Airborne Testing of the TWiLiTE Direct Detection Doppler Lidar

Transcription

1 Airborne Testing of the TWiLiTE Direct Detection Doppler Lidar Bruce Gentry 1, Huailin Chen 2, Jaime Cervantes 2, Roman Machan 3, Daniel Reed 3, Ryan Cargo 3, Catherine Marx 4 and Patrick Jordan 4 16 th Coherent Laser Radar Conference June 20-24, 2011 Long Beach, CA Acknowledgements: TWiLiTE was developed with support from the NASA ESTO IIP program. Additional support was provided by the Airborne Instrument Technology Transition program, Dr. Ramesh Kakar, Program Manager

2 2007 NRC Decadal Survey Recommendations for 3DWinds 3D Tropospheric Winds mission called transformational and ranked #1 by Weather panel. with concurrence by Water panel. Overall prioritized in 3 rd tier of 15 NASA recommended missions. The Panel strongly recommends an aggressive program early on to address the high-risk components of the instrument package, and then design, build, aircraft-test, and ultimately conduct space-based flights of a prototype Hybrid Doppler Wind Lidar (HDWL). The Panel recommends a phased development of the HDWL mission with the following approach: Stage 1: Design, develop and demonstrate a prototype HDWL system capable of global wind measurements. Stage II: Launch of a HDWL system that would meet fully-operational threshold tropospheric wind measurement requirements

3 Tropospheric Wind Lidar Technology Experiment (TWiLiTE) IIP The TWiLiTE instrument is a compact, rugged direct detection scanning Doppler lidar designed to measure wind profiles in clear air from 20 km to the surface. TWiLiTE operates autonomously on NASA research aircraft (ER-2, DC-8, WB-57, Global Hawk). Engineering flight tests on the NASA ER-2 in 2009 and 2011 demonstrated autonomous operation of all major systems. TWiLiTE will be reconfigured to fly on the NASA Global Hawk as part of the Hurricane and Severe Storm Sentinel Earth Venture Class Mission. TWiLiTE system configured for ER-2 QBay TWiLiTE LOS wind profiles from Feb 14, 2011 ER2 test flight. A 10 minute segment taken over Fresno, CA is shown. Inset is a single TWiLiTE profile compared with wind profile data from the 00Z, Feb 15 NWS radiosonde launched from Oakland, CA.

4 Double Edge Measurement Principle Molecular Channel at 355 nm DOP Aerosol Edge Filter 1 Edge Filter 2 Molecular Frequency

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

6 TWiLiTE Instrument Parameters Wavelength nm Telescope/Scanner Area 0.08 m 2 Laser Linewidth (FWHH) 150 MHz Laser Energy/Pulse (8 W) pps Etalon FSR GHz Etalon FWHH 2.84 GHz Edge Channel Separation 6.64 GHz Locking Channel Separation 4.74 GHz Interference filter BW (FWHH) 120 pm PMT Quantum Efficiency 25% 6

7 TWiLiTE Laser FUNCTIONS: Generates single frequency uv laser pulses. Injection seeded Nd:YAG ring oscillator with single amplifier Frequency tripled to λ=355 nm Pulse energy = nm Pulse Rep Frequency = 200 pps Optical canister is 28x33x14 cm 3 FEATURES: High 3 rd harmonic conversion efficiency (~50%). Excellent beam quality (M nm) Compact, ruggedized laser optical and electronics modules. Fully autonomous laser control software STATUS : Assembled laser optical (gold) and electronics (black) modules Subsystem tested in lab Integrated in TWiLiTE system System level demo on ground Flight operation in ER-2 Remaining issues: None FIBERTEK, INC.

