卫星测控系统多通道地面测试平台设计

一般地面测试平台无法同时支持卫星对地测控测试和中继测控测试,需要开发多通道地面测试平台满足卫星测试需求.基于此,对卫星测控系统多通道地面测试平台设计进行讨论,采用彼此相对独立的2套地面测试设备,通过特定连接关系同时接入卫星对地测控链路和中继测控链路中,实现卫星多通道测控并行测试和地面测试设备的双机备份,在无须更改外部连接关系的基础上,通过模式选择、参数配置,可适用于不同模式下卫星测控通道地面测试需求.经过分析,该平台具有功能完善、适用性广、稳定性好等优点,已应用于某卫星的地面测试.测试结果表明,平台运行稳定,具有良好的使用效果.     

Spacecraft telemetry link performance in a transfer orbit

There are several critical periods early in the mission of a geo-stationary communication satellite. The first is the period from launch vehicle ignition until the upper stage final successful burn. The second is after the above span until the vehicle reaches its final altitude of a synchronous orbit. For a nominal low thrust apogee boost ascent subsystem during that later time, almost continuous telemetry is mandatory. This is especially true during the crucial periods of main engine burns and attitude correction phases. Maintaining a strong telemetry link throughout this phase requires an adequate RF signal link from the spacecraft to a ground station in the telemetry RF channel. An analysis of this link performance during each orbit until final position has two major aspects. One, the location of the spacecraft in relation to the ground tracking station at each moment in the mission is a matter of geometry and Keplerian physics. The other is the RF signal and its supporting subsystems, both on the ground and aboard the vehicle. The fundamental theoretical considerations or both the orbit parameters and radio link components are examined and then the individual parameter sensitivities are analyzed. Next, a nominal cast for a generic mission is studied. This survey considers the telemetry performance during each major stage of the flight from the launch through the transfer orbit to the postinjection period to the final orbit. Then abnormal situations due to both orbit and RF faults are examined. Finally, some design and operation concepts which may lessen the impact of the previous anomalies, are presented     

Space-based SSR constellation for global air traffic control

Advanced surveillance and communications are the main functions needed for an efficient Air Traffic Control/Management (ATC/ATM). In order to perform them over the entire Earth, a novel architecture is described and evaluated. It supplies the surveillance and data link capabilities of advanced Secondary Surveillance Radar (SSR) Mode S world-wide by means of a constellation of medium orbit satellites carrying SSR Mode S interrogators with phased-array antennas; no new equipment is required on-board aircraft, because the standard transponders are used. The rationale for the study, the system geometry, the link budget computation, the accuracy requirements as well as the subsequent design of the payload and of the optimized constellations needed for global coverage with high location accuracy are described. Moreover, details are given about the design of the spacecraft and of the main units of the space segment. The encouraging results of this overall system study pave the way to a demonstration based on simulators and ground prototypes of the critical parts     

提高LAAS空间信号可用性的完好性监测新膨胀算法

局域增强系统(LAAS)地面主控站(LGF)广播的差分修正量所包含的非零均值高斯误差和非高斯误差对系统的可用性造成较大的威胁.为此,提出一种均值膨胀和非高斯膨胀相结合的算法以改进传统的sigma膨胀算法.通过恰当地选取各膨胀系数,采用改进算法可在满足各类型误差尾部覆盖的同时,还可有效提高系统的可用性水平.计算机仿真结果...     

Combining the Effects of Rain-Induced Attenuation and Depolarization in Digital Satellite Systems

Rain depolarization causes crosstalk on a dual polarization communications link. The effects of depolarization can be expressed as a degradation of the carrier-to-noise ratio (CNR) which can then be combined with the rain-induced attenuation to yield an effective attenuation. The effective attenuation is computed for a hypothetical satellite link at 11, 14, 20, and 30 GHz. It is shown that at 20/ 30 GHz the increase in system margin required by dual polarized use is small.     

Closed-Loop Transmitting Power Control System for K-band Satellite Communications

In order to cope with K-band link loss variations and also to improve link reliability, a new closed-loop satellite access power control system is proposed. This system controls Earth station transmitting power so that the overall satellite link quality, such as S/N or error rate, converges to the stipulated value. Satellite transmitting power is also optimized by this control, enabling a considerable increase in transmission capacity and improvement in link reliability.     

