GNSS导航卫星抛物面天线系统建设与测试

导航卫星的信号质量是影响卫星导航系统精度、连续性和可靠性的关键因素,为实时监测上海地区可见GNSS导航卫星的信号质量,建成了GNSS导航卫星抛物面天线系统;该系统可以对包括北斗导航卫星系统在内的GNSS导航卫星的空间信号进行监测,分析导航卫星空间信号的质量;GNSS导航卫星抛物面天线系统主要由3.2m抛物面伺服跟踪天线、GNSS信号中频采集器、数据存储装置、监测控制平台以及相关监测设备组成;介绍了导航卫星抛物面天线系统的建设及其测试情况,测试结果表明,所建成的抛物面天线系统可以对观测范围内的各卫星导航系统的各颗卫星的导航信号进行实时信号跟踪与监测,相关技术指标达到了预期要求。     

利用综合评估加权法提高160光电经纬仪跟踪性能

分析了卫星发射场光学测量系统跟踪方式和存在的问题及各跟踪方式的优缺点,并运用系统工程决策论中加权评估方法,充分发挥各跟踪方式的优势,实时进行互补和印证,提出了利用系统工程理论的加权评估法实现160光电经纬仪的自动跟踪,减小了跟踪误差和跟踪稳定性,而且可以实现定点跟踪,提高激光回波率.     

星间激光通信中复合轴系统的带宽设计研究

星间激光通信中,由粗跟踪系统和精跟踪系统组成的复合轴系统完成了系统的大范围、高精度跟踪任务。对复合轴系统进行了基于Z变换的数字模拟以研究其带宽设计。根据计算的卫星轨迹和粗跟踪系统机械误差,得到了粗跟踪系统的带宽设计结果;给出了粗跟踪系统和精跟踪系统的配合工作关系;得到了精跟踪系统的带宽设计结果;最后研究了在中高频扰动下,复合轴系统的带宽设计。以上结果为星间激光通信中的复合轴系统控制系统设计提供了重要依据。     

槽式太阳能聚集阵的间歇跟踪聚光特性

对日间歇跟踪的太阳能聚光电池阵是一种技术难度与效益平衡性好的航天器太阳能电源技术,研究该类空间太阳能聚集系统的在轨聚光特性及间歇跟踪控制方法具有重要意义.本文基于卫星轨道特性与槽式反射聚集阵的光传播特性分析,建立了太阳能聚集阵对日间歇跟踪的时间步长计算方法,考虑太阳光线不平行度等因素影响.以某太阳同步圆轨道卫星上的反射聚集阵为例,采用蒙特卡洛法模拟其间歇跟踪下的聚光特性.结果表明,采用所提出的时间步长计算方法进行聚集阵的对日间歇跟踪,可获得满意的聚光效果.     

低轨微小卫星及小碎片搜索/跟踪机动式大视场光电望远镜

有效反射面积小,运动速度快的空间低轨卫星和小碎片的日益增多对现有地基探测跟踪技术提出了挑战。本文分析了国外现有低轨小目标光电探测技术的发展现状,结合低轨小目标的探测需求,提出了一种用于低轨微小卫星及小碎片搜索/跟踪探测的机动式车载大视场光电望远镜设计方案。介绍了该望远镜的光学系统、跟踪架及载车,描述了它的工作模式和图像处理,讨论了系统的搜索和探测能力。结果表明,该望远镜对300 km轨道高度的目标搜索能力达到13.5星等（相当于直径5 cm目标）,可以满足搜索和跟踪低轨微小卫星及小碎片探测的实际需求。     

卫星激光通信系统设计分析

结合卫星激光通信实验演示系统的研制，对卫星激光通信系统的总体设计以及系统的结构设计、激光器的选择、捕获、对准、跟踪（Acquisition,Pointing and Tracking-APT)技术，背景光抑制与光学滤波器设计，光行程差与超前对准补偿等关键技术进行了深入的分析和讨论，得出了有关结论。     

短波红外用于白天卫星探测的研究

从白天天空背景、卫星光学特性及红外波段在大气中的传输特性三方面分析了白天卫星探测的可行性。在此基础上,采用光谱滤波的方法,利用红外焦平面阵列(IRFPA),在短波红外波段进行了卫星跟踪与测量。理论分析和白天的测星实验表明,用短波红外波段能够实现白天卫星的跟踪与测量;通过与已知星等的G型光谱类型恒星测量值的比对得到了目标卫星的星等为6.34,给出了探测系统的跟踪误差。     

