The Green-OAWL (GrOAWL) Airborne Demonstrator for the ATHENA-OAWL Mission Concept

Transcription

1 The Green-OAWL (GrOAWL) Airborne Demonstrator for the ATHENA-OAWL Mission Concept 18 th Coherent Laser Radar Conference 27 June 1 July 2016 Boulder, CO Sara Tucker & Carl Weimer Ball Aerospace Mike Hardesty & Sunil Baidar NOAA/CIRES/CU 1

2 Space-based Doppler Wind Lidar >30 years of NASA and NOAA investments in wind lidar technology Advancements: Mission concepts and system architecture feasibility studies Ground and airborne demonstration systems Advancements in UV and near-ir laser technology Technologies Coherent detection : 2m wavelength aerosol backscatter (DAWN) Direct detection: 355 nm wavelength molecular backscatter (TWiLiTE) Direct detection: 355 & 532 nm aerosol backscatter lidar (OAWL) Molecular version also possible see Bruneau et al., 2004 ESA s ADM Aeolus Direct-detection, 355 nm, aerosol & molecular backscatter 2

3 ATHENA-OAWL Venture Tech The Green-OAWL Airborne Demonstrator ATHENA-OAWL: Aerosol Transport, Hurricanes, and Extra-tropical Numerical weather using the Optical Autocovariance Wind Lidar EV-I 2013 Mission Concept - rated Category 3 and thus eligible for EV-I Venture Tech funding. ATHENA-OAWL Venture Tech (AOVT) goals: Build a two-look, 532 nm Green OAWL (GrOAWL) airborne system to demonstrate measurement performance (Ball) Provide measurement validation with science team (CU/NOAA) Scale system performance to space, (e.g. Aeolus) Raise OAWL TRL for next EV-I proposal 3

4 Altitude MSL (m) Altitude MSL (m) The Evolution of OAWL 2013 ATHENA-OAWL Mission Proposal 1999-present: Ball design, build and test of OAWL receivers, mission concepts and retrieval/processing algorithms aerosols winds Airborne Demos & spacequalification for Future Missions : OAWL IIP-07 Breadboard system 355 nm only, 4x channels Single look 12 telescope Ground validation with NOAA Coherent system Autonomous flight tests on NASA WB : HOAWL ACT Breadboard System Demonstrate 532 nm wavelength channels & depolarization channels Total 10 channels HSRL Aerosol retrieval algorithms : ATHENA-OAWL Venture-Tech: GrOAWL Airborne demonstrator System (WB-57) 2-lasers = 400 Hz eff. PRF 4x 532 nm channels 2 looks, 2 telescopes to demonstrate geometry : HAWC-OAWL IIP HSRL Validation study with NCAR (2016) Two look airborne system (build on GrOAWL) Dual Wavelength (355& 532 nm) + depol. Channels Athermal interferometer 4

5 OAWL: Optical Autocovariance Wind Lidar Direct detection aerosol wind lidar Measures Doppler shifts using a fieldwidened, quadrature-channel, Mach Zehnder interferometer. Operates at both the 355 nm (UV) and 532 nm (green) wavelengths Current configuration: 1.5 year rebuild + fly effort Two-look system to demonstrate a two look concept for space-based platforms Parameter Pulse Energy 532 nm Pulse Energy 355 nm Laser Pulse Repetition Telescopes Sample Rate Interferometer OPD Value (look1/look2) 200 J 6 mj 0.5/11 mj 200 Hz per look ~25 cm diameter 140 MHz/channel 0.9 meters Variabl e 532 nm output power Laser Electronic s Laser-1 Fiber coupled OAWL Interferometer GPS/ IMU 2-looks, 2 telescope s Payload Controlle r Laser-2 5

6 Optical Bench New Optical Bench Two-lasers (one new, one refurbished) synchronized to interleave pulses Two ~25cm diameter (effective) telescopes, transmit/receive optics Variable 532 nm laser transmission Two axis boresighting GPS/IMU Fiber coupling connects the combined returns into the interferometer. Laser Electronics rack Lasers Electronics chassis Telescopes Interferometer with thermal cover 6