Advanced Picosatellite Experiment

The design of the CAPE I satellite was underway for approximately three years. This interdisciplinary project incorporates electrical, mechanical, and aerospace engineering, as well as computer science and physics. The project hoped to teach students how to design, develop, and maintain a lower Earth orbiting satellite. This satellite was delivered to San Luis Obispo, California, December 5, 2006, where it passed the final integration test in order to qualify for launch. After qualification, the satellite was loaded into the poly-picosatellite orbital deployer or P-POD, which is the deployment system for the satellite. The P-POD holds three CubeSats. Once all three satellites were integrated, it was delivered to Kazakhstan and loaded into the DNEPR Russian Rocket on March 17, 2007. After a few delays, the rocket was launched on April 17,2007. The team is currently monitoring and decoding the CW beacons transmitted by the satellite. The project was broken into several subsystems including mechanical, communications, control and data handling, and power. Each of the systems proved to have their own unique challenges. Being that the majority of the team was electrical engineering students, the mechanical subsystem presented the most difficulty. There is currently a design in progress for the next satellite project, CAPE II. This new satellite will attempt a new benchmark by incorporating more advanced technologies than CAPE I and include other campus entities such as The Wetlands Research Center. The team hopes to deploy buoys into the Gulf of Mexico that will communicate to the CAPE 11 satellite in space and then send data to the ground station at the University. This data will include subjects such as coastal erosion, water temperatures, and drift currents throughout the Gulf. With this data, we can give other organizations the information obtained for their use as well.     

Predicting the visibility of LEO satellites

We present a simple algorithm to determine the visibility-time function of a circular low Earth orbit (LEO) satellite at a terminal on the Earth's surface. The simplicity of the algorithm is based on approximating the ground trace of the satellite (which is not a great circle due to Earth's rotation) during a time interval of the order of in-view period, by a great-circle are. This enables us to use spherical geometry to compute the location and time epoch of the observation of the closest approach of the satellite's ground trace to the terminal. This is also the epoch of the observation of the maximum elevation angle from the terminal to the satellite. Applying a result derived relating the maximum elevation angle to the in-view period, we obtain the visibility-time function of the satellite at the terminal. Numerical results illustrate the accuracy of the algorithm for a wide range of LEO orbit altitudes     

星间链路数量受限的导航卫星网络链路分配问题

对星间链路数量非常有限、需要同时满足星间测距和星间通信需求的导航卫星网络的链路分配问题进行了研究。首先,分析了导航卫星网络的特点,并设计了一种基于有限状态自动机(FSA)的拓扑处理机制。然后,将星间测距需求作为一个约束,以星间通信的延时性能为优化目标,将导航卫星网络的链路分配问题建模为一个多目标优化问题。最后,针对建立的多目标优化问题,分别提出一种基于首次改善(FI)的本地搜索算法和基于模拟退火(SA)的启发式优化算法以对链路分配问题进行求解,并提出一种基于分支交换策略的新链路分配生成方法。仿真结果表明,通过FI算法和SA算法获得的优化链路分配的网络延时性能均得到了改进,且SA算法的性能要优于FI算法;同时,FSA的状态持续时间的减小有利于获得网络延时性能好的链路分配。     

卫星筒式偏心在轨分离动力学分析

偏心安装的子卫星在轨分离是一类特殊的卫星在轨分离问题。为了给分离地面试验和分离系统设计提供依据,在惯性参考系中分析了筒式偏心在轨分离问题的运动特性。以刚体运动学原理和动力学动量定理、角动量定理及能量定理为依据,建立了分离过程的动力学模型。运用数值求解方法,给出了不同初始条件下的模型求解算例,并对求解结果进行了比较和分析。分析结果表明,分离弹簧物性参数是影响分离速度的主要因素;卫星相对安装位置是影响分离角速度的主要因素。     

面向制造的卫星零件设计系统的研究与实现

针对卫星零件的设计和加工特点,提出了一种基于特征的卫星零件面向制造的设计系统体系结构,研究了基于特征的面向制造设计系统中的零件信息模型,确定了该设计系统中可制造性评价的内容,并建立了基于知识和几何推理的可制造性评价系统,以实现面向制造的设计技术在卫星零件设计中的应用.     

科学实验卫星高速上行链路设计

为保障在卫星与地面之间开展空间量子科学实验的条件,必须为科学实验载荷建立一条星—地高速数据双向传输链路.通过跟踪CCSDS-SLS-NGU（空间数据系统咨询委员会-空间链路业务-下一代上行链路）工作组对NGU的研究进展,结合科学实验卫星有效载荷建立高速上行链路的需求,采用高带宽利用率调制技术、高效信道编码方式及适用的链路数据传输协议,设计了一种传输速率为1Mbit/s、误码率优于1×10-9的高速上行链路方案,并给出星载设备实现方案和地面初步测试结果.该方案在技术体制上兼容已有CCSDS规范,便于地面站及星载接收机实现,完全满足开展空间量子科学实验的需要.     

