IET TElEcommunIcaTIons sErIEs 38Series Editors:Professor C.J. Hughes Professor J.D. Parsons Professor G. WhiteSatellite Communication Systems 3rd EditionOther volumes in this series:Volume 9Phase noise signal sources W.P. RobinsVolume 12Spread spectrum in communications R. Skaug and J.F. HjelmstadVolume 13Advanced signal processing D.J. Creasey (Editor)Volume 19Telecommunications traffc, tariffs and costs R.E. FarrVolume 20An introduction to satellite communications D.I. DalgleishVolume 25Personal and mobile radio systems R.C.V. Macario (Editor)Volume 26Common-channel signalling R.J. ManterfeldVolume 28Very small aperture terminals (VSATs) J.L. Everett (Editor)Volume 29ATM: the broadband telecommunications solution L.G. Cuthbert and J.C. SapanelVolume 31Data communications and networks, 3rd edition R.L. Brewster (Editor)Volume 32Analogue optical fbre communications B. Wilson, Z. Ghassemlooy and I.Z. Darwazeh (Editors)Volume 33Modern personal radio systems R.C.V. Macario (Editor)Volume 34Digital broadcasting P. DambacherVolume 35Principles of performance engineering for telecommunication and information systems M. Ghanbari, C.J. Hughes, M.C. Sinclair and J.P. EadeVolume 36Telecommunication networks, 2nd edition J.E. Flood (Editor)Volume 37Optical communication receiver design S.B. AlexanderVolume 38Satellite communication systems, 3rd edition B.G. Evans (Editor)Volume 40Spread spectrum in mobile communication O. Berg, T. Berg, J.F. Hjelmstad, S. Haavik and R. SkaugVolume 41World telecommunications economics J.J. WheatleyVolume 43Telecommunications signalling R.J. ManterfeldVolume 44Digital signal fltering, analysis and restoration J. JanVolume 45Radio spectrum management, 2nd edition D.J. WithersVolume 46Intelligent networks: principles and applications J.R. AndersonVolume 47Local access network technologies P. FranceVolume 48Telecommunications quality of service management A.P. Oodan (Editor)Volume 49Standard codecs: image compression to advanced video coding M. GhanbariVolume 50Telecommunications regulation J. BuckleyVolume 51Security for mobility C. Mitchell (Editor)Volume 52Understanding telecommunications networks A. ValdarVolume 904Optical fbre sensing and signal processing B. CulshawVolume 905ISDN applications in education and training R. Mason and P.D. BacsichSatellite Communication Systems 3rd EditionEdited by B.G. EvansThe Institution of Engineering and TechnologyPublished by The Institution of Engineering and Technology, London, United KingdomFirst edition 1999 The Institution of Electrical Engineers Reprint with new cover 2008 The Institution of Engineering and TechnologyFirst published 1999 Reprinted 2000, 2008This publication is copyright under the Berne Convention and the Universal Copyright Convention. All rights reserved. Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act, 1988, this publication may be reproduced, stored or transmitted, in any form or by any means, only with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms of licences issued by the Copyright Licensing Agency. Inquiries concerning reproduction outside those terms should be sent to the publishers at the undermentioned address:The Institution of Engineering and Technology Michael Faraday House Six Hills Way, Stevenage Herts, SG1 2AY, United Kingdomwww.theiet.orgWhile the author and the publishers believe that the information and guidance given in this work are correct, all parties must rely upon their own skill and judgement when making use of them. Neither the author nor the publishers assume any liability to anyone for any loss or damage caused by any error or omission in the work, whether such error or omission is the result of negligence or any other cause. Any and all such liability is disclaimed.The moral rights of the author to be identifed as author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.British Library Cataloguing in Publication DataA catalogue record for this product is available from the British LibraryISBN (10 digit) 0 85296 899 X ISBN (13 digit) 978-0-85296-899-4Printed in the UK by Short Run Press Ltd, Exeter Reprinted in the UK by Lightning Source UK Ltd, Milton KeynesContentsPreface and acknowledgDlentsContributorsxxiiixxv12Introduction. B. G. Evans1.1 Satellite systems1.2 Radio regulations and frequency bands1.3 Satellite orbits1.4 The basic satellite system1.5 Satellite communications in transition1.6 Towards the futureHistorical overview of satellite cODlDlunications. P. T Thompson and]. D.Thompson2.1 The visionaries2.1.1 The start ofspace activities2.2 The pioneers2.3 The early days2.4 International activities2.4.1 History and development of INTELSAT2.4.2 History and development ofEUTELSAT2.4.3 History and development of INMARSAT2.5 Television satellite broadcasting2.6 Technological considerations2.7 Overall developments2.7.1 1945-1960 Imagination2.7.2 1960-1970 Innovation2.7.3 1970-1980 Commercialisation2.7.4 1980-1990s Liberalisation2.7.5 1990s Privatisation and private ventures1124913161919212121222223252628313132323233VI Contents2.82.92.10The futureConclusionsReferences3334343 The satellite co:rn:rnunications business.3.1 Introduction3.2 Satellite organisations3.2.1 INTELSAT3.2.2 EUTELSAT3.2.3 INMARSAT3.3 Private satellite networks3.4 Ka-band satellite systems3.5 Starting up a satellite business3.6 Trade issues3.7 The business plan3.7.1 Mission statement3.7.2 Objectives3.7.3 Marketing audit3.7.4 Strategic marketing plan3.7.5 SWOT analysis3.8 Finance3.8.1 Project costs3.8.2 User equipment costs3.8.3 Insurance costs3.8.4 Financing the project3.9 Technical design3.10 Frequency coordination3.11 Billing3.12 Operations and maintenance3.13 AcknowledgmentsN. Cartwright 37373939414547495051525353535555575758595964646667684 Radio regulatory considerations relating to satelliteco:rn:rnunications syste:rns. P. T. Thompson and A. G. Reed 694.1 Introduction 694.2 The nature of satellite services 704.3 Objectives offrequency/ orbit management 704.4 Frequency allocations 724.5 Frequency management regimes 724.5.1 A priori planning 734.5.2 Allotment plans 734.5.3 Coordination 744.5.4 Coordination of earth stations 754.6 Responsibilities of large satellite organisations 764.7 Coordination with terrestrial services 764.8 NonGSO systems 774.9 The workload of the lTU satellite systems frequency management regime 794.10 Conclusions 824.11 Acknowledgments 824.12 References 82Contents VB567Introduction to antennas. B. Claydon5.1 Introduction5.2 Basic aperture antenna definitions and relationships5.2.1 Principle of reciprocity5.2.2 Antenna radiation pattern5.2.3 Antenna half-power beamwidth5.2.4 Gain, directivity and efficiency5.2.5 Antenna noise temperature5.2.6 Reflection coefficient, voltage standing-wave ratio and returnloss5.2.7 Polarisation5.2.8 Crosspolarisation and polarisation discrimination5.2.9 Aperture distribution and illumination taper5.3 Typical antenna configurations for satellite communications5.3.1 Horn antennas5.3.1.1 Simple pyramidal and conical horn antennas5.3.1.2 Dual-moqe conical horns5.3.1.3 Hybrid-mode corrugated conical horn5.3.2 Reflector antennas5.3.2.1 Prime-focus paraboloidal reflector antenna5.3.2.2 Dual-reflector axisymmetric reflector antennas5.3.2.3 Asymmetric(or offset)reflector antennas5.3.3 Array antennas5.4 ReferencesPropagation considerations relating to satellite cOllllllunicationssystellls. P. T. Thompson6.1 Introduction6.2 Radio noise6.3 Ionospheric effects6.3.1 Ionospheric absorption6.3.2 Ionospheric effects depending on total electron content6.3.3 Ionospheric .scintillation6.4 Tropospheric effects6.4.1 Attenuation due to precipitation and clouds6.4.2 Atmospheric absorption6.4.3 Site diversity6.4.4 Depolarisation6.4.4.1 Frequency and polarisation scaling ofXPD6.4.5 Tropospheric refraction and scintillation effects6.4.6 Shadowing and multipath effects6.5 Acknowledgments6.6 ReferencesInterference considertions relating to satellite cOllllllunicationssystellls. P.T. Thompson7.1 General7.2 Interference between satellite networks7.2.1 Basic first-stage analysis8383838384848687888889909292929393959596969798999999101102102102103103109110III113114114115115117117118119VI11 Contents7.2.2 Detailed analysis 1207.3 Interference with terrestrial networks 1217.3.1 Basic first-stage analysis 1227.3.2 Detailed analysis 1237.4 Acknowledgments 1247.5 References 1258 Satellite access techniques. T Tozer 1278.1 Introduction 1278.2 Network architectures 1288.3 Traffic multiplexing 1308.3.1 Frequency-division multiplex (FDM) 1pO8.3.2 Time-division multiplex (TDM) 1318.4 Multiple access, and assignment strategies 1328.5 Frequency-division multiple access (FDMA) 1338.5.1 Description 1338.5.2 Transponder effects 1358.5.3 Demand-assigned FDMA 1378.6 Time-division multiple access (TDMA) 1388.6.1 Description 1388.6.2 Synchronisation in TDMA 1418.6.3 Demand-assigned TDMA schemes 1428.7 Satellite-switched TDMA and onboard processing 1428.8 Spread spectrum and CDMA 1448.8.1 Spread spectrum for satellite communications 1448.8.2 CDMA 1478.9 Packet-access techniques 1508.9.1 Applications 1508.9.2 ALOHA schemes 1518.9.3 Enhancements to ALOHA 1518.10 Hybrid access techniques, and comparisons 1538.11 Conclusions 1558.12 Acknowledgment 1558.13 References 1559 Modulation and DlodeDls. TG.]eans 1579.1 Introduction 1579.2 Channel characteristics 1589.2.1 AWGN 1589.2.2 Doppler effect 1599.2.3 Multipath and shadowing 1599.2.4 Other considerations 1609.3 Analogue amplitude modulation 1619.4 Analogue frequency modulation 1629.4.1 Preemphasis and deemphasis 1649.4.2 Spectral spreading 1649.5 Digital modulation methods 1659.5.1 Filtering and bandwidth considerations 1659.5.2 Bipolar phase-shift keying (BPSK) 1689.5.2.1 Frequency and phase recovery9.5.2.2 The squaring method9.5.2.3 The Costas loop9.5.2.4 Error rate ofBPSK9.5.3 Quadrature phase shift keying (QPSK)9.5.4 Derivative PSK modulation schemes9.5.4.1 Offset quadrature phase-shift keying9.5.4.2 n/4 QPSK9.5.4.3 Continuous phase-shift keying9.5.4.4 Mary phase-shift keying (MPSK)9.5.4.5 Quadrature amplitude modulation9.6 Practical satellite modems9.6.1 Bit synchronisation10 Channel coding. P. Sweeney10.1 Introduction10.2 Coded systems10.2.1 Types of code10.2.2 Channel types10.3 Error-detection strategies10.4 Forward error correction10.4.1 Effects offorward error correction10.5 Convolutional codes10.6 Binary block codes10.7 Coding for bursty channels10.8 Concatenation10.9 Coding for bandwidth-limited conditions10.10 Application considerations10.11 References11 Satellite systetns planning. B. G. Evans11.1 Introduction11.2 Basict ~ a n s m i s s i o n principles11.2.1 Power levels11.2.2 Noise levels11.3 Downlink budgets11.4 Uplink budgets11. 5 Satelli te path11.6 Overall link quality11.7 Satellite-link design for specified quality11.7.1 Analogue frequency modulation11.7.2 Digital modulation11.7.3 Channel coding11.7.4 Interference degradation11.7.5 Service quality and availability11.8 Link budgets11. 