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Jan 2006 TWiLiTE (Tropospheric Wind Lidar Technology Experiment) IIP Update B. Gentry 1, G. Schwemmer 6, M. McGill 1, M. Hardesty 2, A. Brewer 2, T. Wilkerson.

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Presentation on theme: "Jan 2006 TWiLiTE (Tropospheric Wind Lidar Technology Experiment) IIP Update B. Gentry 1, G. Schwemmer 6, M. McGill 1, M. Hardesty 2, A. Brewer 2, T. Wilkerson."— Presentation transcript:


2 Jan 2006 TWiLiTE (Tropospheric Wind Lidar Technology Experiment) IIP Update B. Gentry 1, G. Schwemmer 6, M. McGill 1, M. Hardesty 2, A. Brewer 2, T. Wilkerson 5, R. Atlas 2, M.Sirota 3, S. Lindemann 4 1 NASA GSFC; 2 NOAA; 3 Sigma Space Corp.; 4 Michigan Aerospace Corp.; 5 Space Dynamics Lab; 6 SESI Working Group on Space Based Lidar Winds January 17 - 19, 2006 Key West, FL

3 Jan 2006 Outline TWiLiTE Overview Requirements and Error Budget WB57 Aircraft Instrument Development Status Summary

4 Jan 2006 ESTO’s Instrument Incubator Program

5 Jan 2006 Entrance TRL Exit TRL High spectral resolution all solid state laser transmitter 45-6 High spectral resolution optical filters 45-6 Efficient 355 nm photon counting molecular Doppler receiver technologies 45-6 Novel UV Holographic Optical Element telescopes and scanning optics 35-6 TWiLiTE Direct Detection Wind Lidar Key Technologies

6 Jan 2006 Project Management PI – Gentry PM, Sys Eng – Sirota, Chauvet, Mathur Science Requirements and Applications Atlas,Gentry, Hardesty, McGill, Brewer… HOE Telescope/ Scanner POC:Schwemmer Supplier: SDL Laser POC: Li Supplier: TBD Doppler Receiver GSFC POC: Gentry Mech: Cooperider, Optics: Bos I&T : Scott Thermal: Greer System Integration/ ‘Glue’ Sigma POC: Mathur C&DH Sigma POC: Machan FP Etalon MAC Lindemann 10 Ch MCS+ Sigma Machan 355 nm HOE’s Wasach Photonics Ralison Aircraft accomodations WB57- McGill, Chauvet GIV – Brewer, Hardesty TWiLiTE Project Organization

7 Jan 2006 Proposed TWiLiTE Measurement Requirements ParameterWB57 Velocity accuracy (HLOS projected) (m/s) 2.0 Range of regard (km)0-18 Vertical resolution (km)0.25 Horizontal resolution (km)25 Groundspeed (m/s)200 Nadir angle (deg)45 Scan patternUp to 16 pt step-stare Horizontal integration per LOS (seconds)//ground track (km) 10//2 * Assumes scanner average angular velocity of 12 deg/sec

8 Jan 2006 16 point step stare scan pattern Top view Scanning parameters: Constant dwell of 10s/LOS Scanner angular velocity of 12 deg/sec 192 sec to complete one cycle Radial HLOS wind speed measured in a single range bin for 3 cycles of the 16 point step stare scan pattern. Assumes constant velocity (maximum = 40 m/s)

9 Jan 2006

10 Top level error budget (4 W laser) Total LOS velocity accuracy 2.0 m/s Photon shot noise 1.75 m/s Doppler receiver spectral calib 0.35 m/s Laser spectral 0.25 m/s Margin 0.8 m/s Total error =2.0 m/s = 1.75 2 + 0.35 2 + 0.25 2 + 0.25 2 + 0.8 2 AC motion comp. 0.25 m/s

11 Jan 2006 SpecificationWB57 Max. Altitude18 km Duration6.5 hours Cruise Speed210 m/s @ 18 km Payload mass1814 kg (incl. pallets) Payload Electrical Power 4 X 25 A, 3 phase, 400 Hz Payload mountingModular pallet Nadir view Window diameter; viewing orientation 45 cm; nadir view NASA Johnson WB57 Aircraft

12 Jan 2006 3’ pallet6’ pallet Looking forward from inside the payload bay WB57 Instrument Mounting Pallet integration

13 Jan 2006 Engine On Take Off Steep Ascent Slow Ascent Cruising

14 Jan 2006 Three axis accelerometer data from WB57 at operating altitude - Flight 2, 12/18/2005

15 Jan 2006 IRAD Receiver Design Summary Volume reduced by 90% versus current GLOW receiver Optical path lengths minimized to improve mechanical, thermal stability End-to-end throughput increased by 60% Signal dynamic range increased by 2 orders of magnitude

16 Jan 2006 Michigan Aerospace TWiLiTE Etalon Design Features Discretely ‘stepped’ plate creates three spectrally distinct resonant cavities –Plate steps of 20.2 nm and 70.7 nm Plate reflectivity of 73% @ 355 nm Surface flatness of /150 @ 633 nm Intragap capacitive feedback provides direct knowledge of gap dynamics –Capacitors fabricated from Expansion Class 0 Zerodur for minimal thermal contributions Stacked ring piezoelectric actuators provide > 3 microns dynamic range –Closed loop operation provides sub-nanometer resolution of motion Invar construction provides thermal stability and mechanical robustness Vibration tests to confirm operation in aircraft environment scheduled in early February

