Satelite Technology : Principles & Application

PART I SATELLITE TECHNOLOGY

1 Introduction to Satellites and their Applications 3

1.1 Ever-expanding Application Spectrum 3

1.2 What is a Satellite? 4

1.3 History of the Evolution of Satellites 7

1.3.1 Era of Hot Air Balloons and Sounding Rockets 7

1.3.2 Launch of Early Artificial Satellites 8

1.3.3 Satellites for Communications, Meteorology and Scientific Exploration -- Early Developments 10

1.3.4 Non-geosynchronous Communication Satellites: Telstar and Relay Programmes 11

1.3.5 Emergence of Geosynchronous Communication Satellites 12

1.3.6 International Communication Satellite Systems 15

1.3.7 Domestic Communication Satellite Systems 16

1.3.8 Satellites for other Applications also made Rapid Progress 19

1.3.9 Small or Miniature Satellites 22

1.4 Evolution of Launch Vehicles 27

1.5 Future Trends 33

1.5.1 Communication Satellites 33

1.5.2 Weather Forecasting Satellites 33

1.5.3 Earth Observation Satellites 33

1.5.4 Navigational Satellites 34

1.5.5 Military Satellites 35

Further Reading 35

Glossary 35

2 Satellite Orbits and Trajectories 37

2.1 Definition of an Orbit and a Trajectory 37

2.2 Orbiting Satellites -- Basic Principles 37

2.2.1 Newton’s Law of Gravitation 39

2.2.2 Newton’s Second Law of Motion 40

2.2.3 Kepler’s Laws 41

2.3 Orbital Parameters 44

2.4 Injection Velocity and Resulting Satellite Trajectories 61

2.5 Types of Satellite Orbits 67

2.5.1 Orientation of the Orbital Plane 67

2.5.2 Eccentricity of the Orbit 68

2.5.3 Distance from Earth 70

2.5.4 Sun-synchronous Orbit 73

Further Readings 76

Glossary 76

3 Satellite Launch and In-orbit Operations 79

3.1 Acquiring the Desired Orbit 79

3.1.1 Parameters Defining the Satellite Orbit 80

3.1.2 Modifying the Orbital Parameters 83

3.2 Launch Sequence 95

3.2.1 Types of Launch Sequence 95

3.3 Launch Vehicles 100

3.3.1 Introduction 100

3.3.2 Classification 100

3.3.3 Anatomy of a Launch Vehicle 104

3.3.4 Principal Parameters 106

3.3.5 Major Launch Vehicles 108

3.4 Space Centres 127

3.4.1 Location Considerations 127

3.4.2 Constituent Parts of a Space Centre 128

3.4.3 Major Space Centres 129

3.5 Orbital Perturbations 144

3.6 Satellite Stabilization 146

3.6.1 Spin Stabilization 146

3.6.2 Three-axis or Body Stabilization 147

3.6.3 Comparison between Spin-stabilized and Three-axis Stabilized Satellites 149

3.6.4 Station Keeping 149

3.7 Orbital Effects on Satellite’s Performance 149

3.7.1 Doppler Shift 149

3.7.2 Variation in the Orbital Distance 150

3.7.3 Solar Eclipse 150

3.7.4 Sun Transit Outrage 150

3.8 Eclipses 150

3.9 Look Angles of a Satellite 154

3.9.1 Azimuth Angle 154

3.9.2 Elevation Angle 155

3.9.3 Computing the Slant Range 156

3.9.4 Computing the Line-of-Sight Distance between Two Satellites 158

3.10 Earth Coverage and Ground Tracks 166

3.10.1 Satellite Altitude and the Earth Coverage Area 166

3.10.2 Satellite Ground Tracks 167

3.10.3 Orbit Inclination and Latitude Coverage 170

Further Readings 172

Glossary 172

4 Satellite Hardware 174

4.1 Satellite Subsystems 174

4.2 Mechanical Structure 175

4.2.1 Design Considerations 176

4.2.2 Typical Structure 176

4.3 Propulsion Subsystem 177

4.3.1 Basic Principle 178

4.3.2 Types of Propulsion System 178

4.4 Thermal Control Subsystem 185

4.4.1 Sources of Thermal Inequilibrium 186

4.4.2 Mechanism of Heat Transfer 186

4.4.3 Types of Thermal Control 187

4.5 Power Supply Subsystem 189

4.5.1 Types of Power System 189

4.5.2 Solar Energy Driven Power Systems 190

4.5.3 Batteries 195

