用蒙特卡罗方法计算2004年7月电子暴事件对星上分系统的内部充电效应

在太阳的剧烈爆发事件期间,空间环境中的带电粒子能量和通量都得到显著增强,有时使卫星介质发生严重的内部充电而导致星上系统发生故障.但由于粒子与介质相互作用的过程较为复杂,以往一般采用粒子射入介质的经验公式对带电粒子在介质中的沉积进行模拟计算,而近年来蒙特卡洛方法逐渐成为能够进行更准确模拟的有效办法.本文以2004年7月底至8月初的空间天气事件为例,用基于蒙特卡罗方法的GEANT工具包模拟空间高能电子在卫星分系统的印刷电路板（PCB）中的沉积,计算由于内部充电效应造成的PCB内部电场的强度.利用该计算方法,并基于此次事件期间GOES卫星对空间高能粒子环境的监测数据,得到的计算结果表明这次事件期间的空间高能电子暴可能使星上介质发生显著的内部充电,并可能是此期间在轨航天器上发生的一些仪器运行异常的原因.本文采用的蒙特卡罗方法计算内部充电效应方法可以应用于对复杂位形和结构的星上系统的计算,结果可作为卫星抗辐射设计的参考,以有效应对灾害性的空间天气事件.     

卫星遥感热红外辐射信息与云南永胜6.0级地震

对利用气象卫星遥感热辐射信息进行地震监测预报时必须考虑的不同星号、不同通道、不同时段及不同分辨率等问题进行了讨论，并为此进行了多种应用方法的计算和比较，介绍了相应的气象卫星遥感热辐射信息资料处理方法及研制的计算软件。在此基础上，对200l年10月27日云南水胜6．0级地震前的卫星遥感热辐射信息及其异常的时空分布特征进行了分析和研究。研究表明：地震前一个月左右，从计算结果中可以发现明显的高频次异常图像；同时，在空间分布上呈现出“大范围减温异常一大范围增温异常-地震”这样一个过程。     

卫星介质深层充电的计算机模拟研究

卫星介质深层充电效应是诱发地球同步轨道卫星运行故障和异常的重要因素之一,文中介绍了介质深层充电的物理机制,给出了初步的物理模型和计算机模拟方法,该模型的模拟计算结果与欧空局的深层充电分析软件DICTAT的计算结果吻合得很好. 深层充电导致的最大电场总是出现在介质的接地侧,因此,介质的接地侧是发生放电的危险区域;对于典型的外辐射带高能电子能谱情况,介质的充电时间为小时量级.     

风云二号03批卫星空间环境监测器

风云二号卫星以自旋稳定方式工作于地球静止轨道,自1997年以来,01批与02批卫星空间环境监测器成功的业务运行获得了大量重要探测成果;在继承01批与02批产品研制技术的基础上,提高了03批空间环境监测器的探测性能指标和技术设计,更好地满足空间天气预警业务发展的新需求.本文对风云二号03批卫星空间环境监测器的新设计、关键技术研制和发射前的定标试验结果进行分析和讨论.     

On the prediction of relativistic electron fluence based on its relationship with geomagnetic activity over a solar cycle

A study has been carried out to determine the relationship between high energy relativistic (>2 MeV) electron fluence and auroral zone geomagnetic activity for a solar cycle. Data for 1987–1997, spanning Solar Cycle 22, were used in the study. The relativistic electron fluence data were based on fluxes observed by the GOES geosynchronous satellites. The geomagnetic data were the DRX indices derived from a Canadian magnetic observatory located in the auroral zone at Fort Churchill, near the footprint of field lines passing through geostationary satellites. This work, based on data from a solar cycle, confirms earlier findings using limited data from segments of a solar cycle of enhancement in fluence 2–3 days after increases in geomagnetic activity, and shows the cycle dependence of fluence with respect to geomagnetic activity. This study underlines the influence of recurrent coronal holes on fluence level as well as the possible role of Pc5 magnetic pulsations as an electron acceleration mechanism, and highlights the predictability of fluence from ground geomagnetic data. A fluence prediction algorithm can now solely be based on derived expressions relating fluence and DRX. Thus, a simple fluence prediction scheme can easily be implemented to provide a 2–3 day advance warning of space weather conditions hazardous to geosynchronous satellites, since during days of high fluence, the likelihood of internal charging in a satellite is high, with possible discharges that could result in satellite operational anomalies. For verification purpose, daily values of fluence for 1997–2000 and for January 1994 were postcast using the derived expressions. The postcast values were validated, and the results give credence to the fluence prediction scheme.     