7 Electrical & Software Subsystems Conduction cooled payload controller running linux Conduction cooled Single board computer 2X System Control & Auxiliary data boards One per laser and transmit path Boresight and 532 nm attenuator control 2X Lidar Data Acquisition and Processor boards Up to 12 channels of data acquisition sample ranges as low as 1.1 m real-time, FPGA-based, LOS wind speed profile processing Detector electronics & controls WB-57 wiring ICD & system harness Remote system operation 7

8 Pallet Integration Layout WB-57 quasi-pressurized pallet Two new pallet floor panels with windows Custom fluid loop system integrated into floor panels to provide cooling for the lasers and payload controller Pumps Circulation heaters Heat exchangers Pallet interior- GrOAWL instrument & environmental control 8

9 355 nm 532 nm Spring 2016 ground testing results: two looks (separate days), two wavelengths, 30⁰ elevation Look 1: 12 March 2016 Look 2: 24 April ⁰ Elevation facing west over Boulder foothills 9

10 GrOAWL Airborne Flight Testing Flew on the NASA WB-57 Jet in the quasipressurized pallet All flights out of Ellington Field (Johnson Space Center) One pilot and one backseater Sensor Equipment Operator (SEO) System operated remotely from ground or from SEO seat for laser operations Ground telemetry and control via INMARSAT satellite link 8 flights for approximately 38 flight hours Total lasing time ~22 hours (TBR) 3 flights with dropsondes All lidar data are being post-processed with 200 Hz GPS/IMU data to remove platform motion. Precise pointing angles still TBD 10

11 GrOAWL Airborne Flight Testing, cont d Flew racetrack patterns over the Gulf of Mexico to provide revisit times (~1 hr/loop) views of the atmosphere region from opposite sides more validation for models Study of variability Flew over restricted areas: Real-time flight pattern variability: altitude changes, cloud avoidance, airspace coordination, etc. Testing with variable laser output power Dropping the ONR/YES sondes for winds validation 11

12 Doppler measurements from first GrOAWL flights Multiple challenges met Room for improvement Fluid loop Cooling systems (2X loops): kept their laser cooling fluid at desired flow rates and precise temperatures Kinematic mount installation and vibration isolators worked as expected. High Houston humidity + cold window temperatures = condensation. Mitigated by purging the pallet and blowing warm air over the windows and heating them Fiber coupled interferometer ensured no overlap bias in the phase measurements as observed in previous OAWL design LOS Doppler wind measurements were made with both looks. System contrast partially reduced in flight, affecting precision/sensitivity Ground testing between flights showed high system contrast: We are investigating thermal and vibration differences High vibration environment on the WB-57: Residual vibration signatures were observed Some processing steps may be worked to mitigate effects, TBD Refurbished laser started showing new multi-moding behavior Observed signal variations throughout the flight (Laser output? Overlap? Aerosol conditions? TBD) Just starting to process, analyze, and understand the extent of any issues 12

13 10 May 2016: Very first flight results No active control of cooling loops due to fusing failure on heaters (fixed for other flights) Flew low (16-18kft, 5-6km) to balance external cooling with laser heating Sub-optimal laser thermal control Low altitude required low 532 nm output energy setting for eye-safety: 532 (top): only 200 J/pulse 355 (bottom): ~11 mj/pulse Still got good returns comparing well with NOAA forecast model. 532 nm - only 200 J/pulse 355 nm ~11 mj/pulse 13

14 Simultaneous two-look airborne profile results Preliminary data from 17 th June nm wavelength with up-to 300 mw per laser (less at times) 8.5km altitude, 12 km slant path to the surface Very low aerosol backscatter conditions: below background levels Daytime operation with scattered clouds Look 1 (forward) 17 June 2016 Look 2 (aft) 14

15 Summary: AOVT adhered to a tight schedule, built GrOAWL, and made the airborne wind measurements AOVT funding awarded March 2015 System build started spring 2015 Electronics boards delivered late summer, fall Optical Components delivered fall/late fall Optical bench aligned January 2016 Telescopes delivered end of January 2016 Data system delivered February/March 2016 Lasers delivered February & April 2016 First ground-based atmospheric returns: March (look1) and April (look 2) 2016 Installation in pallet: end of April 2016 Flight control software finalized: May 2016 Ship to Houston May 5, 2016 WB-57 flights May 10-June 24, 2016 Analysis & additional testing/validation July/August/September

