共查询到18条相似文献,搜索用时 187 毫秒
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利用卫星导航信号实现高轨航天器的自主定轨与导航已成为当前国内外的研究热点, 高轨星载导航接收机面临可见卫星数少、接收导航信号微弱、动态性较大等问题。针对以上问题, 分析了高轨环境下星载导航接收机获取到的信号功率、可见星数、DOP 值及多普勒频移状态。首先建立了北斗星座模型与高轨航天器动力学模型,构建星间测距链路,对高轨卫星的可见性进行了仿真分析,结果表明当星载接收机功率为-177 dBw 时,可见星数能达到 4 颗以上,能满足定轨需求;然后对高轨卫星的定轨精度进行了仿真,DOP 值的均值为 15.657 8;最后对导航卫星和高轨卫星之间的多普勒频移进行了分析,仿真的多普勒范围为±14 kHz。相关研究结果可支撑高轨航天器星载接收机的开发。 相似文献
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低轨(Low Earth Orbit, LEO)卫星互联网相较于地面网络有更大的网络覆盖范围与更强的网络稳定性,有利于实现全球立体无缝网络覆盖,是未来6G网络重要的发展趋势。低轨卫星相较于中高轨卫星具有更高的运行速度,因此,低轨卫星信号具有更大的多普勒频移和动态特性,而低轨卫星信号的高精度捕获与跟踪是低轨卫星通信的基础。随着相控阵天线在低轨卫星和卫星终端上的推广应用,多波束和跳波束技术也为信号的捕获与跟踪带来挑战。从低轨卫星信号互联网的信号特点出发,提出了信号捕获与跟踪过程中的技术挑战,重点阐述了现有捕获与跟踪方法的基本原理与适用范围,探讨了低轨卫星网络中信号捕获与跟踪技术的未来发展方向。 相似文献
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提出了一种利用星间距离信息和扩展卡尔曼滤波算法确定卫星的位置和速度的方法。利用STK软件建立GPS星座,将1颗目标卫星与3颗参考卫星之间的距离引入一定的误差作为星间观测值,利用扩展卡尔曼滤波算法实现卫星的自主定轨。并对算法进行了改进,利用几何准确度因子GDOP值控制参考卫星的选择,消除了误差峰值。运算结果表明改进后的算法有很好的收敛性,提高了定轨准确度。 相似文献
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基于卫星通信信号的多站时差测轨是一种重要的新型无源测轨方法,分析其定轨精度对系统应用具有重要意义.介绍了四站时差测轨原理与系统组成,提出了基于四站时差测量数据的自校准统计定轨策略,采用计算机仿真了同步轨道卫星的统计定轨精度.仿真结果表明:当无系统误差时,24h观测数据统计定轨位置误差约为11m,预报1周位置误差约100 m;当存在系统误差时,可用自校准方法同步估计系统误差,系统误差估计精度约为4m,位置误差约为120 m,预报1周的位置误差约为200 m. 相似文献
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We address the issue of optimal energy allocation and admission control for communications satellites in Earth orbit. Such satellites receive requests for transmission as they orbit the Earth, but may not be able to serve them all, due to energy limitations. The objective is to choose which requests to serve so that the expected total reward is maximized. The special case of a single energy-constrained satellite is considered. Rewards and demands from users for transmission (energy) are random and known only at request time. Using a dynamic programming approach, an optimal policy is derived and is characterized in terms of thresholds. Furthermore, in the special case where demand for energy is unlimited, an optimal policy is obtained in closed form. Although motivated by satellite communications, our approach is general and can be used to solve a variety of resource allocation problems in wireless communications. 相似文献
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以天基监视为背景,依据几何学原理和矢量计算工具,主要研究了双星相对运动模型。一方面,突破力学求解方式,采用一种区别于传统轨道根数的卫星轨道生成规则,可清晰直观地描述卫星轨道;另一方面,结合光电跟踪系统,研究了双星运动过程中的相对方向变化。通过对异面太阳同步圆轨和共面地球同步圆轨双星相对运动模型的仿真计算,获得了卫星轨道、相对距离、方位角、俯仰角、方位角速率、俯仰角速率的变化结果,分析结果证明了此方法的合理性,可为天基监视中的工作区域选择、卫星轨道设计、监视系统设计和捕获跟踪瞄准控制系统设计等物理问题和关键技术提供定性和半定量参考。 相似文献
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Andreas Winterstein Lukasz A. Greda 《International Journal of Satellite Communications and Networking》2018,36(2):207-219
High throughput data links from low Earth orbit satellites through a geostationary orbit satellite data relay have been proposed to increase the available contact times to ground stations. Accurate antenna beam pointing and tracking of moving targets are key requirements for the relay satellite. In this work, we propose an adaptive calibration and beamforming methodology on the basis of least mean squares, which is suitable for a geostationary orbit data relay. The target system consists of the combination of a high gain reflector fed by a digitally steerable patch antenna array. The proposed method is first presented by numerical cosimulation of the antenna and the calibration algorithm. The results are then validated in an outdoor experimental setup with all digital signal processing implemented in a field‐programmable gate array. We demonstrate the tracking ability and pointing performance of the digitally enhanced reflector antenna with gain fluctuations smaller than 3 dB over a field of view of at least 2,5°. The demonstrated performance shows that the digitally enhanced reflector antenna is a suitable candidate for long‐distance space communications. 相似文献
