ABSTRACT
Overview......................................... 509 7.4.1.2. Heterodyne Detection CNR
and Related Concepts..................... 510 7.4.1.3. Target-Plane Formalism
— General CNR and Antenna Efficiency ........................................ 523
7.4.1.4. Antenna Efficiency Calculations ... 532 7.4.1.5. Alignment Errors ........................... 545 7.4.1.6. Refractive Turbulence Effects........ 546 7.4.1.7. Pulsed Coherent Lidar Velocity
Estimation Accuracy ...................... 550 7.4.1.8. Example System Performance
Estimation ...................................... 564 7.4.1.9. Coherent Detection Doppler
Wind Lidar Theory Summary........ 567 7.4.2. Direct Detection Doppler Wind
Lidar Theory .................................................. 570 7.4.2.1. Direct Detection Concept
Overview......................................... 572 7.4.2.2. Direct Detection SNR..................... 574 7.4.2.3. The Fabry-Perot Etalon ................ 577 7.4.2.4. Velocity Measurement Accuracy.... 579 7.4.2.5. Detector Truncation or
Overlap and Alignment Efficiency 596 7.4.2.6. Refractive Turbulence Effects........ 597 7.4.2.7. Direct Detection Wind Lidar
Theory Summary............................ 598 7.4.3. Comparison of Coherent and Direct
Detection Receivers ....................................... 600 7.4.3.1. Coherent Detection Receiver ......... 603 7.4.3.2. Direct Detection Receiver .............. 605 7.4.3.3. Example Transmitter
Requirement Comparison .............. 608 7.5. System Architectures and Example Systems........... 610
7.5.1. Coherent Detection Lidar Systems............... 610
7.5.1.1. Coherent Lidar System Architecture.................................... 610
7.5.1.2. Representative CO2 Coherent Lidar Systems................................. 617
7.5.1.3. Representative Solid-State Coherent Lidar Systems ................ 625
7.5.2. Direct Detection Lidar................................... 631 7.5.2.1. Direct Detection Lidar
Architecture.................................... 632 7.5.2.2. Direct Detection Lidar
Receiver Details ............................. 637 7.5.2.3. Detectors and Detection
Efficiency for Direct Detection Doppler Lidar ................................. 646
7.5.2.4. A Representative Double-Edge Wind Lidar System ........................ 656
7.5.2.5. A Representative Fringe-Imaging Doppler Wind Lidar System .......... 659
7.6. Wind Measurement Applications .............................. 661 7.6.1. Wind Shear, Gust Front, and Turbulence
Measurements ............................................... 662 7.6.1.1. NOAA’s 10.6mm Coherent Lidar ... 662 7.6.1.2. E´cole Polytechnique 10.6mm
Transportable Wind Lidar ............. 664 7.6.1.3. NOAA’s 2.0mm Coherent
High-Resolution Doppler Lidar ..... 664 7.6.1.4. Coherent Technologies’
WindTracer ..................................... 667 7.6.2. Ground Wind Profiling .................................. 668
7.6.2.1. Coherent Technologies’ Flashlamp-Pumped 2.0mm Coherent Lidar ............................... 670
7.6.2.2. ALOMAR DWTS 532 nm ‘‘Fringe-Imaging’’ Direct Detection Lidar ............................................... 671
7.6.2.3. Goddard’s ‘‘Double-Edge’’ Direct Detection Lidar ................... 671
7.6.2.4. Michigan Aerospace’s GroundWinds 532 nm ‘‘FringeImaging’’ Direct Detection Lidar ... 673
7.6.3. Airborne Wind Profiling ................................ 673 7.6.3.1. DLR’s 10.6mm CW WIND
Coherent Lidar ............................... 673 7.6.3.2. Coherent Technologies’ 2mm
Coherent Lidar ............................... 675 7.6.4. Airborne Clear Air Turbulence Detection .... 678
7.6.4.1. QinetiQ’s (formely DRA) LATAS 10.6mm CW Coherent Lidar ............................................... 678
7.6.4.2. Coherent Technologies’ ACLAIM 2.012mm Coherent Lidar ............... 680
7.6.5. Aircraft Wake Vortex Detection and Tracking ......................................................... 680 7.6.5.1. QinetiQ’s (formerly DRA)
10.6mm CW Coherent Lidar.......... 682 7.6.5.2. Coherent Technologies’ 2.0mm
Coherent Lidar ............................... 684 7.6.5.3. DLR 2.0mm Lidar .......................... 684
7.6.6. Aerosol Detection and Tracking.................... 688 7.7. Summary and Future Prospects ............................... 690 Acknowledgments................................................................ 693 References............................................................................ 700
7.1. INTRODUCTION
Lidar systems for wind velocity measurements have demonstrated their efficacy in many different applications where spatially resolved measurements of atmospheric wind velocity from a remote location are needed. Examples include: measurement of aircraft true airspeed, detection and tracking of clear air turbulence, wind shear, gust fronts, aircraft wake vortices, and measurement of atmospheric wind profiles from the ground up to 50 km altitude.