Satellite system

Abstract: A wireless telephone system capable of servicing a roaming wireless telephone user includes a satellite communications system consisting of one or more orbiting satellites, each carrying a database of users, destination codes and call codes, within a satellite service area, a satellite control center, and a plurality of terrestrial communications links. The system operates by effecting communication between a terrestrial wireless telephone end user transceiver apparatus and a terrestrial communications link via a single relay through a single satellite or a succession of satellites wherein the relay station may be in motion relative to the end user transceiver apparatus and the terrestrial communications link, wherein the orbiting relay station effects the ultimate decision on linking based on stored on-board information and on-board processing, and wherein the end user transceiver apparatus, the orbiting satellite and the terrestrial communications link are operative in cooperation with the on-board database to effect hand-off from a first orbiting satellite to a second orbiting satellite. The satellite system is a single satellite or preferably a constellation of satellites orbiting near the earth, all of which are capable receiving requests for calls and participating in the call routing and call setup on an autonomous basis. The satellites are capable of decoding the calls, switching, handing off of calls to other satellites, and updating databases of users based on information provided by network control.

Abstract: ACKNOWLEDGEMENT ACRONYMS NOTATION 1 INTRODUCTION 11 Birth of satellite communications 12 Development of satellite communications 13 Configuration of a satellite communications system 14 Types of orbit 15 Radio regulations 16 Technology trends 17 Services 18 The way forward References 2 ORBITS AND RELATED ISSUES 21 Keplerian orbits 22 Useful orbits for satellite communication 23 Perturbations of orbits 24 Conclusion References 3 BASEBAND SIGNALS AND QUALITY OF SERVICE 31 Baseband signals 32 Performance objectives 33 Availability objectives 34 Delay 35 Conclusion References 4 DIGITAL COMMUNICATIONS TECHNIQUES 41 Baseband formatting 42 Digital modulation 43 Channel coding 44 Channel coding and the power-bandwidth trade-off 45 Coded modulation 46 End-to-end error control 47 Digital video broadcasting via satellite (DVB-S) 48 Second generation DVB-S 49 Conclusion References 5 UPLINK, DOWNLINK AND OVERALL LINK PERFORMANCE INTERSATELLITE LINKS 51 Configuration of a link 52 Antenna parameters 53 Radiated power 54 Received signal power 55 Noise power spectral density at the receiver input 56 Individual link performance 57 Influence of the atmosphere 58 Mitigation of atmospheric impairments 59 Overall link performance with transparent satellite 510 Overall link performance with regenerative satellite 511 Link performance with multibeam antenna coverage vs moonbeam coverage 512 Intersatellite link performance References 6 MULTIPLE ACCESS 61 Layered data transmission 62 Traffic parameters 63 Traffic routing 64 Access techniques 65 Frequency division multiple access (FDMA) 66 Time division multiple access (TDMA) 67 Code division multiple access (CDMA) 68 Fixed and on-demand assignment 69 Random access 610 Conclusion References 7 SATELLITE NETWORKS 71 Network reference models and protocols 72 Reference architecture for satellite networks 73 Basic characteristics of satellite networks 74 Satellite on-board connectivity 75 Connectivity through intersatellite links (ISL) 76 Satellite broadcast networks 77 Broadband satellite networks 78 Transmission control protocol 79 IPv6 over satellite networks 710 Conclusion References 8 EARTH STATIONS 81 Station organisation 82 Radio-frequency characteristics 83 The antenna subsystem 84 The radio-frequency subsystem 85 Communication subsystems 86 The network interface subsystem 87 Monitoring and control auxiliary equipment 88 Conclusion References 9 THE COMMUNICATION PAYLOAD 91 Mission and characteristics of the payload 92 Transparent repeater 93 Regenerative repeater 94 Multibeam antenna payload 95 Introduction to flexible payloads 96 Solid state equipment technology 97 Antenna coverage 98 Antenna characteristics 99 Conclusion References 10 THE PLATFORM 101 Subsystems 102 Attitude control 103 The propulsion subsystem 104 The electric power supply 105 Telemetry, tracking and command (TTC) and on-board data handling (OBDH) 106 Thermal control and structure 107 Developments and trends References 11 SATELLITE INSTALLATION AND LAUNCH VEHICLES 111 Installation in orbit 112 Launch vehicles References 12 THE SPACE ENVIRONMENT 121 Vacuum 122 The mechanical environment 123 Radiation 124 Flux of high energy particles 125 The environment during installation References 13 RELIABILITY OF SATELLITE COMMUNICATIONS SYSTEMS 131 Introduction of reliability 132 Satellite system availability 133 Subsystem reliability 134 Component reliability INDEX

Abstract: The implementation of synthetic apertures by means of a distributed satellite system requires tight control of the relative motion of the participating satellites. This paper investigates a formation-flying concept able to realize the demanding baselines for aperture synthesis, while minimizing the collision hazard associated with proximity operations. An elegant formulation of the linearized equations of relative motion is discussed and adopted for satellite formation design. The concept of eccentricity/inclination-vector separation, originally developed for geostationary satellites, is here extended to low-Earth-orbit (LEO) formations. It provides immediate insight into key aspects of the relative motion and is particularly useful for orbit control purposes and proximity analyses. The effects of the relevant differential perturbations acting on an initial nominal configuration are presented, and a fuel-efficient orbit control strategy is designed to maintain the target separation. Finally, the method is applied to a specific LEO formation (TanDEM-X/TerraSAR-X), and realistic simulations clearly show the simplicity and effectiveness of the formation-flying concept.

Abstract: A mobile satellite system includes a network engineering/systems engineering (NE/SE) system. The NE/SE performs the processes of comparing expected traffic loads with capability and availability of space and ground resources in the mobile satellite system, formulating tactical plans to maximize available resources of the satellite, and producing frequency plans for different geographical regions and defining circuit pools for different groups of users of the METs. The NE/SE also performs the processes of defining contingency plans for failure situations, such as failure in the satellite or a ground-based equipment outage, configuring the mobile satellite system including logical resources and physical components generating logical and physical configurations, the logical and physical configurations designed to expand the mobile satellite system capacity for increases in traffic demand, while also supporting new features and services of the mobile satellite system. The NE/SE further configures communication paths to external organizations operatively connected to the mobile satellite system, and tracks logistics of network additions to the mobile satellite system via generation of work orders.

Abstract: Orbital resonances are defined as any system of two or more satellites (including planets) orbiting the same primary and whose orbital mean motions are in a ratio of small whole numbers. Known orbital resonances in the solar system are identified, including those involving Jupiter's satellites Io, Europa, and Ganymede; Saturn's satellites Mimas and Tethys, Enceladus and Dione, and Titan and Hyperion; Saturn's ring gaps and Mimas; various asteroids and Jupiter; and the planets Neptune and Pluto. The stability of orbital resonances is examined, the origin of orbital commensurabilities is investigated, and a simple model of the simplest kind of eccentricity-type resonance is outlined. A method is described by which tides carry a noncommensurate pair of satellites into a stable libration, and current ideas concerning the formation of the gaps in Saturn's rings and the asteroid belt are discussed. Various approaches to the analysis of orbital resonances are laid out and illustrated. Three two-body commensurabilities in Saturn's satellite system are analyzed numerically.