4.6 Attitude and Orbit Control 199

4.6.1 Attitude Control 200

4.6.2 Orbit Control 200

4.7 Tracking, Telemetry and Command Subsystem 201

4.8 Payload 203

4.9 Antenna Subsystem 205

4.9.1 Antenna Parameters 207

4.9.2 Types of Antennas 210

4.10 Space Qualification and Equipment Reliability 224

4.10.1 Space Qualification 224

4.10.2 Reliability 225

Further Readings 226

Glossary 227

5 Communication Techniques 229

5.1 Types of Information Signals 229

5.1.1 Voice Signals 230

5.1.2 Data Signals 230

5.1.3 Video Signals 230

5.2 Amplitude Modulation 231

5.2.1 Frequency Spectrum of the AM Signal 232

5.2.2 Power in the AM Signal 233

5.2.3 Noise in the AM Signal 233

5.2.4 Different Forms of Amplitude Modulation 235

5.3 Frequency Modulation 241

5.3.1 Frequency Spectrum of the FM Signal 243

5.3.2 Narrow Band and Wide Band FM 245

5.3.3 Noise in the FM Signal 246

5.3.4 Generation of FM Signals 250

5.3.5 Detection of FM Signals 252

5.4 Pulse Communication Systems 259

5.4.1 Analogue Pulse Communication Systems 259

5.4.2 Digital Pulse Communication Systems 261

5.5 Sampling Theorem 265

5.6 Shannon--Hartley Theorem 266

5.7 Digital Modulation Techniques 267

5.7.1 Amplitude Shift Keying (ASK) 268

5.7.2 Frequency Shift Keying (FSK) 268

5.7.3 Phase Shift Keying (PSK) 269

5.7.4 Differential Phase Shift Keying (DPSK) 270

5.7.5 Quadrature Phase Shift Keying (QPSK) 271

5.7.6 Offset QPSK 273

5.7.7 8PSK and 16PSK 274

5.7.8 Quadrature Amplitude Modulation (QAM) 274

5.7.9 Amplitude Phase Shift Keying (APSK) 276

5.8 Multiplexing Techniques 277

5.8.1 Frequency Division Multiplexing 277

5.8.2 Time Division Multiplexing 279

5.8.3 Code Division Multiplexing 281

Further Readings 282

Glossary 283

6 Multiple Access Techniques 286

6.1 Introduction to Multiple Access Techniques 286

6.1.1 Transponder Assignment Modes 287

6.2 Frequency Division Multiple Access (FDMA) 288

6.2.1 Demand Assigned FDMA 290

6.2.2 Pre-assigned FDMA 290

6.2.3 Calculation of C/N Ratio 290

6.3 Single Channel Per Carrier (SCPC) Systems 293

6.3.1 SCPC/FM/FDMA System 293

6.3.2 SCPC/PSK/FDMA System 294

6.4 Multiple Channels Per Carrier (MCPC) Systems 295

6.4.1 MCPC/FDM/FM/FDMA System 295

6.4.2 MCPC/PCM-TDM/PSK/FDMA System 296

6.5 Time Division Multiple Access (TDMA) 297

6.6 TDMA Frame Structure 297

6.6.1 Reference Burst 298

6.6.2 Traffic Burst 298

6.6.3 Guard Time 299

6.7 TDMA Burst Structure 299

6.7.1 Carrier and Clock Recovery Sequence 299

6.7.2 Unique Word 299

6.7.3 Signalling Channel 300

6.7.4 Traffic Information 301

6.8 Computing Unique Word Detection Probability 301

6.9 TDMA Frame Efficiency 302

6.10 Control and Coordination of Traffic 303

6.11 Frame Acquisition and Synchronization 305

6.11.1 Extraction of Traffic Bursts from Receive Frames 305

6.11.2 Transmission of Traffic Bursts 305

6.11.3 Frame Synchronization 305

6.12 FDMA vs. TDMA 307

6.12.1 Advantages of TDMA over FDMA 308

6.12.2 Disadvantages of TDMA over FDMA 308

6.13 Code Division Multiple Access (CDMA) 308

6.13.1 DS-CDMA Transmission and Reception 309

6.13.2 Frequency Hopping CDMA (FH-CDMA) System 311

6.13.3 Time Hopping CDMA (TH-CDMA) System 313

6.13.4 Comparison of DS-CDMA, FH-CDMA and TH-CDMA Systems 314

6.14 Space Domain Multiple Access (SDMA) 316

6.14.1 Frequency Re-use in SDMA 316

6.14.2 SDMA/FDMA System 317

6.14.3 SDMA/TDMA System 318

6.14.4 SDMA/CDMA System 319

Further Readings 319

Glossary 320

7 Satellite Link Design Fundamentals 322

7.1 Transmission Equation 322

7.2 Satellite Link Parameters 324

7.2.1 Choice of Operating Frequency 324

