An Alternative Direct Detection Approach to Doppler Winds that is Independent of Aerosol Mixing Ratio and Transmitter Frequency Jitter Ball Aerospace & Technologies Corp. Presented by: Chris Grund Presented to: Space Winds Lidar Working Group Miami, Florida 2/8/2007

OAWL Theory

3 Optical Autocovariance Theory V = *  * c / (4 * (d 2 -d 1 )) Optical Autocovariance Wind Lidar: OAWL Pronounced: ALL Pulse Laser d 2 d 1 Detector Data System CH 1 CH 3 CH 2 From Atmosphere Stepped mirror Beam Splitter Distance d 2 -d 1 Arbitrary Intensity CH 1 CH 3 CH 2 CH 1 CH 3 Doppler shifted Atmospheric Return at t>0 Laser at t=0  M Wings A+M Aerosol +center of molecular Receiver Telescope Doppler Shift Due to wind A M A+M+BG BG Return spectrum from a Monochromatic source Measured as a fraction Prefilter Note: Scale of molecuar and cycle of autocovariance function are arbitraqry for illustration

4 OAWL Advantages Laser simplifications: Injection seeding not necessary Shot to shot mode hopping no problem Passive Q-switch feasible – no HV No 800 km coherence length LO needed 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 OAWL does it ALL

5 OAWL Combines/Augments the Best Traits of Both Coherent and Incoherent Lidar Methods Yes Yes (UV laser) Yes Maybe/Yes Maybe Yes (UV laser) Yes No Some No (IR laser) N/A Synergies/Compatibilities HSRL (calibrated aerosols/clouds) DIAL (chemical species) Raman (Chemical species, T, P) Photon counting potential (next time!) Yes No Yes No Yes No Phenomenology Measure Aerosol Measure Molecular Sensitive to Aer/Mol mixing ratio Full precision 0-20 km profile None 3(6) Yes No None Many Yes Maybe >800 km 1 No Yes Receiver Reference laser coherence length Detector Elements Single multi-speckle averaging/shot Orbital velocity correction in hardware Single/hopping OK No Single/stable Yes Single/stable Yes Transmitter Laser Mode Absolute frequency lock Direct Detection OAWL Direct Detection Etalons (edge/image) Coherent Detection Challenges

Brassboard Development

7 Demonstration System Architecture

8 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

9 Development Team nMick Cermak – Lab and fabrication support, experiment support and logistics nDina Demara – Data system software nDoug Frazier – brassboard mechanical design nDennis Gallagher – final brassboard optical design and modeling (left Ball in ’06) nChris Grund – PI, system and experiment design, signal processing, calibration, validation nBob Pierce – ongoing optical engineering, experiment support nRon Schwiesow – proposed original concept (retired from Ball 10/05) nMichelle Stephens – Spaceborne performance modeling nSteve Stone – Procurement assistance, electronics support nInternal R&D funding support through Ray Demara gratefully acknowledged

Proof of Concept Testing

11 Proof of Concept Test Range OAWL System in Lab Turning Mirror Sonic Anemometer Focal volume Lidar beam path Terminal Beam Block FA Cleanroom Building Rooftop at Ball Aerospace in Boulder, CO

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

13 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.

14 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)

Preliminary OAWL Space Lidar Winds Performance Modeling

16 Performance Requirements Addressed (so far) for OAWL Space Wind Lidar Operation From: Kavaya and Gentry: Status of Laser/Lidar Working Group Requirements DemoThresholdObjective Vertical depth of regard (DOR) km Vertical resolution: Tropopause to top of DOR Top of BL to tropopause (~12 km) Surface to top of BL (~2 km) Not Req. 2 1 Not Req km Horizontal resolution km Velocity error Above BL In BL m/s Minimum wind measurement success rate50 %

17 Preliminary OAWL System Performance for Spaceborne Operations Conditions: Wavelength 355 nm Pulse Energy 550 mJ Pulse rate 50 Hz Receiver diameter 1m LOS anglewith vertical 45 0 Vector crossing angle 90 0 Horizontal resolution 350 km OPD 1 m System transmission 0.35 Alignment error 5  R Background bandwidth 35 pm Orbit altitude 400 km Vertical resolution 1 km Phenomenology CALIPSO model Daytime Nighttime Horizontal Wind Velocity Error (m/s) Altitude (km) Objective Demo & Threshold

Wrap-up

19 Conclusions nOptical Autocovariance Wind Lidar (OAWL) has advantages for space operations  Potentially, one system DOES IT ALL, from and boundary layer to free trop  Simpler laser Injection seeding not needed, passive Q-sw feasible single mode per pulse, but pulse to pulse frequency hopping OK  No velocity calibration dependence on aerosol/molecular backscatter mixing ratio  Laser coherence length only needs to exceed the interferometer path length  Compatibility with secondary aerosol or chemical species missions nFirst OAWL brassboard lidar completed, aligned, and calibrated in 2006 nDevelopments ongoing, intercomparison campaign sought (NOAA, NASA) nSuccessful, range-resolved atmospheric proof of concept tests completed nPreliminary wind retrieval/calibration algorithms developed/working nMeasurements validate brassboard system performance model and hardware

20 What’s in the works? nImproved 0-velocity, 0-range sampling apparatus in progress for brassboard nRuggedizing and field enclosure for brassboard cross-validation n Field test alongside existing wind lidar system. Perhaps the NOAA/ETL HRDL system. nDesign (in progress this year) and construction (next year?$$$) of a ruggedized, field-widened receiver suitable for aircraft testing, environmental testing to achieve TRL 6 nEvaluating laser scaling issues and options. nExtensive performance model development based on the validated CALIPSO model, but including detailed OAWL components, wind mission scenarios, and spacecraft interactions.