Deep Space Optical Communications

Foreword.

Preface.

Acknowledgments.

Contributors.

Chapter 1 : Introduction (James R . Lesh).

1.1 Motivation for Increased Communications.

1.2 History of JPL Optical Communications Activities.

1.3 ComponentlSubsystem Technologies.

1.3.1 Laser Transmitters.

1.3.2 Spacecraft Telescopes.

1.3.3 Acquisition, Tracking. and Pointing.

1.3.4 Detectors.

1.3.5 Filters.

1.3.6 Error Correction Coding.

1.4 Flight Terminal Developments.

1.4.1 Optical Transceiver Package (OPTRANSPAC).

1.4.2 Optical Communications Demonstrator (OCD).

1.4.3 Lasercom Test and Evaluation Station (LTES).

1.4.4 X2000 Flight Terminal.

1.4.5 International Space Station Flight Terminal.

1.5 Reception System and Network Studies.

1.5.1 Ground Telescope Cost Model.

1.5.2 Deep Space Optical Reception Antenna (DSORA).

1.5.3 Deep Space Relay Satellite System (DSRSS) Studies.

1.5.4 Ground-Based Antenna Technology Study (GBATS).

1.5.5 Advanced Communications Benefits Study (ACBS).

1.5.6 Earth Orbit Optical Reception Terminal (EOORT) Study.

1.5 .7 EOORT Hybrid Study.

1.5.8 Spherical Primary Ground Telescope.

1.5.9 Space-Based versus Ground-Based Reception Trades.

1.6 Atmospheric Transmission.

1.7 Background Studies.

1.8 Analysis Tools.

1.9 System-Level Studies.

1.9.1 Venus Radar Mapping (VRM) Mission Study.

1.9.2 Synthetic Aperture Radar-C (SIR-C) Freeflyer.

1.9.3 ER-2 to Ground Study.

1.9.4 Thousand Astronomical Unit (TAU) Mission and Interstellar Mission Studies.

1.1 0 System-Level Demonstrations.

1 .1 0. 1 Galileo Optical Experiment (GOPEX).

1.10.2 Compensated Earth-Moon-Earth Retro-Reflector Laser Link (CEMERLL).

1.1 0.3 Groundlorbiter Lasercomm Demonstration (GOLD).

1.10 .4 Ground-Ground Demonstrations.

1.11 Other Telecommunication Functions.

1.11.1 Opto-Metric Navigation.

1.11.2 Light Science.

1.12 The Future.

1.12.1 Optical Communications Telescope Facility (OCTL).

1.12.2 Unmanned Aria1 Vehicle (UAVFGround Demonstration.

1.12.3 Adaptive Optics.

1.12.4 Optical Receiver and Dynamic Detector Array.

1.1 2.5 Alternate Ground-Reception Systems.

1.13 Mars Laser Communication Demonstration.

1.14 Summary of Following Chapters.

References.

Chapter 2: Link and System Design (Chien-Chung Chen).

2.1 Overview of Deep-Space Lasercom Link.

2.2 Communications Link Design.

2.2.1 Link Equation and Receive Signal Power.

2.2.2 Optical-Receiver Sensitivity.

2.2.2.1 Photon Detection Sensitivity.

2.2.2.2 Modulation Format.

2.2.2.3 Background Noise Control.

2.2.3 Link Design Trades.

2.2.3.1 Operating Wavelength.

2.2.3.2 Transmit Power and Size of Transmit and Receive Apertures.

2.2.3.3 Receiver Optical Bandwidth and Field of View versus Signal Throughput.

2.2.3.4 Modulation and Coding.

2.2.4 Communications Link Budget.

2.2.5 Link Availability Considerations.

2.2.5.1 Short-Term Data Outages.

2.2.5.2 Weather-Induced Outages.

2.2.5.3 Other Long-Term Outages.

2.2.5.4 Critical-Mission-Phase Coverage.

2.3 Beam Pointing and Tracking.

2.3.1 Downlink Beam Pointing.

2.3.1.1 Jitter Isolation and Rejection.

2.3.1.2 Precision Beam Pointing and Point Ahead.

2.3.2 Uplink Beam Pointing.

2.3.3 Pointing Acquisition.

2.4 Other Design Drivers and Considerations.

2.4.1 System Mass and Power.

2.4.2 Impact on Spacecraft Design.

2.4.3 Laser Safety.

2.5 Summary.

References.