7.2.2 Propagation Considerations 324

7.2.3 Noise Considerations 325

7.2.4 Interference-related Problems 325

7.3 Frequency Considerations 326

7.3.1 Frequency Allocation and Coordination 326

7.4 Propagation Considerations 330

7.4.1 Free-space Loss 330

7.4.2 Gaseous Absorption 331

7.4.3 Attenuation due to Rain 333

7.4.4 Cloud Attenuation 334

7.4.5 Signal Fading due to Refraction 334

7.4.6 Ionosphere-related Effects 335

7.4.7 Fading due to Multipath Signals 338

7.5 Techniques to Counter Propagation Effects 341

7.5.1 Attenuation Compensation Techniques 341

7.5.2 Depolarization Compensation Techniques 342

7.6 Noise Considerations 342

7.6.1 Thermal Noise 342

7.6.2 Noise Figure 343

7.6.3 Noise Temperature 344

7.6.4 Noise Figure and Noise Temperature of Cascaded Stages 345

7.6.5 Antenna Noise Temperature 346

7.6.6 Overall System Noise Temperature 350

7.7 Interference-related Problems 353

7.7.1 Intermodulation Distortion 354

7.7.2 Interference between the Satellite and Terrestrial Links 357

7.7.3 Interference due to Adjacent Satellites 357

7.7.4 Cross-polarization Interference 361

7.7.5 Adjacent Channel Interference 361

7.8 Antenna Gain-to-Noise Temperature (G/T) Ratio 365

7.9 Link Design 367

7.9.1 Link Design Procedure 368

7.9.2 Link Budget 368

7.10 Multiple Spot Beam Technology 371

Further Readings 374

Glossary 375

8 Earth Station 378

8.1 Earth Station 378

8.2 Types of Earth Station 380

8.2.1 Fixed Satellite Service (FSS) Earth Station 381

8.2.2 Broadcast Satellite Service (BSS) Earth Stations 382

8.2.3 Mobile Satellite Service (MSS) Earth Stations 383

8.2.4 Single Function Stations 384

8.2.5 Gateway Stations 385

8.2.6 Teleports 386

8.3 Earth Station Architecture 386

8.4 Earth Station Design Considerations 387

8.4.1 Key Performance Parameters 388

8.4.2 Earth Station Design Optimization 390

8.4.3 Environmental and Site Considerations 391

8.5 Earth Station Testing 392

8.5.1 Unit and Subsystem Level Testing 392

8.5.2 System Level Testing 392

8.6 Earth Station Hardware 398

8.6.1 RF Equipment 398

8.6.2 IF and Baseband Equipment 408

8.6.3 Terrestrial Interface 409

8.7 Satellite Tracking 412

8.7.1 Satellite Tracking System -- Block Diagram 412

8.7.2 Tracking Techniques 412

8.8 Some Representative Earth Stations 419

8.8.1 Goonhilly Satellite Earth Station 419

8.8.2 Madley Communications Centre 421

8.8.3 Madrid Deep Space Communications Complex 421

8.8.4 Canberra Deep Space Communications Complex 422

8.8.5 Goldstone Deep Space Communications Complex 423

8.8.6 Honeysuckle Creek Tracking Station 424

8.8.7 Kaena Point Satellite Tracking Station 426

8.8.8 Bukit Timah Satellite Earth Station 426

8.8.9 INTELSAT Teleport Earth Stations 426

8.8.10 SUPARCO Satellite Ground Station 428

8.8.11 Makarios Satellite Earth Station 428

8.8.12 Raisting Earth Station 428

8.8.13 Indian Deep Space Network 429

Glossary 430

9 Networking Concepts 433

9.1 Introduction 433

9.2 Network Characteristics 433

9.2.1 Availability 434

9.2.2 Reliability 434

9.2.3 Security 435

9.2.4 Throughput 436

9.2.5 Scalability 437

9.2.6 Topology 437

9.2.7 Cost 437

9.3 Applications and Services 437

9.3.1 Satellite and Network Services 438

9.3.2 Satellite Services 438

9.3.3 Network Services 438

9.3.4 Internet Services 439

9.4 Network Topologies 442

9.4.1 Bus Topology 442

9.4.2 Star Topology 443

9.4.3 Ring Topology 444

9.4.4 Mesh Topology 444

9.4.5 Tree Topology 445

9.4.6 Hybrid Topology 446

9.5 Network Technologies 447

9.5.1 Circuit Switched Networks 447

