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在中国探月工程一期圆满成功的同时,中国探月工程二期也已启动. 据中国探月工程领导小组组长、国防科工局局长陈求发透露,对一期工程的备份星进行技术改进的嫦娥二号卫星,将作为二期工程的先导星,用于试验验证二期工程轨道、测控和软着陆等相关的五个方面的关键技术,降低二期工程的技术风险.同时,嫦娥二号卫星搭载的CCD相机分辨率由120米提高到10米,深化月球科学探测. 相似文献
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嫦娥二号卫星是探月二期工程中嫦娥三号、四号的探路者,是个"先锋".它所承担的重要科学试验、验证任务对探月工程具有承前启后、继往开来的作用,将给后续探月工程带来重大影响. 相似文献
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全面回顾了中国探月工程"绕""落""回"三步走战略顺利实施17年,测控系统从近地走向深空的发展历程和建设成就.探月一期工程突破了远距离测控技术;探月工程二期率先建设两个深空站,初步建成深空测控网;探月工程三期建成了阿根廷深空站,形成了完整的深空测控能力.目前中国深空测控系统已成为世界上三大全球布局的深空测控网之一,具备... 相似文献
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<正>2014年10月24日-11月1日,我国探月三期再入返回飞行试验器—嫦娥-5T(CE-5T)任务圆满完成,成功着陆在预定区域。嫦娥-5T任务对探月三期下一步实施有什么重要意义?嫦娥-5探测器到底如何"采样返回"?本刊记者专访了中国航天科技集团公司科技委副主任、探月工程副总设计师于登云。记者:于总,您好,感谢您接受采访。请问探月工程三期在最初论证时是否规划了嫦娥-5T任务?于登云:由于考虑探月工程经费规模,所以在探月工程三期立项之前的最初论证时只计划了嫦娥-5/6两次任务,其中嫦娥-6作为嫦娥-5的备份,并未列入嫦娥-5T高速再入返回飞行试验任务,只是把高速再入返回作为一项关键技术。但是在后来的立项评估时,以中国航天科技集团公司王礼恒 相似文献
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Research on the Relation Between the Seeker's Handover and the Geometrical Position of the Missile and the Target 总被引:8,自引:0,他引:8
研究了雷达导引头的交班误差以及截获概率与交班时刻弹目几何位置的关系,提出了单个误差角的导引头天线指向角误差模型,它与两个误差角的导引头指向角误差模型相比可以更好地分析天线指向角误差,并得到使指向角误差最小的弹目几何位置;然后进一步得到使多普勒频率误差最小的弹目几何位置;给出了最终的截获概率的表达式,截获概率由目标处于导引头天线主波束的概率、目标回波多普勒频率落入接收机频带内的概率和目标的检测概率组成的;最后分析了一种典型的中末交班情况. 相似文献
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本文在准地转模式的假定下,讨论了火星地形对火星大气的影响,并根据文章所提供的信息对火星尘暴发生的物理机制作了粗略的解释。 相似文献
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Maria S. Pulinets Elizaveta E. Antonova Maria O. Riazantseva Svetlana S. Znatkova Igor P. Kirpichev 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Crossings of the magnetopause near the subsolar point are analyzed using data of THEMIS mission. Variations of the magnetic field near magnetopause measured by one of THEMIS satellites are studied and compared with simultaneous measurements in the solar wind by another THEMIS satellite. The time delay of the solar wind arrival at the subsolar point of the magnetopause is taken into account. 30 and 90 s averaging of the magnetic field in the magnetosheath is produced. The results of averaging are compared with the results of measurements in the solar wind before the bow shock and foreshock. It is shown, that Bx component of the magnetic field near magnetopause is near to zero, which supports the possibility to consider the magnetopause as the tangential discontinuity. Comparatively good correlation of By component in the solar wind and near the magnetopause is observed. The correlation of Bz component near the magnetopause and IMF is practically absent, the sign of the Bz near the subsolar point does not coincide with the sign of IMF Bz in ∼30% cases. 相似文献
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利用TIMEGCM模拟了2005年9月10日至20日由日冕物质抛射引起的地磁暴事件,研究了此地磁暴恢复相高纬度中间层低热层(MLT)区域温度的变化,揭示了磁暴恢复相时温度、垂直风、总加热项和NO辐射冷却的内在联系.结果表明:地磁暴恢复相刚开始时,温度对磁暴的响应在晨侧为负扰动(降温),在其他地区都为正扰动(增温);随着磁暴的恢复,整个北半球都变为正的温度扰动(增温).这种高纬MLT区域的温度响应主要与垂直风密切相关.当垂直风为正时,总加热为负,增温减弱;当垂直风为负时,总加热为正,增温变强.辐射冷却特别是NO辐射冷却作用在热层被称为恒温器,降低了磁暴期间80%的热层增温.但是,在MLT区域NO辐射冷却作用不明显,一般比总加热项小一个量级,对温度响应造成的影响较小. 相似文献
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Samy El-Jaby Leena Tomi Lembit Sihver Tatsuhiko Sato Richard B. Richardson Brent J. Lewis 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
This paper describes a methodology for assessing the pre-mission exposure of space crew aboard the International Space Station (ISS) in terms of an effective dose equivalent. In this approach, the PHITS Monte Carlo code was used to assess the particle transport of galactic cosmic radiation (GCR) and trapped radiation for solar maximum and minimum conditions through an aluminum shield thickness. From these predicted spectra, and using fluence-to-dose conversion factors, a scaling ratio of the effective dose equivalent rate to the ICRU ambient dose equivalent rate at a 10 mm depth was determined. Only contributions from secondary neutrons, protons, and alpha particles were considered in this analysis. 相似文献
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Caitano Luiz da Silva Fernanda T. São Sabbas 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