16 Conclusions and Future plans GrOAWL was built to be an airborne demonstrator for a two-look OAWL-type mission concept such as ATHENA-OAWL April 2016: New system ground demonstrations May/June 2016: GrOAWL Demonstrated Doppler wind measurements from the NASA WB-57 aircraft Initial validation comparisons are promising Next talk by Baidar et al. Next Steps: Validate GrOAWL windmeasurements with dropsondes, balloonsondes, and Numerical Weather Reanalysis Evaluate instrument sensitivity under the various environmental, cloud and aerosol conditions observed Validate performance model and scale for space-based performance prediction 2017: Airborne Aeolus CalVal OAWL is the only U.S. 355 nm Aerosol wind lidar Use 355 nm OAWL for validating Aeolus 355 nm aerosol channel 16

17 Extras

18 Satellite wind data coordination (simplified newcomer perspective) CGMS IROWG Radio Occultation ICWG Clouds IWWG Winds ITWG TOVS IPWG Precipitation Wind data product producers: retrievals from imagery, scatterometry, etc. Analysis, Validation, & Impact (& lots of acronyms) Wind data product end users (forecast, NWP, etc.) Satellite bus & orbit providers Active vs Passive Swath vs curtain Polar, GEO, LEO, etc. Orbit time Satellite Instrument Providers General Public 18

19 Optical Autocovariance Wind Lidar (OAWL) Field-widened,.9 m OPD, Mach- Zehnder Interferometer (MZI) works well with large telescopes; Patent #s: US B1, US B1 Four channels sample interferometer fringe phase (wind) and amplitude (aerosol). Outgoing T0 pulse Atmospheric Returns Fringes wrap no out of band concerns, T0 phase used to adjust every pulse: no laser pulse-to-pulse stability requirements The phase difference Δϕ is related to the line-of-sight wind speed, V LOS by c V LOS 2 2OPD QWP d1 d2 d3 d Detectors at constant ACF phase 19

20 A partial timeline of space-based Doppler wind lidar CO2 Solid State Heterodyne DAWN Flights Direct Detection TWiLiTE Flights 20 GTWS GWOS WISSCR ATHENA ESA s ADM Aeolus (single look) Ball/NASA CALIPSO Decadal Survey 3D-Winds Hybrid launched Optical Autocovariance (OA) Wind Lidar >10 Years on orbit! Original OA system development at Ball OAWL Prototype OAWL OSSE OAWL IIP OAWL IDL HOAWL & FIDDL ACT HAWC-OAWL IIP AOVT Aeolus Launch

21 Laser Eye Safety Drives SNR/Flight locations 532 nm wavelength: CALIPSO & ATHENA-OAWL CALIPSO: 110 mj, 20 Hz, 705 km altitude, radian divergence ATHENA-OAWL: 160 mj, 150 Hz, 350 km altitude, 150 -radian divergence The same eye-safe level is achieved through the additional divergence Vs. GrOAWL Aircraft Eye Safety mj, 200 Hz, km altitude, 120 -radian divergence Similar ground footprint intensities (different size footprints!) Very different intensities from ground to aircraft altitude puts restrictions on airborne operation at 532 nm Easier for 355 nm (eyesafe at 1km from aircraft) Eye-safe range for 2.5 mj 532 nm 20 km Eye-safe range for ATHENA-OAWL Commercial aircraft 350 km orbit = 17.5X Altitude of airborne system 21

22 ATHENA-OAWL: Aerosol Transport, Hurricanes, and Extra-tropical Numerical weather using the Optical Autocovariance Wind Lidar Path-finding science for next-generation global weather prediction and climate analysis Design to cost approach to Earth Venture Instrument call building on CALIPSO (now 10 years on orbit) and ISS technologies Mission Objectives: Co-located wind and aerosol profiles breakthroughs in modeling and prediction of low and mid-latitude weather and climate. better understand relationships between aerosol radiative forcing, atmospheric dynamics and the genesis and lifecycle of tropical cyclones study impacts of long-range dust and aerosol transport on global energy and water cycles, air quality, and climate. ATHENA-OAWL 22