9.5.2 Packet Switched Networks 448

9.5.3 Circuit Switched versus Packet Switched Networks 449

9.6 Networking Protocols 450

9.6.1 Common Networking Protocols 450

9.6.2 The Open Systems Interconnect (OSI) Reference Model 453

9.6.3 Internet Protocol (IP) 456

9.6.4 Transmission Control Protocol (TCP) 457

9.6.5 Hyper Text Transfer Protocol (HTTP) 457

9.6.6 File Transfer Protocol (FTP) 457

9.6.7 Simple Mail Transfer Protocol (SMTP) 458

9.6.8 User Datagram Protocol (UDP) 458

9.6.9 Asynchronous Transfer Mode (ATM) 459

9.7 Satellite Constellations 459

9.7.1 Constellation Geometry 459

9.7.2 Major Satellite Constellations 460

9.8 Internetworking with Terrestrial Networks 465

9.8.1 Repeaters, Bridges, Switches and Routers 465

9.8.2 Protocol Translation, Stacking and Tunnelling 466

9.8.3 Quality of Service 466

Further Readings 467

Glossary 467

PART II SATELLITE APPLICATIONS

10 Communication Satellites 473

10.1 Introduction to Communication Satellites 473

10.2 Communication-related Applications of Satellites 474

10.2.1 Geostationary Satellite Communication Systems 475

10.2.2 Non-geostationary Satellite Communication Systems 475

10.3 Frequency Bands 475

10.4 Payloads 475

10.4.1 Types of Transponders 477

10.4.2 Transponder Performance Parameters 478

10.5 Satellite versus Terrestrial Networks 479

10.5.1 Advantages of Satellites Over Terrestrial Networks 479

10.5.2 Disadvantages of Satellites with Respect to Terrestrial Networks 480

10.6 Satellite Telephony 481

10.6.1 Point-to-Point Trunk Telephone Networks 482

10.6.2 Mobile Satellite Telephony 482

10.7 Satellite Television 484

10.7.1 A Typical Satellite TV Network 484

10.7.2 Satellite--Cable Television 485

10.7.3 Satellite--Local Broadcast TV Network 486

10.7.4 Direct-to-Home Satellite Television 487

10.7.5 Digital Video Broadcasting (DVB) 490

10.7.6 DVB-S and DVB-S2 Standards 491

10.7.7 DVB-RCS and DVB-RCS2 Standards 493

10.7.8 DVB-T and DVB-T2 Standards 493

10.7.9 DVB-H and DVB-SH Standards 494

10.8 Satellite Radio 496

10.9 Satellite Data Communication Services 496

10.9.1 Satellite Data Broadcasting 496

10.9.2 VSATs (Very Small Aperture Terminals) 497

10.10 Important Missions 502

10.10.1 International Satellite Systems 502

10.10.2 Regional Satellite Systems 512

10.10.3 National Satellite Systems 513

10.11 Future Trends 514

10.11.1 Development of Satellite Constellations in LEO Orbits 516

10.11.2 Development of Personal Communication Services (PCS) 516

10.11.3 Use of Higher Frequency Bands 517

10.11.4 Development of Light Quantum Communication Techniques 517

10.11.5 Development of Broadband Services to Mobile Users 517

10.11.6 Development of Hybrid Satellite/Terrestrial Networks 517

10.11.7 Advanced Concepts 518

Further Readings 519

Glossary 521

11 Remote Sensing Satellites 524

11.1 Remote Sensing -- An Overview 524

11.1.1 Aerial Remote Sensing 525

11.1.2 Satellite Remote Sensing 525

11.2 Classification of Satellite Remote Sensing Systems 526

11.2.1 Optical Remote Sensing Systems 526

11.2.2 Thermal Infrared Remote Sensing Systems 528

11.2.3 Microwave Remote Sensing Systems 529

11.3 Remote Sensing Satellite Orbits 531

11.4 Remote Sensing Satellite Payloads 531

11.4.1 Classification of Sensors 531

11.4.2 Sensor Parameters 534

11.5 Passive Sensors 535

11.5.1 Passive Scanning Sensors 536

11.5.2 Passive Non-scanning Sensors 539

11.6 Active Sensors 540

11.6.1 Active Non-scanning Sensors 540

11.6.2 Active Scanning Sensors 540

11.7 Types of Images 542

11.7.1 Primary Images 542

11.7.2 Secondary Images 542

