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.