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911.
卫星导航调制方式的非线性和兼容性分析 总被引:1,自引:0,他引:1
对比研究了最小频移键控(Minimum Shift Keying,MSK)和正交相移键控(Quadrature Phase Shift Keying,QPSK)调制信号的非线性和兼容性。首先建立MSK调制卫星导航信号的时域和频域模型,讨论了MSK调制对码片脉冲形状的影响,指出MSK调制作为卫星导航信号候选调制方式的可行性。然后建立非线性信道模型,仿真了MSK和QPSK调制卫星导航信号的带外功率损耗、相关损耗和码跟踪误差以及与同频段信号的谱分离系数。仿真结果表明,在保证信号跟踪性能的前提下,卫星导航信号采用MSK调制时的非线性和兼容性优于同参数下的QPSK调制。 相似文献
912.
H.L.K. Manning I.L. ten Kate S.J. Battel P.R. Mahaffy 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
Electric discharge between two electrically charged surfaces occurs at a well-defined, gas-dependent combination of atmospheric pressure and the distance between those two surfaces, as described by Paschen’s law. The understanding of when the discharge will occur in the conditions present on Mars is essential for designing space-flight hardware that will operate on the Martian surface as well as understanding electrical discharge processes occurring in the Martian atmosphere. Here, we present experimentally measured Paschen curves for a gas mixture representative of the Martian atmosphere and compare our results to breakdown voltages of carbon dioxide, nitrogen, and helium as measured with our system and from the literature. We will discuss possible implications for instrument development as well as implications for processes in the Martian atmosphere. The DC voltage at which electric discharge occurred between two stainless steel spheres was measured at pressures from 10−2 to 100 torr in all gases. We measured a minimum voltage for discharge in the Mars ambient atmosphere of 410 ± 10 V at 0.3 torr cm. As an application, the breakdown properties of space-qualified, electrical wires to be used in the Sample Analysis at Mars (SAM) instrument suite on the Mars Science Laboratory (MSL) were studied. 相似文献
913.
914.
S.G. Pavlov E.K. Jessberger H.-W. Hübers S. Schröder I. Rauschenbach S. Florek J. Neumann H. Henkel S. Klinkner 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Jupiter’s icy moon Europa is one of most promising places in our Solar System where possible extraterrestrial life forms could exist either in the past or even presently. The Europa Lander mission, an exciting part of the international Europa Jupiter System Mission (EJSM/Laplace), considers in situ planetary exploration of the moon. The distance of Europa from the Earth and the Sun asks for autonomous analytical tools that maximize the scientific return at minimal resources, demanding new experimental concepts. We propose a novel instrument, based on the atomic spectroscopy of laser generated plasmas for the elemental analysis of Europa’s surface materials as far as it is in reach of the lander for example by a robotic arm or a mole, or just onboard the lander. The technique of laser-induced plasma spectrometry provides quantitative elemental analysis of all major and many trace elements. It is a fast technique, i.e. an analysis can be performed in a few seconds, which can be applied to many different types of material such as ice, dust or rocks and it does not require any sample preparation. The sensitivity is in the range of tens of ppm and high lateral resolution, down to 50 μm, is feasible. In addition, it provides the potential of depth profiling, up to 2 mm in rock material and up to a few cm in more transparent icy matrices. Key components of the instrument are presently developed in Germany for planetary in situ missions. This development program is accompanied by an in-depth methodical investigation of this technique under planetary environmental conditions. 相似文献
915.
W. Wang D.P. Gu Q. Zheng Y.Q. Sun 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
To explore the proteomic changes of heritable variant rice plants induced by space environment, three mutants were selected after seed space flight by comparing the phenotypes with their on-ground controls. R955 grew more tillers and became dwarf, 971-5 acquired higher grain yield and better stress resistance, 974-5 matured earlier. Leaf proteins were extracted during the tiller development and analyzed by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). More than 300 proteins were detected as reproducible Coomassie Brilliant Blue stained spots with pI values from around 4.0 to 7.0. Five proteins that changed significantly over the controls were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). The main functions of these proteins were photosynthesis, stress defense and metabolism including RuBisCO activase, glycine rich RNA binding protein, peroxidase, triosephosphate isomerase and phosphoenolpyruvate carboxylase, which might be probably associated with the altered phenotypes. Quantitative analyses were also applied: less total protein spots and more down-regulated protein spots were detected in the mutants, indicating there might be a major loss of protein in heritable variant rice plants after seed space flight. These results may provide new insights to understand the biological effects of space environment to rice. 相似文献
916.
空间科学实验地面支持系统平台 总被引:1,自引:0,他引:1
相对于其他空间任务, 空间科学实验具有用户分散、实验进程控制 (遥科学实验)要求实时或准实时、多种类型空间科学数据处理要求等特点. 针对空间科学实验的特点和对地面支持系统的要求, 结合实践八号卫星(SJ-8)、探测双星(TC-1, TC-2) 和神舟系列飞船(SZ) 的空间科学实验地面支持系统的任务完成情况, 以及未来空间科学实验任务的需求, 提出了地面支持系统平台的构架设想. 该系统平台支持空间科学实验的状态监视与控制, 支持遥科学实验, 能够支持空间科学实验数据标准产品的定制处理, 满足空间科学实验多任务的要求, 具有通用性和可扩展性. 相似文献
917.
918.
神舟七号微小卫星伴随飞行技术试验 总被引:2,自引:0,他引:2
神舟七号 (SZ-7) 载人航天任务中释放的一颗微小伴随卫星 (BX-1), 首次开展了卫星在轨释放、对飞船观测和对轨道舱接近及绕飞等技术试验. 该卫星首次进行了GaInP2/GaAs/Ge 中国产太阳电池阵、锂离子蓄电池、微型液氨推进模块、小型化姿态跟踪控制模块、双焦距一体化可见光相机及小型化USB 测控应答机等技术验证. 本文介绍了SZ-7 微小卫星的设计方案, 讨论了形成稳定伴随飞行的轨道设计等技术, 并根据卫星在轨运行情况对试验任务进行了评价. 相似文献
919.
920.
G. Souvatzoglou H. Mavromichalaki C. Sarlanis G. Mariatos A. Belov E. Eroshenko V. Yanke 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Within the last years, a real-time system to monitor high energy cosmic rays for space weather use has been operated at Athens cosmic ray station. Neutron monitors and satellite high resolution data in real time are used, making it possible to observe cosmic rays in dual energy range observations. In large solar energetic particle (SEP) events, ground level enhancement (GLE) can provide the earliest alert for the onset of the SEP event. This system watches for count rate increases recorded in real time by 23 neutron monitors, which triggers an alarm if a ground level enhancement (GLE) of cosmic ray intensity is detected. 相似文献