G O D D A R D S P A C E F L I G H T C E N T E R

AITT

Flight demonstration of the TWiLiTEdirect detection Doppler lidar: status and

future plans Bruce Gentry, Matt McGill, Ryan Cargo, Bill Hart, Roman

Machan, Dan Reed, Stan Scott, Shane Wake, David Wilkens, John Yorks

Working Group on Space-based Lidar Winds February 8-9, 2011

Miami, FL

G O D D A R D S P A C E F L I G H T C E N T E R

AITTTWiLiTE Flight Test Objectives

• Complete integration and flight testing of the TWiLiTE airborne direct detection molecular Doppler lidar instrument, developed in the ESTO IIP program, on NASA research aircraft (ER-2, DC-8).

• Evaluate the effects of atmospheric constituents (clouds, aerosols) on instrument performance

• Advance the development of key technologies and subsystems for future spaceborne tropospheric wind-measurement systems in support of the 3DWinds Decadal Survey Mission.

• Validate algorithms and methods of processing full troposphericwind profiles

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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

G O D D A R D S P A C E F L I G H T C E N T E R

AITT

•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).

• Initial engineering flight tests on the NASA ER-2 in 2009 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.

Tropospheric Wind Lidar Technology Experiment (TWiLiTE) IIP

TWiLiTE system configured for ER-2 QBay

TWiLiTE LOS wind profiles from Oct 1, 2009 ER2 test flight. A 10 minute segment taken over Grand Junction, CO is shown. Inset is a single TWiLiTE profile compared with wind profile data from the 00Z, Oct 2 NWS radiosonde launched from Denver.

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AITTTWiLiTE Development Timeline

2007

2008

2009

CRITICALDES REVIEWMAY, 2007

1st ENGINEERING TEST FLIGHTS - ER2

FEB, 2009

Ground Testing:AUG, 2008

ETALONDELIVERYAPR 2007

RECEIVERDELIVERYJUN 2008

TELESCOPEDELIVERYDEC 2007

LASERDELIVERYMAY 2008

INTEG & TEST3Q/2007- 3Q/2008

2010

Repackage data syselectronics

APR-JULY, 2009

IIP04 AITT

2nd ENGINEERING TEST FLIGHTS - ER2

OCT, 2009

3rd ENGINEERING TEST FLIGHTS ER2

FEB, 2011*

2011

Redesign Thermal Sys; Upgrade user console; Quick Look Software

FEB-JULY, 2010

*delayed due to aircraft availability

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AITTTWiLiTE CompatibleNASA Airborne Science Platforms

DC8

WB57ER2

25

20

15

10

5

Max

Alti

tude

(km

)

6-8 hrs durationUnattended operation

Global Hawk

36 hrs durationUnmanned vehicle

TWiLiTE configured for DC8 Nadir Port 7

(AITT)

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)

G O D D A R D S P A C E F L I G H T C E N T E R

AITT

1. 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 Bench5. HOE telescope6. ER-2 Qbay instrument pallet (mechanical interface defined by aircraft.)7. 80-20 structure (modular framework can be easily redesigned for different aircraft)

5

4

2A

2B

2C1

3

6

7

TWiLiTE Modular Assembly-IIP ER-2 Configuration

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AITT

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TWiLiTE configured for DC-8 Nadir Port 7

TWiLiTE DC-8 Mechanical Integration

• As part of the AITT 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.

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AITTER-2 Engineering FlightsSeptember, 2009

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AITTOctober 1, 2009 flight track Edwards AFB to Boulder, CO

9:25 PDT launch; 5.4 hours

x -1

8:52

x -1

9:02

x -20:12x -20:23

S3

S1

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AITTEdge Channel Signals Data Collection Period S3 - 20:12 to 20:22 UT

1 second average; Δz=70 m

Cloud tops Ground returns

Aerosol signals

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TWiLiTE Quick Look LOS WindsOctober 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, 2009. For this comparison the sonde speed is projected to the TWiLiTE LOS direction determined from the ER-2 nav data.

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AITT

– 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.

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TWiLiTE ER-2 Flight Test Summary

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AITTHurricane and Severe Storm Sentinel

Science Goal: To understand hurricane genesis and intensification.

Key Science Questions:• How do hurricanes form?• What causes rapid intensity changes?• How are intensity changes after formation related to upper-

tropospheric flow features?• What’s the role of the Saharan Air Layer?