8 TWiLiTE Doppler Receiver FUNCTIONS: Fiber optic delivers atmospheric backscattered signals from the telescope. Doppler shift measured using high resolution tunable Fabry-Perot etalon. Photomultipler tubes operating in photon counting mode measure atmospheric signals. Vibration isolate, temperature controlled pressure vessel minimizes environmental effects. Fiber pickoff of small fraction of transmitted laser signal used to measure outgoing laser frequency FEATURES: Performance improvements* Volume reduced by 90% Optical path lengths minimized to improve mechanical, thermal stability Throughput increased by 60% Signal dynamic range increased by 2 orders of magnitude * versus 1 st gen ground-based DDDL lidar receiver Doppler receiver modules (left) are enclosed in an environmentally controlled vessel (right) STATUS : Subsystem tested in lab Integrated in TWiLiTE system System level demo on ground Flight operation in ER-2 Remaining issues: None

9 TWiLiTE Tunable Fabry-Perot Etalon and Digital Controller FUNCTIONS: Designed to measured Doppler frequency shift using molecular double edge approach. Step coatings in three sub-apertures offset the resonance peak of the etalon to produce the two edge channel filters used for the wind measurement and a locking channel which is used to measure the outgoing laser frequency The etalon plates are piezoelectrically tunable and have capacitive sensors to maintain plate paralellism FEATURES: 50 mm clear aperture plates Three 20 cm diameter subapertures defined by step coatings 9 mm gap 16.6 GHz FSR Plate reflectivity = 0.75 Fabry Perot Etalon Triple aperture step etalon (left) has 3 sub-apertures offset in frequency as shown in the etalon calibration scan (right) from the Oct 1, 2009 ER-2 flight. STATUS : Edge2 Subsystem tested in lab Integrated in TWiLiTE system System level demo on ground Flight operation in ER-2 Remaining issues: None Lock Edge1

10 TWiLiTE Holographic Telescope FUNCTIONS: Transmits laser pulses co-aligned with telescope optical axis Collect laser backscattered light and focus into multimode fiber. Rotating HOE to scan laser and FOV in azimuth Provide precise pointing knowledge to C&DH system FEATURES: Primary Optic: Rotating 40-cm diameter HOE, 1-m focal length 45-deg off-nadir FOV Compact, folded optical path Coaxial laser transmission Active laser bore-sight and alignment system Holographic Optical Element (HOE) telescope seen from below. The HOE is mounted in a rotating ring bearing in order to scan. The HOE focuses the collected laser light and diffracts the FOV off-nadir by 45 deg STATUS : Subsystem tested in lab Integrated in TWiLiTE system System level demo on ground Flight demo in ER-2 () Remaining issues: 1)Azimuth step stare scanning 2)Auto-alignment boresight maintenance (software) 3)Transmission down by 2-3x (thermal effects: HOE efficiency; defocus )

11 25 TWiLiTE Compatible NASA Airborne Science Platforms 6-8 hrs duration Unattended operation 36 hrs duration Unmanned vehicle Global Hawk 20 WB57 ER2 Max Altitude (km) TWiLiTE configured for DC8 Nadir Port 7 () DC8 TWiLiTE configured for WB57 3 Pallet (ESTO IIP04) TWiLiTE configured for ER-2 Q-Bay (ESTO IIP04) TWiLiTE configured for Global Hawk Zone 25 (HS3)

12 TWiLiTE Modular Assembly- IIP ER-2 Configuration 1 2A 2B 2C Doppler receiver (Notes: insulated pressurized box; vibration isolated from frame; on liquid cooling loop; weighs about 100 lbs) 2. A) Data system electronic box; B) power distribution box; C) laser electronics module (LEM) 3. Laser Optical Module (LOM) (Notes: insulated pressurized box; on liquid cooling loop; 3 pt titanium flex mounts to opt bench) 4. Optical Bench 5. HOE telescope 6. ER-2 Qbay instrument pallet (mechanical interface defined by aircraft.) structure (modular framework can be easily redesigned for different aircraft) 4

13 ER-2 Engineering Flights October, 2009 & February, 2011

14 February 14, 2011 flight over California Central Valley 14

15 TWiLiTE Flight Test Modes Fast Steering Mirror Alignment 15

16 TWiLiTE Flight Test Modes Etalon Calibration 16

17 TWiLiTE Flight Test Modes Science Data Acquisition Edge1 Ratio=Edge1/Edge2 Edge2 1. Merge lidar and GPS/IMU 2. Background subtracted 3. Deadtime corrected 4. Averaged in range 5. N shots averaged 6. Ratio signals E1/E2 1, Utilize etalon scan with simulated Rayleigh Brillouin spectral lineshape to generate calibration curve. 2. Calculate LOS wind speed 3. Apply correction for aircraft motion* LOS Wind Speed 17