Chapter 3: The Atmospheric Channel (Abhijit Biswas and Sabino Piazzolla).

3.1 Cloud Coverage Statistics.

3.1.1 National Climatic Data Center Data Set.

3.1.2 Single-Site and Two-Site Diversity Statistics.

3.1.3 Three-Site Diversity.

3.1.4 NCDC Analysis Conclusion.

3.1.5 Cloud Coverage Statistics by Satellite Data Observation.

3.2 Atmospheric Transmittance and Sky Radiance.

3.2.1 Atmospheric Transmittance.

3.2.2 Molecular Absorption and Scattering.

3.2.3 Aerosol Absorption and Scattering.

3.2.3.1 Atmospheric Attenuation Statistics.

3.2.4 Sky Radiance.

3.2.4.1 Sky Radiance Statistics.

3.2.5 Point Sources of Background Radiation.

3.3 Atmospheric Issues on Ground Telescope Site Selection for an Optical Deep Space Network.

3.3.1 Optical Deep Space Network.

3.3.2 Data RateJBER of a Mission.

3.3.3 Telescope Site Location.

3.3.4 Network Continuity and Peaks.

3.4 Laser Propagation Through the Turbulent Atmosphere.

3.4.1 Atmospheric Turbulence.

3.4.2 Atmospheric "Seeing" Effects.

3.4.3 Optical Scintillation or Irradiance Fluctuations.

3.4.4 Atmospheric Turbulence Induced Angle of Arrival.

References.

Chapter 4: Optical Modulation and Coding (Samuel J . Dolinar. Jon Hamkins. Bruce E . Moision and Victor A . Vilnrotter).

