电离层斜向传播异常信号特性的研究

在对固定电路电离层斜向传播特性的长期连续观测过程中,发现了大量异常斜测电离图.通过对电离层行波扰动情况下电波传播路径的仿真计算,分析了它对电离层斜向传播信号的影响,并利用斜向探测数据,讨论分析了确定行波扰动基本参数的方法.     

地球电离层对短波通信的影响分析

现代通信中,短波通信凭借发射功率小、传输距离远、建站速度快、机动性能好的特点,被广泛用于文电传输、语音电话、低速数据和静态图像业务场景,并在远程通信、应急通信中占据极其重要的地位。本文首先介绍了短波通信的特点,分析了其优势和不足;其次介绍了电离层产生的原因及分层;再次重点分析了电离层对短波通信的影响,并给出了附加电离层影响和最新研究方向;最后对全文进行总结。     

Tethered-Satellite system (TSS): Preliminary results on the active experiment core equipment

Summary The first Tethered-Statellite System (TSS-1) Electrodynamic mission has been launched aboard the Space Shuttle STS-46 on July 31, 1992, as a joint mission between the United States and Italy. A 500 kg spherical Satellite (1.6 m diameter) attached to the Orbiter by a thin (0.24 cm), conducting, insulated wire (Tether), has been reeled upwards from the Orbiter payload bay to a distance of 257 m when the Shuttle was at a projected altitude of 300 km. ASI, the Italian Space Agency, had the responsibility for developing the reusable Satellite, while NASA had the responsibility for developing the Deployer system and the Tether, integrating the payload and providing transportation into space. One of the main scientific goals of this first mission was to demonstrate the possibility of energy conversion from mechanical to electrical by using a long Tether orbiting through the Earth's magnetic field. ASI designed and developed an active experiment, referred to as Core Equipment, in order to carry out this demonstration. The experiment used two Electron Generator Assemblies (EGAs), located on the Orbiter, to re-emit into the ionosphere as an electron beam the electrons collected on the Satellite from the ionosphere. Each EGA had the capability to emit an electron beam with a programmed intensity from 10 mA up to 750 mA with a resolution of 3 mA. The perveance of each EGA was 7.2 microperv, and the beam energy, up to 3 kV, was provided as part of the e.m.f. induced across the TSS due to its motion through the Earth's magnetic field. Other instruments provided current, voltage, and ambient-pressure measurements, and allowed, via a series of switches, different electrical configurations of the TSS. Moreover, the Core Equipment provided a dynamic package, to study the TSS dynamics, as a first goal, and to verify the possibility of using the TSS Satellite as a platform for future experiments in the microgravity field. The expected voltage across the TSS was estimated to be 5 kV for a full Tether deployment of 20 km. During the mission, and due to unforeseenable reasons, the Tether deployment achieved was only of 257 m. Despite this limitation, there is evidence that the experiment was working nominally in the very low-voltage range across the TSS. This result strongly increases the confidence in the possibility of high-voltage operation of the electrodynamic TSS, as the Tether deployment will achieve the 20 km, as expected in the future reflight. The paper describes the experiment, and reports some preliminary results achieved during the first mission. Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992.     

掩星观测中电离层延迟对LEO卫星轨道误差的响应

从Haselgrove和Budden方程出发，模拟了GPS信号在电离层中的传播过程，利用GPS/MET实验中5组GPS和LEO卫星的实际轨道，分别模拟了无LEO卫星轨道扰动和有轨道扰动情况下的GPS信号在电离层中的传播，并生成了对应的电离层延迟量，以同步生成的模拟精度序列为参照，就掩星观测中电离层延迟对LEO卫星轨道误差的响应程度进行了估计和分析，初步结果显示：在掩星观测中，电离层延迟对LEO卫星轨道误差的响应比中性层延迟要弱得多，这可能同采用了电离层掩星观测的采样频率比中性层采样频率低两个数量级的技术手段有关。     

电离层斜向返回探测仪中主程序的设计与实现

使用面向对象的程序设计方法和可视化的开发工具 ,实现了电离层斜向返回探测仪的硬件控制、系统检测和数据的实时处理、显示与保存 ,并使软件具有较好的可移植性、可维护性和便于操作的特点。系统的开放性与灵活性使得在一台探测仪上实现多模式电离层探测成为可能     

电离层中Ba和SF6复杂释放的电波传播效应研究

单一点源方式的化学物质释放, 一般仅能形成较简单的电离层扰动结构, 对电磁波的影响频段和影响程度都较为局限, 难以对甚高频(Very High Frequency, VHF)以上频段的无线电波产生显著影响.文章提出了一种Ba和SF₆两种不同性质物质组合的复杂释放方法, 并利用水平分层介质传播理论, 分别以150、400、1 000 MHz三个典型频率为代表, 估算了VHF、超高频(Ultrahigh Frequency, UHF)和L频段常用卫星电波信号穿越扰动区后幅度和相位的闪烁情况.仿真结果表明, 复杂释放方法产生的电离层扰动结构能够对VHF以上波段信号传播产生显著影响, 且信号所受影响随着频率的提高而变弱.     

异常环境下GNSS接收机性能测试平台开发

为了验证全球导航卫星系统(GNSS)接收机在电离层异常环境下的性能是否满足相应的技术规范要求,文章设计开发了GNSS接收机性能测试平台;该平台主要由信号仿真器、轨迹发生器、误差仿真模块、待测接收机以及性能测试模块组成,可以仿真不同电离层环境下的卫星信号,从而测定接收机在不同环境下的性能;详细介绍了误差仿真模块与测试模块的设计方案,并利用信号仿真器与接收机进行测试验证,证明了该平台的有效性。     

一种去除电离层相位污染的方法

天波超视距雷达在传播过程中会受到电离层的相位干扰,这将导致信号频谱的展宽,电离层的相位污染影响了雷达的探测性能.介绍分析了一种简单有效的去除电离层相位污染的方法,并进行了仿真研究.结果表明,该方法具有稳健的去污染效果.     

VHF/UHF波段星载SAR电离层效应研究

星载UHF／VHF波段合成孔径雷达对隐蔽目标有很强的探测能力,在军事和民用中都有重要应用前景,但其实现受到电离层效应的严重限制。文中介绍了此研究方向的现状、主要问题、以及相应的解决方法。     

50年来的中国电离层物理研究

简要叙述了电离层物理这门基础学科的主要研究对象和领域,强调电熟层研究应作为整个日地２环境的一部分,从它与太阳和行星际空间、磁层、热层和中低层大气相互作用角度开展整体的研究,描述了电离层、磁层和中性大气耦合过程的基础图像。对我国电离层研究概况和现状,从探测、形态资料分析、模式建立、物理过程机制研究、新技术应用等几个方面作了介绍,并对某些重要的进展和特色加以简要的评述,同时也特别强调了大力加强我国电离