Ionospheric disturbances detected by MEXART

The radio telescope MEXART was developed to make observations of interplanetary scintillation (IPS) produced by large scale disturbances associated with solar events. In this work it is shown that on occasion there are disturbances in the ionosphere that are related with these events and which cannot only contaminate the IPS but actually be the main contribution to the observed oscillations. This was the case of the event of 15 December 2006 observed by MEXART, which presented clear scintillation. The total electron content (TEC) of the ionosphere above Mexico was calculated for the same period. It was found that the variations in TEC were associated with the scintillations detected by MEXART.     

Energy dependence of the rigidity spectrum of Forbush decrease of galactic cosmic ray intensity

We show that rigidity spectrum of Forbush decrease (Fd) of galactic cosmic ray (GCR) intensity in September 9–23, 2005 clearly depends on energy. We calculated rigidity spectrum of the Fd based on the neutron monitors and Nagoya muon telescope channels’ data divided in three groups according to their cut off rigidities. We found that temporal changes of rigidity spectrum exponent γ are approximately similar for all cut off rigidity groups, but γ values are the larger the higher are cut off rigidities. We conclude that rigidity spectrum of Fd is hard for lower energy range and is soft for the higher energy range. We believe that an energy dependence of the power law rigidity spectrum of Fd is observed owing to the preferential convection–diffusion mechanism during Fd in September 9–23, 2005. It is a reflection of an influence of the temporal changes of the structure of the interplanetary magnetic field (IMF) turbulence in different range of frequency f during Fd. Particularly, a decisive role in formation of the character of the rigidity spectrum belongs to the changes of the exponent ν of the power spectral density (PSD) of the IMF turbulence (PSD ∝ f^−ν). The exponent ν is greater for high frequency region of the IMF turbulence (responsible for scattering of low rigidity particles of GCR), than for low frequency region of the IMF turbulence (being responsible for scattering of higher rigidity particles). Also, we challenge to estimate an existence of slab/2D structure of solar wind turbulence during the Fd in September 9–23, 2005 based on the distribution of average turbulence energy among the IMF’s components.     

Hierarchical approach for fast searching optimal launch opportunity in a wide range

Launch opportunity search is crucial for preliminary design of interplanetary trajectories. However, it is difficult to obtain the optimum solution efficiently when the range of search is wide. In this paper, a new fast search algorithm based on a modified hierarchical approach is proposed. At the top level, a simplified Pork-Chop diagram is plotted by sampling interpolation to delimit the candidate regions of the optimal solution. Each candidate region contains only one optimal solution, which fundamentally avoids the local optimal problem of genetic algorithms. At the bottom level, a hybrid optimization approach combining the genetic algorithm and the conjugate directions method is used to solve the accurate optimal solution of each candidate region and obtain the global optimal launch opportunity in the whole wide range of search. Simulation results show that the proposed hierarchical approach can quickly and robustly find the global optimal launch opportunity in a wide search space.     

基于WWW的分布式计算

介绍了基于ＷＷＷ（Ｗｏｒｌｄ ｗｉｄｅ ｗｅｂ）服务,在Ｃｌｉｅｎｔ／Ｓｅｒｖｅｒ计算模式上采用分布对象技术和ＣＯＲＢＡ（Ｃｏｍｍｏｎ ｏｂｊｅｃｔ ｒｅｑｕｅｓｔ ｂｒｏｋｅｒ ａｒｃｈｉｔｅｃｔｕｒｅ）,并采用分布式计算语言Ｊａｖａ进行编程实现的企业分布式计算模型。Ｊａｖａ增强了ＷＷＷ的交互性,但它并不是一种解决Ｃ／Ｓ系统中互操作对象透明性的有效方法。当Ｊａｖａ和分布对象技术结合起来时,形成了     

延迟/中断容忍网络技术及其在行星际因特网中的应用

延迟/中断容忍网络(DTN)采用一种新的端到端的覆盖层网络体系结构,是实现行星际因特网(IPN)的一种重要技术途径。文章首先论述了DTN应用于航天的几种网络协议的特点,包括束协议、利克里德传输协议(LTP)、空间数据系统咨询委员会文件传输协议(CFDP)和Saratoga协议,并分析了DTN路由算法的特点和DTN网络软件的实现,然后总结了NASA在遥感、空间站、中继通信和深空探测等任务情景下进行的DTN飞行验证试验的技术特点。针对我国未来天基综合信息网建设的需求,提出了DTN技术在体系结构、汇聚层协议、路由算法和网关节点设计方面值得关注的问题。     

GPS信号的新近发展及其应用思考

GPS信号的新发展将为GPS信号接收机的功能改善提供运作基础,也将为构建物联网提供新思路。针对由30颗BlockⅡA/ⅡR、ⅡR-M和ⅡF卫星构成的现行GPS星座所发送的GPS信号进行综合分析,进而提出如何使用GPS信号新分量的两点建议:①巧用L2-C码和L1-C/A码实现高精度、高置信度的单点定位;②善用三个导航信号(L1、L2、L5)开创GPS动态载波相位测量应用新天地。     

IP网网络时延探讨

随着计算机互联网在世界范围内的广泛应用,许多原来由电信公网承载的业务,逐步移植到了互联网上,如语音业务(VOIP)、视频电话业务、IPTV业务等.采用TCP/IP协议构建的互联网,如何能保证上述业务的服务质量(QoS)是目前业内经常讨论的话题之一,在实际的应用过程中,分析影响服务质量的各种因素,网络时延是主要的原因之一,本文就时延的产生及改善进行深入的探讨.     

太阳风中动力论Alfven波湍流谱(b)二次激发

根据行星际Alfven湍流是由动力论Alfven波集合形成的模型理论。将行星际Alfven湍流分为三个区域:湍流耗散区、二次激发区和湍流惯性区。并对各区湍流谱的特性分别给出解释。由动力论Alfven波的二次激发和衰减,解释了太阳风高速流质子温度高于电子的事实。      

面向三网融合的宽带通信卫星系统发展建议

文章主要介绍了目前国际上几种宽带通信卫星系统,对近几年的全球宽带通信卫星市场及我国宽带卫星通信市场作了深入分析。最后,从应用需求、系统组成、技术指标和技术基础等方面入手,给出了我国宽带通信卫星系统的发展建议。文章对于探讨我国目前正在积极推动的互联网、电信网及广播电视网的“三网融合”技术,具有重要的参考价值。     

大尺度场向电流的控制因素

将ＩＳＥＥ－１和ＩＳＥＥ－２飞般测量的地球内磁层场向电流作为行星际磁场与极区地磁活动水平（由ＡＬ表征）的函数。发现大约７５％的场向电流发生在行星际磁场南向时,其余２５％发生在行星际磁场由南向转到北向的半小时内。而且,发生在ＡＬ〈－１５０ｎＴ的场向电流也大约是７５％。场向电流的强度和密度随行星际磁场南向分量及ＡＬ的负值增加而增大。由此而得出结论,内磁层场向电流的产生主要是由行星际磁场控制的,是太阳风