Deep SpaceOptical Communications

Edited by

Hamid Hemmati

WILEY-INTERSCIENCE

A JOHN WILEY & SONS, INC., PUBLICATION

Table of ContentsForeword xvii

Preface xix

Acknowledgments xxiii

Contributors xxv

Chapter 1: Introduction 1

by James R. Lesh

1.1 Motivation for Increased Communications 1

1.2 History of JPL Optical Communications Activities 5

1.3 Component/Subsystem Technologies 71.3.1 Laser Transmitters 81.3.2 Spacecraft Telescopes 101.3.3 Acquisition, Tracking, and Pointing 101.3.4 Detectors 121.3.5 Filters 141.3.6 Error Correction Coding 14

1.4 Flight Terminal Developments 161.4.1 Optical Transceiver Package (OPTRANSPAC) 161.4.2 Optical Communications Demonstrator (OCD) 171.4.3 Lasercom Test and Evaluation Station (LTES) 191.4.4 X2000 Flight Terminal 201.4.5 International Space Station Flight Terminal 22

1.5 Reception System and Network Studies 231.5.1 Ground Telescope Cost Model 241.5.2 Deep Space Optical Reception Antenna (DSORA) 251.5.3 Deep Space Relay Satellite System (DSRSS) Studies 261.5.4 Ground-Based Antenna Technology Study (GBATS) 271.5.5 Advanced Communications Benefits Study (ACBS) 281.5.6 Earth Orbit Optical Reception Terminal (EOORT) Study 291.5.7 EOORT Hybrid Study 301.5.8 Spherical Primary Ground Telescope 301.5.9 Space-Based versus Ground-Based Reception Trades 31

1.6 Atmospheric Transmission 34

VI

1.7 Background Studies 36

1.8 Analysis Tools 37

1.9 System-Level Studies 381.9.1 Venus Radar Mapping (VRM) Mission Study 381.9.2 Synthetic Aperture Radar-C (SIR-C) Freeflyer 381.9.3 ER-2 to Ground Study 391.9.4 Thousand Astronomical Unit (TAU) Mission and Interstellar

Mission Studies 40

1.10 System-Level Demonstrations 411.10.1 Galileo Optical Experiment (GOPEX) 411.10.2 Compensated Earth-Moon-Earth Retro-Reflector

Laser Link (CEMERLL) 431.10.3 Ground/Orbiter Lasercomm Demonstration (GOLD) 441.10.4 Ground-Ground Demonstrations 47

1.11 Other Telecommunication Functions 501.11.1 Opto-Metric Navigation 501.11.2 Light Science 51

1.12 The Future 521.12.1 Optical Communications Telescope Facility (OCTL) 521.12.2 Unmanned Arial Vehicle (UAV)-Ground Demonstration 521.12.3 Adaptive Optics 531.12.4 Optical Receiver and Dynamic Detector Array 551.12.5 Alternate Ground-Reception Systems 56

1.13 Mars Laser Communication Demonstration 57

1.14 Summary of Following Chapters 58

References 60

Chapter 2: Link and System Design 83

by Chien-Chung Chen

2.1 Overview of Deep-Space Lasercom Link 85

2.2 Communications Link Design 872.2.1 Link Equation and Receive Signal Power 892.2.2 Optical-Receiver Sensitivity 91

2.2.2.1 Photon Detection Sensitivity 952.2.2.2 Modulation Format 952.2.2.3 Background Noise Control 96

2.2.3 Link Design Trades 982.2.3.1 Operating Wavelength 98

Table of Contents vii

2.2.3.2 Transmit Power and Size of Transmit andReceive Apertures 99

2.2.3.3 Receiver Optical Bandwidth and Field of Viewversus Signal Throughput 99

2.2.3.4 Modulation and Coding 1002.2.4 Communications Link Budget 1002.2.5 Link Availability Considerations 100

2.2.5.1 Short-Term Data Outages 1012.2.5.2 Weather-Induced Outages 1032.2.5.3 Other Long-Term Outages 1042.2.5.4 Critical-Mission-Phase Coverage 106