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The constraints imposed by the RF environment are reviewed. An overview of present and planned mobile satellite systems is given. Present systems refer to those already in operation, while planned systems refer to those that have authority to offer the services and have either a satellite in orbit or one being built to support the systems. Future directions for mobile satellite communications systems are discussed. One approach emerging is the use of large satellites, with large antennas. operating at much higher carrier frequencies. A second approach is to use low-earth orbit (LEO) satellites. in order to reduce the path loss. The LEO approach also results in much smaller propagation delays than those experienced with geostationary satellites 相似文献
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王存良 《太赫兹科学与电子信息学报》2012,10(4):421-425
为了对地面某一区域在未来某一时段连续覆盖,需要对在轨卫星变轨,并计算变轨后的卫星轨道参数。基于在轨卫星部分轨道参数(椭圆轨道a,i,e,圆轨道a,i)和t时刻星下点的位置坐标及卫星的地面高度,计算卫星的6个轨道参数,从而得到t时刻对星下点位置为中心的区域覆盖所需要的卫星轨道参数。利用t时刻卫星在J2000.0平天球坐标系3个坐标轴的位置与速度分量计算其卫星轨道参数。用STK卫星工具箱软件6.0高精确度轨道产生器仿真,输入所得的t时刻卫星轨道参数,运行STK 6.0得到的星下点位置与事先设置的星下点相距6.63 m,完全满足卫星对地面覆盖的需要。欲对该区域在t时刻以后的一段时间连续覆盖,所需要的卫星轨道参数可按共地面轨迹计算;通过STK 6.0高精确度轨道产生器对计算得到的卫星轨道参数进行仿真,验证了计算结果的正确性。 相似文献
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欧洲下一代气象卫星及其红外遥感仪器概要 总被引:1,自引:0,他引:1
总结了欧洲气象卫星组织(EUMETSAT)与欧空局(ESA)的气象卫星发展情况以及他们对下一代地球同步轨道和极轨气象卫星的规划.下一代地球同步轨道气象卫星计划为MTG系列,将以MTG-I(成像卫星)和MTG-S(探测卫星)双星运行,各自承载不同的探测仪器,计划发射6颗卫星(4颗MTG-I和2颗MTG-S).而极轨气象卫星MetOp-SG则与美国国家海洋和大气管理局(NOAA)/美国航空航天局(NASA)的卫星系统联合.ESA当前的MetOp卫星和下一代MetOp-SG卫星在“上午”轨道上运行,NOAA/NASA的下一代JPSS卫星在“下午”轨道上运行,双方共享两个轨道卫星数据. 相似文献
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GPS-based navigation and attitude determination of LEO satellites is presently considered as an alternative to the conventional systems which utilize earth sensors and magnetometers. The onboard GPS receiver determines the orbit position of the LEO satellite by the conventional system of linearized navigation equations, requiring the simultaneous reception of ranging signals from four GPS satellites by a single antenna. For attitude determination, pairs of antennae, suitably mounted on the satellite and feeding a common receiver, form several interferometric baselines. The baselines vectors, defined in a given coordinate system, determine the attitude of the satellite. For each baseline and each GPS satellite, the difference in phase of the received signal carriers is measured. The differencing operation eliminates the receiver clock bias. Solutions for the baseline vectors can be obtained with signals received from only three GPS satellites. If the coverage of a receive antenna is restricted to less than the hemisphere it will not have four GPS satellites in view all the time. It is demonstrated that a GPS pseudolite transmitter located on earth supplements the system, which then provides a usable geometric dilution of precision (GDOP) for position determination and an improved position dilution of precision (PDOP) for attitude determination. Pseudolites can be co-located with the gateways which provide access to the public switched telephone networks (PSTNs) for the LEO communication satellites. 相似文献
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Cost-Estimate Relations (CER's) are derived for launch/orbit insertion, payload/satellite(s), and the total satellite system. These CER's are expressed in terms of orbit altitude (or apogee), orbit type (circular or elliptical), and payload weight. The CER's are also presented briefly in terms of number of rings, number of satellites per ring, and satellite weight. They are applicable only to recurring (production) costs and include an 80percent "learning-curve rate." Satellite-subsystem percent weights are also discussed for single-axis and three-axis stabilized satellites, and guidance is developed for estimating total satellite weight given the required RF power. 相似文献