18 Feb 14, 2011 ER-2 Flight Track- Oakland NWS sonde comparison Oakland NWS Sonde 00Z Feb 15, 2011 Sonde Speed Projected to TWiLiTE LOS azimuth 18

19 Feb 14, 2011 ER-2 Flight Track S2 S1 S4 S3 19

20 February 14 flight over California Central Valley-Track S1 t avg =1 second, R=30 m, z=21 m

21 February 14 flight over California Central Valley t avg =1 second, z=253 m 11x31-139

22 February 14 flight over California Central Valley-Track S2 t avg =1 second, R=30 m, z=21 m

23 February 14 flight over California Central Valley t avg =11 second, z=253 m 11x31-139

24 February 14 flight over California Central Valley-Track S3 t avg =1 second, R=30 m, z=21 m

25 February 14 flight over California Central Valley t avg =11 second z=253 m 11x31-139

26 February 14 flight over California Central Valley-Track S4 t avg =1 second, R=30 m, z=21 m

27 February 14 flight over California Central Valley t avg =11 second z=253 m 11x31-139

28 February 15, 2011 flight Palmdale, CA to Denver, CO 28

29 February 15, 2011 Flight Track 8 t avg =1 second, R=30 m, z=21 m 17x11-139

30 February 15,2011 flight Palmdale, CA to Denver, CO - 8 t avg =11 seconds, z=253 m

31 February 15, 2011 Flight Track 12 t avg =1 second, R=30 m, z=21 m 17x11-139

32 February 15,2011 flight Palmdale, CA to Denver, CO - 12 t avg =11 seconds, z=253 m

33 February 15, 2011 Flight Track 13 t avg =1 second, R=30 m, z=21 m 17x11-139

34 February 15,2011 flight Palmdale, CA to Denver, CO - 13 t avg =11 seconds, z=253 m

35 February 15, 2011 Flight Track 14 t avg =1 second, R=30 m, z=21 m 17x11-139

36 February 15,2011 flight Palmdale, CA to Denver, CO - 14 t avg =11 seconds, z=253 m

37 February 15, 2011 Flight Track 23 t avg =1 second, R=30 m, z=21 m 17x11-139

38 February 15,2011 flight Palmdale, CA to Denver, CO -23 t avg =11 seconds, z=253 m 17x11-139

39 February 15, 2011 Flight Track 25 t avg =1 second, R=30 m, z=21 m 17x11-139

40 February 15,2011 flight Palmdale, CA to Denver, CO - 25 t avg =11 seconds, z=253 m 17x11-139

41 February 15, 2011 Flight Track 26 t avg =1 second, R=30 m, z=21 m 17x11-139

42 February 15,2011 flight Palmdale, CA to Denver, CO - 26 t avg =11 seconds, z=253 m 17x11-139

43 February 15, 2011 Flight Track 27 t avg =1 second, R=30 m, z=21 m 17x11-139

44 February 15,2011 flight Palmdale, CA to Denver, CO - 27 t avg =11 seconds, z=253 m 17x11-139

45 February 15,2011 flight Palmdale, CA to Denver, CO - 28 t avg =11 seconds, z=253 m 17x11-139

46 and Severe Storm Sentinel Hurricane and Severe Storm Sentinel (HS3) Hurricane and Severe Storm Sentinel (HS3) 3 Application of the Global Hawk for Hurricane Studies PI: Scott A. Braun (GSFC) Science Goal: Science Goal: To understand hurricane genesis and intensification. To understand hurricane genesis and intensification. Key Science Questions: Key Science Questions: How do hurricanes form? How do hurricanes form? What causes rapid intensity changes? What causes rapid intensity changes? How are intensity changes after formation related to upper- How are intensity changes after formation related to uppertropospheric flow features? tropospheric flow features? What s the role of the Saharan Air Layer? What s the role of the Saharan Air Layer? Science Objectives: Science Objectives: Observing the genesis of tropical cyclones and the intensification from Observing the genesis of tropical cyclones and the intensification from a tropical storm to a hurricane over an extended period - surveillance a tropical storm to a hurricane over an extended period - surveillance rather than reconnaissance rather than reconnaissance Providing 3-D observations of the wind field both within tropical Providing 3-D observations of the wind field both within tropical cyclones and in the environment cyclones and in the environment Measuring moisture fields, clouds, aerosols, and precipitation Measuring moisture fields, clouds, aerosols, and precipitation Two Global Hawk (GH) aircraft Two Global Hawk (GH) aircraft Environment GH instrumentation Environment GH instrumentation TWiLiTE (direct detection wind lidar) TWiLiTE (direct detection wind lidar) CPL (cloud & aerosol lidar) CPL (cloud & aerosol lidar) Scanning HIS (T, RH) Scanning HIS (T, RH) Dropsondes (wind, T, RH) Dropsondes (wind, T, RH) Over-storm GH instrumentation Over-storm GH instrumentation HIWRAP (3-D winds plus sfc winds) HIWRAP (3-D winds plus sfc winds) HIRAD (sfc winds and rain) HIRAD (sfc winds and rain) HAMSR (T, RH) HAMSR (T, RH) Environment GH Over storm GH