2.3 Beam Pointing and Tracking 1062.3.1 Downlink Beam Pointing 107

2.3.1.1 Jitter Isolation and Rejection 1072.3.1.2 Precision Beam Pointing and Point Ahead 108

2.3.2 Uplink Beam Pointing 1102.3.3 Pointing Acquisition 111

2.4 Other Design Drivers and Considerations 1132.4.1 System Mass and Power 1132.4.2 Impact on Spacecraft Design 1142.4.3 Laser Safety 115

2.5 Summary 115

References 118

Chapter 3: The Atmospheric Channel 121by Abhijit Biswas and Sabino Piazzolla

3.1 Cloud Coverage Statistics 1233.1.1 National Climatic Data Center Data Set 1243.1.2 Single-Site and Two-Site Diversity Statistics 1263.1.3 Three-Site Diversity 1303.1.4 NCDC Analysis Conclusion 1353.1.5 Cloud Coverage Statistics by Satellite Data Observation 137

3.2 Atmospheric Transmittance and Sky Radiance 1403.2.1 Atmospheric Transmittance 1403.2.2 Molecular Absorption and Scattering 1413.2.3 Aerosol Absorption and Scattering 145

3.2.3.1 Atmospheric Attenuation Statistics 1483.2.4 Sky Radiance 151

3.2.4.1 Sky Radiance Statistics 1563.2.5 Point Sources of Background Radiation 159

VIII

3.3 Atmospheric Issues on Ground Telescope Site Selection foran Optical Deep Space Network 1693.3.1 Optical Deep Space Network 1693.3.2 Data Rate/BER of a Mission 1743.3.3 Telescope Site Location 1743.3.4 Network Continuity and Peaks 178

3.4 Laser Propagation Through the Turbulent Atmosphere 1843.4.1 Atmospheric Turbulence 1843.4.2 Atmospheric "Seeing" Effects 1903.4.3 Optical Scintillation or Irradiance Fluctuations 1983.4.4 Atmospheric Turbulence Induced Angle of Arrival 204

References 207

Chapter 4: Optical Modulation and Coding 215by Samuel J. Dolinar, Jon Hamkins, Bruce E. Moision,and Victor A. Vilnrotter

4.1 Introduction 215

4.2 Statistical Models for the Detected Optical Field 2194.2.1 Quantum Models of the Optical Field 219

4.2.1.1 Quantization of the Electric Field 2204.2.1.2 The Coherent State Representation of a

Single Field Mode 2224.2.1.3 Quantum Representation of Thermal Noise 2234.2.1.4 Quantum Representation of Signal Plus

Thermal Noise 2234.2.2 Statistical Models for Direct Detection 224

4.2.2.1 The Poisson Channel Model for IdealPhotodetectors or Ideal PMTs 225

4.2.2.2 The Mclntyre-Conradi Model for APDDetectors 226

4.2.2.3 The Webb, Mclntyre, and ConradiApproximation to the Mclntyre-Conradi Model 228

4.2.2.4 The WMC Plus Gaussian Approximation 2294.2.2.5 Additive White Gaussian Noise Approximation 229

4.2.3 Summary of Statistical Models 231

4.3 Modulation Formats 2314.3.1 On-Off Keying (OOK) 2334.3.2 Pulse-Position Modulation (PPM) 2344.3.3 Differential PPM (DPPM) 2354.3.4 Overlapping PPM (OPPM) 236

Table of Contents ix

4.3.5 Wavelength Shift Keying (WSK) 2374.3.6 Combined PPM and WSK 237

4.4 Rate Limits Imposed by Constraints on Modulation 2384.4.1 Shannon Capacity 239

4.4.1.1 Characterizing Capacity: Fixed Duration Edges 2404.4.1.2 Characterizing Capacity: Variable Duration Edges. 2414.4.1.3 Characterizing Capacity: Probabilistic

Characterization 2414.4.1.4 Characterizing Capacity: Energy Efficiency 243

4.4.2 Constraints 2434.4.2.1 Dead Time 2444.4.2.2 Runlength 245

4.4.3 Modulation Codes 2454.4.3.1 M-ary PPM with Deadtime 2464.4.3.2 A/-ary DPPM with Deadtime 2474.4.3.3 Synchronous Variable-Length Codes 248