We present the results of a streamer-fluid model used to investigate the electrodynamical coupling between the troposphere and upper atmosphere due to the penetration of lightning electric fields into the mesosphere and the lower ionosphere, generating sprites. The model solves the continuity equation for electrons and ions coupled to Poisson equation. The dominant physical response of the atmosphere is the formation of a screening-ionization wave. The wave shields the atmosphere above it from the action of the lightning field and, together with the conductivity reduction below it due to attachment, the wave amplifies the total field below it, allowing for the penetration of intense electric fields in the mesosphere as it propagates downwards into regions of higher density that compress the wave. This is the key physical mechanism for sprite inception. We evaluated the effects of the thundercloud charge geometry, lightning current waveshape, atmospheric conductivity, via different electron density profiles, and the effect of ionization, attachment and electron mobility coefficients in the electrical breakdown process, related to halo production, and sprite streamer initiation. The results showed that electrons with higher mobility are more efficient in shielding the lightning electric field before breakdown, causing delay, and they contribute to the formation of the streamer seed after breakdown, anticipating the sprite streamer inception. Similarly, a higher effective ionization rate, produced by modifications in the attachment and ionization coefficients, anticipates sprite inception. The simulations with 6 different electron density profiles, and therefore conductivities, spanning 4 orders of magnitude, showed that the altitude of breakdown and sprite initiation, as well as their time delays from the lightning discharge are directly related to atmospheric conductivity: higher conductivities produce halo and sprite inception at lower altitudes with longer delays and may hinder sprite formation. We document that variations of 30 times in the lightning current leads to sprite initiation altitudes in the range 66.0–73.5 km, with delays between 1.550 and 34.500 ms, while variations of 4 orders of magnitude in the conductivity profile lead to initiation altitudes 61.0–70.6 km, with delays in the range 3.825–9.825 ms. Consequently, we suggest that lightning characteristics dominate over atmospheric parameters in determining sprites’ initiation altitude and delay. The simulation of a −CG, with a constant current of 30 kA, did not produce a sprite seed, confirming an asymmetry in the response of the atmosphere to positive and negative lightning. This is due to the free electron drift direction that is away from the screening ionization wave, preventing the formation of the streamer seed for the great majority of −CGs. The same does not apply to halos, which depend on the occurrence of breakdown and can be produced by discharges of both polarities. 相似文献
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Results of our investigation showed that occurrence frequency of Pi2 over a 24 hour period undergoes seasonal variations in time coincidence with foF2. In the winter months, at sunrise and sunset (when foF2gradients are the largest) the observation probability of these oscillations is minimal. At periods of summer solstice when the F2-layer persists almost round the clock, no effect of Pi2 pulsation attenuation is observed at sunrise and sunset. The pulsation amplitudes behave in a similar manner. Results of this study suggest the conclusion that the propagation of signal from the Pi2 sourse into the mid-latitudes, and also the parameters of these pulsations are essentially affected by electron density in the ionospheric F2-layer. 相似文献
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W. Miyake Y. Saito H. Hayakawa A. Matsuoka 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,36(12):2328-2332
The L5 point is a promising location for forecasting co-rotating high-speed streams in the solar wind arriving at the Earth. We correlated the solar wind data obtained by the Nozomi spacecraft in interplanetary space and by the Advanced Composition Explorer (ACE) at the L1 point, and found that the correlation is significantly improved from that of the 27-day recurrence of ACE data. Based on the correlation between the two spacecraft observations, we estimated the correlation of the solar wind velocity between the L5 point and at the Earth, and found that the correlation coefficient was about 0.78 in late 1999, while that of the 27-day recurrence was 0.51. Eighty-eight percent of the velocity difference falls within 100 km/s between the L5 point and the Earth. This demonstrates the potential capability of solar wind monitoring at the L5 point to forecast the geomagnetic disturbances 4.5 days in advance. 相似文献