9 Conclusions11.10 Appendix: service specifications11.10.1 Analogue11.10.2 DigitalContents IX170170170171172175175175176178178180180183183184184185185186187189191192193195196197199199201201203206208209211212212215217218218219220220220222x Contents12 Earth-station engineering. ]. Miller12.1 Introduction12.2 What is an earth station?12.3 Typical system configuration12.4 Major subsystems12.4.1 Power amplifiers12.4.2 Low-noise amplifiers-12.4.3 Ground communications equipment12.4.3.1 Frequency converters12.4.3.2 Modulation/demodulation12.4.4 Multiplex equipment12.4.5 Control and monitor equipment12.5. Equipment costs12.6 System design12.6.1 Standard earth-stationd ~ s i g n12.6.2 Customer's premises earth-station design12.7 Environmental and site considerations12.8 Testing and acceptance12.8.1 Unit testing12.8.2 Equipment testing12.8.3 System testing12.8.4 Line-up testing12.9 Maintenance12.10 Conclusions13 Satellite engineering for cODlDlunications satellites. P. Harris and].]. Pocha13.1 Introduction13.2 Satellite design drivers13.2.1 Communications payload13.2.2 Orbit impacts13.2.3 Space environment13.2.4 Launch vehicles13.3 Satellite orbits13.3.1 Introduction13.3.2 Principles of orbital motion13.3.3 Orbital elements13.3.4 Orbital perturbations13.4 Satellite design13.4.1 Types ofsatellite13.4.2 Attitude determination and control subsystem, ADCS13.4.3 Power subsystem13.4.4 Telemetry, command and ranging subsystem, TCR13.4.5 Combined propulsion subsystem, CPS13.4.6 Structure13.4.7 Thermal subsystem13.5 Future large geostationary mobile communication satellites13.6 Launch vehicles13.6.1 General22322322322422722722822922922923123223423623623824124124224224224324324324524524724724824925025025025325525626226226226727127227427527727827813.713.6.2 Launch-vehicle interfaces13.6.3 ReliabilityCommercial satelli te programmes13.7.1 Satellite procurement13.7.2 Satellite development13.7.3 Launch and early-orbit operations and in-orbit test13.7.4 Satellite operationsContents Xl28128228228228328628714 Payload engineering. D. R. O'Connor14.1 Payload definition14.2 Payload function14.2.1 Amplification14.2.2 Frequency translation14.2.3 Channelisation and on-board processing14.3 Payload constraints14.3.1 Mass14.3.2 Power consumption14.3.3 Thermal control14.3.4 Transmission requirements14.3.5 Noise14.3.6 Spurious signals14.3.7 Reliability14.3.8 Electromagnetic compatibility14.3.9 Ionising radiation14.4 Payload specification14.5 Payload configurations14.6 Typical configurations14.6.1 FSS and DBS payloads14.6.2 Mobile and personal communications payloads14.7 Payload equip?1ent14.7.1 Antennas14.7.2 Input filter14.7.3 Receivers14.7.4 Channelisation filters14.7.5 Channel amplifiers14.7.6 High-power amplifier (HPA)14.7.7 Onboard processors14.8 Future systems14.9 Acknowledgments15 Earth-station and satellite antennas. B. Claydon15.1 Introduction15.2 Earth-station antennas15.2.1 Typical RF performance specifications15.2.2 Earth-station antenna configurations15.2.2.1 Axisymmetric reflector antennas15.2.2.2 Asymmetric (or offset)reflector antennas15.2.2.3 Primary feed system15.2.2.4 Array antennas289289289290290291291292292292292293294296297297298299304304306309310312312316317317318319320321321322322324324327330331XlI Contents15.2.3 Antenna tracking consideration15.3 Satellite antennas15.3.1 Circular and elliptical beam coverage15.3.2 Shaped and contoured beam coverage15.3.3 Multibeam antennas15.4 References33133333433634134416 Satellite networking. M. A. Kent 34716.1 Introduction 34716.2 Services 34716.2.1 Main network services 34716.2.1.1 Voice 34816.2.1.2 Voiceband data (facsimile, datel etc.) 34816.2.1.3 64 kbit/s digital data (ISDN and leased network) 34816.2.1.4 Broadband 34816.2.2 Custom networks 34916.2.2.1 Broadcast television 34916.2.2.2 Television distribution 34916.2.2.3 Small dishjVSAT-type data networks 34916.3 Network description 35016.3.1 Generalised network discription 35016.3.2 Leased networks 35116.3.3 Switched networks 35116.3.4 Main-network service rates 35216.3.4.1 Local access 35216.4 Main-network transmission technologies 35316.4.1 Analogue transmission 35316.4.2 P1esiochronous transmission-PDH 35316.4.3 PDH and satellites 35316.4.4 Synchronous transmission, SDH 35416.4.4.1 Overview ofSDH hierarchical levels 35516.4.4.2 Transporting PDH signals within SDH 35516.4.5 Transporting ATM signals in SDH 35616.4.6 SDH frame structures 35616.4.6.1 Virtual containers (VCs)/tributary units(TUs) 35616.4.6.2 Virtual containers 35716.4.6.3 Synchronous transport module (STM) 1, Nand R 35916.4.6.4 SDH pointers (TU, AU) 36016.4.6.5 SDH protocols, e.g. the DCCr and DCCmseven-layer protocol stacks 36016.4.6.6 SDH management 36016.4.6.7 Synchronisation and pointers 36116.4.6.8 New equipment 36116.4.7 SDH and satellites 36216.4.7.1 INTELSATscenarios 36216.4.7.2 Full STM-1 transmission point to point 36216.4.7.3 STM-R uplink with STM-1 downlink-point tomultipoint 36216.4.7.4 Extended TU-12 IDR 363Contents XlII16.4.7.5 PDH IDR link with SDH to PDH conversion at theearth station 36316.4.7.6 Variations 36316.5 Asynchronous transfer mode 36316.5.1 General 36316.5.2 ATM and B-ISDN 36316.5.3 ATM cell structure 36416.5.4 Adaption of ATM cells into SDH and PDH transmissionnetworks 36416.5.5 Current ATM trials 36516.5.6 ATM performance parameters 36516.5.6.1 Delay and echo cancellation 36516.5.6.2 ATM and error performance 36616.6 Major network features which impact on service-carrying ability 36616.6.1 Digital cricuit multiplication equipment (DCME) 36616.6.2 Network synchronisation 36716.6.3 Signalling (routing control) 36816.7 Satellite system performance in relation to service requirements 36916.7.1 Echo 36916.7.2 Delay 37016.7.3 Digital transmission errors 37016.8 Standards 37116.8.1 ITU-T recommendations 37116.8.1.1 Recommendation G.821 37216.8.1.2 Recommendation M.2100 37216.8.1.3 Recommendation G.826 37216.8.1.4 Recommendation M.2101 37216.8.2 ITU-R 37316.8.2.1 Recommendation 614 37316.8.2.2 Report 997 37316.8.2.3 Recommendation 1062 37316.9 Future network developments 37416.9.1 Optical-fibre-cable developments 37416.9.2 Mobile voice and telemetry 37416.9.3 Internet protocol 37416.9.4 Network management 3746.10 Conclusions 37516.10.1 Unique strengths 37516.10.2 Differing constraints 37516.10.3 Future developments 37517 Digital audio broadcasting by satellite. P. Shelswell 37717.1 General introduction 37717.2 The Eureka 147 DAB system 38017.2.1 The soun-d coding 38017.2.2 COFDM 38117.2.3 The data multiplex 38317.2.4 Receivers 38317.3 Satellite-specific options 383XIV Contents17.4 System engineering 38417.4.1 Receivers 38517.4.2 Propagation and satellite orbits 38517.4.3 Coverage requirements 38817.4.4 Number of programmes 38917.4.5 Frequency 38917.4.6 Power 38917.4.7 The cost 39217.5 Experimental evidence 39317.6 The way forward 39417.7 Conclusions 39417.8 References 395(18 Digital video broadcasting by satellite. G. M.Drury 39718.1 Introduction 39718.2 Standards and regulation 40118.2.1 The infrastructure of broadcasting 40118.2.2 Regulation 40118.2.3 Administration of technical standards 40318.2.4 Implementing new television services 40418.2.5 Funding matters-conditional access(CA) 40518.3 Current television standards 40618.3.1 Introduction 40618.3.2 Co1our-NTSC, PAL and SECAM 40718.3.3 The MAC family 40918.4 New television standards 41018.4.1 Introduction 41018.4.2 High-definition television 41018.4.3 W-MAC 41218.4.4 HD-MAC 41218.4.5 MUSE 41218.4.6 Enhanced PAL-PALPlus 41218.5 The WARC77 DBS plan for Europe 41318.6 Digital coding 41418.6.1 Introduction 41418.7 Source coding 41618.7.1 General 41618.7.2 ISO/IEC MPEG 41818.8 Channel coding 42018.8.1 Transmission performance of media 42018.8.2 Harmonisation of standards 42018.8.3 Satellite channels-link budgets 42218.8.4 Digital modulation systems-PSK family 423~ 8 . 8 . 5 Modulation schemes-spread spectrum 42618.8.6 Error control techniques 42818.8.6.1 Introduction 42818.8.6.2 Outer code 42818.8.6.3 Inner code 42918.8.6.4 Interleaving 431Contents xv18.918.1018.1118.1218.1318.1418.15Transmission aspects18.9.1 Satellite access methods18.9.2 Point-to-point applications18.9.3 Point-to-multipoint applications18.9.3.1 Satellite newsgathering (SNG)18.9.3.2 Direct broadcasting18.9.3.3 Video on demand(VOD)Applications18.10.1 Professional systems18.10.2 DBS systems18.10.2.1 Overview18.10.2.2 System management-service information (SI)18.10.2.3 Receivers18.10.2.4 SoftwareConditional accessPicture quality issuesDigital audio broadcasting (DAB)18.13.1 Some history18.13.2 Digital satellite radio systems18.13.3 Audio coding18.13.4 Transmission media18.13.5 The European digital audio broadcasting (DAB)projectThe futureReferences43343343543643643743843943944044044144244444544644944945045045145145245219 Mobile satellite cOllllllunications. I. E. Casewell 45719.1 Introduction 45719.2 Frequency allocations 45819.3 INMARSATsystem and standards 46119.3.1 Introduction 46119.3.2 Space segment 46119.3.3 INMARSAT-A 46219.3.4 INMARSAT-B 46419.3.5 INMARSAT-C 46519.3.6 INMARSAT-M 46619.3.7 INMARSAT-Aero 46819.3.8 INMARSAT-D 46919.4 Regional systems 47019.4.1 OPTUS 47019.4.2 The North American mobile system 47119.4.3 European land mobile satellite system (ELMSS) 47319.4.4 Qualcomm Omni TRACS and EUTELSAT EUTELTRACSsystems 47419.5 Propagation 47619.5.1 A basic fading model 47719.5.2 Maritime experiments 4791 9 . 5 . ~ Aeronautical experiments 48019.5.4 Land mobile experiments 48119.5.5 Fading-channel mitigation techniques 485XVI Contents19.6 Mobile terminals19.6.1 Introduction19.6.2 Antennas for mobile terminals19.6.2.1 Low-gain antennas19.6.2.2 Medium-gain antennas19.6.2.3 High-gain antennas19.6.3 Mobile terminal electronics19.7 Satellite transponders for mobile systems19.7.1 Introduction19.7.2 INMARSAT-219.7.3 INMARSAT-319.7.4 M-SATsatellite19.7.5 Future satellites19.8 References20 Satellite personal cODlDlunication networks. L. Ghedia20.1 Introduction and overview20.2 Wireless mobile radio systems20.3 Second-generation systems20.4 Third-generation systems20.5 Personal communications systems/networks-PCS/PCN20.6 Satellite PCN20.6.1 Functionalities of SPCN systems20.6.1.1 Mobility management20.6.1.2 Service availability20.6.1.3 Call management20.6.1.4 Charge management20.6.1.5 Customer control20.6.1.6 Security20.7 Satellite PCN-challenges20.7.1 Key technical areas20.7.1.1 Frequency sharing and management20.7.1.2 Access techniques20.7.1.3 Radiation and user safety20.7.1.4 Physical-layer issues-margins, modulation andcoding20.7.1.5 Channel modelling-propagation issues20.7.1.6 Satellite-cellular integration20.7.1.7 Mobility management20.7.1.8 Call alerting-high-penetration paging20.7.2 Terminal challenges20.7.2.1 Handheld~ n t e n n a20.7.2.2 Battery technology20.7.2.3 Radiation exposure-safety20.7.2.4 Multimode operation (satellite and cellular)20.7.2.5 Receiver (single mode and diversity)20.7.2.6 Low-rate vocoder20.7.2.7 Size-MMIC/VLSI integration20.7.3 Satellite challenges48548548748748748949049149149149249449549649949950050050250350450450450550550550550650650650650750750750850850850950950950951051051051051151120.7.3.1 GSa orbits20.7.3.2 GSa and non-GSa orbits20.7.4 SPCN design drivers20.7.5 SPCN-space-segment orbit options20.7.6 Comparisons of orbit options20.7.6.1 GEO mobile systems20.7.6.2 MEa systems20.7.6.3 ICO Global Communications20.7.7 LEO systems20.7.7.1 LEO system-OrbComm20.7.7.2 LEO system-Iridium20.7.7.3 LEO system-Globalstar20.8 SPCN system comparisons20.8.1 