4.5 Performance of Uncoded Optical Modulations 2504.5.1 Direct Detection of OOK on the Poisson Channel 2514.5.2 Direct Detection of PPM 252

4.5.2.1 Poisson Channel 2544.5.2.2 AWGN Channel 258

4.5.3 Direct Detection of Combined PPM and WSK 2604.5.4 Performance of Modulations Using Receivers Based on

Quantum Detection Theory 2604.5.4.1 Receivers Based on Quantum Detection Theory 2604.5.4.2 Performance of Representative Modulations 264

4.6 Optical Channel Capacity 2684.6.1 Capacity of the PPM Channel: General Formulas 2694.6.2 Capacity of Soft-Decision PPM: Specific Channel Models .... 270

4.6.2.1 Poisson Channel 2704.6.2.2 AWGN Channel 271

4.6.3 Hard-Decision Versus Soft-Decision Capacity 2724.6.4 Losses Due to Using PPM 2734.6.5 Capacity of the Binary Channel with Quantum Detection 275

4.7 Channel Codes for Optical Modulations 2774.7.1 Reed-Solomon Codes 2784.7.2 Turbo and Turbo-Like Codes for Optical Modulations 279

4.7.2.1 Parallel Concatenated (Turbo) Codes 2794.7.2.2 Serially Concatenated Codes with Iterative

Decoding 280

4.8 Performance of Coded Optical Modulations 2814.8.1 Parameter Selection 2814.8.2 Estimating Performance 284

4.8.2.1 Reed-Solomon Codes 2844.8.2.2 Iterative Codes 286

4.8.3 Achievable Data Rates Versus Average Signal Power 286

References 289

Chapter 5: Flight Transceiver 301by Hamid Hemmati, Gerardo G. Ortiz, William T. Roberts,Malcolm W. Wright, and Shinhak Lee

5.1 Optomechanical Subsystem 301by Hamid Hemmati5.1.1 Introduction 3015.1.2 Optical Beam Paths 3025.1.3 Optical Design Requirements, Design Drivers, and

Challenges 3045.1.4 Optical Design Drivers and Approaches 3065.1.5 Transmit-Receive-Isolation 3075.1.6 Stray-Light Control 309

5.1.6.1 Operation at Small Sun Angles 3095.1.6.2 Surface Cleanliness Requirements 310

5.1.7 Transmission, Alignment, and Wavefront Quality Budgets.... 3105.1.8 Efficient Coupling of Lasers to Obscured Telescopes 311

5.1.8.1 Axicon Optical Element 3115.1.8.2 Sub-Aperture Illumination 3115.1.8.3 Prism Beam Slicer 3125.1.8.4 Beam Splitter/Combiner 313

5.1.9 Structure, Materials, and Structural Analysis 3145.1.10 Use of Fiber Optics 3165.1.11 Star-Tracker Optics for Acquisition and Tracking 3165.1.12 Thermal Management 3175.1.13 Optical System Design Example 317

5.1.13.1 Afocal Fore-Optics 3175.1.13.2 Receiver Channel 3175.1.13.3 Stellar Reference Channel 3225.1.13.4 Align and Transmit Channels 3245.1.13.5 Folded Layouts 3255.1.13.6 Tolerance Sensitivity Analysis 3265.1.13.7 Thermal Soak Sensitivity Analysis 3285.1.13.8 Solid Model of System 329

Table of Contents xi

5.2 Laser Transmitter 331by Hamid Hemmati5.2.1 Introduction 3315.2.2 Requirements and Challenges 3335.2.3 Candidate Laser Transmitter Sources 337

5.2.3.1 Pulsed Laser Transmitters 3385.2.3.2 Fiber-Waveguide Amplifiers 3405.2.3.3 Bulk-Crystal Amplifiers 3425.2.3.4 Semiconductor Optical Amplifiers 345

5.2.4 Lasers for Coherent Communications 3465.2.5 Laser Modulators 3465.2.6 Efficiency 3475.2.7 Laser Timing Jitter Control 348

