低轨卫星导航增强监测站系统故障模拟仿真

低轨卫星导航信号质量监测是低轨卫星导航增强监测站系统（以下简称监测站系统）设计和运行过程的重要环节。为了更好地了解系统及监测设备的工作原理,当出现故障时能够及时进行故障定位和排除,本文从监测站系统监测原理出发,对监测站系统建立全故障库和仿真模拟,借助深度学习算法分析故障的传递特点,并通过实例进行仿真实验。仿真结果表明,该研究对监测站系统的健康运行具有一定的实际意义。     

北斗GEO导航卫星广播星历拟合算法设计

本文介绍了北斗 GEO 广播星历参数的最小二乘估计方法,提出了相应的计算过程和计算公式,并给出了部分计算偏导公式。计算结果表明,文中给出的具体计算过程和计算公式是正确的,其拟合精度以特定时间间隔的轨道的误差表示时,RMS 误差精度小于 2cm。     

基于低轨通信星座的全球导航增强系统

针对我国难以全球建站实现全球连续监测,以及当前全球卫星导航系统(GNSS)精密定位收敛速度慢的难题,提出一种基于低轨全球通信星座的全球导航增强系统。该系统不需独立建设,可与低轨通信星座融合发展。低轨卫星既可作为“天基监测站”,又可作为“导航信息源”。结合正在发展的低轨鸿雁全球通信系统进行仿真分析,作为“天基监测站”时,通过配置高精确度GNSS接收机,采用“地面区域监测网+天基全球监测网”的观测体制,实现中高轨导航卫星与低轨通信卫星的联合精密定轨与钟差确定;作为“导航信息源”时,可降低几何精确度因子(GDOP)值和缩短精密单点定位首次收敛时间,相比只利用北斗单系统,在收敛时间方面具有显著优势,收敛时间从30 min缩短到5 min以内。     

基于星载GNSS数据的低轨卫星精密定轨

本文介绍了基于星载GNSS观测数据的低轨卫星精密定轨和轨道精度评估方法,并基于GRACE卫星的实测数据开展定轨试验。分析结果表明,基于星载GNSS的动力学定轨可获取厘米级的卫星轨道,为未来低轨星座的精密轨道确定提供参考。     

国外低轨通信卫星的发展

将介绍国外低轨道通信卫星的发展现状及其在军用通信当中的潜在地位,并指出发展低轨通信卫星是目前通信卫星发展中的新苗头和新趋向。     

方兴未艾的低轨卫星移动通信市场

进入90年代,世界上掀起一阵低轨卫星手持移动电话旋风,“铱”系统于今年9月23日正式投入商业运营,紧随其后的“全球星”系统也将于今年底或明年初投入运营。投资39亿美元、64颗卫星的“空中之桥”和投资达90亿美元、840颗卫星的“空中因特网”(Ｔｅｌｅｄｅｓｉｃ)系统也都将于世纪之交投入运行。据悉,目前全球正在运转的各类卫星总数已超过500颗,将要发射的还有1500颗,其中已进入轨道的低轨卫星近300颗,将要发射完成的低轨卫星有900多颗,占到卫星总数六成以上。可见低轨(ＬＥＯ)卫星系统已越来越成为今后几年新的增长热点。低轨卫星通信系…     

一种新插值法在卫星导航广播星历中的应用简

导航卫星广播星历是卫星导航定位的基础,要求有较高的精度和实时性.利用广义延拓插值法来拟合GPS导航卫星轨道,插值系数作为广播星历的参数发播,是一种新的广播星历形式.而且具有精度高,计算快捷等特点,另外对于具有其他多种轨道类型共存的导航系统来说也具有一定的参考意义.     

地面基准站网与星载GNSS融合的高中低轨卫星联合精密定轨

下一代导航系统拟纳入低轨卫星（LEO）作为增强和备份。研究了地面基准站网与星载GNSS融合的高中低轨卫星联合精密定轨（POD）理论与方法,基于实测国际地面站（IGS）和低轨卫星星载GNSS数据,通过建立高精度动力学模型和观测模型,根据全球测站和区域测站两种情况进行了导航星与低轨星的联合精密定轨试验。结果表明,联合定轨可同时获得导航星和低轨星厘米级的定轨精度。低轨星作为高动态天基测站,对导航星定轨精度的提升程度可达20%~90%。     

低轨卫星移动通信系统的星间链设计

从分析铱星通信系统的特点出发,研究了低轨卫星移动通信系统波束覆盖面积和星间切换、波束切换的频率,以及系统用户位置管理方案和数据包路由策略对星间链的要求;分析了星间链的多普勒特性,提出星间链应采用频分双工体制、采用Ka(或更高)频段的载波频率,并设计了星间链传输的帧结构方案。仿真验证了该帧结构方案的可行性。     

Alternatives for Instructional Broadcast Satellites

Half the cost of education is that of students' time; this paper suggests methods of progranmning instructional broadcast satellites to reduce this cost. For fixed satellite ERP and ground station cost, 200 audio channels could replace a TV channel. If a 100-hour course were broken into 30-minute blocks, each could be transmitted simultaneously. Students would listen through earphones and follow the course in illustrated workbooks. At the end of a block, a student would answer questions by resetting dials before him to choose the block he hears. If he answers correctly, he branches ahead; otherwise, back. Continuous 12-year sequences of math, science, and verbal skills instruction could be available. The advantages of radio programnming are that, with no ground-to-satellite feedback, a student can: 1) be obliged to actively respond, 2) have feedback on his accuracy, 3) begin at his own level, 4) advance at his own pace, 5) miss school and resume where he left off, and 6) spend extra time (weekends or evenings) without waiting for his class. Additional sections of the paper deal with frequency allocation, interference, and ground station design.     