SPCN system services20.8.2 SPCN access20.8.3 SPCN space-segment20.8.4 SPCN satellite and payload20.8.5 Globalmobile comparisons20.9 Conclusion20.10 References21 Satellite navigation: a brief introduction. l. E. Casewell21.1 Introduction21.2 Applications21.3 Fundamentals of time ranging21.3.1 Basic concept21.3.2 The navigation solution21.3.3 Spread-spectrum ranging21.4 System description ofGPS21.4.1 Space segment21.4.2, Control segment21.4.3 User segment21.4.4 Navigation message21.4.5 System accuracy21.5 The future of global positioning systems21.5.1 The twentieth century21.5.2 The twenty-first century21.6 References22 VSATs for business system.s. R. Heron22.1 VSATs for business systems22.2 Applications ofVSAT systems22.2.1 One-way and two-way VSATs22.2.2 Data distribution22.2.3 Rural applications22.2.4 Disaster monitoring22.2.5 Business applications22.3 Regulatory issues22.3.1 LicencingContents XVll511511512512512513515515523523523529532532533534534534535537539539540542542542543544544546547547548549549550551553553554554554555556556557557XVlll Contents22.3.2 Frequency 55822.3.3 Performance specifications 55822.4 Service provision 55822.4.1 Procuring a VSATsystem 55822.4.2 Vendor-provided services 55922.4.3 Private services 55922.4.4 Service features 55922.5 Voice and data 55922.5.1 Speech 55922.5.2 Bulk data 56022.5.3 Transactional data 56022.5.4 Store and forward 56022.6 Example systems 56022.6.1 Hughes Olivetti Telecom 56022.6.2 Matra-Marconi Space 56122.6.3 GE Spacenet 56322.6.4 AT&T (now part ofGE Spacenet) 56322.6.5 Scientific Atlanta 56322.6.6 DVB and satellite interactive terminals 56322.7 Design considerations 56422.7.1 Antennas 56422.7.2 Receive-only VSATs 56522.7.3 Two-wayVSATs 56522.7.4 Size constraints 56622.7.5 Phase noise and carrier recovery 56622.7.6 VSAT advantages 56722.8 Modulation and coding 56722.8.1 Modulation and coding methods 56722.8.2 Modulation techniques 56922.8.3 Coherent and noncoherent 56922.8.4 Noise 56922.8.5 Coding 57022.8.6 Spread spectrum 57022.9 Data transmission and protocols 57222.9.1 Quality ofservice 57222.9.2 Circuit and packet switching 57222.9.3 Error detection and correction 57222.9.4 ACKs and NACKs 57322.9.5 Frame formats 57322.9.6 VSATs and interface standards 57322.9.7 DVB 57522.9.8 ATM and frame relay 57522.10 Satelli te access techniques 57622.10.1 Sharing the satellite 57522.10.2 Addressing and channel-access techniques 57522.10.3 Access methods 57722.10.3.1 FDMA (frequency-division multiple access) 57722.10.3.2 TDMA (time-division multiple access) 57722.10.3.3 FM2 (FM squared) 57722.10.3.4 CDMA (code-division multipl,e access)22.10.3.5 Sharing transponders22.10.4 Multiple access strategies22.10.4.1 Fixed assigned(or preassigned)22.10.4.2 Demand assigned22.10.4.3 Voice activation22.11 Network configurations and availability22.11.1 Star network22.11.2 Mesh network22.12 Link budgets22.12.1 One-way systems22.12.2 Two-way link budget22.13 ReferencesContents XIX57757857857857857857857857957957958158123 Military satellite coltlltlunications. D. Bertram 58323.1 Background 58323.2 Military applications 58523.3 Frequency bands 58623.3.1 UHF 58623.3.2 SHF 58723.4 Satellites 58723.5 Traffic and terminals 59423.5.1 Traffic 59423.5.2 Modulation 59523.5.3 Coding 59623.5.4 Terminals 59623.6 Link budgets and multiple access 60123.6.1 Link budgets 60123.6.2 Link margins 60123.6.3 Multiple-access techniques 60223.7 Threats and countermeasures 60623.7.1 General 60623.7.2 Nuclear threats 60623.7.3 Jamming 60723.7.4 ECCM 60723.7.5 Antenna nulling 60823.7.5.1 Spread-spectrum techniques 60923.7.6 Low probability of exploitation (LPE) 61223.7.7 Geolocation 61323.8 Future trends in milsatcom 61523.8.1 Political and military context 61523.8.2 Use of LEOs/MEOs-military use of commercialsatellite communications 61523.8.3 Enhanced onboard processing 61623.8.4 EHF and optical frequencies 61623.8.5 System management and networking 61823.8.6 Cost reduction 61823.8.7 Extended coverage 61823.9 Brief conclusions 619xx Contents23.1023.11AcknowledgmentsReferences62062024 Microsatellites and lD.inisatellites for affordable access to space.M. N. Sweeting24.1 Introduction24.2 Surrey microsatellites24.3 Applications of,micro/minisatellites24.3.1 LEO communications24.3.2 Space science24.3.3 Earth observation24.3.4 In-orbit technology verification24.3.5 Military applications24.3.6 Education and training using microsatellites24.4 Microsatellite ground stations24.5 SSTL minisatellites24.5.1 UoSAT-12 minisatellite24.6 Project management24.7 Summary and conclusions24.8 Acknowledgments24.9 References25 Future trends in satellite cOlD.lD.unications. B. G. Evans25.1 Introduction25.2 Television and audio broadcasting25.3 Mobile and personal communications25.4 Broadband multimedia systems25.5 Satellite navigation25.6 Messaging and monitoring25.7 Conclusions25.8 Acknowledgments6216216226296296316326G5636637639641642643643644644647647650652656664665666667Appendix A Link budgets and planning: worked exalD.ples. B. G. Evansand T.C. Tozer 669A.l Introduction 669A.2 Television transmission from medium power satellite toTVRO 670A.3" FDMA system design 672A.3.1 Solution 673A.4 TDMA systems design (high bit rate) 675A.5 Mobile system link budget 676A.6 SCPC system design 678A.6.1 Solution SCPC 679A.7 Military systems design 681A. 7.1 Large terminal power budget 682A.7.2 Small terminal(e.g. Manpack)budget 682A.8 VSAT link budget 685Appendix B DODlestic satellite systeDls design-a case study(INUKSAT systeDl). B. G. EvansB.l IntroductionB.2 RequirementsB.2.1 TrafficB.2.2 OperatingB.3 System performance characteristicsB.3.1 Performance objectivesB.3.2 Satellite specificationsB.3:3 Earth-station parametersB.3.4 System marginB.3.5 Modulation parametersB.4 System designB.4.1 Quarter transponder leaseB.4.2 Off-axis radiationsB.5 Coordination and earth-station sitingB.6 Link-budget calculationsAppendix C List of abbreviations. IndexContents XXI689689690690692692692692693695696699699699700700703717Preface and acknowledgtnentsForthelast 15yearswehavehosted vacation schoolsorganisedbythelEEonsatellite communications at the Universityof .Surrey. Over this time, SurreyUniversity has become synonomous with satellites, both from an education andtraining viewpoint, as well as a centre for research and latterly forthe commer-cial production and sale of small satellites. The vacation courses have producedgenerations oftrained engineers who are nowthe backbone ofthe satelliteindustryintheUKandabroad. Manyex-studentshavereturnedaslecturers(and areauthors of chapters inthisbook) and some havenowrisentobecomethe captains of the satellite industry itself.This isthethird edition of the book which is based on the material presentedat this dejacto industry-standard training course. It is my privilege tu once againedit thebookandoverseetheupdatingprocess. It isdifferent fromthemanyother texts in the same field that have come and gone over the last ten years. Thematerialhas been designedtoenablethosewithabasicengineering or mathe-maticallybasededucationto enter, and tospecialisein, thefield of satellitecommunications with the minimum of effort. The approach has been to concen-trate onthedesignandplanning of systems andthusthereaderwillnotfindahighlytheoretical approachtothesubject. Basicequationsarequotedratherthan derived, but their use in the planning and design procedures is explained indetail. The authors of the chapters have between them a wealth of experience aspractitioners in the satellite field, and we aim to capture this and to pass it on tothe next generation in a digestable manner.Wehavealsoaimedat abroadapproachtothesubject andit isnoticeablethat the third edition is larger than its predecessors. We have added newmaterial on the historyand background to the subject andon the businessaspectsof satellite communications. I wasconcernedthat therewasoverlap insomeof thesechapters, but I cametotheconclusionthat eachauthorhadadifferent and valuableperspective onthescene whichwas complementary andworth retaining. Many of the chapters have been updated toreflect the changesthat have occurred in the ITU and its structure and recommendations in the lastXXI V Preface and acknowledgmentsfewyears, as well as the general privatisationofsatellite organisations. Wewith gratitude the lTD in particular, and other sources of materialused in the text. We have attempted to give credits in the text where due, but weapologise in advance to any that have been omitted.Theadvanceof thesatellitebusinessinareas suchas mobileandpersonalcommunication systems, multimedia systems, military business and small satel-lites, navigation and positioning are allreflected by new chapters. I feel that wehave produced a book that truly covers the subject better than any other in themarket and I hope that you will agree.Asgeneral editor of thebook, Iwould liketoacknowledgethe contributionsof all of the individualauthors, lecturers andexcellent administrators fromthelEE at the successive vacation schools. Almost700 students at the schools them-selves have made valuable contributions and suggestions andIwould especiallylike tothankthem. I wouldhowever singleoutTimTozer, Thompson,BarryClaydonandDaveO'Connor for their contributionontheorganisingcommitteeandinparticularTimfor his contributions as tutor at the manyschools.Manythanks alsoto JonathanSimpsonandFionaMacDonaldat thelEEPublicationsDepartmentfor theirhelpandpressure, without whichthisbookwould have not appeared.(B.G. EvansGuildford, October 1998ContributorsDrDBetraInSatellite Communications CentreDefence Research AgencyDRA DeffordVVorcesterWR89DUMr N CartwrightTithe HouseStutton LaneTattingstoneIP92NZMr I E Casewell andMr A BachelorRacalResearch Ltd\!