5.2.7.1 Jitter Control Options 3485.2.8 Redundancy 3505.2.9 Thermal Management 350

5.3 Deep-Space Acquisition, Tracking, and Pointing 351by Gerardo G. Ortiz and Shinhak Lee5.3.1 Unique Challenges of Deep Space Optical Beam Pointing 351

5.3.1.1 State-of-the-Art ATP Performance 3525.3.2 Link Overview and System Requirements 353

5.3.2.1 Pointing Requirement 3535.3.2.2 Pointing-Error Budget Allocations 357

5.3.3 ATP System 3575.3.3.1 Pointing Knowledge Reference Sources 3575.3.3.2 Pointing System Architecture 3605.3.3.3 Design Considerations 363

5.3.4 Cooperative Beacon (Ground Laser) Tracking 3735.3.5 Noncooperative Beacon Tracking 374

5.3.5.1 Earth Tracker-Visible Spectrum 3755.3.5.2 Star Tracker 3825.3.5.3 Earth Tracker—Long Wavelength Infrared Band... 391

5.3.6 ATP Technology Demonstrations 3995.3.6.1 Reduced Complexity ATP Architecture 3995.3.6.2 Centroiding Algorithms-Spot Model Method 4015.3.6.3 High Bandwidth, Windowing,

CCD-Based Camera 4075.3.6.4 Accelerometer-Assisted Beacon Tracking 412

5.4 Flight Qualification 419by Hamid Hemmati, William T. Roberts, and Malcolm W. Wright5.4.1 Introduction 4195.4.2 Approaches to Flight Qualification 420

XI I

5.4.3 Flight Qualification of Electronics and Opto-ElectronicSubsystem 4225.4.3.1 MIL-PRF-19500 4225.4.3.2 MIL STD 750 4225.4.3.3 MIL STD 883 4225.4.3.4 Telcordia 4235.4.3.5 NASA Electronics Parts and Packaging (NEPP) 423

5.4.4 Number of Test Units 4235.4.5 Space Environments 425

5.4.5.1 Environmental Requirements 4255.4.5.2 Ionizing Radiation 4265.4.5.3 Vibration Environment 4285.4.5.4 Mechanical, Thermal, and Pyro Shock

Environment 4295.4.5.5 Thermal Gradients Environment 4295.4.5.6 Depressurization Environment 4305.4.5.7 Electric and Magnetic Field Environment 4305.4.5.8 Outgassing 431

5.4.6 Flight Qualification of Detectors 4315.4.6.1 Flight Qualification Procedures 4325.4.6.2 Detector Radiation Testing 440

5.4.7 Flight Qualification of Laser Systems 4435.4.7.1 Past Laser Systems Flown in Space 4445 A.I2 Design of Semiconductor Lasers for High

Reliability Applications 4475.4.7.3 Degradation Mechanisms 4485.4.7.4 Qualification Process for Lasers 449

5.4.8 Flight Qualification of Optics 454

References 454

Chapter 6: Earth Terminal Architecturesby Keith E. Wilson, Abhijit Biswas, Andrew A. Gray,Victor A. Vilnrotter, Chi-Wung Lau, Mera Srinivasan,and William H. Farr 467

6.1 Introductionby Keith E. Wilson 4676.1.1 Single-Station Downlink Reception and Uplink

Transmission 469by Keith E. Wilson6.1.1.1 Introduction 4696.1.1.2 Deep-Space Optical Ground Receivers 470

Table of Contents xiii

6.1.2

6.1.1.3 Mitigating Cloud Cover and Sky BackgroundEffects at the Receiver 472Daytime Sky Background Effects 475Earth-Orbiting and Airborne Receivers 476Uplink Beacon and Command 476Techniques for Mitigating Atmospheric Effects 482Adaptive Optics 484Multiple-Beam Propagation 486Safe Laser Beam Propagation into Space 488Concept Validation Experiments SupportingFuture Deep-Space Optical links 493Conclusion 514

Optical-Array Receivers for Deep-Space Communication 516by Victor A. Vilnrotter, Chi-Wung Lau, and Meera Srinivasan

