海南探空火箭试验和地面综合观测站简介(英文)

中国科学院原空间物理研究所(现空间科学与应用研究中心)1986年开始建设海南空间物理观测试验场. 火箭发射场位于海南儋县西面的富克镇(19°31’N,109°08E),拥有发射区、遥测站、雷达站、数据处理系统等设施.配套的地面观测设备是电离层数字式探测仪DGS—256,还将设立电离层偏振仪、电离层浑浊度仪等.地面设施除进行常规观测外,还可与探空火箭进行同步探测。在国际合作项目中,近期将同联帮德国共同利用VHF雷达进行电离层E层不均匀性研究。同美国、联邦德国、日本合作项目也正在酝酿中。 空间中心还正在海口建设一个地面综合观测站,将是中国自北至南在东经120°台站链上的一环。计划中的观测设备有电离层偏振仪、哨声仪、数字探测仪斜向接收机、电场测试记录仪等,并考虑筹建激光雷达、气辉观测和F—P干涉仪等项目。现已成立的中国科学院空间科学与应用研究中心海南探空部将负责规划、筹建和管理海口富克两处地面综合观测站的工作。此外,空间中心已与武汉大学空间物理系商议合作在三亚地区建立第三个观测点。 海南探空火箭和地面综合观测站的研究课题有:近赤道区中、高层大气结构、动力学和光化学过程的研究、电离层异常、漂移和运动的研究、低纬近赤道区大气声重波产生机制和传播特性、电离层和低中层、     

双地下物质变化区参数解算方法研究

经典天体测量仪器以铅垂线为基准测量本地的天文经纬度,因而能探测到本地铅垂线的偏转.本地铅垂线的偏转代表着测站周围重力场的变化,而这一变化与地下物质的再分布相关,由此有望帮助了解地下物质变化的情况.将本地的铅垂线偏转(Plumb Line Variation, PLV)与地下物质变化联系起来,建立了双质量体模型.在97°E–107°E和21°N–29°N范围内,考虑了3480个包含正、负质量变化(相对地质背景)的质量体组合算例,并利用差分进化(Differential Evolutionary, DE)算法进行了解算.解算得到的质量体相对于模拟值的位置误差小于米量级,质量误差小于10¹¹kg,结果精度较高.     

同波束VLBI双差分电离层电子总量抖动天顶方向统计特性研究

深空探测器和射电源的信号通过地球大气和电离层时相位发生抖动,对地面观测系统如VLBI(Very Long Baseline Interferometry)的测量精度产生极大影响.基于日本SELENE工程的两颗小卫星Rstar和Vstar 4测站长达1 yr的同波束VLBI观测数据,考虑视线方向不同仰角的影响并利用投影函数进行归一化处理,首次得到天顶方向的双差分电离层电子总量抖动统计数据.利用结构函数分析研究了6条基线的双差分电离层电子总量抖动的统计特性,并反演得到4个测站的统计特性.首次解算出天顶方向双差分电离层电子总量抖动的均方根与角距离的关系模型.6条基线天顶方向的双差分电离层电子总量抖动的均方根σ(单位为TECU)和角距离θ(单位为?)的关系模型为:σ=0.50928θ+0.39534,由基线反演出4个测站天顶方向的关系模型为:σ=0.36595θ+0.27974.     

1989年8月太阳事件的电离层效应

1989年8月太阳爆发了一系列的大活动,引起了多种日地空间和地球物理事件。在此期间武汉电离层观象台(30.5°N,114.4°E;磁倾纬度26.4°N)利用垂测仪观测到了明显的电离层扰乱。最低测量频率(f_(min))增高,甚至电离图上回波描迹全部消失,造成短波无线电通讯中断;突发Es增强,有时foEs超过仪器测量范围,大于     