\forton DriveWorton Grange Industrial EstateReadingBerkshireRG20SBDrB ClaydonERATechnologyCleeve RoadLeatherheadSurreyKT227SAMrGDruryNDSLimitedGamma HouseEnterprise RoadChilworthHantsSOl67NSProfessor B G EvansCentre for Communications SystemsResearchUniversity of SurreyGuildfordSurreyGU2,')XHMrL GhediaICO Global CommunicationsIncI Caroline StreetLondonW69BNMrRHeronDelta CommunicationLtdBusiness andInnovation CentreAngel Way, ListerhillsBradfordWest YorkshireBD7lBXXXVI ContributorsMrTGJeansCentre for Communications SystemsResearchUniversity of SurreyGuildfordSurreyGU25XHMrMAKentBTPPI.Oi Broadway House3 High StreetBromleyBRIILFMrJ MillerCable and Wireless picGrelton House28- 30 Kirby StreetLondonECI 8RNMr D R O'ConnorMatra Marconi Space UK Ltd.Gunnels Wood RoadStevenageHerts.SGI2ASMrJ J Pocha and Mr PHarrisMatraMarconi Space UKLtdCOB Post Code 205Gunnels WoodRoadStevenag('SCI2i\SMr P ShellswellBBC Research and DevelopmentDepartmentKingswood vVarrenTadworthSurreyKT206 ~ PDrP SweeneyDepartment of Electronic andElectricalEngineeringuniversity of SurreyGuildfordSurreyGC25XHProfessor M N SweetingSurrey SatelliteTechnology LtdCniversity of SurreyGuildfordSurreyGC25XHDrs P TandJ D Thompson andMrAGReedERATechnology LtdClee\'e RoadLeatherheadSurreyKT227SAMrTCTozerDepartment of ElectronicsCni\crsit)' ofVorkHesl ington\r)rkYOI0.1DDChapter 1IntroductionB.G. EvansThis initial Chapter provides an overviewofthe components ofa satellitesystem and the major parameters for consideration in its design. It also attemptstogiveabrief review of the current status andposition of satellite communica-tions.1.1 Satellite systeDlsAlthough we shall deal with the communication aspects, satellite systems are infact used for many different services as defined by the ITU and given in Chapter4. Those specifically addressed in this book are: fixed satellite service (FSS); broadcast satellite service (BSS); mobile satellite service (MSS);although communications clearly remaIns a major part of other satelliteservices as well.FSS includes all of the current radiocommunication services operated via themajor operators such as INTELSAT, EUTELSAT, PANAMSATetc. (seeChapter 2), and operates essentiallyto fixed earth stations. BSS covers the areaof direct broadcasting satellites(DBS),which are addressed in Chapter17. Thisconsists of much smaller earth stations on domestic premises together with fixedearth stations providing the uplink feeder to the satellite. MSS currentlyoperatesinthemaritimemobileservice (MMS), aeronautical mobileservice(AMS), land mobile service(LMS)via INMARSAT, plus a number of regionaloperators e.g. AMSC, OPTUSetc. These services consist of earthterminalslocatedonthemobiles as well as fixedbasestationsfor connectionbackinto2 Satellite communication systemsmajorterrestrial networks. Anumberof global mobilesatellitepersonal com-municationsystems (GMPCS), e.g. Iridium, GlobalstarandlCD, will start tooperate in the 1998-2000 era (see Chapters 17, 18).Withthese systems in mind we shall look at the design of networks consistingof satellites andearthstations together withtheir connectiontousers, whichmay involve the use ofexisting terrestrial-network tails. It is important to realisethat the design of such networks is based upon the provision of aservice, be thisvoice, data,facsimile, videoetc, andthe quality of the service as defined by theITU-R andITU-T(seeChapter 4) isthemajorrequirement tobe metbythedesign. A point-to-point satellite link may be all that the network consists of (e.g.aprivatebusinesslink), but thesatellitelink couldbe just one part of amajornetworkconsistingof manyotherlinks. Inthelattercasethesatelliteportioncannot be considered in isolation from the rest of the network. Hence, the designof satellite systems is complex and involves many variables whichall needto betradedoff inorder toreachanoptimumeconomicengineeringdesignwhichmeets the service requirements. The quality of service(QoS)and its availabilityare the key design aims for users in the coverage area of the satellite.Inthisbookweshall exploretheinterplaybetweenthesevariablesandtheengineering, organisational andmanagement constraints whichdictate theirchoice.1.2Radio regulations and frequency bandsAs satellitesystemsemploythettansmissionandreceptionof radiowaves wehaveapotential interferencesitu(J;tionwhereusersinsimilar frequencybandscouldinterferewitheachother, tothe commondegradationof their systemquality. Hence theinternational regulationof their transmissionis crucial tosatisfactoryperformance. Themechanisms for achievingthis arediscussedinChapter4; itissufficient tonoteherethat thereareinternational agreements(via the ITU)for spectrum allocation for different services(IFRB), e.g. Figure1.1 shows the allocations for satellite services. Some of the bands are shared withterrestrialsystems andnearlyallare shared among different satellite operatorsandhencecoordinationisnecessarytoavoidexcessiveinterference. TheITUprovides radio regulations which outline in detail the methods to be employed inorder to avoid this excessive interference between users(see Chapter 4).These are broken down into:(i) Satellite internetwork coordination.(ii) Earth station coordination with fixed terrestrial links.(iii) Interference between orbits.Suchproceduresneedtobecompletedprior toauthorisationfor transmissionbeing given.5.725 GHz()37.5 GHz cO-"'Osa. :::J0 a.

:::J40.5 GHz ....... 7.075 GHzG)

7.25 GHzIN00-42.5 GHz

c:::J:::J"'043.5 GHza.7.75 GHz7.9 GHzc"'08.4 GHz47.2 GHzkeyc "'050.2 GHz50.4 GHz downlink51.5 GHz 001G)I\:)IG)NINFigure1.1 Frequency allocationsfor satellite communication services4 Satellite communication systems1.3Satellite orbitsThere is a large range of satellite orbits, but not all ofthemareofuse forsatellite communications. Those most used are shown in Figure 1.2, and here the24-hour geostationary(circular) orbit with an altitude of 35786km is the mostcommonly used for fixed communications. All of the major operators,INTELSAT, EUTELSAT, INMARSAT etc., haveusedthis orbit, as, having a24-hour period, it imposes minimal tracking constraints on the earth stations. Itis, in fact, only the perturbations of the orbit caused by the gravitational forcesof the stars and planets and the nonsphericity of the earth which requiretracking, andthenonlyfor thelargerearth-stationantennas (seeChapters5and12). However, forearth stations located at extreme latitudes, the elevationangles become very small and this causes propagation problems associated withthe longer paths in the troposphere.Intheextreme, at thepolar caps, thegeostationary (circular) orbit is notvisible. Thus, for systems that require coverage of these regions,w:e need to inves-tigate alternative orbits. It transpires that highly eccentric, elliptical orbitsinclined by 63.4 to the equatorial p l a ~ e exhibit significant apsidal dwellsaroundtheirapogee. ThusthesatellitesappeartoremainquasistationaryandFigure1.2 Satellite orbitsIntroduction 5areuseable forperiods of eightto12 hours for such coverageregions. A full 24-hour servicecanbemaintainedbytwoor threesuchsatellites withsuitablephased orbits and hand-over facilities between them. Owing to the motion of thesatellite aroundtheapogee with respect to anobserver oneartha sizeableDoppler shift is associatedwiththese orbits andthe radioreceivers must bedesignedtocopewiththis. Twosuchorbits areshowninFigure 1.2, thefirstbeing the Molnya orbit, first used by the Soviet Union in the1960s for televisiontransmission to its remote areas. This has an apogee of around 40000km and aperigee of around1000km. Similar characteristics are exhibited by the second,the Tundra orbit, which has an apogee of 46300km and a perigee of25 250km.Both orbits are candidates for mobile (in particular land'inobile) satellitesystems and for complementing the geostationary orbit in achieving betterworldwide coverage. As an example of the different views of the earth from theseorbits we compare in Figures1.3 and1.4 a view of the earth froma Molnya andgeostationary satellite placed at 3.5W. This clearly demonstrates the improvedcoverage and elevationfor the Molnya system. The advantage in terms ofreduced link margin for the Molnya can be used to offset other parameters in thesatellite link design(see Chapter 11). Such highly elliptic orbits(HEO) are nowbeing considered for digital audio broadcasting(DAB)services(see Chapter 17)as well as mid-earth orbit (MEa)applications of HEas for mobile applications(see Chapter 20).Finally, we should mention the low-earth circular orbits (at altitudes of500-1500km) shown in Figure1.2. These have in thepast been usedforearthresources, data-relayand navigationsatellites as well as low-cost store-and-forward communications systems(see Chapter 24).Inrecent yearstheuseof LEOsat around1000kmaltitudeshasincreasedowingtotheir abilitytoprovide global coverage formobile andpersonal com-municationusers. TwoexamplesaretheIridiumsystem of 66(sixplanes of11satellites each)satellites and Globalstar system of 48(eight planes with six satel-lites each)satellites. The coverage from these systems is shown in Figure 1.5. Thelower altitude improves the power budget especially for omnidirectionalhandheld terminals where transmitted power is severely constrained. Theadvantages are obtained at the expense of considerable complexity in handoverbetween themultiple spot beams(16 for Globalstar and48 forIridium) andtothe gateway earth stations(GES)linking with the terrestrial network which canhave up to five separate tracking antennas and terrestrial interconnectionnetworks. (Note: Iridium uses intersatellite links(ISLs) to avoid terrestrial GESinterconnections. )The LEO orbits are not the only ones to allow good global coverage, and theGPS series of navigation satellites has used inclined circular orbits at 24000kmaltitude foranumber of years(see Chapter 21). Between LEO and GEO,satel-lites aresaidtobeinmid-earthorbit andICO, anoffshoot of INMARSAT,planstooperateten(fivesatellites intwoplanes) satellites ininclinedcircularorbit (hence ICO)in MEa at 10350km altitude to provide mobile communica-tionstohandhelds. Thecoverageof ICOisshowninFigure1.6andit canbe6 Satellite communication systemsbeamfootprintfor 1.5mantennaFigure1.3 Viewof the earth fromthe apogee of a12-hour Molnya orbit centredat3.5 oWFigure1.4 View of the earth froma geostationary position at 3.5 Wwith a similar sizefootprint to that ofFigure 1.3) centred on the UKseen that a muchlarger number of spot beams (163 for ICO) is needed toachieve the same power budgets for the higher altitudes (see Chapter 20).However, thenumberof GESs neededismuchlower, at_around 12, thanforLEO constellations. Inall of the above orbitsthe choice of the number of satel-Introduction 7abFigure1.5 Coverage of ( a)Iridium and (b) Globalstar LEO constellationslites, planes andphasing withintheplanesneedstobeperformed foroptimumcoverage of the service area and efficient system design. LEO and MEO constel-lationshavealsobeenproposedfor thenext generationof multimediaservicesatellites at Ka- and V-bands via such systems as Skybridge, EuroSkyWay, West,Astrolink, Spaceway and Teledesic etc(see Chapter 25).One of themajorproblemswiththeextensiveuse of thegeostationary orbithas been the congestion(see Figure1.7)which is caused by operators seeking tousethe morepreferential parking positions for both international and domesticuse(particularly overthe Americas andtheoceans). Clearly, satellites must be8 Satellite communication systemsFigure1.6 Coverage ofICO, MEO constellations,/ 0 / 30 0~ / 0, . ~ 1\, ...". -I: ....-4\..' __-' 60../-.