北斗卫星导航接收机跟踪环技术设计与实现

跟踪环路设计是实现北斗卫星导航接收机的关键环节,为实现接收机的环路跟踪,设计了一种基于DSP+FPGA的数字BDS接收机实时高精度跟踪环路,并阐述了环路跟踪的原理和方法。采用二阶锁频环辅助三阶锁相环完成北斗载波信号的高精度稳定闭环跟踪,同时使用载波来实时地辅助码环跟踪,从而完成北斗卫星信号的实时高精度跟踪。试验结果表明,该跟踪环路能实现对北斗卫星信号的跟踪,并且环路在0.4s就进入稳态,同时具有良好的动态性能。     

基于伪相关函数的多级电平编码符号信号通用无模糊跟踪方法

针对新一代全球导航卫星系统(GNSS)中多级电平编码符号(MCS)信号存在的跟踪模糊问题,本文提出了一种通用的MCS信号无模糊跟踪方法.首先推导了不同MCS信号互相关函数的统一表达式,并给出了伪相关函数的定义;然后深入分析了实现无模糊跟踪需要满足的约束条件,推导了两路参考信号的通用构造方法以及相互之间的关系,为具体MCS信号的求解提供了极大的便利;进而给出了利用本文方法的GNSS接收机码跟踪环路模型.作为MCS信号的特例,分别讨论了本文方法在四种二进制偏移载波信号跟踪中的应用.仿真结果表明,本文方法能够有效解决MCS信号的跟踪模糊问题,具有良好的性能和广阔的应用前景.     

基于双星双目跟踪方式的空间目标定轨技术研究

以天基监视为背景,主要研究了一种基于双星双目跟踪方式的空间目标定轨技术,其物理思想为:利用星载光学测量系统获得目标的相对方位指向与角度传感器测量系统获得卫星的姿态角变化和光电跟踪架的随动角信息,通过坐标变换和数据处理解算出目标在地心惯性坐标系中的绝对运动信息。依次从物理模型、坐标体系、定轨原理方面进行了描述和推导,获得了目标在地球坐标系下的测量方程,并且通过对天基监视卫星轨道模型、星载光电跟踪控制模型、光学成像模型分析后,进行了数学建模仿真,计算结果表明该定轨方法的可行性。     

Applications of two-way satellite time and frequency transfer in the BeiDou navigation satellite system

A two-way satellite time and frequency transfer(TWSTFT) device equipped in the BeiDou navigation satellite system(BDS)can calculate clock error between satellite and ground master clock. TWSTFT is a real-time method with high accuracy because most system errors such as orbital error, station position error, and tropospheric and ionospheric delay error can be eliminated by calculating the two-way pseudorange difference. Another method, the multi-satellite precision orbit determination(MPOD)method, can be applied to estimate satellite clock errors. By comparison with MPOD clock estimations, this paper discusses the applications of the BDS TWSTFT clock observations in satellite clock measurement, satellite clock prediction, navigation system time monitor, and satellite clock performance assessment in orbit. The results show that with TWSTFT clock observations, the accuracy of satellite clock prediction is higher than MPOD. Five continuous weeks of comparisons with three international GNSS Service(IGS) analysis centers(ACs) show that the reference time difference between BeiDou time(BDT) and golbal positoning system(GPS) time(GPST) realized IGS ACs is in the tens of nanoseconds. Applying the TWSTFT clock error observations may obtain more accurate satellite clock performance evaluation in the 104 s interval because the accuracy of the MPOD clock estimation is not sufficiently high. By comparing the BDS and GPS satellite clock performance, we found that the BDS clock stability at the 103 s interval is approximately 10.12, which is similar to the GPS IIR.     

