电离层的探测与骚扰预报

电离层是指位于地面60km至1000km处的被电离了的大气层。电离层对电波传播的影响与人类活动密切相关,通过对电离层的探测可获取电离层物理特性参量随日、季节、年、太阳活动、地理环境等变化的分布、变化规律。本文主要讲述了电离层探测的方法、太阳活动对电离层的影响、电离层扰动对人类的影响、对电离层进行常规监测及骚扰预报的重要性以及电离层扰动与地震的关系。     

电离层误差对卫星导航系统测距误差影响分析

电离层延迟误差是单频接收机的主要定位误差之一。电离层延迟误差具有多变性,不易准确描述。本文探讨了几种常用单频接收机电离层延迟改正模型,Bent模型IRI模型、Klobuchar模型、NeQuick模型以及IGGSH模型。并利用单频GPS接收机实测数据统计分析各模型对定位误差的修正效果,为单频接收机用户选择合适的电离层改正模型提供参考。     

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。     

赤道地区L-波段电离层闪烁的形态特性

利用空间中心海南台站GPS电离层闪烁监测仪2003年7月到2005年6月两年间的观测资料,对太阳活动下降期间海南地区L-波段电离层闪烁特性进行了分析,主要分析结果表明:闪烁主要发生在日落后到午夜附近,其在春秋分附近出现的时间最早,集中出现于22LT左右,在冬季出现一定的时间延迟,在夏季出现的时间最晚,主要出现在午夜附近;闪烁的频率和强度春秋季明显增大,在冬季和夏季明显减小;闪烁主要发生于磁静日期间,这种情形主要集中于春秋分附近;电离层闪烁也可能发生于磁扰/暴期间,这种情形多发生于夏季和冬季期间.相对于地磁活动,太阳活动对闪烁活动的影响相对不明显.     

一种利用C/A码GPS接收机实现电离层延时双频改正的方法

电离层传播延迟是C/A码GPS导航定位的主要误差源之一。本文提出了一种利用C/A码GPS接收机实现电离层延迟实时双频改正的方法,并对实现这一方法的电路框图的原理进行了分析,从理论上说明了其可行性。     

新乡观测的电离层TEC和板厚的统计与建模研究

利用１９８２年至１９９０年在新乡接收ＥＴＳ－Ⅱ同步卫星１３６ＭＨｚ信标所取得的电离层总电子含量ＴＥＣ月中值和相应的Ｆ２层临界频率，计算了电离层板厚，分析比较了电离层板厚、ＴＥＣ和Ｆ２层临界频率的日变化、季节变化和太阳活动变化的差异，给出了板层随太阳活动的抛物关系，建立了新乡的电离层板厚模式，并与国际参考电离层和中国参考电离层模式的结果进行了比较。结果表明，本文的板厚模式预报的结果在太阳活动高年较国     

近距离高频单站定位技术

介绍了电离层参数的模式化预测方法和实时反演、重构技术,导出基于多层准抛物模型的电离层虚高公式,并给出基于Martyn等效理论的高频单站定位迭代算法,利用实测数据验证了算法在近距离上的实用性,即在约600～1200km范围内单站定位误差不超过5％。     

大气层对卫星导航信号的时延影响及修正

详细论述了电离层、对流层对卫星导航信号传播时延的影响，讨论了修正大气层时延影响的相对定位、延迟模型改正方法，详细分析了双频观测量电离层时延误差修正方法。     

提高增强系统电离层延迟改正数估计的方法研究

在对中国建立的 GPS 广域增强系统相关理论进行分析和研究的基础上,对广域增强系统的组成和基本原理进行了分析和研究,探讨了传统差分增强系统存在的缺点,在汲取已有研究成果和相关理论的基础上,研究了与电离层延迟改正数相关的理论和计算模型,研究了在单参考站情况下提高和改善电离层延迟估计的模型和理论方法,设计的算法模型成功实现了电离层延迟和频率间偏差的分离和估计,最后通过对观测数据的分析和仿真处理,验证了设计模型的合理性,取得了预期效果。     

利用人工神经网络重构区域电离层临界频率分布

提出了利用人工神经网络重构区域电离层临界频率分布的方案.对太阳活动高年和太阳活动低年白天的电离层临界频率分布进行了重构,讨论了站点分布对重构的影响,利用境外的历史资料对重构结果进行了验证.研究表明,拉萨站和重庆站对重构影响较大,兰州站和乌鲁木齐站对重构的结果影响较小.     

基于卫星双向法的时间比对系统构建与分析

为了实现高精度时间同步,采用了卫星双向法,对时间比对系统进行了构建,并对影响比对系统不确定度的因素进行了分析。卫星双向法即两个台站同步发送和接收时间信号,可消除传递路径引起的误差,如：卫星位置引起的误差、电离层和对流层修正误差、卫星转发器误差。分析表明：在所有不确定度影响因素中,发射与接收设备时延的不稳定性是最大影响分量,系统对时精度可控制在4ns以内。系统的构建为高精度时间同步提供了可操作的方法。     

GPS多普勒差分测速算法

全球卫星定位系统(GPS)多普勒单点测速技术是单GPS天线测姿技术的核心,但其测速精度易受卫星速度误差、卫星钟漂、电离层延迟、对流层延迟以及飞行器位置误差等因素的影响。针对上述问题,提出结合GPS地面基准站卫导观测数据,对机载GPS多普勒观测量进行双差处理,从而得到GPS多普勒双差方程。求解该双差方程,能够有效缓解上述不利因素的影响,得到精度更好的飞行器实时速度。半实物仿真计算结果与跑车实验计算结果都表明多普勒差分测速精度大幅优于多普勒单点测速精度。     