-Figure1.7 Congestion in the geostationary orbitrestricted in their proximity in the orbit(currently 2), and this has implicationsfor internetworkcoordinationandonantennaperformance (seeChapter 12).Thephilosophyadoptedinallocatingorbit positionsonanequitablebasis isdiscussed in Chapter 4. Such allocations must maximise the efficiency of the useof the orbit and frequency bands as both are valuable resources.Onemajoreffect oncommunicationsinusingthegeostationaryorbit isthecoverage, whichhasalreadybeenmentioned, but notefromFigure1.8that aglobal coveragebeamisproducedbyanantennaonthespacecraftwith17.4beam width, and that this precludes coverage of polar regions.Introduction 9Figure1.8 Geostationary earth coverageRe =: earth radius =: 6378kmRo =: satellite altitude =: 35 786kmTheother effect of importanceis thepropagationtimedelayonanearth-satellite-earth link which has limits given by:min==2Ro/c==238 ms(17.40)2(Ro+Re) cos -2-max== ==284 mscSuchdelayshavesevereimplicationsfor theuseof someservicessuchasvoicecircuitswhicharerequired, therefore, touseechocancellorstoproducegoodquality on a single hop.However, the GEO orbit is perfectly acceptable for tele-vision and some interactive computer/data services. Double-hop working(linking adomesticto an international satellite)is not normally used for speechowing to the unacceptable degradations which result.It isimportant tonote that theechoes aregeneratedwithinthe terrestrialnetworkontransitionfromtwo- tofour-wire PSTNworking. Full four-wireworkingwill thereforenot generatesuchechoes. Even if echoesaregeneratedthey can becontrolledsuccessfullybytheuse of echocancellors, even inGEOsystems, but this does imply careful implementation on the part of the terrestrialoperators.Owingtothedynamicorbital perturbationsof thesatellite, thedelays willvary in time andthis is an important issue for consideration in the synchronisa-tion and control of time-division multiple-access(TDMA)systems(see Chapter8).For more details oforbit dynamics the reader is referred to Chapter 13.1.4The basic satellite systentThe basic satellite system consists of aspace segment anda ground segment, asshown in Figure1.9. The space segment consists of the satellitesplus control, or10 Satellite communication systemsspaceandgroundsegmentsspacesegmentuplinksdownlinks\transmittersgroundsegmentFigure1.9 Satellite-communication-system architecturereceiverstelemetry, trackingandcommand(TT&C) stations, tomaintainthesatellitesin orbit. For a GEO operational systemto be considered secure the operationalsatelliteisbackedupbyanin-orbit sparesatelliteaswell as, insomecases, agroundspare, readyforlaunchincase of malfunction of either of theorbitingsatellites. TheTT&Cstationis necessary to keep the satellites operatinginspace. It provides constant checking of the satellite subsystems' status,monitorsoutputs, provides ranging data,acts as a testing facility and updates the satelliteconfiguration via the telemetry links.It generally performs all the housekeepingroutinesneededto maintainthesatellitesasoperationalrepeaters. The TT&Cstationis usually duplicated for security reasons. For satellite constellations(LEO or MEO) the control of asatellite in orbittransfers fromGESto GESasthe satellites precess in their orbits around the earth. Thus, the TT&C control isa distributed function rather than a centralised one as in the GEO case.The satellites themselves consist of two major components:(i) Communications payload.(ii ) Spacecraft bus.Introduction 11The communications payload(see Chapter14)consists 9f the satellite antennasplustherepeateritself. Thelatterprovidesfor low-noisereceptionviaanRFfront end, frequency conversion between the up- and down-link frequencies anda final power amplifier to boost the signal prior to transmission on the downlink.Twodifferent types of payloadare showninFigure 1.10. All of the existingpayloadsareof thetransparent typeshown inFigure1. lOaandconsist of onlyRF amplification and frequency conversion. Some future payloads will be regen-erative or processing in nature and demodulate the signals to baseband,regeneratedigitallyandremodulate(andrecode) fordownwardtransmission.This is an important innovation as it will enable the up- and downlink designs tobe separated andmuchmoreefficientsystemsshouldthusresult.Thereare, ofcourse, additional problems of reliability and radiation-hardened basebandequipment tobeconsidered(seeChapter 12). Thebandwidthhandledbythesatellite is usually broken down (demultiplexed) into traffic-manageablesegments (40-80MHz for FSSand 5-10 MHz for MSS) each ofwhich ishandledby separaterepeaters (calledtransponders), whichareconnected by aswitching matrix to the various onboard antennas.----------------,power __.-.t amplifierfrequency conversion- - -- ---- transponderNt________transponder 2RFt----------I frontendtransponder 1receive RF -l- transmit RFfrequency frequency------------- -------- QpoweramplifierRF frontend------ transponder N _t_______ 2 _transponder1receive RF 1baseband1 transmit RFfrequency signals frequency -------- bFigure1.10 Communications payloadsa Conventional transparent (nonregenerative)satelliteb Processing(regenerative)satellite12 Satellite communication systemsThe spacecraft bus contains the housekeeping systems to support thepayload and consists of: spacecraft structure; electrical-power subsystem; propulsion subsystem; altitude-control subsystem; thermal-control subsystem; TT&C subsystem.Foraparticularsatelliteserviceandchoiceof orbit eachof theabovecanbedesignedtosupport thepayload(orpayloads) andthisprocessisdiscussedinChapter 13. Themass, sizeandvolumeconstraintsarealsoverymuchdeter-mined by the available launchers.Thegroundsegment of thesatellitesystemconsistsof all of thecommuni-cating earth stationswhichaccesstheoperationalsatellite. As shown in Figure1.11, these earth stations consist of: antenna(plus tracking subsystem); feed system (polarisers, duplexers, orthomode junctions etc.); high-power amplifiers(HPAs); low-noise amplifiers(LNAs); up convertors/down convertors (between microwave to IF); ground communications equipment (GCE) (modems, coders, multiplexetc.); control and monitoring equipment (CME); power supplies.The larger stations involved in the INTELSATglobal network have fullprovision of these subsystems, but the smaller business and mobile stations are ofmuch smaller scale and have much reduced provision. The latter point isdiscussed in detail in Chapters 12 and 22.Anetworkmayconsist of afewtohundredsof earthstations, andtheseallhave to access the satellite in an equitable manner. This is usually accomplishedbyeither frequency-division multiple access (FDMA), time-divisionmultipleaccess (TDMA), code-divisionmultiple access (CDMA) or a random-accessscheme (RA). Sometimes a hybridcombinationof theseis used. All of theseschemes are discussed in Chapter 8 as well as the optimum choice of access for aparticular service provision and network.Finally, the satellite system(consisting ofthe earthstation to satellite toearth station link)must be interfaced to the user, either directly or via a networke.g. the PSTN, ISDNor PLMN. Standards in the interconnectionof earthstations tousers are animportant feature of thedesignandarediscussedinChapter 16.Introduction 13antennaax iselevation, angle elocal horizonI tracking" Imonitoring&control '"RF~ - - - - - t highpoweramplifierRF----.----1front end(lownoise amp)Jt'for largestations onlyFigure1.11 Earth-station architectureupconvertordownconvertorIFmodulatorIFdemodulatorbasebandsignals(fromusers)basebandsignal(tousers)1.5Satellite cOlDlDunications in transitionFromtheearly days of satellite communication systems (1964 onwards forFSSand INTELSAT and 1976 onwards for MSS and INMARSAT)up until the late1980s/early1990s, themajor operatorswereintergovernmental organisations(IGOs)with specific missions. The INTELSAT treaty was formedas an offshotofthe UNtreatyandhadthe assistance of developingcountries as anaim.INMARSAT was a similar IGO with specific responsibility for safety at sea andsearch and rescue operations. The only other satellite organisations in these firsttwenty years or so were either regional systemse.g. EUTELSAT forEurope orARABSAT,set up to provide educational, cultural andtelevision links betweenthe countries of the Arab league, which were also I GOs, or standalone domesticsystems. Examples of the latter include Indonesia and its PALAPA series of sate1-lites, ANIKsatellites in Canada or the OPTUSsystemin Australia. Suchsystems were national in their structure and organisation and government14 Satellite communication systemscontrolledor influenced. Muchof the technological developments e.g. singlechannel per carrier (SCPC)and demand assignment(DA), TDMA, shaped andmultibeam antennas, frequency reuse using geographic and orthogonal polarisa-tion separations, digital signal processing such as DSI, speech and videocompression etc. were results of R&D supported by these IGOs. Such R&D wascentrallyfundedfromthemember countrycontributions. Themembers sub-scribed according to their usage of the systems and became shareholders on suchaproratabasis. Thus, the development andfinance of thespacesystemwascentrallyplannedaswell astheresulting standards of theearthstationstousethe systems. Hence, we saw INTELSAT and INMARSAT standard A, B, C etc.earth terminals(see Chapter 15).Communications over themajor oceans hadbeena major feature of bothINTELSATand INMARSAT, which initially concentrated entirely on themaritime sector. It was competition in this area that initiated a change in the oldorder. This occurredinthe 1980s withtheintroductionof digital fibre-opticcablesacrossthe Atlanticwith capacitiesmuchgreater thanthose of thesatel-lites which had hitherto ruled supreme attheserates. Although satellites foughtbackusing digital-circuitmultiplicationequipment (DCME) thecableswouldalways providegreater capacityandhencelower circuit costs ona point-to-point link. Thus the balance of traffic was transferred from satellite to cable withthe former being an important back up and still remaining on some world routesthecheaper option. Diversificationintelecommunications was anestablishedprincipleandthussatelliteswouldneverbecompletelyreplaced, butonthesepoint-to-point routes cables now had the edge.IntheFSSband, satellitescouldnowlooktoexploit their real advantagese.g. their broadcast nature. Small stations(VSATs)were beginning to appear onthe scene and satellites could be designed with particular spot-beam coverage toallowinterconnectionof large networks (1 OOs ofterminals) ofsuch smallerstations. Inaddition, televisiontransmission either direct tohomesmalldishesortocable headcollectorswasbecomingbigbusiness and dominatingsystemssuch as EUTELSAT. INTELSATcould not respond to these newmarkets,largely in the developed world, because ofits mission, highly bureaucraticcontrol and committee structure and because its satellites had been designed fordifferentmissions and werethusexpensive forthenew markets. Inevitablythispromoted an opportunity for competition, and private systems such asPANAMSAT and ORION appeared to address the new FSS markets.IntheMSSarenasimilarmoveswereafootwithnewregionalsystemssuchas AMSCinAmerica andOPTUSinAustralia challenging INMARSAT'sdominance. Alsoemergingwerenewprivateorganisationstotackletheglobalhandheld telephone market which, although successful in urban areas viacellular, was still doggedwithpoorcoverageoutsideurbanareas andwithaplethora of standards which mitigated against true global roaming. Much of therural worldstill didnot have access to a telephone andthis representedanenormous market. Thus major systemproposals (Iridium, Globalstar) usingconstellations of satellites andcosting$2-10billionappeared. INMARSATIntroduction 15recognisedthechallenge but couldnot competeas an IGO andthus spun off aprivatesubsidiarycalledICOGlobal Seriesinwhichit hadaminorityshare-holding. In1998 both INTELSAT and INMARSAT announced plansto makethe transitionfromIGOs to private operatingcompanies bythe year 2000.Hence, the transitionfor satellitecommunications hadtakenplace, andthismerelymirroredwhat was happeninginthebroaderfieldof telecommunica-tions -liberalisation andderegulation- theonset of anew era of competitionandprivate companies andorganisations. We must not forget, however, theimportantroleof theIGOs, withoutwhich satellite communication wouldnotbe in the position in which it is today.Perhapswethus stand atthecrossroads inthedevelopment of satellite com-munications which is represented by the current small-dish/mobile era. This erais characterised by new markets of:(i) Direct digital broadcasting of television.