Compact Ka-Band Lens Antennas for LEO Satellites

Two new compact lens antenna configurations are presented and compared for data link communications with LEO satellites at 26 GHz. These lenses match a secant type radiation pattern template in the elevation plane while having a mechanically scanned sector beam in azimuth to enhance gain as much as possible. No rotary joints or multiple feeds are required and emphasis is put also on the compactness of the proposed solutions (< 6lambda₀). Two alternative lens configurations are evaluated numerically and experimentally: one is based on modified axial-symmetric dome lens geometry, and the other one consists of a full 3-D double-shell lens antenna. In contrast to current nearly omnidirectional antennas, the directivity of our lens prototypes is above 15.4 dBi. Up to 4.2 dB loss obtained in the prototypes can be significantly reduced by using lower loss dielectrics and matching layers, without affecting the conclusions. The numerical and experimental results are in good agreement with the radiation specifications given the compact size of the antennas.     

近地卫星天基测控现状研究

针对现有中继卫星系统主要为特定用户服务、难以满足蓬勃发展的航天事业带来的海量天基测控需求难题,研究了利用现有地球同步通信卫星系统和近地轨道通信卫星星座对近地卫星测控的可行性和实用性,分析了它们的优缺点,并给出了中继测控应用实例。理论分析、实际用例和完成的仿真计算表明,上述3种类型的卫星系统设计都可以为近地卫星提供中继测控服务,但由于各系统设计的初衷和服务对象不同,在具体的应用效果上各有优缺点,这些优缺点为不同需求的卫星中继测控服务提供了多样性选择,用户可以据此根据其卫星平台测控管理要求、有效载荷的应用需求和性价比等因素,选择最佳的天基中继测控方式,实现高覆盖和低成本。     

First-Generation RCA Direct Broadcast Satellites

In October 1982, the Satellite Television Corporation (STC), a subsidiary of the Communications Satellite Corporation (Comsat), contracted with RCA Astro-Electronics to design, develop, and manufacture the first direct broadcast satellite for use in the United States. The contract is for two spacecraft with an early 1986 launch from either Kourou, Guiana, or Kennedy Space Center, Florida. The program is on schedule with all designs finalized, component qualification virtually complete, and the first spacecraft undergoing integration. Although the system will be implemented in phases, some recent design changes will permit the two collocated satellites to deliver six DBS channels to the entire conterminous United States (CONUS), three channels per satellite. Orbital location will be 110° W longitude, which is one of the eight orbit locations specified for the United States at the Regional Area Radio Conference (RARC) in 1983. Each channel is designed to generate 220 W of RF power in the 12.2-12.7 GHz band at the beginning of life; an allowance is made for TWTA efficiency degradation with life to provide 200 W of RF power at the end of life. The three channels per spacecraft are provided whenever the spacecraft is illuminated by the sun, with no requirement for eclipse operation. Each spacecraft has the capability to transmit in either of two different coverage configurations: it can provide coverage to CONUS or to half-CONUS at an increase in e.i.r.p. of approximately 3 dB. This provides additional margin should STC need the higher e.i.r.p. in the future or provides for a flexible time-zone coverage of the United States.     

星载自适应调零天线在LEO卫星中的应用研究

分析了LEO卫星系统对自适应调零天线的需求,针对地基干扰站对LEO卫星实施大功率阻塞式干扰的可行性进行了量化分析。在星载多波束天线的应用背景下,提出了适合LEO卫星的自适应调零天线的构架,给出了系统框图,并对相关问题进行了分析讨论。在此基础上,提出了凝视干扰波束的概念,极大地简化了LEO卫星调零天线在干扰调零后的波束重组的过程,并给出了波束重组过程的示意图。     

低轨卫星L频段中继通信载荷技术研究

针对深远海和陆基间高速率实时数据通信需求,完成了一种应用于低轨卫星的高集成度、低成本、低功耗L频段中继通信载荷的设计和实现。该中继通信载荷将通信天线、射频前端、信号处理单元、电源变换单元和接口单元等集成化设计。接收前端采用有源相控阵天线设计,发射前端设计了GaN功率放大器以提高接收单元獹/T值和发射单元等效全向辐射功率(Effective Isotropic Radiated Power,EIRP)。信号处理单元集成了零中频接收结构和直接射频调制结构,可完成反向链路8Mb/s载荷数据接收解调及前向链路数据处理转发的功能。载荷单机和装星后的环境模拟测试以及星地通信回路模拟测试结果表明,装星载荷可实现L频段卫星通信。整机质量为12.87 kg,在工作温度-25℃～+55℃范围内,发射端功率放大器输出大于30 W时,最大功耗为91.2 W(3.04 A/30 V)。     

Television Broadcast From Satellites?Sharing Considerations

This paper covers the feasibility of direct television broadcasts from satellites, the problems of sharing with terrestrial stations, questions of co-channel and adjacent channel interference, and the effect of directivity of receiving antennas and detection.     

一种低轨道卫星传输链路干扰仿真分析方法

全球范围内低轨道小卫星数量越来越多,已被世界各国广泛用于通信、遥感、导航等各领域.国际电联对非静止轨道卫星的协调要求日益收紧,对在轨卫星的干扰冲突评估越发务实.本文针对上述现实情况,提出了一种低轨道卫星传输链路干扰仿真分析方法,分别从频域、空间、时间、能量四个层面逐级评估链路影响,为开展国际卫星网络协调提供了切实可行的量化方法.