基于数据包的航天器数管模拟器软件设计

随着空间技术的快速发展,使用数管模拟器模拟数管分系统进行测试已成为趋势。为了使数管模拟器软件能够适应航天器数据管理新的变化,降低软件实现难度,根据用户需求和已有硬件平台,提出了一种软件设计。本设计采用数据处理分层体制协议来降低软件实现的复杂性,使用数据包进行数据处理,并利用数据帧来完成数据的传输。该模拟器进行了100 h的各项功能老练试验,结果表明,该设计可靠、稳定、能满足设计要求。     

GPS‐Based Orbit Determination for KOMPSAT‐5 Satellite

Korea Multi‐Purpose Satellite‐5 (KOMPSAT‐5) is the first satellite in Korea that provides 1 m resolution synthetic aperture radar (SAR) images. Precise orbit determination (POD) using a dual‐frequency IGOR receiver data is performed to conduct high‐resolution SAR images. We suggest orbit determination strategies based on a differential GPS technique. Double‐differenced phase observations are sampled every 30 seconds. A dynamic model approach using an estimation of general empirical acceleration every 6 minutes through a batch least‐squares estimator is applied. The orbit accuracy is validated using real data from GRACE and KOMPSAT‐2 as well as simulated KOMPSAT‐5 data. The POD results using GRACE satellite are adjusted through satellite laser ranging data and compared with publicly available reference orbit data. Operational orbit determination satisfies 5 m root sum square (RSS) in one sigma, and POD meets the orbit accuracy requirements of less than 20 cm and 0.003 cm/s RSS in position and velocity, respectively.     

Recent advances in ‘in-orbit testing’ of communications satellites

After a successful launch of a new communications satellite, it is essential to test the communications subsystem while the spacecraft is in orbit so as to compare with prelaunch data in order to ensure that no impairment has resulted from the stress of the launch and to verify that the spacecraft payload is compliant with the specifications sought. The thrust of in-orbit test technology has stemmed from the fact that the spacecraft has to be operational very quickly while not sacrificing the number of tests that have to be performed and increasing their measurement accuracies. Thus, in order to respond favourably to the cited criteria, microwave measurement techniques with more powerful computers and software technology have been used to automate the measurements. The paper is geared to the history, design, implementation and operation of EUTELSAT's in-orbit test (IOT) facilities, and mostly reflects technological advances in communications satellite payload testing. The paper will first detail the hardware/software novel concepts of the measurement environment. Then new measurements are summarized. New spacecraft antenna mapping procedures are detailed both in measurement and spacecraft attitude aspects.     

Development and Testing of Satellite Operation System for Korea Multipurpose Satellite‐I

The Satellite Operation System (SOS) has been developed for a low earth orbiting remote sensing satellite, Korea Multipurpose Satellite‐I, to monitor and control the spacecraft as well as to perform the mission operation. SOS was designed to operate on UNIX in the HP workstations. In the design of SOS, flexibility, reliability, expandability and interoperability were the main objectives. In order to achieve these objectives, a CASE tool, a database management system, consultative committee for space data systems recommendation, and a real‐time distributed processing middle‐ware have been integrated into the system. A database driven structure was adopted as the baseline architecture for a generic machine‐independent, mission specific database. Also a logical address based inter‐process communication scheme was introduced for a distributed allocation of the network resources. Specifically, a hot‐standby redundancy scheme was highlighted in the design seeking for higher system reliability and uninterrupted service required in a real‐time fashion during the satellite passes. Through various tests, SOS had been verified its functional, performance, and interface requirements. Design, implementation, and testing of the SOS for KOMPSAT‐I is presented in this paper.     