6.16.16.16.16.16.16.16.1

.1.4

.1.5

.1.6

.1.7

.1.8

.1.9

.1.10

.1.11

6.1.1.12

.2.1 Introduction 516

.2.2 The Optical-Array Receiver Concept 516

.2.3 Aperture-Plane Expansions 519

.2.4 Array Receiver Performance 527

.2.5 Conclusions 540

6.2 Photodetectors 5416.2.1 Single-Element Detectors 541

by Abhijit Biswas and William H. Farr6.2.1.1 Deep-Space Detector Requirements and

Challenges 5416.2.1.2 Detector System Dependencies 5446.2.1.3 Detectors for Deep-Space Communications 545

6.2.2 Focal-Plane Detector Arrays for Communication ThroughTurbulence 551by Victor A. Vilnrotter and Meera Srinivasan6.2.2.1 Introduction 5516.2.2.2 Optical Direct Detection with Focal-Plane

Arrays 5536.2.2.3 Numerical Results 5626.2.2.4 Summary And Conclusions 566

5676.3 Receiver Electronicsby Andrew A. Gray, Victor A. Vilnrotter, and Meera Srinivasan6.3.1 Introduction 5676.3.2 Introduction to Discrete-Time Demodulator Architectures 5716.3.3 Discrete-Time Synchronization and Post-Detection

Filtering Overview 5726.3.3.1 Discrete-Time Post-Detection Filtering 573

xiv

6.3.3.2 Slot and Symbol Synchronization and DecisionProcessing 580

6.3.4 Discrete-Time Demodulator Variations 5846.3.5 Discrete-Time Demodulator with Time-Varying

Post-Detection Filter 5856.3.6 Parallel Discrete-Time Demodulator Architectures 5896.3.7 Asynchronous Discrete-Time Processing 5926.3.8 Parallel Discrete-Time Demodulator Architectures 603

6.3.8.1 Simple Example Architecture 6036.3.8.2 Performance with a Simple Optical Channel

Model 6066.3.8.3 Evolved Parallel Architectures 608

6.3.9 Primary System Models and Parameters 6166.3.10 Conclusion and Future Work 618

References 626

Chapter 7: Future Prospects and Applications 643by Hamid Hemmati and Abhijit Biswas

7.1 Current and Upcoming Projects in the United States,Europe, and Japan 6437.1.1 LUCE (Laser Utilizing Communications Experiment) 6437.1.2 Mars Laser-Communication Demonstrator (MLCD) 644

7.2 Airborne and Spaceborne Receivers 6467.2.1 Advantages of Airborne and Spaceborne Receivers 6467.2.2 Disadvantages of Airborne and Spaceborne Receivers 6477.2.3 Airborne Terminals 648

7.2.3.1 Balloons 6487.2.3.2 Airships 6497.2.3.3 Airplanes 649

7.2.4 Spaceborne Receiver Terminals 6507.2.5 Alternative Receiver Sites 650

7.3 Light Science 6507.3.1 Light-Propagation Experiments 6517.3.2 Occultation Experiments to Probe Planetary Atmospheres,

Rings, Ionospheres, Magnetic Fields, and the InterplanetaryMedium 6517.3.2.1 Atmospheric Occultations 6527.3.2.2 Ring-Investigation Experiments 652

7.3.3 Enhanced Knowledge of Solar-System-Object Masses andGravitational Fields, Sizes, Shapes, and Surface Features 652

Table of Contents xv

7.3.3.1 Improved Knowledge of Solar-System BodyProperties 653

7.3.3.2 Optical Reference-Frame Ties 6537.3.4 Tests of the Fundamental Theories: General Relativity,

Gravitational Waves, Unified Field Theories, Astrophysics,and Cosmology 6537.3.4.1 Tests of General Relativity and Unified Field

Theories, Astrophysics, and Cosmology 6547.3.4.2 Effects of Charged Particles on Electromagnetic

Wave Propagation, Including Test of 1/fHypothesis 654

7.3.5 Enhanced Solar-System Ephemerides 6547.3.5.1 Science Benefits of Remote Optical Tracking:

Ephemeris Improvement 6557.3.6 Applications of Coherent Laser Communications

Technology 656

7.4 Conclusions 657

References 657