11.8 Image Classification 545

11.9 Image Interpretation 546

11.9.1 Interpreting Optical and Thermal Remote Sensing Images 546

11.9.2 Interpreting Microwave Remote Sensing Images 547

11.9.3 GIS in Remote Sensing 547

11.10 Applications of Remote Sensing Satellites 548

11.10.1 Land Cover Classification 548

11.10.2 Land Cover Change Detection 549

11.10.3 Water Quality Monitoring and Management 550

11.10.4 Flood Monitoring 551

11.10.5 Urban Monitoring and Development 552

11.10.6 Measurement of Sea Surface Temperature 552

11.10.7 Deforestation 553

11.10.8 Global Monitoring 553

11.10.9 Predicting Disasters 555

11.10.10 Other Applications 558

11.11 Major Remote Sensing Missions 558

11.11.1 Landsat Satellite System 558

11.11.2 SPOT Satellite System 561

11.11.3 Radarsat Satellite System 564

11.11.4 Indian Remote Sensing Satellite System 565

11.12 Future Trends 573

Further Readings 574

Glossary 575

12 Weather Satellites 577

12.1 Weather Forecasting -- An Overview 577

12.2 Weather Forecasting Satellite Fundamentals 580

12.3 Images from Weather Forecasting Satellites 580

12.3.1 Visible Images 580

12.3.2 IR Images 582

12.3.3 Water Vapour Images 583

12.3.4 Microwave Images 584

12.3.5 Images Formed by Active Probing 585

12.4 Weather Forecasting Satellite Orbits 586

12.5 Weather Forecasting Satellite Payloads 587

12.5.1 Radiometer 588

12.5.2 Active Payloads 589

12.6 Image Processing and Analysis 592

12.6.1 Image Enhancement Techniques 592

12.7 Weather Forecasting Satellite Applications 593

12.7.1 Measurement of Cloud Parameters 594

12.7.2 Rainfall 594

12.7.3 Wind Speed and Direction 595

12.7.4 Ground-level Temperature Measurements 596

12.7.5 Air Pollution and Haze 596

12.7.6 Fog 596

12.7.7 Oceanography 596

12.7.8 Severe Storm Support 597

12.7.9 Fisheries 598

12.7.10 Snow and Ice Studies 598

12.8 Major Weather Forecasting Satellite Missions 599

12.8.1 GOES Satellite System 599

12.8.2 Meteosat Satellite System 605

12.8.3 Advanced TIROS-N (ATN) NOAA Satellites 608

12.9 Future of Weather Forecasting Satellite Systems 612

Further Readings 612

Glossary 613

13 Navigation Satellites 614

13.1 Development of Satellite Navigation Systems 614

13.1.1 Doppler Effect based Satellite Navigation Systems 615

13.1.2 Trilateration-based Satellite Navigation Systems 615

13.2 Global Positioning System (GPS) 621

13.2.1 Space Segment 621

13.2.2 Control Segment 622

13.2.3 User Segment 623

13.3 Working Principle of the GPS 625

13.3.1 Principle of Operation 625

13.3.2 GPS Signal Structure 627

13.3.3 Pseudorange Measurements 628

13.3.4 Determination of the Receiver Location 629

13.4 GPS Positioning Services and Positioning Modes 631

13.4.1 GPS Positioning Services 631

13.4.2 GPS Positioning Modes 632

13.5 GPS Error Sources 634

13.6 GLONASS Satellite System 637

13.6.1 GLONASS Segments 638

13.6.2 GLONASS Signal Structure 639

13.7 GPS-GLONASS Integration 641

13.8 EGNOS Satellite Navigation System 642

13.9 Galileo Satellite Navigation Systems 645

13.9.1 Three-Phase Development Programme 645

13.9.2 Services 646

13.10 Indian Regional Navigational Satellite System (IRNSS) 647

13.11 Compass Satellite Navigation System 648

13.12 Hybrid Navigation Systems 648

13.13 Applications of Satellite Navigation Systems 650

13.13.1 Military Applications 650

13.13.2 Civilian Applications 651

13.14 Future of Satellite Navigation Systems 654

Further Readings 655

Glossary 656

14 Scientific Satellites 658

14.1 Satellite-based versus Ground-based Scientific Techniques 658