17 Jan 2006 Double Edge Etalon Channels

18 Jan 2006 3 point rigid mount at input creates stress free reference plane and stable angle of incidence ‘Soft’ diaphragm mounting on actuated ring allows for tuning with a minimal amount of stress imparted to the ring/plate assembly while holding the etalon rigidly centered on optical axis. Invar housing machined from solid piece ensures material homogeneity, rigidity and minimizes thermal deformation Michigan Aerospace TWiLiTE Etalon

19 Jan 2006 TWiLiTE Holographic Telescope FUNCTIONS Collect and focus laser backscatter Scan laser and FOV Provide pointing knowledge to CDH FEATURES Primary Optic: Rotating 40- cm HOE, 1-m f.l. 45-deg off-nadir FOV Compact, folded optical path Coaxial laser transmission Active laser bore-sight

20 Jan 2006 TWiLiTE Telescope Team Geary Schwemmer (SESI) – lead POC Space Dynamics Lab Team Thomas Wilkerson – SDL lead Brent Bos (GSFC) –Optical Engineering Jason Swasey – Lead Engineer Caner Cooperrider(GSFC) Mechanical Eng. Jed Hancock – Optical Engineering Brian Thompson – Mechanical Engineering Adam Shelley – Mechanical Engineering Marc Hammond – consultant Richard Rallison (Wasatch Photonics) – HOE consultant

21 Jan 2006 TWiLiTE System Concept - As of Dec. 2005 TWiLiTE System Integrated on 3 foot pallet Enclosure proposed to mitigate environmental extremes

22 Jan 2006 TWiLiTE Milestones MilestoneMonths after task start* System Definition Review5 mos Fabry-Perot etalon optical head delivered6 mos Preliminary Design Review8 mos Doppler Receiver delivered8 mos Digital etalon controller delivered14 mos Critical Design Review14 mos Laser and electronics delivered22 mos HOE Telescope/scanner delivered24 mos Data acquisiton and control electronics delivered24 mos Phase 2 Annual Review24 mos Instrument pallet and support equipment delivered26 mos Flight instrument integration and ground testing28 mos Flight Readiness Review28 mos Initial TWiLiTE flight test34 mos Project complete / Final Report36 mos *Project Start August, 2005

23 Jan 2006 TWiLiTE Summary The TWiLiTE IIP is a three year R&D project to design and build an airborne scanning direct detection Doppler lidar The primary objective is to advance the TRL of key component technologies as a stepping stone to space. At the end of the project we will have a fully autonomous, integrated Doppler lidar designed to measure full profiles of winds from a high altitude aircraft. We are actively seeking input on the instrument design requirements from the community. This includes input on potential applications, target field experiments, etc for the TWiLiTE instrument.

24 Jan 2006 Backups

25 Jan 2006 Doppler Lidar Measurement Concept DOPPLER RECEIVER - Multiple flavors dependent on scattering target - Aerosol return gives high accuracy and high spatial and temporal resolution when aerosols present Molecular return gives lower accuracy and resolution but signal is always there Molecular (  ) Aerosol (  ) Backscattered Spectrum Frequency  DO P

26 Jan 2006 High altitude airborne direct detection scanning Doppler lidar Serves as a system level demonstration and as a technology testbed Leverages technology investment from multiple SBIRs, ESTO, IPO and internal funding Consistent with the roadmap and planning activities for direct detection and ‘hybrid’ Doppler lidar implementations

27 Jan 2006


29 Photon shot noise v err 1.75 m/s Optical throughput (Mean value and vs polarization,T,P and g rms ) Spatial and temporal Averaging Boresight and alignment Transmit optics HOE receiver Diffraction eff Transmission Doppler receiver End to end trans per edge channel PMT QE Etalon transmission Fiber optic coupling attenuation bulkhead feedthru Laser Far field diverg Pointing jitter FOV fiber diam HOE fl HOE Spot size Rotational/optical axis alignment Bearing TIR HOE/laser mechanical mounting Active alignment mechanism HOE collecting area Energy (mean, jitter and drift) PRF Seeding efficiency Spectral purity

30 Jan 2006 Doppler receiver v err 0.35 m/s Etalon spectral (Mean value and vs polarization,T,P and g rms ) Atmospheric effects (vs altitude) Instrument function (total response measured in calibration) Etalon finesse Plate flatness Angluar broadening (pinhole finesse) Gap (FSR) Plate parallelism Edge channel separation PMT Temperature Density (Rayleigh Brillouin lineshape) Backscatter ratio Clouds Optical constants QE Response linearity Dynamic range Intensity split ratio of edge channels

31 Jan 2006 Laser spectral 0.25 m/s Laser linewidth at 355 nm Laser frequency stabilty (jitter and drift) over measurement interval Laser reference measurement Etalon locking channel finesse and transmission analog PMT response analog sampling and detection (‘boxcar’) number of shots averaged per ref meas

32 Jan 2006 A/C motion compensation 0.25 m/s Knowledge of Aircraft ground speed and direction Aircraft orientation (Pitch, roll, yaw) measured in instrument reference frame by POS Transceiver pointing angle measured in instrument reference frame Coarse Doppler compensation offset (receiver or laser) if used

33 Jan 2006 TWiLiTE Schedule August 2005 start Initial Test Flights in 2008

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