Cross‐layer packet scheduler for QoS support over Digital Video Broadcasting‐Second Generation broadband satellite systems

This article presents a cross‐layer packet scheduler to provide end‐to‐end QoS guarantees for Digital Video Broadcasting‐Second Generation (DVB‐S2) broadband satellite systems. The scheduler design is based on a cross‐layer mechanism defined between the physical and the network layer. It includes an algorithm to guarantee the required QoS specifications established in the service level agreement. The algorithm calculation depends basically on two parameters: the available bandwidth present in a DVB‐S2 satellite link and the QoS requirements of each traffic class defined by the satellite operator. The cross‐layer scheduler's operation is demonstrated using the NS‐2 simulator tool. The results show that the proposed mechanism maximizes the bandwidth utilization while enforcing the priority level of each service class when an extreme reduction of bandwidth caused by rain events is experienced. Copyright © 2012 John Wiley & Sons, Ltd.     

Model‐based guidelines for user‐centric satellite control software development

Three persistent common problems in satellite ground control software are obsolescence, lack of desired features and flexibilities, and endless software bug fixing. The obsolescence problem occurs when computer and ground equipment hardware become obsolete, usually after only one‐third into the satellite mission lifetime. The software needs to be updated to accommodate changes on the hardware side, requiring significant work of satellite operators to test, verify, and validate these software updates. Trying to help solve these problems, we have proposed an object‐process methodology model and guidelines for developing satellite ground control software. The system makes use of a database‐driven application and concepts of object‐process orientation and modularity. In the new proposed framework, instead of coding each software function separately, the common base functions will be coded, and combining them in various ways will provide the different required functions. The formation and combination of these base functions will be governed by the main code, definitions, and database parameters. These design principles will make sure that the new software framework would provide satellite operators with the flexibility to create new features and enable software developer to find bugs quicker and fix them more effectively. Copyright © 2015 John Wiley & Sons, Ltd.     

飞行器卫星通信链路设计与分析

介绍了飞行器与卫星间通信链路的组成、工作原理和系统设计考虑,讨论了系统信息传输 体制和飞行器载设备的实现。通过理论计算及仿真,进行了系统关键技术及主要性能指标的 可实现性分析,对工程应用具有一定参考价值。     

Design and Development of an Advanced Real-Time Satellite Simulator

An advanced real-time satellite simulator (ARTSS) has been developed to support the ground operations activities of the ETRI satellite control system, such as testing of the system facilities, validation of flight control procedures, verification of satellite commands as well as training of the ground operators. The design of ARTSS is based on the top-down approach and makes use of a modular programming to ensure flexibility in modification and expansion of the system. Graphics-based monitoring and control facilities enhance the satellite simulation environment. The software spacecraft model in ARTSS simulates the characteristics of a geostationary communication satellite using a momentum bias three-axis stabilization control technique. The system can be also interfaced with a hardware payload subsystem such as Ku-band communication transponder to enhance the simulator capability. Therefore, ARTSS is a high fidelity satellite simulation tool that can be used on low-cost desk top computers. In this paper, we describe the design features, the simulation models and the real-time operating functions of the simulator.     

卫星激光测距系统中图像处理子系统设计

为了提高卫星激光测距系统的自动化程度,设计了一套用于卫星激光测距系统的图像处理子系统。本子系统通过图像处理手段,解算出激光束光尖和卫星位置,并将位置偏差反馈给控制计算机,用以调整激光束的出光方向和修正预报偏差。首先给出了该系统的软硬件框架和实现流程;然后重点介绍了图像处理部分算法;最后结合实际观测对系统进行性能验证,结果表明本系统功能正常,稳定可靠,在一定程度上提高了激光测距系统的精度和实时性。     

静止卫星闪电测绘仪设计特点研讨

自然闪电是一种全球现象.静止闪电测绘仪探测涉及全球范围内自然闪电发生的时间、地点和强度分布.这一飞行任务的功能和性能与其他对地光学遥感器有很大差别,因此仪器的设计必须完全建立在新的理论和技术基础上.分析自然闪电的光谱特性、时间特性和空间特性,了解空间探测闪电环境,以及研究自然闪电和其探测环境间的相互作用,对这种仪器的设...     