47 Hurricane and Severe Storm Sentinel (HS3) TWiLiTE on the Global Hawk: Option 1 Use TWiLiTE instrument modules reconfigured to mount in Global Hawk Zone 25 Modified AESA deep fairing in Zone 25 Use Northrup LCS (Liquid Cooling System) for thermal control ~540 lbs HS3 Environmental payload MODIFIED AESA RADOME FAIRING TWiLiTE reconfigured for Zone 25

48 Conclusions and Future plans In October, 2009 and February, 2011 we completed two deployments to Edwards AFB to integrate TWiLiTE in the ER-2 Q-Bay and fly 40 hours of test flights. During these flights TWiLiTE demonstrated fully autonomous operation of the major lidar functions including etalon calibration, telescope/laser bore sight alignment and science data acquisition Collected >9 hours of LOS wind profile measurements (~3000 second average, 253 m vertical resolution) with a variety of atmsospheric conditions. Comparison with NWS sondes shows excellent agreement. Remaining issues: Azimuth scanning with the rotating HOE still needs to be demonstrated. Auto-alignment algorithm needs to be fine tuned and stability demonstrated in flight. Additional flight testing of TWiLiTE on the ER-2 to address these issues is planned. Future plans: TWiLiTE will be reconfigured to fly in Zone 25 of the NASA Global Hawk for the HS3 EV-1 Mission. 48

49 Backups 49

50 TWiLiTE ER-2 Flight Test Summary Demonstrated fully autonomous operation of TWiLiTE including in flight calibration, bore sight alignment and data acquisition Established liquid cooling system operational parameters Tested auto alignment system in flight. Identified software algorithm issues and fixes. Demonstrated etalon calibration and alignment holds for >6 hours continuous operation in aircraft Photon counting data acquisition of clear air molecular backscatter returns, as well as low level aerosols, clouds and surface returns Last flight included ground validation in Boulder, CO area NOAA Doppler lidar, sondes, Vaisala and NOAA profilers Additional test flights on the ER-2 are planned early in FY11 to complete engineering testing. 50

51 TWiLiTE ER-2 Flight Testing Feb, Integrated TWiLiTE in ER-2 Q-Bay and verified mechanical, electrical and thermal interfaces. Initial engineering flights demonstrated basic operations. Site visit to DFRC to discuss integration on DC-8. July, Developed a dual pallet design to reconfigure TWiLiTE for flights on DC-8. Requires minimal new structural elements to mount instrument to DC-8 rails. DC-8 payload engineer defined hatch cover/window mods to minimize beam obscuration. Aug, Redesigned and repackaged data system electronics boxes to improve cooling, access and maintainability of boards. Improved user interface (in preparation for possible DC-8 flights). July, 2010 Redesigned liquid cooling loop thermal system to improve reliability. Implemented flexible user interface. Developed Quicklook software to display engineering data, calibration information and atmospheric data (raw and averaged backscatter signals and uncalibrated LOS winds). Oct, 2009 Second deployment to Edwards AFB. Flew 22 hours on ER-2. Verified autonomous operation of all major instrument functions except azimuth step-stare scanning of HOE telescope. Feb, 2011* Third deployment to DFRC to complete ER-2 engineering flights, demonstrate step-stare scanning capability and generate horizontal wind profile data sets. *delayed due to aircraft availability 51