4.1 Introduction.

4.2 Statistical Models for the Detected Optical Field.

4.2.1 Quantum Models of the Optical Field.

4.2.1.1 Quantization of the Electric Field.

4.2.1.2 The Coherent State Representation of a Single Field Mode.

4.2.1.3 Quantum Representation of Thermal Noise.

4.2.1.4 Quantum Representation of Signal Plus Thermal Noise.

4.2.2 Statistical Models for Direct Detection.

4.2.2.1 The Poisson Channel Model for Ideal Photodetectors or Ideal PMTs.

4.2.2.2 The McIntyre-Conradi Model for APD Detectors.

4.2.2.3 The Webb, McIntyre, and Conradi Approximation to the McIntyre-Conradi Model.

4.2.2.4 The WMC Plus Gaussian Approximation.

4.2.2.5 Additive White Gaussian Noise Approximation.

4.2.3 Summary of Statistical Models.

4.3 Modulation Formats.

4.3.1 On-Off Keying (OOK).

4.3.2 Pulse-Position Modulation (PPM).

4.3.3 Differential PPM (DPPM).

4.3.4 Overlapping PPM (OPPM).

4.3.5 Wavelength Shift Keying (WSK).

4.3.6 Combined PPM and WSK.

4.4 Rate Limits Imposed by Constraints on Modulation.

4.4.1 Shannon Capacity.

4.4.1.1 Characterizing Capacity: Fixed Duration Edges.

4.4.1.2 Characterizing Capacity: Variable Duration Edges.

4.4.1.3 Characterizing Capacity: Probabilistic Characterization.

4.4.1.4 Characterizing Capacity: Energy Efficiency.

4.4.2 Constraints.

4.4.2.1 Dead Time.

4.4.2.2 Runlength.

4.4.3 Modulation Codes.

4.4.3.1 M-ary PPM with Deadtime.

4.4.3.2 M-ary DPPM with Deadtime.

4.4.3.3 Synchronous Variable-Length Codes.

4.5 Performance of Uncoded Optical Modulations.

4.5.1 Direct Detection of OOK on the Poisson Channel.

4.5.2 Direct Detection of PPM.

4.5.2.1 Poisson Channel.

4.5.2.2 AWGN Channel.

4.5.3 Direct Detection of Combined PPM and WSK.

4.5.4 Performance of Modulations Using Receivers Based on Quantum Detection Theory.

4.5.4.1 Receivers Based on Quantum Detection Theory.

4.5.4.2 Performance of Representative Modulations.

4.6 Optical Channel Capacity.

4.6.1 Capacity of the PPM Channel: General Formulas.

4.6.2 Capacity of Soft-Decision PPM: Specific Channel Models.

4.6.2.1 Poisson Channel.

4.6.2.2 AWGN Channel.

4.6.3 Hard-Decision Versus Soft-Decision Capacity.

4.6.4 Losses Due to Using PPM.

4.6.5 Capacity of the Binary Channel with Quantum Detection.

4.7 Channel Codes for Optical Modulations.

4.7.1 Reed-Solomon Codes.

4.7.2 Turbo and Turbo-Like Codes for Optical Modulations.

4.7.2.1 Parallel Concatenated (Turbo) Codes.

4.7.2.2 Serially Concatenated Codes with Iterative Decoding.

4.8 Performance of Coded Optical Modulations.

4.8.1 Parameter Selection.

4.8.2 Estimating Performance.

4.8.2.1 Reed-Solomon Codes.

4.8.2.2 Iterative Codes.

4.8.3 Achievable Data Rates Versus Average Signal Power.

References.

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

5.1 Optomechanical Subsystem (Hamid Hemmati).

5.1 . 1 Introduction.

5.1.2 Optical Beam Paths.

5.1.3 Optical Design Requirements, Design Drivers, and Challenges.

5.1.4 Optical Design Drivers and Approaches.

5.1.5 Transmit-Receive-Isolation.

5.1.6 Stray-Light Control.

5.1.6.1 Operation at Small Sun Angles.

5.1.6.2 Surface Cleanliness Requirements.

5.1.7 Transmission, Alignment, and Wavefront Quality Budgets.

5.1.8 Efficient Coupling of Lasers to Obscured Telescopes.

5.1.8.1 Axicon Optical Element.

5.1.8.2 Sub-Aperture Illumination.

5.1.8.3 Prism Beam Slicer.

5.1.8.4 Beam Splitter/Combiner.

5.1.9 Structure, Materials, and Structural Analysis.

5.1.10 Use of Fiber Optics.

5.1.1 1 Star-Tracker Optics for Acquisition and Tracking.

5.1 . 12 Thermal Management.