14.2 Payloads on Board Scientific Satellites 659

14.2.1 Payloads for Studying Earth’s Geodesy 659

14.2.2 Payloads for Earth Environment Studies 660

14.2.3 Payloads for Astronomical Studies 661

14.3 Applications of Scientific Satellites -- Study of Earth 665

14.3.1 Space Geodesy 665

14.3.2 Tectonics and Internal Geodynamics 669

14.3.3 Terrestrial Magnetic Fields 670

14.4 Observation of the Earth’s Environment 670

14.4.1 Study of the Earth’s Ionosphere and Magnetosphere 671

14.4.2 Study of the Earth’s Upper Atmosphere (Aeronomy) 677

14.4.3 Study of the Interaction between Earth and its Environment 679

14.5 Astronomical Observations 680

14.5.1 Observation of the Sun 681

14.6 Missions for Studying Planets of the Solar System 686

14.6.1 Mercury 691

14.6.2 Venus 692

14.6.3 Mars 694

14.6.4 Outer Planets 697

14.6.5 Moon 703

14.6.6 Asteroids 705

14.6.7 Comets 706

14.7 Missions Beyond the Solar System 707

14.8 Other Fields of Investigation 710

14.8.1 Microgravity Experiments 710

14.8.2 Life Sciences 711

14.8.3 Material Sciences 712

14.8.4 Cosmic Ray and Fundamental Physics Research 713

14.9 Future Trends 714

Further Readings 715

Glossary 715

15 Military Satellites 717

15.1 Military Satellites -- An Overview 717

15.1.1 Applications of Military Satellites 718

15.2 Military Communication Satellites 718

15.3 Development of Military Communication Satellite Systems 719

15.3.1 American Systems 720

15.3.2 Russian Systems 724

15.3.3 Satellites Launched by other Countries 725

15.4 Frequency Spectrum Utilized by Military Communication Satellite Systems 726

15.5 Dual-use Military Communication Satellite Systems 727

15.6 Reconnaisance Satellites 728

15.6.1 Image Intelligence or IMINT Satellites 728

15.7 SIGINT Satellites 732

15.7.1 Development of SIGINT Satellites 733

15.8 Early Warning Satellites 735

15.8.1 Major Early Warning Satellite Programmes 736

15.9 Nuclear Explosion Satellites 738

15.10 Military Weather Forecasting Satellites 738

15.11 Military Navigation Satellites 739

15.12 Space Weapons 739

15.12.1 Classification of Space Weapons 740

15.13 Strategic Defence Initiative 745

15.13.1 Ground Based Programmes 746

15.13.2 Directed Energy Weapon Programmes 749

15.13.3 Space Programmes 751

15.13.4 Sensor Programmes 752

15.14 Directed Energy Laser Weapons 752

15.14.1 Advantages 753

15.14.2 Limitations 753

15.14.3 Directed Energy Laser Weapon Components 754

15.14.4 Important Design Parametres 755

15.14.5 Important Laser Sources 756

15.14.6 Beam Control Technology 763

15.15 Advanced Concepts 764

15.15.1 New Surveillance Concepts Using Satellites 765

15.15.2 Long Reach Non-lethal Laser Dazzler 765

15.15.3 Long Reach Laser Target Designator 766

Further Readings 767

Glossary 767

16 Emerging Trends 769

16.1 Introduction 769

16.2 Space Tethers 769

16.2.1 Space Tethers -- Different Types 770

16.2.2 Applications 774

16.2.3 Space Tether Missions 775

16.2.4 Space Elevator 779

16.3 Aerostat Systems 781

16.3.1 Components of an Aerostat System 782

16.3.2 Types of Aerostat Systems 782

16.3.3 Applications 783

16.4 Millimetre Wave Satellite Communication 784

16.4.1 Millimetre Wave Band 784

16.4.2 Advantages 785

16.4.3 Propagation Considerations 787

16.4.4 Applications 788

16.4.5 Millimetre Wave Satellite Missions 789

16.5 Space Stations 793

16.5.1 Importance of Space Stations 794

16.5.2 Space Stations of the Past 794

16.5.3 Currently Operational Systems 797

16.5.4 Planned Space Stations 799

16.5.5 Emerging Space Station Concepts 801

Further Readings 803

Glossary 804

Index 807