无线电掩星技术探测电离层的误差分析研究

无线电掩星技术探测中性大气和电离层已经成为探索地球空间环境、科学研究以及天气预报的较为成熟的手段,如何更好地了解数据采集和计算处理过程中出现的误差和它们的作用机制,是现今该领域的研究热点。掩星探测技术的误差主要包括平台及星上测量误差和地面反演算法误差。基于EGOPS软件和自编程序,分别采用球对称电离层双查普曼(double Chapman)模型和非球对称的国际参考电离层(international reference ionosphere,IRI)模型,模拟GPS电离层掩星数据,从而分析星上的各种测量和平台误差源以及基于球对称假设的算法误差的影响,通过反演的电离层F2层电子峰值密度来进行误差统计。结果表明:一方面,几项主要的测量和平台误差对掩星反演电离层的影响均较小,其中,2mm以下的接收机噪声误差可以保证反演精度基本不受影响;钟稳定度在10~(-13)3~10~(-12)量级范围内时,接收机钟误差对反演的影响较小,可以满足基本的精度需求;局部多路径效应的模拟正弦波信号通过误差幅度和周期共同影响反演误差;20 cm以下的轨道误差可以确保电离层反演的精度,电离层反演时采用定轨误差为10 cm量级的现有轨道,则反演结果基本不受影响。另一方面,电离层的电子密度球对称假设是反演的主要误差源,可引起高达30%的峰值密度相对误差,其误差分布具有地方时、地磁纬度和季节特性:在冬季,日出(地方时4.00 h-8.00 h)和日落(16.00 h-20.00 h)时段误差最大,冬半球误差大于夏半球,中纬(30°-60°)地区比低纬(0°-30°)和高纬区(60°-90°)的反演结果好。在夏季,误差的分布在地方时、纬度尺度上都与冬季情况相反。     

电离层掩星反演的正则最大熵法

电离层掩星数据现已成为电离层观测数据的重要来源,对掩星数据的反演研究一直是掩星研究的热点.传统采用的改正TEC(1btal Electron Content)的Abel变换反演法为线性反演法,它会把测量误差带入反演结果中.为改善反演效果受测量误差的影响,引入两种非线性的反演方法一正则化和正则最大熵反演法.随后设计模拟试验,对3种方法进行验证、比较,得到正则最大熵反演法可以很好地减小测量误差的影响.     

基于多源GNSS观测数据的三维电离层研究现状及发展

近年来,随着GNSS (global navigation satellite system)技术的发展,利用地基和空基GNSS电离层探测的空间特征,形成了更加完善的三维电离层观测系统,获得了丰富的多源GNSS电离层观测数据,促进了电离层在理论模型、经验模型及同化模型方面的进展,同时,通过结合中性大气及等离子层等方面的研究,为极端气象、太阳活动及磁暴等事件的监测与物理机制研究提供了数据基础与研究手段。介绍了多模地基及星载GNSS电离层观测数据发展现状,并讨论了空基GNSS电离层观测数据在电离层顶部区域经验模型改进方面的进展。指出电离层经验模型可作为同化模型的初始场,而电离层理论模型可将其作为卡尔曼滤波的动力学部分,以通过同化算法利用多源数据重建或预测电离层,并阐述了多源及多模GNSS电离层观测数据的增加背景下电离层同化模型构建过程中新的要求与发展。最后,提出自适应格网与机器学习可成为电离层同化算法方面的新研究方向,以促进三维电离层研究。     

大型地面太阳望远镜选址云量调查

利用中国756个地面基本、基准气象站1961～2008年云量年值、月值数据集,分析全国地面太阳望远镜选址的云量条件,结果表明;40°N纬度带和藏西南地区,云量条件最优;其次是新疆西部和北部、东北北部和东部、青藏高原南部拉萨、江孜一带;西藏东部、四川西部及云南大部,云量条件居中;33° N以南,包括江南华南、青藏高原东南部林芝附近及四川盆地、重庆、贵州一带,云量条件较差.     

GIM在LEO卫星单频GPS定轨中的应用

电离层延迟误差是单频GPS(Global Positioning System)数据最主要的误差源,为提高基于单频GPS数据的LEO(Low Earth Orbiting)卫星定轨精度,必须消除/减弱GPS观测数据中电离层延迟影响.研究了全球电离层模型GIM(Global IonosphericMaps)在基于单频GPS伪距数据的低轨卫星运动学和动力学定轨中的应用,并通过估算电离层尺度因子的方法消除C/A码伪距观测量中电离层延迟影响.由于LEO卫星星载GPS信号受电离层延迟影响与卫星轨道高度相关,选取了轨道高度在300～800 km的CHAMP(CHAllenging Mini-satellite Payload)、GRACE(Gravity Recovery AndClimate Experiment)、TerraSAR-X及SAC-C等LEO卫星C/A码伪距观测量作为试算数据.CHAMP等卫星实测数据计算结果表明:以JPL(Jet Propulsion Laboratory)发布的GIM模型作为背景模型,通过电离层比例因子法能很好地消除C/A码伪距观测量中电离层延迟影响,提高LEO卫星运动学和动力学定轨精度,其中,CHAMP卫星轨道最低,受电离层延迟影响最严重,定轨精度提高最显著,分别为55.6%和47.6%;SAC-C卫星轨道高度最高,受电离层延迟影响最小,相应的定轨精度提高幅度也最低,分别为47.8%和38.2%.     