(ii) Small-dish business systems.(iii) Mobile, portable multimedia systems.Thefirst of these, DBS, has beena longtimecoming, but 1989sawthefirstoperational analogue system and1998 the first digital systems. It is still a specu-lative market with the major technological innovations beinghigher powersatellitesandverysmall, low-costintegrateddomesticearthstations. Therealchallengeliesintheother twomarkets, andespeciallythemobilesystemsforwhich the broadcast nature of satellites is ideal.Business (VSAT) systemshavebeen verysuccessfulintheUSA andsome ofthe developing world (China and East Europe) but less so in Europe where regu-latingregimeshavepersistedandspacesegment hasremainedexpensive. Themaritimemobile and latterly land mobile areas have been very successful, withthe aeronautical area less so. Again, expensive space segment as a result of lowerpower, wider beam and nonprocessing satellites has been the reason. The key toopening these new markets lies in the development of: onboard processing; multibeam coverage deployable antennas;and when developed, we will be in the next era of satellite communications, theintelligent era.Thus, our market-driven crossroadsalsoleadsustoatechnologycrossroads,from dumb to intelligent satellites. This involves the placement of processors onboard, regenerativetransponders andtheuse of abaseband switchto intercon-nectbetweenthebeamsof amultibeamcoverageantennaasshowninFigure1.12. Besides the functions ofbasebandsignal processing (regeneration) andtraffic or message switching, the presence of onboard processing power opens upthepossibility of overall systems resource control. Thus, the satellite is designedto meet the needs of the user rather than the user fitting in with the satellite.Users with a whole range of traffic requirements and capacities can then inter-communicateefficientlyviathesatellite, whichsortsout therelativebit rates,16 Satellite communication systemsFigure1.12 Onboard processing(intelligent) satellite using multiple-beam antennas andonboard switchingswitches, reformats theinformationandassemblesit intosuitableformats fortransmission andreception by simple and cheap earth stations. Such asatellite,asaswitching node in the sky, is likely to alter the currently accepted hierarch-ical communication-networkstructures andallowdirect access toa rangeoflevels simultaneously.The intelligent era is not likelyto arrive until around the year 2003 when weshould also be well on our way to personal multimedia communication systems,with satellites playing an important role in a synergy with terrestrial systemstoproduce a truly integrated network infrastructure.1.6Towards the futureAs we enter the second millennium satellite communications has alreadyestab-lished direct broadcastingoftelevision, small-dishVSATsystems, maritime,aeronauticaland landmobilesystemsandisabout toembark onglobalhand-held satellite telephone systems. So what of the future?Surprisinglytechnologyhasnot progressedas rapidlyas theorganisationalchanges which have beset the field. Satellites have become more powerful, havelarger numbers of beamsandhave some digitalsignalprocessing on board buthavenot yet (1998) reachedthefull onboardprocessing(OBP) stagesasillu-stratedinFigure 1.12. TheIridiumsatellitesarearguablythemost advancedwith some OBP and with ISLs. These will be the model for future satellites, bothIntroduction 17FSSand MSS, and this represents a major change i:q. the satellite payload,enabling more complex routing onboard right down to the level ofserviceswitching-the switchboard in the sky.IntheFSS area thereareplans forsatellite systemsdesignedformultimediaKa-band communicationsusing ATMswitching onboardthesatellite. Systemswill use LEO, MEO and GEO orbits and some will useISLs and IOLs in ordertooptimisetheservicedelivery. ATMsystemswill bedesignedfor interactivemultimedia at BERs of 10-10andavailabilities in excess of 95% This will beachallenge bothtothesatellitepayloaddesignersaswell asthecommunicationengineers. Asthe Internet becomes more pervasive, Internet protocol (IP) oversatellite will feature more and a complete multicasting IPsatellite network(Teledesic's constellation of 288 satellites in LEOis based upon such a concept)will become a reality by 2005.Thedigital-processingrevolutionhas seencompressionof broadcast videodown to around 2-6Mbit/s and hence a tremendous saving in satellitebandwidthfromtheoldanaloguetelevisionof 27MHz tothenewdigital ofaround 4-6MHz. This heralds theeraof100sof digital televisionchannelsfrom the sky. Standards such as MPEG 2 and 4 for the source coding and DVB-Sfor the transmission have played important roles in the new digital satellite revo-lution. Once in digital format theTVsatellites canprovide for interactivemultimedia to the home and open up a vast range of new services. Digital audiobroadcastingisanother area inwhichsatelliteswill benefit andwesee in1998the first DAB systems (Worldspace) coming into existence to deliver high qualityradio channels globally. Again, once in the digital domain such systems can alsobe used for interactive multimedia services.Inthe mobile/personal satellite area the first-generation GMPCSsystemsusingconstellations forglobalcoverage and super GEOsforregionalcoverageare limited to voice and low-rate data. The second-generation systems in 2003-2006 will be part of the IMT-2000 standard set and provide multimedia servicesin the range 64 kbits-2Mbits/s to mobiles and portables. Beyond this it is likelythat mobile, portable and fixed will merge into giant hybrid constellationsproviding a full multimedia service - set across the old boundaries in a seamlessmanner andby2010weshouldhavereachedthefullyintegratedsystemsthathave so long been the dream- or will there be unseen disruptions?Chapter 2Historical overview of satellitecOInInunicationsP.T. Thompson andJ.D. Thompson2.1The visionariesThe concept of satellite communications is normally accredited to an'Englishman, Arthur C. Clarke, becauseof a famous paperlpublishedintheBritishWireless World. However, Dr Clarkeproducedat least twodocumentsprior to this inwhichelements of the ideaof satellite communications werepresented. He published a letter2in the 'Letters to the Editor' column of WirelessWorldon'PeacetimeusesforV2' inFebruary1945inwhichhepostulatesan'artificial satellite'in a24-hour orbit and even goes on to suggest the use of threesuchsatellites at 120 degreespacing. Modestly, hefinishesthearticlewith 'I'mafraidthisisn'tgoingtobe of theslightest usetoourpostwarplanners, but Ithink is the ultimate solution to the problem.'Following that short letter hewroteamoreextensive paper on25May1945entitled 'The space station:its radio applications'which he circulated to severalkey council members of the British Interplanetary Society(whose motto is aptlyFrom imagination to reality) who gave it their whole-hearted support. The top copyis nowinthe archivesof theSmithsonianInstituteinWashingtonDCandafacsimile is published in 'How the world was one's along with a copy of his laterandnow famousWirelessWorld paper of October1945. Inthispaper ArthurC.Clarkeproposedthat threecommunicationsstationsbeplacedinsynchronous24-hour orbit whichcouldforma global communications systemandmakeworldwide communications possible. An interesting but seldom recognised char-acteristicof his ideais that heenvisionedthe useof staffedspacestationsinsynchronous orbit. The communications equipment would be installed,operatedandmaintained by the space-stationcrew. To date, we have seenhundreds of unstaffedcommunications satellites launched into geosynchronous20 Satellite communication systemsorbit for commercial and military use, with thenewest spacecraft lasting ten ormoreyearswithout maintenance, but asyet permanent staffedspacestationsare rare and none are in geostationary orbit.Arthur C. Clarkewas not theonlypersonthinkingabout communicationssatellites. In1946, theUSArmy'sProject Rand pointed outinaclassifiedstudythe potential. commercial use of synchronous communications. satellites.Unfortunately, thisreportremained secret forso long that it hadlittle impact.In1954, JohnPierce4of Bell Laboratories consideredthecommunicationssatellite problem independently of Clarke. ToPiercethereseemed littlereasonat that time to replace overland cables or terrestrial microwave relays with satel-lites. Satellites, the electronic equivalent of high microwave relay towers, seemedbest suited for spanning the oceans, which so far could only be done withexpensive undersea cables oflimited capacity or via high-frequency wavesbounced off theionosphere. There weretwo generalpossibilities forsuchsatel-lites: passive reflectors that would bounce the radio waves betweengroundantennas, andactive repeaters whichwouldamplifythe receivedsignal andretransmit ittothe ground. Either kind of satellite could be placed in medium-altitude orbits, requiring a constellation of many satellites and steerableantennasontheground, oronesatelliteinsynchronousorbit, whereit wouldappear to remain stationary at one location.At thetime it seemedto Pierce that nothing practical could be doneto facili-tate satellite communications, although the communications equipment was nottheproblem. Theinvention of thetransistor, thesolarcell andthetravelling-wavetubeamplifierinthe1940sand1950sallowedrelativelycompact highlyreliable repeatersto be built. The difficulty was the rockets. It was not until thedevelopmentof suitablelaunchvehiclesthat theseconceptscouldberealised.Launch vehicles of thepowerrequiredbecameavailableinthemid1960sasaby-product of the military development of the intercontinental ballistic missile.Several private companies in the United States, including RCA andLockheedin the early 1950s, investigated the possibilityofcommunicationssatellites before the government became interested. The Hughes AircraftCompany spent company money from1959 to 1961 to demonstrate the feasibilityof adesign forsynchronous satellites before convincing NASA andtheDefenceDepartment to fundthe rest of the project.However,by far the greatest activitywas in AT& T's Bell Telephone Laboratories.In the UKtwo major studies were undertaken,both of which showed signifi-cant innovation and application of advanced satellite technologies. The first was'Astudy ofsatellite systems for civil communications', RAE, Farnborough,report 26(March1961). ThesecondwasundertakenbyG.K.C. Pardoe of theBritish Satellite Development Company entitled 'World communicationssatellite system' and published at the 13th congress of the InternationalAstronautical Federation(IAF) inSeptember1962.5However, thepace of theevolution and developments in this field,the cautiousness of the UK governmentand t ~ e problemswhichbeset theUK/EuropeanlaunchvehiclesresultedinaUK preference for international cooperation with the USA.Historical overview ofsatellite communications 