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53 October 1, 2009 flight track Edwards AFB to Boulder, CO 9:25 PDT launch; 5.4 hours S3 x -18:52 S1 x -19:02 x -20:12 x -20:23

54 Edge Channel Signals Data Collection Period S3-20:12 to 20:22 UT 1 second average; Δz=70 m Cloud tops Ground returns Aerosol signals

55 TWiLiTE Quick Look LOS Winds October 1, 2009 Period S3, 20:12 to 20:22 UT A Quicklook algorithm is used to process the Edge1 and Edge2 PMT signals to determine uncalibrated LOS wind profiles. Below: LOS wind profiles from a 10 minute segment from the Oct 1, 2009 ER-2 flight are shown. Ten second averaging is used (~2 km along track resolution). Vertical resolution is 210m. Right: A 10 sec TWiLiTE LOS profile (20:17:07 UT) is shown along with wind data from the NWS sonde launched from Denver at 00Z on October 2, For this comparison the sonde speed is projected to the TWiLiTE LOS direction determined from the ER-2 nav data. 55

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57 TWiLiTE DC-8 Mechanical Integration As part of the program we developed a mechanical integration plan to reconfigure TWiLiTE for the DC-8, Nadir Port 7. We also developed an enhanced user console to interactively control instrument functions (not required for ER-2) and Quick look software package to monitor signals, etc DC-8 flights facilitate airborne demonstration of the hybrid Doppler lidar concept by flying TWiLiTE with the DAWN aerosol Doppler lidar. Proposed to fly TWiLiTE, along with DAWN, in 2010 GRIP mission but were not selected Dual pallet design requires limited structural modifications to existing design to mount instrument to seat tracks in DC-8 cargo bay Modified hatch cover design with recessed window mount was proposed by Adam Webster, DC-8 Payload Engineer, to minimize beam obscuration. Also may require fused silica window with correct laser coatings. TWiLiTE configured for DC-8 Nadir Port 7 57

58 TWiLiTE Assembly and testing November, January, 2009 Laser electronics, Data electronics and power distribution TWiLiTE atmospheric testing using turning mirror & roof hatch (vertical only) Looking up at 45 degrees into blaze of HOE TWiLiTE assembly on ground support cart 58

59 ER-2 Engineering Checkout Feb 17-27,

60 TWiLiTE Development Timeline IIP04 TELESCOPE DELIVERY DEC 2007 LASER DELIVERY MAY 2008 RECEIVER DELIVERY JUN 2008 Redesign Thermal Sys; Upgrade user console; Quick Look Software FEB-JULY, 2010 CRITICAL DES REVIEW MAY, st ENGINEERING TEST FLIGHTS - ER2 FEB, nd ENGINEERING TEST FLIGHTS - ER2 OCT, 2009 INTEG & TEST 3Q/2007-3Q/2008 Ground Testing: AUG, rd ENGINEERING TEST FLIGHTS ER2 FEB, 2011* Repackage data sys electronics ETALON APR-JULY, 2009 DELIVERY APR *delayed due to aircraft availability

61 February 15, 2011 Flight Track 11 t avg =1 second, R=30 m, z=21 m 17x11-139

62 February 15,2011 flight Palmdale, CA to Denver, CO - 11 t avg =11 seconds, z=253 m

63 February 15, 2011 Flight Track 22 t avg =1 second, R=30 m, z=21 m 17x11-139

64 February 15,2011 flight Palmdale, CA to Denver, CO -22 t avg =11 seconds, z=253 m 17x11-139

65 February 15, 2011 Flight Track 11 t avg =1 second, R=30 m, z=21 m 17x11-139

66 February 15,2011 flight Palmdale, CA to Denver, CO - 11 t avg =11 seconds, z=253 m

67 February 15, 2011 Flight Track 22 t avg =1 second, R=30 m, z=21 m 17x11-139

68 February 15,2011 flight Palmdale, CA to Denver, CO -22 t avg =11 seconds, z=253 m 17x11-139