The method and experiment analysis of two-way common-view satellite time transfer for compass system

Time synchronization between ground and satellites is a key technology for satellite navigation system. With dual-channel satellite, a method called Two-Way Common-View(TWCV) satellite time transfer for Compass system is proposed, which combines both characteristics of satellite common-view and two-way satellite-ground time transfer. By satellite-ground two-way pseudo-range differencing and two stations common-view differencing, this TWCV method can completely eliminate the influence of common errors, such as satellite clock offset, ephemeris errors, troposphere delay and station coordinates errors. At the same time, ionosphere delay related to signal frequency is also weakened significantly. So the precision of time transfer is improved much more greatly than before. In this paper, the basic principle is introduced in detail, the effect of major errors is analyzed and the practical calculation model in the Earth-fixed coordinate system for this new method is provided. Finally, experiment analysis is conducted with actual Compass observing data. The results show that the deviation and the stability of the satellite dual channel can be better than 0.1 ns, and the accuracy of the two-way common-view satellite time transfer can achieve 0.4 ns. All these results have verified the correctness of this TWCV method and model. In addition, we compare this TWCV satellite time transfer with the independent C-band TWSTFT(Two-Way Satellite Time and Frequency Transfer). It shows that the result of the TWCV satellite time transfer is in accordance with the C-band TWSTFT result, which further suggests that the TWCV method is a remote high precision time transfer technique. The research results in this paper are very important references for the development and application of Compass satellite navigation system.     

空间弥散X射线对脉冲星导航精度的影响

基于RXTE卫星天基数据,建立了时空坐标系转换、时间修正及历元折叠方法,构建了用于提取导航信息的Crab脉冲星轮廓,剖析了该天基载荷结构及特性,对卫星运行空间背景辐射进行了模拟计算。结果表明,在设定导航条件下,空间弥散X射线对航天器单星定轨及多星定位影响在km量级以上。同时阐述了实用化脉冲星导航探测中,改进导航定位精度急需注意的技术问题。     

BeiDou Short-Message Satellite Resource Allocation Algorithm Based on Deep Reinforcement Learning

The comprehensively completed BDS-3 short-message communication system, known as the short-message satellite communication system (SMSCS), will be widely used in traditional blind communication areas in the future. However, short-message processing resources for short-message satellites are relatively scarce. To improve the resource utilization of satellite systems and ensure the service quality of the short-message terminal is adequate, it is necessary to allocate and schedule short-message satellite processing resources in a multi-satellite coverage area. In order to solve the above problems, a short-message satellite resource allocation algorithm based on deep reinforcement learning (DRL-SRA) is proposed. First of all, using the characteristics of the SMSCS, a multi-objective joint optimization satellite resource allocation model is established to reduce short-message terminal path transmission loss, and achieve satellite load balancing and an adequate quality of service. Then, the number of input data dimensions is reduced using the region division strategy and a feature extraction network. The continuous spatial state is parameterized with a deep reinforcement learning algorithm based on the deep deterministic policy gradient (DDPG) framework. The simulation results show that the proposed algorithm can reduce the transmission loss of the short-message terminal path, improve the quality of service, and increase the resource utilization efficiency of the short-message satellite system while ensuring an appropriate satellite load balance.     

Satellite virtual atomic clock with pseudorange difference function

Satellite atomic clocks are the basis of GPS for the control of time and frequency of navigation signals. In the Chinese Area Positioning System (CAPS), a satellite navigation system without the satellite atomic clocks onboard is successfully developed. Thus, the method of time synchronization based on satellite atomic clocks in GPS is not suitable. Satellite virtual atomic clocks are used to implement satellite navigation. With the satellite virtual atomic clocks, the time at which the signals are transmitted from the ground can be delayed into the time that the signals are transmitted from the satellites and the pseudorange measuring can be fulfilled as in GPS. Satellite virtual atomic clocks can implement the navigation, make a pseudorange difference, remove the ephemeris error, and improve the accuracy of navigation positioning. They not only provide a navigation system without satellite clocks, but also a navigation system with pseudorange difference. Supported by the National Basic Research Program of China (Grant No. 2007CB815502) and the National High Technology Research and Development Program of China (Grant No. 2007AA12Z300)     

卫星振动对星间光码分多址系统性能的影响

卫星振动是影响星间光CDMA通信系统性能的一个重要因素.考虑多用户干扰、背景光噪音、热噪音、接收机噪音和卫星振动,给出了基于PPM信号格式的星间二维光CDMA通信系统的系统模型.采用数值分析的方法,详细分析了卫星振动对该系统误码率性能的影响.结果表明,码速率、通信波长和卫星振动都会影响星间二维光CDMA通信系统的误码率性能.当卫星振动标准偏差σ≤4×10－7时,卫星振动对系统误码率性能的影响较小；当卫星振动标准偏差σ≥1.2×10－6,卫星振动对系统误码率性能的影响很大,得到的误码率难以满足系统的通信要求,需要采用卫星振动抑制或补偿等技术提高星间二维光CDMA通信系统的误码率性能.     