Radically new design of SAR satellite: short vertical antennaapproach

The idea of this work is the use of a vertical antenna (antenna placed in the orbit plane) for a spaceborne radar. This surprising geometry is proven to work properly and to simplify the design of the instrument, particularly when it is associated with a short antenna length (<5 m, along speed vector). The number of antenna control points is greatly reduced, which saves cost and mass of an active antenna. A single pencil beam allows all the incidences and modes to be achieved. Viewing on both sides of the satellite track is enabled. Spotlight mode is no longer needed and therefore most of the operational constraints attached to high resolution are removed. Merits of the geometry are not limited to the instrument, a cascade of other innovations converges into a radically new design of the whole satellite for an ultimate goal of simplification and cost reduction, this is radar SAIL concept. The merits and cost savings of short vertical antenna are illustrated with a 1 m resolution X band mission, and the extra merits of the integrated SAIL architecture with respect to the standard satellite architecture are discussed     

Automobile Navigation: Where is it Going?

Automobile navigation systems based on dead reckoning, map matching, satellite positioning and other navigation technologies are under active development. ``Map intelligent' systems achieve high relative accuracy by matching dead-reckoned paths with road geometry encoded in a digital map data base that may also serve other functions such as vehicle routing and geocoding. Satellite-based navigation systems achieve high absolute accuracy but require dead reckoning augmentation because of signal aberrations in the automotive environment. Future systems will probably include multiple navigation technologies. Issues influencing the design of future systems include safety concerns regarding the driver interface, and the future availability of comprehensive map data bases, real-time traffic data, and mobile data communication links necessary for on-board generation of optimum routes.     

一种单低轨星北斗备份与辅助方法及在轨验证

在低轨卫星上搭载导航载荷,为北斗系统提供有效的备份及辅助性能提升手段,是近年来卫星导航领域专家学者探讨的热点问题.针对全球卫星导航系统信号在恶劣电磁环境下的受扰问题,提出了一种利用单颗低轨卫星实现北斗备份和辅助的方法.北斗备份是指通过单颗低轨星独立为地面用户提供导航服务.北斗辅助是指利用单颗低轨星信号及信息,为地面用户...     

Earth-moon libration points: Theory,existence and applications

The availability of reliable satellites and space probes makes it timely to review our state of knowledge in detail on all aspects of our solar system so that these new tools can be used to maxi-mum advantage in scientific exploration and technical use.Earth-Moon libration points have been of theoretical interest as a concrete example in the three body problem. In analogy with the Trojan Asteroids they may also be collection points for dust or particles or other small bodies which are shown to be of geophysical interest. Finally, they may find use in applications where relatively long time stationary behavior relative to the Earth and the Moon is desirable; for example: for long term Solar observation or as a communication link.The leading question of interest at the present is confirmation of reported ground observations on dust clouds in the vicinity of the stable points through satellite based observations.The Authors are indebted to the Space Sciences Board of the U.S. National Academy of Sciences for permission to use background material of the Space Research Summer Study 1965.     

Optimal air-launching rocket design using system trades and a multi-disciplinary optimization approach

Compared with the conventional ground rocket launching, air-launching has many advantages. However, a comprehensive and integrated system design approach is required because the physical geometry of air launch vehicle is quite dependent on the installation limitation of the mother plane. For the selection of the best system alternative, a trade study for the first stage engine type and launching speeds is performed using a sequential optimization technique, confirming the feasibility of the baseline air-launching rocket. Then, a system design has been performed using the multi-disciplinary feasible (MDF) design optimization method. Analysis modules include mission analysis, staging, propulsion analysis, configuration, weight analysis, aerodynamics analysis and trajectory analysis. As a result of multi-disciplinary system optimization, a supersonic air launching rocket with total mass of 1244.9 kg, total length of 6.36 m, outer diameter of 0.60 m has been successfully designed to launch a satellite of 7.5 kg to the 700 km circular orbit.     

Low cost satellite ground control facility design

A design approach common to the areas of satellite operations command and control, tracking, subsystem analysis, system planning and scheduling, orbit determination and maintenance, and data routing and control is discussed. Specific satellite mission applications and operations are isolated from the remainder of the design to allow application to a broad variety of satellite systems. Discussions of specific satellite missions are limited to the context of understanding the general magnitude and scope of what a ground control facility is required to support. By isolating the common satellite operational functions, a low cost generic approach that allows for phased implementation of system changes with minimal impact to on-orbit assets and mission performance is developed. The goals of this approach are to provide the capability for growth, maintainability, and operability of the satellite system. A brief discussion of satellite systems followed by the introduction of the general function of any satellite control facility sets the stage for the overall design approach. The factors that define the design along with the key design features are presented, with a discussion of each product available in each functional area     

数据分发用户协议模型研究

通过分析某型号卫星用户地面链路的实际应用情况,结合互联网应用协议模型,面向系统未来发展需要,提出了数据分发用户协议模型,分析了协议模型的层次关系,介绍了协议模型的具体工作过程,并对其工程可行性进行了分析,解决了地面链路连接管理以及应用负载分配的应用问题,在一定程度上避免了系统安全隐患,为系统实际工程应用提供了切实可行的途径。