Performance of the GLONASS P-code at L1 and L2 frequencies

The transmission of satellite signals at two widely spaced frequencies allows correction of the ionospheric delay. Both GPS and GLONASS transmit such signals, and to date there have been no published dual frequency GLONASS studies. This paper shows the fundamental accuracy of the Leeds University multichannel GPS/GLONASS receiver. Details are then given of the processing methods that have been used to obtain the ionospheric group delay using GLONASS L1 and L2 P-code measurements. Examples of the measured delay are provided and compared with the GPS model. Navigation results are shown using the P-code phase at L1 only and with a combination of the L1 and L2 measurements. An analysis of the accuracy of the P-code pseudorange and navigation capability is presented.     

Degradation of navigational accuracy with Global Positioning Systemduring periods of scintillation at equatorial latitudes

The effect of ionospheric scintillation on navigational accuracy with the GPS (Global Positioning System) in the equatorial region is presented. The accuracy of position fixing with the GPS as indicated by the PDOP (position dilution of precision) factor is degraded when the raypath from the satellite shows deep fading. It is understood that navigation, particularly using a moderately sophisticated GPS receiver, in the equatorial zone will be severely affected during maximum sunspot number years     

De-noising of GPS Receivers Positioning Data Using Wavelet Transform and Bilateral Filtering

The need for precise position and navigation aids in many areas of industry is becoming increasingly apparent. There are many errors associated with the navigation solution of the global positioning system (GPS), including satellite ephemeris error, satellite clock error, ionospheric delay, tropospheric delay, multipath, receiver measurement error and selective availability (SA). Noise can create an error between centimeters to several meters. In this paper, the proposed technique applied to smooth noise for GPS receiver positioning data is based upon the analysis of wavelet transform (WT), bilateral filter (BF) and diffusivity function. The WT is a powerful tool of signal processing for its multiresolutional possibilities. BF is a local, non-linear and non-iterative technique. It is applied to approximation subband. We decompose a GPS positioning data into low-frequency and high-frequency components and apply BF on the approximation coefficients and diffusivity function on the detail coefficients at each decomposition level for data smoothing. A single-frequency and low-cost commercial GPS receiver manufactured by Rockwell Company is used to test our method. The experimental results on measurement data demonstrate the effectiveness of the proposed method; so that the total root mean square (RMS) error reduces to less than 0.29 m with SA on and 0.15 m with SA off using Daubechie wavelet.     

双模电离层闪烁监测系统设计与实现

伴随着北斗卫星导航系统的发展成熟,采用多个卫星导航系统可以获得更多的观测卫星进行电离层闪烁监测,极大提高监测的性能,因此利用GPS系统与北斗系统结合进行电离层闪烁监测成为趋势。文中介绍了所研制的GPS/BD双模电离层闪烁监测系统,它可以实时地监测分析GPS卫星L1/L2频点与北斗卫星B1/B2频点信号的电离层幅度闪烁指数和电离层相位闪烁指数,并可显示和存储各项观测数据。文中对电离层闪烁监测系统的硬件、系统嵌入式软件和电离层闪烁监测上位机软件的设计进行了介绍,对消趋势滤波器的设计和闪烁指数的计算进行了详细的讨论,并在最后给出了系统运行测试结果。     

GPS-Based Satellite Tracking System for Precise Positioning

NASA is developing a Global Positioning System (GPS) based measurement system to provide precise determination of Earth satellite orbits, geodetic baselines, ionospheric electron content, and clock offsets between worldwide tracking sites. The system will employ variations on the differential GPS observing technique and will use a network of nine fixed ground terminals. Satellite applications will require either a GPS flight receiver or an on-board GPS beacon. Operation of the system for all but satellite tracking will begin by 1988. The first major satellite application will be a demonstration of decimeter accuracy in determining the altitude of TOPEX in the early 1990's. By then the system is expected to yield long-baseline accuracies of a few centimeters and instantaneous time synchronization to 1 ns.     

GPS电离层闪烁实时监测系统的设计与实现

给出了一种用于电离层闪烁测量和显示的GPS电离层闪烁实时监测系统,它既能实时监测分析GPS信号的幅度闪烁和相位闪烁指数,也能自动存储闪烁发生时间段内的原始幅度和相位数据,用于对闪烁事件的详细分析.此外,对电离层闪烁的测量原理和闪烁指数的计算也作了详细讨论,这对利用我国北斗卫星信号测量电离层闪烁也具有指导意义.     

An Improved Ionospheric Delay Correction Metho d for SBAS

The existing ionospheric delay correction methods in Satellite based augmentation system (SBAS) were just for single constellation and over conservative. In this paper, we propose a new method to make more accurate ionospheric delay correction and tighter error bound orienting towards GPS and GLONASS. Considering that some Ionospheric pierce points (IPPs) are almost motionless, we make a filtering process to estimate the ionospheric delays at Ionospheric grid points (IGPs) to better reflect the ionospheric temporal variation. Then we conduct a simulation on ionospheric delay estimation at IGPs in dual constellations through planar fit method and filtering method. It can be concluded that the filtering method can bound the ionospheric delay correction error more tightly, simultaneously the ionospheric delay correction accuracy is improved a bit.