基于卫星共视法的电网时频测量及同步技术

时间同步对电网的安全和管理有着重要影响,如何准确可靠地同步电网时间值得研究。为此,提出利用卫星共视技术进行电网时间频率的远程校准、进而实现电网时间同步的方法。首先,提出电力系统的四级时间频率溯源体系,明确了电网时间频率溯源关系。其次,研究建立了可以满足卫星共视要求的时间频率计量标准装置,依托标准装置,将卫星共视技术应用于电力系统时间频率远程校准中,利用卡尔曼滤波算法去除干扰,并分析了基于卫星共视技术的电网时间频率同步方法。为定量评价提出方法的有效性,研究了采用提出的方法进行溯源时的时间不确定度和频率不确定度。实验及分析结果表明,提出的方法可以实现时间频率量值的高精度远程传递,从而保障电力系统中的时间同步。     

光学星间链路技术

通过卫星间直接通信实现数据中继是空间通信技术发展的一个重要方面。光学星间链路与传统的微波链路相比具有重量轻、体积小、功耗低等诸多优点,但在捕获和跟踪等方面也存在着巨大的困难。描述了光学星间链路的系统结构极其关键技术,包括通信收发机、捕获与跟踪、光源与探测器以及空间应用的一些特殊问题。介绍了国际上几个主要研究计划的进展情况,并对光学星间链路的发展前景进行了综述。     

Methods of rapid orbit forecasting after maneuvers for geostationary satellites

A geostationary (GEO) satellite may serve as a navigation satellite, but there is a problem that maneuvers frequently occur and the forces are difficult to model. Based on the technique of determining satellite orbits by transfer, a predicted orbit with high accuracy may be achieved by the method of statistical orbit determination in case of no maneuver force. The predicted orbit will soon be invalid after the maneuver starts, and it takes a long time to get a valid orbit after the maneuver ends. In order to improve ephemeris usability, the method of rapid orbit forecasting after maneuvers is studied. First, GEO satellite movement is analyzed in case of maneuvers based on the observation from the orbit measurement system by transfer. Then when a GEO satellite is in the free status just after maneuvers, the short arc observation is used to forecast the orbit. It is assumed that the common system bias and biases of each station are constant, which can be obtained from orbit determination with long arc observations. In this way, only 6 orbit elements would be solved by the method of statistical orbit determination, and the ephemeris with high accuracy may be soon obtained. Actual orbit forecasting with short arc observation for SINOSAT-1 satellite shows that, with the tracking network available, the precision of the predicted orbit (RMS of O-C) can reach about 5 m with 15 min arc observation, and about 3 m with 30 min arc observation. Supported by the National High Technology Research and Development Program of China (Grant No. 2006AA12Z322), the National Basic Research Program of China (Grant No. 2007CB815503), and the West Light Program of Chinese Academy of Sciences (Grant No. 2007LH01)     

数字域时间延迟积分时间CMOS相机高分“凝视”成像设计分析

为实现凝视卫星高分跟踪成像,设计了数字域时间延迟积分(TDI)互补金属氧化物半导体(CMOS)传感器在凝视姿态下的成像匹配模型,推导了卫星凝视跟踪成像时相对轨道坐标系的姿态变化,采用坐标变换方法实时计算其在凝视过程中随姿态变化的行转移时间,利用蒙特卡罗方法统计计算了凝视模式下姿态指向精度和稳定度对成像的影响。利用数字域TDI CMOS原理样机和小卫星姿态控制系统全物理仿真平台对成像进行了仿真分析。结果表明,卫星的姿态控制精度在成像过程中会引起纵向的像移速度失配和横向匹配的残余像移,成像积分级数越高,图像信噪比越大。积分级数的增加对卫星姿态提出较高要求,仿真平台姿态角和姿态角速度控制精度分别优于0.05°,0.005°/s时,采用积分级数为48级能较好地满足成像质量要求。