简介:简单介绍了法国DEMETER(detectionofelectro—magneticemissionstransmittedfromearthquakeregions)地震电磁卫星的科学任务,以及所搭载载荷和观测模式。利用卫星观测资料研究了2006年6月20日16点52分(UT时间)发生在我国甘肃境内的5.0级地震。结果发现,在此次震前第5天电离层就开始出现异常现象,在震前大约1~2天时,这种异常达到最大。最后简述了发展卫星观测所面临的挑战和机遇。
简介:BithyniaisaregioninthenorthwestofAnatoliaborderedbytheBlackSea(PontusEuxeinos)tothenorth,theDardanelStrait(Hellespontos)andKocacay(Rhyndakos)tothewest,andtheSakaryaRiver(Sangarios)tothesouth.ApointoftheAsiancontinentextendingtowardsEurope,Bithyniaissurroundedbyseasonitsthreesidesandhasalongshore.Nicomedeia,oncethecapitalofBithynia,isanimportantcityduetoitslocation.Sincethegulfis
简介:摘要 :本文论述了在卫星下行信号接收链路中,空间电磁信号的建模与仿真实现方法。文中围绕该主题,以某仿真训练系统的工程实践为例,针对下行信号接收链路中关键环节的建模进行了详细阐述,包括自由空间损耗模型、天线方向图增益模型、多种调制方式的信号频谱模型等。在验证阶段,通过多次仿真和对比,仿真结果与实际设备接收信号表现出特征和趋势上的一致性,证明了建模方法的有效性和可靠性。该方法在多个仿真训练系统的工程实践中成功应用,并多次得到检验。
简介:ThispaperisrelatedtostudyoftheiondensityrecordedbythelowaltitudesatelliteDEMETER.Itwillpresentionosphericperturbationsobservedduringlargeseismicevents.Astheionosphereishighlyvariable,thepaperwillshowastatisticalanalysisperformedontheplasmaparametersduringnighttime.Analgorithmhasbeenimplementedtodetectcrestsandtroughsinthedatabeforeworld-wideearthquakes.Theearthquakeshavebeenclassifieddependingontheirmagnitude,depth,andlocation(land,belowthesea,closetoacoast).Duetotheorbit,DEMETERreturnsabovethesameareaeveryday(onceduringdaytime,onceduringnighttime)butnotatthesamedistanceofagivenepicenter.Then,foreachearthquake,datahavebeencheckeduntil15daysbeforetheshockwhenthedistancebetweenthetraceoftheorbitandtheepicenterislessthan1500km.Theresultsofthestatisticalanalysisarepresentedasfunctionsofvariousparameters.Acomparisonisdonewithtwootherdatabaseswhere,ononehand,thelocationoftheepicentershasbeenrandomlymodified,andontheotherhand,thelongitudeoftheepicentershasbeenshifted.Resultsshowthatthenumberandtheintensityoftheionosphericperturbationsarelargerpriortoearthquakesthanpriortorandomevents,andthattheperturbationsincreasewiththemagnitude.