212.1.1 The start ofspace activitiesTheV-2was thecatalyst for theartificial unmannedsatellite. Inthedays ofearly rocketry researchers concentrated on manned flight. There was also scepti-cism regarding radio waves penetrating the upper atmosphere. More important,inthoseyears of radiovalves, theresimplywas noadequateelectronic tech-nology. For these reasons, radiocommunications studies are conspicuouslyabsent fromthe early astronautical literature. Beginningin 1945, given thelarge-scale' rocketwartime advances in electronics and the develop-ment of transistors, proposalsfor satellitesstartedtobepublished.6,7 In1955Radio Moscow had announced a prospective satellite launch, but this and subse-quent similar announcements were not considered seriously. The USA had longtaken its technological superiority for granted; besides, satellite and space-station proposals were at thattime quite common, andmost of them werecon-sidered to be pie-in-the-sky fantasies. However, on 29July 1955 the USAannounced that it would 'launch small earth-circling satellites' as part of its con-tribution to the International Geophysical Year (Project Vanguard).8On4 October1957, theentireworldreceivedashock: theSoviets launchedSPUTNIK1.9The Americans suddenly lost their complacency over theirpresumed technological superiority. Another shock for them came when the firstcomplete Vanguardexploded inaball of flameless thanasecond afterlift off,dropping its fourpoundtest satellite. Itwasnotuntilthe31 January1958 thatAmerica launched its first satellite, the Explorer1, but the USSR countered thisbylaunchinga 7000pound'flyinglaboratory', andthus thespace racehadbegun.It was to be the space race that accelerated the development of the technologyandthe willto launch satellites into space. However,it was only whentheracesettled down that worthy application satellites began to be developed andlaunched, riding on the spin-offs from the race.'2.2The pioneersArthur C. Clarke'sbook'Howtheworldwasone' was'Dedicatedtotherealfathersof thecommunicationssatellite, JohnPierceandHaroldRosen, by thegodfather'. It is reasonabletoassume that Arthur wasthe visionary and others,especially these two, were pioneers. Both had the backing of significant commer-cial organisations behind them (AT&T and Hughes Aircraft Company,respectively) and therefore had the resources to push the pioneering effortsrequired at that time.2.3The early daysTheearlydays of satellitecommunicationscomprisedmanyexperimentsandfact-finding missions which eventually led to the active transponder-based satel-22 Satellite communication systemslites in commonusetoday. Thebackground of theseearly daysistooextensiveto detail here. Table 2.1 gives some basic information but the reader is referred tothematerial in thereferencesattheend of thischaptertogain furtherinsight.2.4International activities2.4.1 History and development ofINTELSATIn1962theUnitedStates, CanadaandtheUnitedKingdomhelddiscussionson forming an international. satellite organisation based upon the concept estab-lished in the US Congress Communications Satellite Act of 1962.10Laterdiscussions, in1963, were expandedto include most of the European countries.Thus, theUKplayedakeyroleininitiatingthis organisation. Furthermore,alongwithotherEuropeancountries, theUKmadeit clear that its interestswerenot only inusingthesatellite system, butalso in having ownershiprightswhich carried with them an active participationin all aspects of the system.Seriousnegotiations were begun in Rome in February1964 at which partici-pants included representatives fromwestern Europe, the USAand Canada.Shortly thereafter, Australia and]apan were included, recognising that togetherTable 2.1 Early communications satellitesSatellite Country Launchdate NotesSCORE USA 18/12/1958 activefor 13daysECHOA-10 USA 13/5/1960 failureECHO1 USA 12/8/1960 100 ft balloonCOURIER1A USA 18/8/1960 launchfailureCOURIER1B USA 4/10/1960 lost commandcapabilityafter 17daysECHO(AVT-1) USA 14/1/1962 failure, balloonrupturedTELSTAR1 USA 10/7/1962 okuntil 21/2/1963ECHO(AVT-2) USA 18/7/1962RELAY1 USA 12/12/1962 1transponder, okuntil February 1965SYNCOM1 USA 14/2/1963 communications lost at orbit injectionTELSTAR2 USA 7/5/1963 okuntil May 1965SYNCOM2 USA 26/7/1963 useduntil 1966, turnedoff April 1969RELAY2 USA 21/1/1964 useduntil September 1965ECHO2 USA 25/1/1964 usedwith USSR, decayedJune1969MOLNIYA1-F1 USSR 19/2/1964 failureSYNCOM3 USA 19/8/1964 useduntil 1966, turnedoff April 1969INTELSAT1 USA 6/4/1965 useduntil Jan 1969, tempuse(EarlyBird) Jun-Aug1969MOLNIYA1-1 USSR 23/4/1965 decayed 16/8/1979Historical overview of satellite communications 23these countries accounted for some 85 per cent of t h ~ world's internationaltelephone traffic.In the remarkably brief period of just over six months two agreementsenteredintoforceandthenewinternational entity, INTELSAT, wascreated.These interimarrangements on how the organisation was to operate anddisputes settledwereopenedfor signatureon20August 1964andcameintoforce for the11 founder members.Withregardtothedefinitearrangements, twointerrelatedagreementswereopened for signature on20 August 1971. About one and a half years later on12February 1973 these two new agreements entered into force, having received thenecessaryratifications. One is an agreement between governments partytotheagreements(parties)and the other is between signatories which are telecommu-nications entities (public or private) designatedbya partyand as such aresignatories of the operating agreement. In the transition to the definitivearrangements the most radical changes in the organisation were in its structure.This was mainlyundertakenas a result of significant pressurefromtheUKwhichledtherest of Europeonthismatter.llTheinterimarrangementshadrevealed difficulties for the Europeans in the use ofCOMSAT*as a manager ofthe systemwhile also having the role of the major shareholder. This wasovercomebythegradual phasingout of theCOMSATmanagement roleandthe introduction of an executive organ whichtook on apermanent status in theWashington DCHeadquarterstomanagetheorganisation inaccordance withthe Board of Governors' wishes. This transition took some six years to implementbecauseof theneedtoproperlyhandletheongoingcontractsetc. TheroleofINTELSATundertook major changes in the 1990s as detailed later.2.4.2History and development ofEUTELSATIn 1964, the European Conference on Satellite Communications (CETS),which was originally created to coordinate a European position in theINTELSATnegotiations, began to focus attention on a possible Europeansatellite programme. The objective of this work was to give Europe, and in parti-cular itsindustry, technical capabilityinthis areabasedonanexperimentalsatellite programme. 1966 saw the formation and firstmeeting of the EuropeanSpace Conference (ESC), designed to harmonise the work of the differentEuropean bodies dealing with space activities. The European satelliteprogramme under study was originally conceived for the provision ofEurovisiontelevision programmes fortheEuropean Broadcasting Union(EBU) aswell assome telephony in Europe and the Mediterranean basin. The economic viabilityof suchaprojectwaslatercalled intoquestion andtheemphasis, in1969, wasredirectedtowards having asystem primarily dedicated to European telephonyrequirements with some capacity available for EBU television.*The Communication Satellite Corporation (COMSAT) was established by the USGovernmentas an independentbodytomanagetheinternationalsatellite communica-tions access within the US.24 Satellite communication systemsIn August 1970, a European telecommunications satellite working group(SET) was established to collaborate with ESROjELDOin carrying outstudies in this area. The outcome of the initial work wasthe publication inJuly1971of astudy on aEuropean satellite system. One of the conclusions was thatthespacesegment of thesystemshouldbeowned, operatedandmanagedbytelecommunications authorities, acting through a new organisation to beformed, for which the name ofEUTELSAThad been suggested. With theabovedecisionsinmindatwo-phaseapproachwasenvisagedfor thetelecom-municationsprograI!1mecomprisinganexperimental andtechnological phase(1972 - 1976) which would culminate inthelaunch of anexperimentalsatellitein1976, andafurtherphase(1976-1980) whichwouldincludeearth-segmentimplementation, final space-segment development and the procurement ofoperational satellites. At theDecember 1971 ESROjELDOCouncil meetingthiswasapprovedandworkontheexperimental satellite, tobeknownastheOrbital Test Satellite(OTS), commencedat theend of 1972.TheoperationalphasesatellitesweretobeknownastheEuropeanRegional CommunicationsSatellite System(ECS).In March1977, aconferencewasheldtoprepare forthe establishment of aninterim organisation to manage the space segment, called Interim EUTELSAT.As aresult an agreement was opened on13 May1977 for signature and enteredinto force on 30June 1977.Under the ECSarrangement, the European Space Agency (ESA) wouldsecure the provision, launch and maintenance in orbit of the ECS satellites, andprovidereplacement satellites, withaviewto havingacontinuity of the initialspace segment over ten years.OTS-2was successfullylaunchedon 11 May 1978 (after anunsuccessfulattempt inSeptember 1977) andwas to be utilised initiallyfor three years.However, on the completion of three years in orbit, the satellite was still workingproperly,and special financialarrangements were concluded with ESA to keepit there. To finance such payments, it was decided that 80 per cent ofEUTELSAT's contributions to ESA regarding these costs should be provided byuser signatories. In the event the satellite was used until the end of 1983 and theabove funding requirement was not only met but slightly exceeded.In1979Interim EUTELSAT begantoconsider arrangements forthedefini-tive organisation. After much debate the definitive agreements entered intoforce on20July 1985.ECS flight 1 wassuccessfully launched on16 June1983 andfollowedby fourmoreintheperiodupto July1988. Unfortunately, flight 3sufferedalaunchfailure in 1985.Theperiod1983- 1984witnessedconsiderableactivityinthefieldof futureprogrammes. Theinitial systemwas unable to adequately provide sufficientcapacity beyond1990 with theresources available under the EUTELSAT-ESAarrangement. It was concluded that this situation could be addressed byprocuring enhanced satellites which could be available for operation by the endof 1989. In the event, the first of the Eutelsat-II satellite was launched inJanuaryHistorical overview ofsatellite communications 251991with moreto followshortly. By1998 EUTELSAT had addedseveralnewgenerations ofsatellite to its fleet, some specifically designed for televisionservices (HOT BIRDS).2.4.3History and development ofINMARSATIn 1966the International MaritimeOrganisation (IMO), basedinLondon,undertookstudiesonthepossibilitiesof satisfyingthecommunicationneedsofthe maritime mobile service(MMS) by the use of satellite communications andtheneedtoprovide radiofrequenciesfor thispurpose. In1967the ITUWorldAdministrative Radio Conference(WARC)for the MMS adopted a recommen-dation relating to the utilisationofspace communication techniques