利用地基GPS网高精度实时监测电离层TEC

地基GPS网是监测电离层总电子含量(TEC)的有效手段之一,本文基于上海综合GPS应用网建立了高时空分辨率(0.5h×0.1°×0.1°)的垂直TEC格网模型,用于实时地监测该地区上空电离层TEC变化.该模型每30min给出一幅电离层TEC图,详细地反映了区域电离层分布和变化情况,并可用于实时地改正该地区单频GPS接收机的电离层延迟.     

TEC Compensated Inversion Method of Ionospheric Occultation

For the inversion of ionospheric occultation data, the Abel inversion method of calibrated TEC is usually adopted, but the spherical asymmetry of the real ionosphere will bring errors to the inversion result of electron densities. This paper studies a TEC compensated inversion method. By combining with a background field, this method may eliminate the effect of the horizontal variability of electron density on the TEC, and improve the applicability of the assumption of spherical symmetry as well as the inversion accuracy. Applying this method to the inversion of simulative occultation events, the result demonstrates that compared with the traditional Abel transform inversion, the TEC compensated inversion method can reduce the inversion error. Comparing the various background fields obtained in different ways, it is shown that the higher the coincidence level between the background field and the real field, the better the inversion result.     

Maximum Entropy Regularization Method of Ionospheric Occultation

With the increasing of applications of Global Positioning System (GPS), the research on the factors affecting the radio signals is becoming more and more important. One of the most significant effects on ionosphere monitoring is the ionospheric radio occultation (IRO), and the IRO data is now serving as one of the most important monitoring sources for the ionospheric measurements. Meanwhile the inversion of the occultation data is a popular topic. The traditional Abel inversion process through compensated total electron content (TEC) is a linear inversion method, thus it would transfer the measurement errors directly to the inversion results. In order to improve the occultation results, we introduce in this paper two nonlinear methods, namely the regularization method and the maximum entropy regularization method. Through designed simulative experiments, we verify and compare these three methods, and conclude that the maximum entropy regularization method can reduce significantly the influence of measurement errors.     

Mathematical modelling of ionospheric TEC from Turkish permanent GNSS Network (TPGN) observables during 2009–2017 and predictability of NeQuick and Kriging models

The present study examines the ionospheric Total Electron Content (TEC) variations in the lower mid-latitude Turkish region from the Turkish permanent GNSS network (TPGN) and International GNSS Services (IGS) observations during the years 2009 to 2017. The corresponding vertical TEC (VTEC) predicted by Kriging and NeQuick-2 models are evaluated to realize their efficacy over the country. We studied the diurnal, seasonal and spatial pattern of VTEC variation and tried to estimate by a new mathematical model using the long term of 9 years VTEC data. The diurnal variation of VTEC demonstrates a normal trend with its gradual enhancement from dawn to attain a peak around 09:00–14.00 UT and reaching the minimum level after 22.00 UT. The seasonal behavior of VTEC indicates a strong semi-annual variation of VTEC with maxima in September equinox followed by March equinox and minima in June solstice followed by December solstice. Also, the spatial variation in VTEC depicts a meaningful longitudinal/latitudinal pattern altering with seasons. It decreases longitudinally from the west to the east during March equinox and June solstice increases with latitude. The comparative analysis among the GNSS-VTEC, Kriging, NeQuick and the proposed mathematical model are evaluated with the help one way ANOVA test. The analysis shows that the null hypothesis of the models during storm and quiet days are accepted and suggesting that all models are statistically significantly equivalent from each other. We believe the outcomes from this study would complement towards a relatively better understanding of the lower mid-latitude VTEC variation over the Turkish region and analogous latitudes over the globe.     

A Study on the Reliability of the Ionospheric VTEC and Satellite DCB Derived from a Regional GPS Network

According to the requirement of high-precision satellite navigation, we have introduced the method for the quasi-realtime monitoring of variations of the regional ionospheric total electron content (TEC) and GPS satellite differential code bias (DCB), based on the dual-frequency carrier-phase smoothed pseudorange data obtained from a regional GPS network in China. Especially, we have studied the feasibility of retrieving DCB independently from the regional GPS networks with different sizes. For this purpose, 3 regional networks based on the countrywide GPS stations are investigated. The comparisons of the computed DCB and VTEC(vertical total electron content) with those of CODE(the Center for Orbit Determination in Europe) indicate that in order to realize a reliable quasi-realtime measurement of DCB by a regional network, there is a certain requirement on the size of the regional network, and that the relative accuracies of the quasi-realtime VTEC and DCB measured by using a Chinese GPS regional network can reach 2.0TECu and 0.25 ns, respectively.     