基于风云二号X射线监测数据的短波通讯可用频率预报

介绍了风云二号气象卫星空间环境探测资料的处理、显示技术。研究了如何利用风云二号X射线探测数据计算短波通讯最低可用频率及电离层D层的电波吸收,并设计了一个基于风云二号X射线探测数据的短波通讯最低可用频率经验预报模式。     

磁暴期间辐射带电子相空间密度的多卫星联合观测

地球外辐射带是一个高度动态变化的空间环境,辐射带电子通量的变化在磁暴期间尤为明显.要分析潜在的电子动态变化机制,需要排除绝热效应产生的影响.在以三个绝热不变量组成的相空间坐标中,利用相空间密度(PSD)可以反映电子的真实加速和损失情况.本文详细分析两颗范艾伦卫星和三颗GPS导航卫星在2013年3月的同步电子通量观测数据,发现在3月17日磁暴期间,当太阳风动压增大、行星际磁场南向时,辐射带电子通量会发生骤降.进一步将电子通量转换成电子相空间密度并利用不同第一、第二绝热不变量(μ,K)组合条件下PSD径向分布的差异性,深入探究磁暴期间辐射带电子的动态变化机制.结果表明:磁暴初期由于电子的局地加速导致PSD不断上升;磁暴主相期间,由于磁层顶阴影效应以及伴随的向外径向扩散损失导致PSD快速降低;位于不同空间位置的多颗卫星观测为明晰辐射带电子动态物理过程提供了重要的便利.     

地球空间双星探测计划

地球空间双星探测计划包括两颗小卫星,将分别运行于目前国际上地球空间探测卫星尚未覆盖的近地赤道区和近地极区.双星计划的主要科学目标是用高分辨率的仪器在近地空间的主要活动区探测场和粒子的时空变化;研究磁层亚暴、磁暴和磁层粒子暴的触发机制及磁层空间暴对太阳活动和行星际扰动的响应过程;建立地球空间环境的动态模式.为了实现科学目标,赤道卫星和极区卫星上各载有9台探测仪器.赤道卫星的轨道是:近地点550km,远地点60000km,倾角约2.5°;极区卫星轨道是:近地点350km,远地点25000km,倾角约90°左右.为了使双星计划与欧空局ClusterⅡ相配合,赤道卫星计划于2002年12月发射,极区卫星计划于2003年6月发射.双星计划与ClusterⅡ相配合,可形成地球空间6点探测计划,这将成为21世纪初国际上重要的地球空间探测计划.     

Regularities in solar high-energy particle fluxes: Experimental data and probabilistic model

The currently available experimental data, among which the series of particle flux measurements on satellites are of crucial importance, have revealed a number of regularities pertaining to solar cosmic rays (SCRs). Based on these regularities, we have developed a probabilistic model of particle fluxes. This model not only provides a basis for determining radiation conditions in space flights and space weather impacts but also allows such situations as the occurrence of extreme SCR events in the quiet-Sun period in 2005–2006 to be predicted.     

Solar wind and magnetosphere plasma diagnostics by spacecraft electrostatic potential measurements

Several satellites (GEOS-1, GEOS-2, ISEE-1, Viking and CRRES) carried electric field experiments on which probes were driven by a current from the satellite to be close to the plasma potential. The potential difference between an electric field probe and its spacecraft (with conductive surfaces) can be used to determine the ambient electron density and/or electron flux with limited accuracy but with high time resolution, of the order of 10–100 ms. It is necessary for the development of this diagnostic method to understand the photoemission characteristics of probes and satellites. According to the electric field experiments on the above-mentioned satellites, all materials develop very similar photoemission properties when they are beyond the influence of atmospheric oxygen. The photoelectron yield steadily increases over the first few months in space and reaches values well above those measured on clean surfaces in the laboratory. The method can be used for solar radiation levels corresponding to distances from 0.4 to 5 AU from the Sun.     

地球电子外辐射带的数据同化建模与分析

地球电子外辐射带对太阳与地磁活动呈现高度动态变化的响应,了解外辐射带的全球动态变化过程对于近地空间粒子辐射环境的理解认知和预测预报具有重要意义.基于卡尔曼滤波数据同化方法,本文利用范阿伦A星、B星和GOES-13和GOES-15四颗卫星的辐射带电子观测数据,分别利用三种不同维度的辐射带物理模型,将观测结果与数值结果有机融合,对2013年3月地球外辐射带电子通量的径向分布与变化进行数据同化分析.结果表明,考虑了磁层波动与辐射带电子共振作用引起的径向扩散、投掷角扩散以及能量扩散过程的三维同化模型可有效、合理地重现外辐射带电子通量的径向分布.本文进一步利用该三维同化模型对2013年一整年外辐射带电子的相空间密度分布进行重构与分析,得到了不同绝热不变量和不同地磁活动条件下电子辐射带的时空演化过程,从而为深入理解外辐射带电子的变化过程和动力学机制提供了强有力信息.通过分析同化过程中的新息矢量以及度量同化过程中观测数据在多大程度上修改了物理模型结果,还有助于定量分析现有辐射带物理模型中的源项和损失项的相对贡献以及可能忽略的物理机制或过程.     

