT体系的建设.     

多站时差与方位交汇定位系统的适用性分析

为满足提高靶场武器试验任务效益、减轻定岗人员负担、裁减冗余设备的要求,对多站时差定位系统和方位交汇定位系统两种落点测量设备的原理、适用性、定位精度及影响因子进行比较分析,提出两种设备各自适用的试验任务类型以及相互替代的可能性,为参试测控设备配备的决策提供一定参考.     

Analysis on navigation accuracy of high orbit spacecraft based on BDS GEO and IGSO satellites

To make up for the insufficiency of earth-based TT&C systems, the use of GNSS technology for high-orbit spacecraft navigation and orbit determination has become a new technology. It is of great value to applying Geosynchronous Earth Orbit (GEO) and Inclined GeoStationary Orbit (IGSO) navigation satellites for supporting the navigation of high-orbit spacecraft since there are three different types of navigation satellites in BeiDou Navigation Satellite System (BDS): Medium Earth Orbit (MEO), GEO and IGSO. This paper conducts simulation experiments based on Two-Line Orbital Element (TLE) data to analyze and demonstrate the role of these satellites in the navigation of high-orbit spacecraft. Firstly, the spacecraft in GEO was used as the target satellite to conduct navigation experiments. Experiments show that for the spacecraft on the GEO orbit, after adding GEO and IGSO respectively on the basis of receiving MEO navigation satellite signals, the accuracies were improved by 7.22 % and 6.06 % respectively. When adding both GEO and IGSO navigation satellites at the same time, the accuracy can reach 16 m. In the second place, navigation and positioning experiments were carried out on three high elliptical orbit (HEO) satellites with different semimajor axis (32037.2 km, 42385.9 km, 67509.6 km). The experiments show that the number of visible satellites has been improved significantly after adding GEO and IGSO navigation satellites at the same time. The visible satellites in these three orbits were improved by 32.84 %, 41.12 % and 37.68 %, respectively compared with only observing MEO satellites.The RMS values of the navigation positioning errors of these three orbits are 25.59 m, 87.58 m and 712.48 m, respectively.     

Cooperative fault detection and recovery in the GNSS positioning of mobile agent swarms based on relative distance measurements

Relative measurements are exploited to cooperatively detect and recover faults in the positioning of Mobile Agent(MA) Swarms(MASs). First, a network vertex fault detection method based on edge testing is proposed. For each edge, a property that has a functional relationship with the properties of its two vertices is measured and tested. Based on the edge testing results of the network, the maximum likelihood principle is used to identify the vertex fault sources. Second, an edge distance testing...     

展开式薄膜遮光罩设计及重复展开精度研究

针对星敏感器的杂光抑制需求，设计了一种可以实现轴向展开的圆柱状展开式薄膜遮光罩，包括充气支撑管、薄膜蒙皮和挡光环，并完成了各构件的结构和材料设计。建立了薄膜蒙皮的运动学模型，分析了构型随着二面角的变化情况，验证了薄膜蒙皮采用hexagonal折纸样式可以完全折叠和展开。通过试验研究了遮光罩的重复展开精度，包括轴向和径向展开精度等。研制了遮光罩原理样机，并开展了地面展开试验，表明在充气支撑管的驱动下能够顺利展开，为大尺寸遮光罩的工程应用提供了新的技术方案。     

空天飞行器星敏感器安装误差在线标定方法

空天飞行器高动态、长航时的运动特性可能导致一体化安装的惯性/天文组合导航系统中星敏感器与惯导间产生安装误差角。设计了一种星敏感器安装误差角动态辨识方法,建立了星敏感器安装误差角模型,设计了基于天文角度观测的星敏感器安装误差角动态辨识方案,分析了不同机动飞行方式下星敏感器安装误差角的可观测度。仿真结果表明,所设计的基于卡尔曼滤波的动态辨识方法能够在飞行器机动过程中快速地对星敏感器安装误差角进行在线标定,对安装误差角的标定值可以达到实际误差值的85%以上,有效地提高了组合导航系统的精度。