5.1.13 Optical System Design Example.

5.1.13.1 Afocal Fore-Optics.

5.1.13.2 Receiver Channel.

5.1.13.3 Stellar Reference Channel.

5.1.13.4 Align and Transmit Channels.

5.1.13.5 Folded Layouts.

5.1.13.6 Tolerance Sensitivity Analysis.

5.1.13.7 Thermal Soak Sensitivity Analysis.

5.1.13.8 Solid Model of System.

5.2 Laser Transmitter (Hamid Hemmati).

5.2.1 Introduction.

5.2.2 Requirements and Challenges.

5.2.3 Candidate Laser Transmitter Sources.

5.2.3.1 Pulsed Laser Transmitters.

5.2.3.2 Fiber- Waveguide Amplifiers.

5.2.3.3 Bulk-Crystal Amplifiers.

5.2.3.4 Semiconductor Optical Amplifiers.

5.2.4 Lasers for Coherent Communications.

5.2.5 Laser Modulators.

5.2.6 Efficiency.

5.2.7 Laser Timing Jitter Control.

5.2.7.1 Jitter Control Options.

5.2.8 Redundancy.

5.2.9 Thermal Management.

5.3 Deep-Space Acquisition, Tracking, and Pointing (Gerardo G . Ortiz and Shinhak Lee).

5.3.1 Unique Challenges of Deep Space Optical Beam Pointing.

5.3.1.1 State-of-the-Art ATP Performance.

5.3.2 Link Overview and System Requirements.

5.3.2.1 Pointing Requirement.

5.3.2.2 Pointing-Error Budget Allocations.

5.3.3 ATP System.

5.3.3.1 Pointing Knowledge Reference Sources.

5.3.3.2 Pointing System Architecture.

5.3.3.3 Design Considerations.

5.3.4 Cooperative Beacon (Ground Laser) Tracking.

5.3.5 Noncooperative Beacon Tracking.

5.3.5.1 Earth Tracker-Visible Spectrum.

5.3.5.2 Star Tracker.

5.3.5.3 Earth Tracker-Long Wavelength Infrared Band.

5.3.6 ATP Technology Demonstrations.

5.3.6.1 Reduced Complexity ATP Architecture.

5.3.6.2 Centroiding Algorithms-Spot Model Method.

5.3.6.3 High Bandwidth, Windowing, CCD-Based Camera.

5.3.6.4 Accelerometer-Assisted Beacon Tracking.

5.4 Flight Qualification (Hamid Hemmati, William T . Roberts, and Malcolm W . Wright).

5.4.1 Introduction.

5.4.2 Approaches to Flight Qualification.

5.4.3 Flight Qualification of Electronics and Opto-Electronic Subsystem.

5.4.3.1 MIL-PRF-19500.

5.4.3.2 MIL STD 750.

5.4.3.3 MIL STD 883.

5.4.3.4 Telcordia.

5.4.3.5 NASA Electronics Parts and Packaging (NEPP).

5.4.4 Number of Test Units.

5.4.5 Space Environments.

5.4.5.1 Environmental Requirements.

5.4.5.2 Ionizing Radiation.

5.4.5.3 Vibration Environment.

5.4.5.4 Mechanical, Thermal, and Pyro Shock Environment.

5.4.5.5 Thermal Gradients Environment.

5.4.5.6 Depressurization Environment.

5.4.5.7 Electric and Magnetic Field Environment.

5.4.5.8 Outgassing.

5.4.6 Flight Qualification of Detectors.

5.4.6.1 Flight Qualification Procedures.

5.4.6.2 Detector Radiation Testing.

5.4.7 Flight Qualification of Laser Systems.

5.4.7.1 Past Laser Systems Flown in Space.

5.4.7.2 Design of Semiconductor Lasers for High Reliability Applications.

5.4.7.3 Degradation Mechanisms.

5.4.7.4 Qualification Process for Lasers.

5.4.8 Flight Qualification of Optics.

References.