Evaluation of Geometric Modeling for KOMPSAT‐1 EOC Imagery Using Ephemeris Data

Using stereo images with ephemeris data from the Korea Multi‐Purpose Satellite‐1 electro‐optical camera (KOMPSAT‐1 EOC), we performed geometric modeling for three‐dimensional (3‐D) positioning and evaluated its accuracy. In the geometric modeling procedures, we used ephemeris data included in the image header file to calculate the orbital parameters, sensor attitudes, and satellite position. An inconsistency between the time information of the ephemeris data and that of the center of the image frame was found, which caused a significant offset in satellite position. This time inconsistency was successfully adjusted. We modeled the actual satellite positions of the left and right images using only two ground control points and then achieved 3‐D positioning using the KOMPSAT‐1 EOC stereo images. The results show that the positioning accuracy was about 12‐17 m root mean square error (RMSE) when 6.6 m resolution EOC stereo images were used along with the ephemeris data and only two ground control points (GCPs). If more accurate ephemeris data are provided in the near future, then a more accurate 3‐D positioning will also be realized using only the EOC stereo images with ephemeris data and without the need for any GCPs.     

On the impact of link layer retransmission schemes on TCP over 4G satellite links

We study the impact of reliability mechanisms introduced at the link layer on the performance of transport protocols in the context of 4G satellite links. Specifically, we design a software module that performs realistic analysis of the network performance, by utilizing real physical layer traces of a 4G satellite service. Based on these traces, our software module produces equivalent link layer traces, as a function of the chosen link layer reliability mechanism. We further utilize the link layer traces within the ns‐2 network simulator to evaluate the impact of link layer schemes on the performance of selected Transmission Control Protocol (TCP) variants. We consider erasure coding, selective‐repeat automatic request (ARQ) and hybrid‐ARQ link layer mechanisms, and TCP Cubic, Compound, Hybla, New Reno and Westwood. We show that, for all target TCP variants, when the throughput of the transport protocol is close to the channel capacity, using the ARQ mechanism is most beneficial for TCP performance improvement. In conditions where the physical channel error rate is high, hybrid‐ARQ results in the best performance for all TCP variants considered, with up to 22% improvements compared to other schemes. Copyright © 2014 John Wiley & Sons, Ltd.     

MF-TDMA卫星通信网络仿真测试研究

MF-TDMA卫星网络是一个规模大,功能齐全,分布地域广的复杂通信系统,对于大型卫星网络的功能测试,可利用专用工具支持可视化建模,快速测试设计配置缺陷,优化设计结构,尽快设计出大型网络并组织应用。着重介绍了在Rational Rose工具上如何建立一个基于多种业务的大型卫星通信网络模型,并对网络运行下的各种功能测试进行了仿真测试研究,最后给出了实现卫星网络的最佳结构数据。     

A novel QoS routing protocol for LEO and MEO satellite networks

The rapid advance of communication and satellite technology pushes broadband satellite networks to carry on multimedia traffic. However, the function of onboard routing cannot be provided in existing satellite networks with inter‐satellite links, and quality of service (QoS) of satellite networks cannot be reliably guaranteed because of great difficulties in processing of long distance‐dependent traffic. In this paper, a two‐layered low‐Earth orbit and medium‐Earth orbit satellite network (LMSN) is presented. A novel hierarchical and distributed QoS routing protocol (HDRP) is investigated, and an adaptive bandwidth‐constrained minimum‐delay path algorithm is developed to calculate routing tables efficiently using the QoS metric information composed of delays and bandwidth. The performance of LMSN and HDRP is also evaluated through simulations and theoretical analysis. Copyright © 2007 John Wiley & Sons, Ltd.     

基于软件无线电技术的通用卫星模拟器设计

航天测控站配备的传统的卫星模拟器功能单一,通用性差,已经不能满足目前卫星发展的多种测控体制、多种卫星平台的实际需求.为满足这一需求,研究了一种基于软件无线电技术的通用卫星模拟器,在70 MHz中频上进行数字化处理,实现了多体制、多星共用的功能.该卫星模拟器具有体积小、精度高、稳定性好、操作维护简单的特点.     