基于Swarm卫星数据的一次地震电离层现象辨识

为进一步探索基于多颗卫星观测数据的地震电离层现象识别,利用Swarm星座三颗卫星观测的电子密度数据和磁场数据,对已报道的2017年11月12日伊朗MW7.3地震震前第9天震中附近的一次地震电离层扰动现象进行辨识。通过分析三颗卫星相邻轨道的电离层扰动特征,获得了异常扰动存在的空间范围;利用Swarm星座三颗卫星轨道的时间和空间差异,计算出异常扰动在空间中可能的传播特征;使用同步观测的磁场数据判断其电磁辐射特性。最终根据现有对地震电离层耦合的认知,并结合分析的结果,认为该扰动为非震源发出的声重波扰动,非沿纬向传播的电离层行波扰动,非同步电磁辐射引发扰动,而是与伊朗MW7.3地震孕育活动无关的一次高纬度强烈电离层活动所引起的扰动变化。     

地震电磁卫星观测物理量简介

地震引发电离层扰动反映在某些特定的物理量上已经得到人们的共识,但其中哪些量反映的特征最明显,最有利于提取地震电离层异常仍然不明确,需要进一步的深入研究。本文介绍了法国的DEMETER、乌克兰的SICH-1M、意大利的ESPER IA及俄罗斯的COMPASS-2等几个主要地震电磁卫星的观测物理量,以资参考。     

Radiation belt modelling in the framework of space weather effects and forecasting

The Earth's trapped radiation belts were discovered at the beginning of the space age and were immediately recognised as a considerable hazard to space missions. Consequently, considerable effort was invested in building models of the trapped proton and electron populations, culminating in the NASA AP-8 and AE-8 models which have been de facto standards since the 1970s. The CRRES mission has demonstrated that the trapped radiation environment is much more complex than the static environment described by the old models. Spatial and especially temporal variations were shown to be much more important than previously thought, and to require more complex models than those in use at that time. Such models are now becoming available, but they are as yet limited in spatial and temporal coverage. It is vital to coordinate future modelling efforts in order to develop new standard models.The lack of standardisation of radiation belt models complicates their use in engineering applications where particle fluxes are needed as input to radiation effects models. ESA's SPace ENVironment Information System (SPENVIS) provides standardised access to models of the hazardous space environment, including but not limited to radiation effects, through a user-friendly World Wide Web interface. The interface includes parameter input with extensive defaulting, definition of user environments, streamlined production of results (both in graphical and textual form), background information, and on-line help. The system can be accessed at the WWW site http://www.spenvis.oma.be/spenvis/. SPENVIS Is designed to help spacecraft engineers perform rapid analyses of environmental problems and, with extensive documentation and tutorial information, allows engineers with relatively little familiarity to produce reliable results. It has been developed in response to the increasing pressure for rapid-response tools for system engineering, especially in low-cost commercial and educational programmes.     

基于贝叶斯方法的深层充电效应风险模型评估

高能电子穿透航天器并在其内部沉积电荷从而引发深层充电效应,是导致卫星故障的重要因素之一.为了评估深层充电效应诱发卫星异常的风险,本文基于贝叶斯方法,使用一颗地球同步轨道卫星的异常数据和GOES-8卫星的电子通量探测数据,计算了不同能量阈值及累积时间的电子注量、不同卫星配置下模拟仿真的沉积电荷,并分别与卫星异常建立一系列概率风险模型.本文从模型中随机抽样得到模拟异常,并与实测异常构造混淆矩阵以评估模型拟合优度,结果表明1.0MeV电子3日累积注量-卫星异常概率风险模型为该卫星最优模型.本文利用最优模型对该卫星深层充电效应风险进行了计算,在1.0MeV电子3日累积注量达到2.0×10~(10)cm~(-2)·sr~(-1)时,该卫星发生深层充电异常的平均后验概率为27%,且95%最小可信值为22%.根据最优模型,我们对该卫星最可能导致异常的部件的材料和结构等特征做出了推断.     