in theMMS outlining further work to be conducted prior to the 1971 WARC.Following the allocation of frequencies to the maritime mobile satelliteservice by WARC1971, it was decided that the IMO should play an active rolein the early organisation and introduction of an international maritime satellitesystem in full cooperation with the telecommunication authorities of its membergovernments. In March1973the IMOdecidedtorecommend that an interna-tional conferenceof governmentsbeconvenedinearly1975todecideonthe, principle of setting up an international system and, if it accepted that principle,to conclude agreements to give effect to its decision. It transpired that three suchconferences would be neededbeforetheINMARSAT convention wasadopted.After protracteddiscussionsmostmatterswereresolvedbythethirdsession ofthe conference which took place in London from 1-3 September 1976. The con-ference decided to establish a preparatorycommittee to carryout activitiesbetweentheclosing of theconferenceandthecomingintoforceof theinstru-ments establishing INMARSAT. Twenty-two countries participated in this,which providedthe background fortheINMARSAT organisation followingitsestablishment on 16 July 1979. They agreed that the first session of theINMARSAT council should take place immediately after entry into force of theconventionfrom16to27 July1979andthefirst meetingof theINMARSATassembly should take place after 3 September 1979.The UKgovernment was a prime mover in all aspects of establishingINMARSAT. It funded the early European-based MARECS system to the tuneof 39 per cent of thetotal, made way fortheestablishment of theINMARSATheadquartersinLondonandplayedavital rolewiththeIMOingettinganequitable share arrangement.InDecember 1997INMARSAT celebratedtheinstallationof its 100000thterminal, indicating the significant extent of its operations.Figure2.1indicates the magnitude and growth of therevenues earned by thethree major satellite consortia. Growth is still ongoingwith no evidence ofdiminishing interest in satellite services as yet.26 Satellite communication systems2000180016001400Z12000:s1000.J~800~6004002000v \D 00 0 C"I v \0 00 0 C"I v\0 \0 \0 t""- t""- t""- t""- t""- oo 00 00~ ~ ~;:::0-~ ~ ~0\ 0\~YEARDINMARSAT EUTELSATIIINTELSATFigure2.1 Revenue ofthe three major satellite consortia2.5Television satellite broadcastingIt has been recognised for many years that for television, with its widecoverage areas which span both national and international boundaries, satellitesprovide an idealtransmissionmedium. Fromthevery startallcommunicationsatelliteswerecapable of carryingtelevisiontransmissions. Conventionalcom-munications satellites are generally only capable of operating with large receiveantennas on the ground owing to power limitations in the satellite. Special high-powered direct broadcasting satellites(DBS) that can transmit directly to smallindividual receivers wereconceivedintheearlydays of satellitecommunica-tions12but were not economically or technically viable until the mid 1980s.Itwasprobablythesatellitetransmission of the1964 TokyoOlympictelevi-sion coverage that, as 400 million viewers watched, alerted the governments andoperatorstothepotentialof televisioncoverageusingsatellites. Thisgavetheimpression that satellite-based television transmission was a very lucrativemarket with enormous potential for exploitation. Consequently, as early as1965, satellite broadcasting direct tothe individualreceiver wasproposed withan estimated cost of about 49 per household to convert existing televisions. 13In1966therewerecallsfor direct broadcastingof televisiontoEurope, forwhich the costs were estimated to be about one fifth to one tenth that of the con-ventional land relay networks!4 and ESRO proposed a satellite-basedEuropean DBS. In the UK the electronics industry was keen to see DBS developand it was considered feasibleby the British Space Development Company thatsatellites wouldbe feeding four UKnational televisionchannels withinfiveyears. This proved to be too ambitious and the UK had to wait until 1989 for itsownDBSservices, although televisiondistribution services were initiatedin1988viatheASTRA-basedSkyservicesoperatinginthefixedsatelliteservicebands.Historical overview ofsatellite communications 27By 1972 concerns had been expressed over the possibility ofDBS transmissionsinfringingnational boundaries. TheUSSRappliedtotheUNto'protect thesovereignty of states against any outside interference and prevent the turning ofdirect television broadcasting into asource of international conflicts and aggra-vation of relations between states.,15 This factor was one that led to theconvening of an ITU WARC on broadcasting services(known as WARC-BS orWARC-77): Fromthis conference came the allocation of frequency bandsdedicated to DBS and separate fromtelecommunication frequencies. These fre-quencies weretoallow national DBS servicesto be developed andtoexploit allpossibletechnicalapproachesto stop infringement of boundaries andtransmis-sion into other states. Each country was allocated a number of satellite channelsandanassociatednational coverageareafor DBSservices withinanoverallplan. This plancameintoeffect in January1979andalthoughit essentiallyprovides for a worldwide allocation of resources for DBS use it has, to date, had apoortake-up. There are about20 satellites currently in orbit althoughthe planallows for in excess of 300!Itisworthyof notethat Japan, RussiaandEuropewerethefirst toexploittelevision transmission to the home or cable feeder heads.In early 1981 BT, a major satellite-systemoperator in the UK, beganactively studying the concept of establishing a UK-owned satellite which wouldprovideUKDBStelevisionaswell asinternational telecommunicationsfacil-ities. Thegovernment was keenonfree market forces andpermittedUnitedSatellitesLtd. (UNISAT) tousetheUKallocation, butimposedaconstraintthat the BBC must operate two of the DBS television channels. In1984 the BBCannounced it haddifficulties in leasing the whole satellite system and lTVwasinvited to participate. In addition, owing to the prevailing situation, the govern-mentallowedprivatecompanies intotheproject. AconsortiumtoprogrammeUNISAT's threechannelswas establishedunder joint ownershipof theBBC,with a50 per cent stake, lTV network companies, which had 30 per cent, and agroup of twenty-one companies with 20 per cent, which became known as the 21Club. However, by1985theBBChadestimatedthat providingprogrammingforUNISAT wasgoingtoproveexpensive, andthat itmighthavetoresort toadvertisingtoraisethenecessary finance. This approach wasnot liked by lTVand the public, and their concerns led to the BECwithdrawing fromtheprogramme.Without theBBC's support asthemajoruser of theDBSpayloadthe project collapsed.16Following this the Independent Broadcasting Authority (IBA) licensed,under a franchise agreement, a private company called British SatelliteBroadcasting(BSB) to providethree channels of direct-broadcasttelevision. Inthe meantime BT leased several transponders on IN-TELSAT~ n d EUTELSAT,as well as beginning to use ASTRA.17,18In1988a major competitor, Sky, backedbyRupert Murdoch, arose. ThisenterprisehadthePrime Minister's blessing; at the annual Press Associationluncheonshesaid'I thinktheopportunityof morechannelscanenableus tohavesomeveryupmarket television,.19Thegovernment, beingof aviewthat28 Satellite communication systems605040302010YEARFigure2.2 Installed direct to the home terminalssupported market forces and competition, was unable to give BSB any preferen-tial treatment. BSB, as anenterprisingconcern, beganto lose confidenceofgetting government support but the money already invested by the participantsmeantthey would haveto continueto try and achievea marketable product ormakeamajorloss. Skyannouncedit wastobeoperational byFebruary1989while BSBdidnot broadcast until several months later, thus havinglost theinitiative and the audience. From then on BSB went down hill,until it was even-tuallymergedwithSkyasBSkyB in late1989. SkyoperateswiththeASTRAsatellites provided by Societe Europeenne de Satellites(SES)of Luxembourg inthe telecommunications (FSS) frequency bands and has a wide Europeancoverage area.In competition EUTELSAT carries similar services foraverywiderange ofcountries including Turkey, Italy, Croatia, Hungary, Portugal, Greece etc. andhas major plans for enhancing its service offering.As indicatedinFigure2.2, activities onDBSintheUKandEuropewereahead of other parts of the world. Digital direct-to-the-home (DTH)services aredevelopingrapidly andthiswill result inamorerapidpenetration of satellite-based television.2.6Technological considerationsThedevelopment of satellites usedfor civil communicationsintheGSahasbeen paced by the evolution ofadequate payload-bearing launch vehicles.Figure2.3indicates thegrowthof suchcapabilityupto 1994andFigure2.4shows the number of communications payloads launched per year up to 1997.Thedevelopmentof thesatellitesthemselvescanbebest presentedinafewcharts indicating graphically the evolution in terms of mass,power, lifetime andeffort to build(Figures 2.5 to 2.7).Historical overview ofsatellite communications 29GSO CAPABILITY, kg4000---TITANARIANEii -- -----t --iii - !i_--_......-- _.-- -.! A..- - - - - - ...-: . --- _J-- I EUROPAI T.. - J i __ IIir---1---.-.- .-+-- ---+-11 DELTACLASS-+---------+-11 ATLAS CLASSI ARIANE-+--------+-11: ::,:LASS _ _ _ _ t--_+-- iH-lt--__ !---,------,-------' Br-50010002500150020003000350059 6469 74 79 84 89NOTESAEUROPA III, NEVER LAUNCHEDB COMMERCIAL TITAN ONLYYEARFigure2.3 Evolution ofGsa payload capacityfor commercial launch vehicles100.0090.00 1----------------------------------------til'H80.001--------------------------------------m-I70.00 1---------1 til %COMMS ACTUAI.COMMS6O.001------------------------,__-----------fill-----50.00 1-------------------i11----I\tl------=--Irnt-----f;\t--ttt-----40.00 .1-------------------b1-Ul-------iilJ-----lHll}---It')-...m-HHIIHrt-----lHtl-30.00 I--------------------lw__=_20.00 I-----------fi'l-----10.000.00 0"1" '-0 00 0 N "1" '-0 00 0 N "1" '-0 00 0 N "1" '-0\C ...c ...0 \C '-0 t- r- r- r- r- oo 00 00 00 00 0-.. 0'-. 0\ 0\0\ :::Figure2.4 Payload launch history0/0 COMMSindicatesthepercentageof all payloadslaunchedintoorbitwhich are communications payloadsACTUALCOMMSindicates the number of communications payloadslaunched per year30 Satellite communication systems.1960s.197054.1980sX1990so10005000200030004000POW ER, W(End of Life)6000o 500 1000DRYMASS, kg1500 2000Figure2.5 Evolution ofthe dry-mass/electrical power capabilities ofspacecraftExamination of dataonthemassof thesatellitesandtheeffort requiredtobuild them leads to Figure 2.6 which emphasises the fact that large satellite pro-grammes absorb a lot ofworking hours. It is interesting that, despite thesomewhatexoticmaterialsused in spacecraft, areasonableestimate of thecostof a programmecanbederivedfroma simpleconversionof thesalarycostsrequired(along with a representative overhead).Aslaunchvehiclesimprovedintermsof mass-carryingcapabilityandelec-tronic components became more reliable, it was possible to increase significantlythe potential lifetime of asatellite. Figure 2.7 shows thetrends in li