卫星信号模拟器的发展现状与趋势

卫星信号模拟器作为卫星导航接收机开发与验证的必备工具,其相关理论研究与工程应用具有重要学术意义和巨大商业价值.详细介绍了软件、硬件和混合架构三种卫星信号模拟器的国内外理论研究和产品动态,总结了电离层误差、多径效应等主要误差模型的理论研究进展和应用现状,通过对比指出了国内较国外在模拟器产品、仿真理论特别是误差模型理论研究...     

Experimental proof of concept of an SDN‐based traffic engineering solution for hybrid satellite‐terrestrial mobile backhauling

Satellite networks are expected to be an integral part of 5G service deployment. One compelling use case is mobile backhauling, where the exploitation of a satellite component can improve the reach, robustness, and economics of 5G rollout. The envisaged availability of new satellite capacity, together with the development of better integration approaches for the provisioning and operation of the satellite component in a more flexible, agile, and cost‐effective manner than done today, are expected to revamp such use case within the 5G ecosystem. In this context, sustained in the architectural designs proposed within H2020 VITAL research project, this paper presents an experimental proof of concept (PoC) of a satellite‐terrestrial integration solution that builds upon software‐defined networking (SDN) technologies for the realization of end‐to‐end traffic engineering (E2E TE) in mobile backhauling networks with a satellite component. A laboratory test bed has been developed and validated, consisting of a small‐scale private mobile network with a backhaul setting that combines Ethernet‐wired links, a satellite link emulator (OpenSAND), OpenFlow switches, and an OpenFlow controller running the network application for E2E TE. Provided results show the operation of a E2E TE application able to enforce different traffic routing and path failure restoration policies as well as the performance impact that it has on the mobile network connectivity services.     

Software‐defined satellite cloud RAN

This paper provides an assessment study on the virtualization of a Digital Video Broadcasting ‐ Satellite ‐ Second Generation (DVB‐S2)/ Digital Video Broadcasting ‐ Return Channel Satellite ‐ Second Generation (DVB‐RCS2) satellite ground infrastructure and proposes a framework, named Satellite Cloud Radio Access Network (SatCloudRAN), that aims to ease the integration of satellite components in forthcoming 5G systems. Special attention is given to the design of SatCloudRAN by considering the split and placement of virtualized and nonvirtualized functions while taking into account the characteristics of the transport links connecting both type of functions. We assess how virtualization and softwarization technologies, namely, network function virtualization and software‐defined networking, can deliver part of the satellite gateway functionalities as virtual network functions and achieve a flexible and programmable control and management of satellite infrastructure. Under the network function virtualization paradigm, building virtual network function blocks that compose a satellite gateway have been identified, and their interaction exhibited. This paper also gives insights on how the SatCloudRAN approach can allow operators to provide software‐defined networking‐based (1) bandwidth on demand, (2) dynamic Quality of Service, and (3) satellite gateway diversity. Copyright © 2017 John Wiley & Sons, Ltd.     

基于人工神经网络的GPS卫星信号模拟器信号估计方法

多通道全球定位系统(GPS)卫星信号模拟器用来为GPS接收机和导航系统提供逼真的测试信号。该文从模拟器设计的角度对到达GPS接收机天线的卫星信号进行了分析,着重讨论了因众多误差因素影响而不易直接利用经验模型确定的几个波形参量的估计问题。基于人工神经网络(ANN)理论,提出一种利用ANN来模拟信号传播延迟、载波相位、信号功率等参量的方法。给出了基于ANN的模拟器闭环测试系统的结构。并对所设计的ANN进行了训练和验证,仿真实验结果表明,所设计的ANN能够在统计意义上逼真地模拟样本数据,从而使基于ANN的模拟器信号状态参量计算能够满足设计要求,可以直接应用于多通道GPS信号模拟器的研制。