Remote sensing of snow and ice / La télédétection de neige et de glace

Abstract

Monitoring of snow and ice on the Earth's surface will require increasing use of satellite remote sensing techniques. These techniques are evolving rapidly. Active and passive sensors operating in the visible, near infrared, thermal infrared, and microwave wavelengths are described in regard to general applications and in regard to specific USA or USSR satellites. Meteorological satellites (frequent images of relatively crude resolution) and Earth resources satellites such as Landsat (less frequent images of higher resolution) have been used to monitor the areal extent of seasonal snow, but problems exist with cloud cover or dense forest canopies. Snow mass (water equivalent) can be measured from a low-flying aircraft using natural radioactivity, but cannot yet be measured from satellite altitudes. A combination of active and passive microwave sensors may permit this kind of measurement, but not until more is known about radiation scattering in snow. Satellite observations are very useful in glacier inventories, correcting maps of glacier extent, estimating certain mass balance parameters, and monitoring calving or surging glaciers. Ground ice is virtually impossible to monitor from satellites; ice on rivers and lakes can be monitored only with very high-resolution sensors. Microwave sensors, due to their all-weather capability (the ability to see through clouds) provide exciting data on sea ice distribution. Analysis of digital tapes of satellite data requires the archiving and scanning of huge amounts of data. Simple methods for extracting quantitative data from satellite images are described.     

Dust levitation and transport over the surface of the Moon

Exposed to space plasma and solar radiation, electrostatic potential may build up in the lunar regolith, leading to a wealth of dust phenomena, including levitation, oscillation, and transport over the surface. Based on plasma sheath theory, the global near-surface plasma environment is modeled, and the dynamics of charged dust are investigated. Results show that sub-micron sized dust particles can be levitated by the electric field over the surface, forming a dust belt that changes in position and thickness depending on the solar zenith angle. On the dayside of the Moon, stably levitated particles are about ten times smaller, and collect in a thinner belt closer to the surface than do those on the nightside. Although the size and charge of stably levitated dust particles are dependent on ambient plasma conditions, initial charge and velocity, which are closely related to the dynamics of dust particles including charging, oscillation, and damping, will determine whether, or not, a particle can attain stable levitation. Horizontal electrostatic dust transport near to the terminator region may lead to net deposition of dust from the dark into the sunlit hemisphere. Finally, because of different charging processes that result due to rotation of the Moon, before precipitation, dust particles in the dusk terminator region may be transported much longer distances and oscillate to much higher altitude than these in the dawn terminator.     

Two examples of spectral approach to source depth estimation in gravity and magnetics

Fourier transformation of gravity and magnetic anomalies from space to the frequency domain provides aready method for source depth estimation since progressively deeper sources are indicated by the lower frequency components of an anomaly. Two examples are presented here to demonstrate the efficacy of this approach. One example pertains to the interpretation of vertical intensity magnetic anomalies over a layered ultramafic body for estimating the thickness of relatively non-magnetic layer in it and map the dispositions of the layers. The other example is the estimation of crustal thickness in the Indian region from the Bouguer anomaly map. The spectral method is shown, by these two examples, to provide a rapid and elegant tool for the source depth estimation for magnetic and gravity data.     

FY2G卫星新一代高能带电粒子探测器观测数据分析

风云二号系列卫星是我国开展动态空间天气事件和空间环境监测及预警业务的重要观测平台,各系列星上均安装有高能带电粒子探测仪器开展卫星轨道空间带电粒子辐射环境连续实时的动态监测.FY2G卫星于2015年1月发射,星上采用了全新的高能粒子探测器,包括:一台高能电子探测器可监测200keV-4 MeV的高能电子,一台高能质子重离子探测器可监测4~300 MeV的高能质子,从而实现对带电粒子更宽、更精细能谱的监测.本文给出了FY2G高能带电粒子探测器在2015年1月至2015年10月期间几起典型的带电粒子动态观测结果,结合太阳和地磁活动相关参数,对高能带电粒子通量在亚暴、磁暴和太阳爆发等扰动影响下细节变化过程和特征作出了较为详细的分析描述,展现了FY2G卫星高能带电粒子探测器对轨道空间粒子环境动态变化的准确响应能力,表明观测数据可开展更加精细的轨道粒子环境评估.针对FY2G高能带电粒子探测结果进一步开展了与GOES系列卫星同期观测的比对分析,结果反映出在较小的扰动条件下多星观测到的带电粒子响应和通量变化可基本趋于一致或保持相对稳定的偏差,而扰动条件的显著变化会加大多星观测带电粒子响应和通量变化的差异,这些结果可为今后开展多星数据同化应用提供参考,也为发展磁层对扰动响应的更加复杂的图像提供了新的可能.