Grund

Slide1: 

Optical Autocovariance Wind Lidar and Performance from LEO Chris Grund, Michelle Stephens, Carl Weimer Ball Aerospace & Technologies Corp cgrund@ball.com, 303-939-7217 Presented to: Coherent Laser Radar Conference Snowmass, Colorado 7/10/2007

Optical Autocovariance Theory: 

Optical Autocovariance Theory V = l *Df * c / (4 * (d2-d1)) Optical Autocovariance Wind Lidar: OAWL Pronounced: ALL Ball Aerospace patent pending Pulse Laser d 2 d 1 Detector 1 Detector 2 Detector 3 Data System CH 1 CH 3 CH 2 From Atmosphere Stepped mirror Receiver Telescope Doppler Shift Due to wind Return spectrum from a Monochromatic source Measured as a fraction Prefilter Note: Scale of molecuar and cycle of autocovariance function are arbitraqry for illustration

OAWL Advantages: 

OAWL Advantages Laser simplifications: Injection seeding not necessary Shot to shot mode hopping no problem Passive Q-switch feasible – no HV No hardware correction for spacecraft V Receiver: One system for whole atmosphere* Aerosol and molecular in one* No calibration dependence on targets Mixed aerosols, clouds, molecules OK No clean/dirty air calibration bias No absolute frequency lock to laser No absolute temperature controllers No spectral drift calibration requirement No reference laser needed * IF the SNR is high enough or the molecular region velocity precision requirement is modest OAWL does it ALL

OAWL Combines/Augments the Best Traits of Both Coherent and Incoherent Lidar Methods: 

OAWL Combines/Augments the Best Traits of Both Coherent and Incoherent Lidar Methods

Slide5: 

Brassboard Development

Demonstration System Architecture: 

Demonstration System Architecture

The Brassboard System: 

The Brassboard System 3-Beam Interferometer Assembly 3 Detector Assembly Laser Transmitter Assembly Laser Controller Alignment Camera and Monitor PC Data System COTS Newtonian Receiver Telescope 0-Range, 0-Velocity Sampling Assembly Receiver Field Stop Channel Splitting Mirror

Slide8: 

Proof of Concept Testing

Proof of Concept Test Range: 

Proof of Concept Test Range

First light – Experimental Intensity SNR: 

First light – Experimental Intensity SNR 0-range 0-velocity sample

First OAWL POC Wind Retrievals(December 2006) : 

First OAWL POC Wind Retrievals (December 2006) Red: Anemometer-OA cross correlation White: anemometer autocorrelation Blue: cross correlation for pure Gaussian noise distributions ~1 m/s random error with ~0.6 m/s bias demonstrated with 0.3 s averaging and 3m range resolution. Excellent fluctuation correlations.

First Wind Retrievals- continued: 

First Wind Retrievals- continued Statistically very different wind set (see anemometer autocorrelation function) again excellent fluctuation correlations OAWL brassboard: ~1.2 m/s random error, with 0.15 m/s bias (3m res, 0.3 s avg)

Slide13: 

Preliminary OAWL Space Lidar Winds Performance Modeling

Performance Requirements Addressed (so far)for OAWL Space Wind Lidar Operation: 

Performance Requirements Addressed (so far) for OAWL Space Wind Lidar Operation

Comprehensive LEO Performance Model Implemented for Realistic Components: 

Comprehensive LEO Performance Model Implemented for Realistic Components LEO Model Parameters: (unless otherwise noted) Wavelength 355 nm Pulse Energy 550 mJ Pulse rate 50 Hz Receiver diameter 1m LOS angle with vertical 450 Vector crossing angle 900 Horizontal resolution 70 km (10 s avg) System transmission 0.35 Alignment error 5 mR Background bandwidth 35 pm Orbit altitude 400 km Vertical resolution 0-2 km, 500m 2-12 km, 1km 12-20 km, 2 km Phenomenology CALIPSO model Architecture 3-det. OAWL

Small OPD  Molecular and Aerosol contribute, but cannot meet needs with current laser technology: 

Small OPD  Molecular and Aerosol contribute, but cannot meet needs with current laser technology

Small OPD: Molecular and Aerosol can meet needs over most of the atmosphere with single system, but requires: 10J/pulse (500W), or 4.5m dia. telescope, or better detector, or combo: 