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

6.1 Introduction (Keith E . Wilson).

6.1.1 Single-Station Downlink Reception and Uplink Transmission (Keith E . Wilson).

6.1.1.1 Introduction.

6.1.1.2 Deep-Space Optical Ground Receivers.

6.1.1.3 Mitigating Cloud Cover and Sky Background Effects at the Receiver.

6.1.1.4 Daytime Sky Background Effects.

6.1.1.5 Earth-Orbiting and Airborne Receivers.

6.1.1.6 Uplink Beacon and Command.

6.1.1.7 Techniques for Mitigating Atmospheric Effects.

6.1.1.8 Adaptive Optics.

6.1.1.9 Multiple-Beam Propagation.

6.1.1.10 Safe Laser Beam Propagation into Space.

6.1.1. I 1 Concept Validation Experiments Supporting Future Deep-Space Optical links.

6.1.1.12 Conclusion.

6.1.2 Optical-Array Receivers for Deep-Space Communication (Victor A . Vilnrotter, Chi-Wung Lau, and Meera Srinivasan).

6.1.2.1 Introduction.

6.1.2.2 The Optical-Array Receiver Concept.

6.1.2.3 Aperture-Plane Expansions.

6.1.2.4 Array Receiver Performance.

6.1.2.5 Conclusions.

6.2 Photodetectors.

6.2.1 Single-Element Detectors (Abhijit Biswas and William H . Farr).

6.2.1.1 Deep-Space Detector Requirements and Challenges.

6.2.1.2 Detector System Dependencies.

6.2.1.3 Detectors for Deep-Space Communications.

6.2.2 Focal-Plane Detector Arrays for Communication Through Turbulence (Victor A . Vilnrotter and Meera Srinivasan).

6.2.2.1 Introduction.

6.2.2.2 Optical Direct Detection with Focal-Plane Arrays.

6.2.2.3 Numerical Results.

6.2.2.4 Summary And Conclusions.

6.3 Receiver Electronics (Andrew A . Gray, Victor A . Vilnrotter, and Meera Srinivasan).

6.3.1 Introduction.

6.3.2 Introduction to Discrete-Time Demodulator Architectures.

6.3.3 Discrete-Time Synchronization and Post-Detection Filtering Overview.

6.3.3.1 Discrete-Time Post-Detection Filtering.

6.3.3.2 Slot and Symbol Synchronization and Decision Processing.

6.3.4 Discrete-Time Demodulator Variations.

6.3.5 Discrete-Time Demodulator with Time-Varying Post-Detection Filter.

6.3.6 Parallel Discrete-Time Demodulator Architectures.

6.3.7 Asynchronous Discrete-Time Processing.

6.3.8 Parallel Discrete-Time Demodulator Architectures.

6.3.8.1 Simple Example Architecture.

6.3.8.2 Performance with a Simple Optical Channel Model.

6.3.8.3 Evolved Parallel Architectures.

6.3.9 Primary System Models and Parameters.

6.3.10 Conclusion and Future Work.

References.

Chapter 7: Future Prospects and Applications (Hamid Hemmati and Abhijit Biswas).

7.1 Current and Upcoming Projects in the United States, Europe. and Japan.

7.1.1 LUCE (Laser Utilizing Communications Experiment).

7.1.2 Mars Laser-Communication Demonstrator (MLCD).

7.2 Airborne and Spaceborne Receivers.

7.2.1 Advantages of Airborne and Spaceborne Receivers.

7.2.2 Disadvantages of Airborne and Spaceborne Receivers.

7.2.3 Airborne Terminals.

7.2.3.1 Balloons.

7.2.3.2 Airships.

7.2.3.3 Airplanes.

7.2.4 Spaceborne Receiver Terminals.

7.2.5 Alternative Receiver Sites.

7.3 Light Science.

7.3.1 Light-Propagation Experiments.

7.3.2 Occultation Experiments to Probe Planetary Atmospheres, Rings. Ionospheres. Magnetic Fields. and the Interplanetary Medium.

7.3.2.1 Atmospheric Occultations.

7.3.2.2 Ring-Investigation Experiments.

7.3.3 Enhanced Knowledge of Solar-System-Object Masses and Gravitational Fields. Sizes. Shapes. and Surface Features.

7.3.3.1 Improved Knowledge of Solar-System Body Properties.

7.3.3.2 Optical Reference-Frame Ties..

7.3.4 Tests of the Fundamental Theories: General Relativity, Gravitational Waves, Unified Field Theories, Astrophysics, and Cosmology.

7.3.4.1 Tests of General Relativity and Unified Field Theories, Astrophysics, and Cosmology.

7.3.4.2 Effects of Charged Particles on Electromagnetic Wave Propagation, Including Test of I/f Hypothesis.

7.3.5 Enhanced Solar-System Ephemerides.

7.3.5.1 Science Benefits of Remote Optical Tracking: Ephemeris Improvement.

7.3.6 Applications of Coherent Laser Communications Technology.

7.4 Conclusions.

References.