Science Objectives:• Observing the genesis of tropical cyclones and the intensification from

a tropical storm to a hurricane over an extended period - surveillance rather than reconnaissance

• Providing 3-D observations of the wind field both within tropical cyclones and in the environment

• Measuring moisture fields, clouds, aerosols, and precipitation

HS3

Application of the Global Hawk for Hurricane Studies

Hurricane and Severe Storm Sentinel (HS3)

Two Global Hawk (GH) aircraftEnvironment GH instrumentation• TWiLiTE (direct detection wind lidar)• CPL (cloud & aerosol lidar)• Scanning HIS (T, RH)• Dropsondes (wind, T, RH)Over-storm GH instrumentation• HIWRAP (3-D winds plus sfc winds)• HIRAD (sfc winds and rain)• HAMSR (T, RH)

PI: Scott A. Braun (GSFC)

Genesis Locations and Loiter Times

Environment GH

Over-storm GH

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AITTHurricane and Severe Storm Sentinel (HS3)

• Use TWiLiTE instrument modules including HOE telescope• Modified AESA deep fairing in Zone 25• Use Northrup LCS (Liquid Cooling System) for thermal control• ~540 lbs

TWiLiTE on the Global Hawk: Option 1

MODIFIED AESA RADOME FAIRING

HS3 Environmental payload

TWiLiTE reconfigured for Zone 25

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AITTConclusions and Future plans

• During the AITT flight test program we completed two deployments to Edwards AFB to integrate TWiLiTE in the ER-2 Q-Bay and fly 26 hours of engineering 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 including initial LOS wind profile measurements.

• 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 in progress (Deployment: Feb 3 - Feb 16, 2011).

• Future plans: TWiLiTE will be reconfigured to fly in Zone 25 of the NASA Global Hawk for the HS3 EV-1 Mission.

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G O D D A R D S P A C E F L I G H T C E N T E R

AITTBackups

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AITT2007 NRC Decadal Survey Recommendations for 3DWinds

“The Panel recommends a phased development of the HDWL mission withthe 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

3D Tropospheric Winds mission called “transformational” and ranked #1 by Weather panel. with concurrence by Water panel. Overall prioritized in 3rd 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).”

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AITTDouble Edge Measurement Principle

Aerosol

Molecular

Frequency

Molecular Channel at 355 nm

Edge Filter 1 Edge Filter 2

∆νDOP

G O D D A R D S P A C E F L I G H T C E N T E R

AITTTWiLiTE ER-2 Flight Testing• Feb, 2009 - 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, 2009 - 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, 2009 - 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.

19*delayed due to aircraft availability

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AITTEntrance TRL

Exit TRL

• High spectral resolution all solid state laser transmitter

4 5

• High spectral resolution optical filters

4 5

• Efficient 355 nm photon counting molecular Doppler receiver technologies

4 5

• Novel UV Holographic Optical Element telescopes and scanning optics

3 5

TWiLiTE Direct Detection Wind LidarKey Technologies

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AITT

Instrument Status

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FUNCTIONS:• Generates single frequency uv laser pulses. • Injection seeded Nd:YAG ring oscillator with single amplifier• Frequency tripled to λ=355 nm • Pulse energy = 35 mJ @ 355 nm• Pulse Rep Frequency = 200 pps• Optical canister is 28 cm x 33 cm

TWiLiTE Laser

FIBERTEK, INC.

Assembled laser optical (gold) and electronics (black) modules

FEATURES:• High 3rd harmonic conversion

efficiency (~50%).• Excellent beam quality (M2<1.5)• Compact, ruggedized laser optical

and electronics modules.• Fully autonomous laser control

software

Subsystem tested in labIntegrated in TWiLiTE systemSystem level demo on groundFlight demo in ER-2 (AITT)

STATUS :

Remaining issues: None

G O D D A R D S P A C E F L I G H T C E N T E R

AITTTWiLiTE Doppler Receiver

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 1st gen ground-based DDDL lidar receiver

Doppler receiver modules (left) are enclosed in an environmentally controlled vessel (right)

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

Subsystem tested in labIntegrated in TWiLiTE systemSystem level demo on groundFlight demo in ER-2 (AITT)

STATUS :

Remaining issues: None

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AITTTWiLiTE Tunable Fabry-Perot Etalon and Digital Controller

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.

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

Subsystem tested in labIntegrated in TWiLiTE systemSystem level demo on groundFlight demo in ER-2 (AITT)

STATUS :

Remaining issues: None

Fabry Perot Etalon

FEATURES:• 50 mm clear aperture plates• Three 20 cm diameter sub-

apertures defined by step coatings• 9 mm gap • 16.6 GHz FSR• Plate reflectivity = 0.75

Edge2 Edge1Lock

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AITTTWiLiTE 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

STATUS :Subsystem tested in labIntegrated in TWiLiTE systemSystem level demo on groundFlight demo in ER-2 (AITT)

Remaining issues:1) Azimuth step stare scanning2) Auto-alignment boresight maintenance (software)3) Transmission down by 5x (may be mostly due to 2)

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