Small OPD: Molecular and Aerosol can meet needs over most of the atmosphere with single system, but requires: 10J/pulse (500W), or 4.5m dia. telescope, or better detector, or combo

Large OPD  Aerosol Onlyperformance rivals coherent detection hybrid subsystem, but molecular unresolved: 

Large OPD  Aerosol Only performance rivals coherent detection hybrid subsystem, but molecular unresolved

Compromise Single-laser Solution: Couple OAWL and Etalon receivers: 

Compromise Single-laser Solution: Couple OAWL and Etalon receivers OAWL uses most of the aerosol component, rejects molecular. OAWL HSRL retrieval determines residual aerosol/molecular mixing ratio Etalon backend processes molecular backscatter winds, corrected by HSRL Result: single-laser transmitter, single wavelength system single simple, low power and mass signal processor full atmospheric profile using aerosol and molecular backscatter signals Ball Aerospace patent applied for Telescope UV Laser Combined Signal Processing HSRL Aer/mol mixing ratio Aerosol Winds Lower atmosphere profile OAWL Aerosol Receiver Etalon Molecular Receiver Molecular WindsUpper atmosphere profile 1011101100 Full Atmospheric Profile Data

Slide20: 

Wrap-up

Technical Conclusions 1: 

Technical Conclusions 1 Optical Autocovariance Wind Lidar (OAWL) has advantages for space operations Potentially, one laser system DOES IT ALL, from and boundary layer thru the free troposphere Simpler laser Injection seeding not needed, passive Q-switching feasible (no HV) single mode per pulse needed, but pulse to pulse frequency hopping OK No velocity calibration dependence on aerosol/molecular backscatter mixing ratio No reference laser required; pulse coherence length need only exceed the interferometer OPD (best if > range resolution bin length) Easy compatibility with secondary aerosol or chemical species missions To achieve desired molecular signal precision with an all OAWL system requires more laser power than currently practical

Technical Conclusions 2: 

Technical Conclusions 2 First OAWL brassboard lidar completed, aligned, calibrated. Preliminary wind retrieval/calibration algorithms developed/working Successful, range-resolved atmospheric proof of concept tests completed. Combining an etalon back end with an OAWL front end allows full atmospheric profiling with desired precision, using a single laser and a single, simple, low power signal processor. Next week in Snowmass: presenting concept, applications, and performance of imaging, photon-counting OAWL (IPC/OAWL) wind lidar from GEO at the space wind lidar working group

What’s in the works?: 

What’s in the works? Technical Developments: Simultaneous wind and HSRL Proof of Concept tests (this year, in progress) Model performance of an integrated OAWL and Etalon receiver wind system Improved 0-velocity, 0-range sampling apparatus in progress for brassboard Cross validation field test alongside existing wind lidar system. Perhaps the NOAA/ETL HRDL system. Evaluating laser scaling issues and options for space. Mission concepts: Developing 100X100 pixel imaging, photon-counting OAWL for winds from GEO (talk next week at the Space-based Wind Lidar Working Group Meeting: preliminary concept and feasibility for winds from GEO) Extensive integrated performance model development based on the validated CALIPSO model, but including detailed OAWL components, wind mission scenarios, and spacecraft interactions. Design (in progress this year) and construction (next year?$$$) of a ruggedized, field-widened receiver suitable for vibe and environmental environmental testing to achieve TRL 6, and a potential aircraft validation mission.

Ball OA development team : 

Ball OA development team Mick Cermak – lab and fabrication support, experiment support and logistics Dina Demara – data system software Doug Frazier – brassboard mechanical design Dennis Gallagher – final brassboard optical design and modeling (left Ball in ’06) Chris Grund – PI, system and experiment design, signal processing, calibration, validation James Lasnick– purchasing and experiment logistics support Bob Pierce – ongoing optical engineering, experiment support Ron Schwiesow – proposed original concept (retired from Ball 10/05) Steve Stone – Procurement assistance, electronics support Michelle Stephens – Spaceborne performance modeling Carl Weimer – Space systems and Space performance modeling (CALIPSO experience) Internal R&D funding support through Ray Demara gratefully acknowledged