Agreements between ground-based and satellite-based observations

On the basis of records from meridian chains of magnetometers and the KRM inversion method, we have deduced a number of ionospheric quantities, including the distribution of the electric potential, field-aligned currents, the ionospheric currents and its equatorial counterpart and the relationship between the AE index and the cross-polar cap potential. In this paper, we examine the results thus obtained in the light of compatible data which are deduced from satellite observations. It is shown that both results agree fairly well, proving the validity of the polar ionospheric parameters deduced from both the ground-based and satellite-based data. Several important implications of the results are pointed out.     

A PIM-aided kalman filter for gps tomography of the ionospheric electron content

We develop the formalism to perform PIM-based stochastic tomography of the ionospheric electron content with a Kalman filter, in which the inversion problem associated with four-dimensional ionospheric stochastic tomography is regularized. For consistency, GPS data is used to select dynamically the best PIM parameters, in a 3DVAR fashion. We demonstrate the ingestion of (10S and GPS/MEI) GPS data into a parameterized ionospheric model, in order to select the set of parameters that minimize a suitable cost functional. The resulting PIM-fitted model is compared to direct 3D voxel tomography. We demonstrate the value of this method analyzing IGS and GPS/M ET GPS data, and present our results in terms of a 4D model of the ionospheric electronic density.     

The Application of GIM in Precise Orbit Determination for LEO Satellites with Single-Frequency GPS Measurements

With the precise GPS ephemeris and clock error available, the iono- spheric delay is left as the dominant error source in the single-frequency GPS data. Thus, the removal of ionospheric effects is a ma jor prerequisite for an improved orbit reconstruction of LEO satellites based on the single-frequency GPS data. In this paper, the use of Global Ionospheric Maps (GIM) in kine- matic and dynamic orbit determinations for LEO satellites with single-frequency GPS pseudorange measurements is discussed first, and then, estimating the iono- spheric scale factor to remove the ionospheric effects from the C/A-code pseu- dorange measurements for both kinematic and dynamic orbit determinations is addressed. As it is known that the ionospheric delay of space-borne GPS sig- nals is strongly dependent on the orbit altitudes of LEO satellites, we select the real C/A-code pseudorange measurement data of the CHAMP, GRACE, TerraSAR-X and SAC-C satellites with altitudes between 300 km and 800 km as sample data in this paper. It is demonstrated that the approach to eliminating ionospheric effects in C/A-code pseudorange measurements by estimating the ionospheric scale factor is highly effective. Employing this approach, the accu- racy of both kinematic and dynamic orbits can be improved notably. Among those five LEO satellites, CHAMP with the lowest orbit altitude has the most remarkable improvements in orbit accuracy, which are 55.6% and 47.6% for kine- matic and dynamic orbits, respectively. SAC-C with the highest orbit altitude has the least improvements in orbit accuracy accordingly, which are 47.8% and 38.2%, respectively.     

An Emulation Research on the Radio Occultation Exploration of Martian Ionosphere

The technical system of the Sino-Russian joint satellite-to-satellite Mars ionosphere occultation is analyzed and introduced. The analogue computation of the observed values of the radio waves of the ionosphere occultation event is carried out by adopting the three-dimensional ray tracking method and the electron density profile inversion is conducted by means of the simulated occultation observational data, with the result showing that the emulation algorithm is reliable. By taking advantage of the emulation method the case computation and analysis of the inversion errors caused by the observational error of the occultation radio wave phase and the satellite orbital error are respectively carried out, and it is obtained from the result that the effect of the phase measuring error of the 5% circle on the result of the daytime ionosphere occultation exploration may be neglected, while the absolute error of the night electron density measurement is less than 4 × 108 m^?3, and the main effect of the satellite orbital error on the occultation leads to the lifting or falling of the ionospheric height. The result shows that the technical system of the Sino-Russian joint Mars ionosphere occultation exploration is advanced. It can be expected that the high accuracy electron density profile is obtained and the technical system can be applied to the exploration of the lunar ionospheric environment.