SLWG 2005
The Tropospheric Wind Lidar Technology Experiment (TWiLiTE), a NASA IIP
Technology Development and Demonstration Project
B. Gentry, R. Atlas, G. Schwemmer, M. McGill, M. Hardesty, A. Brewer, T. Wilkerson, J. Marzouk, S.
Lindemann
Working Group on Space Based Lidar WindsJune 28 - 30, 2005
Welches, OR
SLWG 2005
• 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
SLWG 2005
Approach
Leverages significant technology investments and instrument development heritage
SBIR+ESTO+IPO+IRAD Laser – LiteCycles,
Fibertek Data System – ASRC HOE – Ralcon FP etalon – MAC
Fielded Systems GLOW, CPL, HARLIE
IPO IR&DSBIR
HARLIE
GLOW
CPL
TWiLiTE
SLWG 2005
Proposed TWiLiTE Measurement Requirements
Parameter Proteus WB57
Velocity accuracy (LOS projected) (m/s) 1.5 1.5
Range of regard km 0-18 0-18
Vertical resolution km 0.25 0.25
Horizontal resolution km 25 25
Groundspeed m/s 100 200
Nadir angle deg 45 45
Scan pattern 16 pt step-stare 8 pt step-stare
Scan cycle time seconds (km)* 192 (19.2 km) 112 (=22.4 km)
Horizontal integration per LOS (seconds)//ground track (km)
10//1 10//2
* Assumes scanner average angular velocity of 12 deg/sec
SLWG 2005
Entrance TRL Exit TRL
High spectral resolution all solid state laser transmitter
– Well developed diode-pumped Nd:YAG technology for efficient, long-life, space qualified laser
4 5-6
High spectral resolution optical filters – High resolution, high throughput, stable, tunable optical filters for Doppler wind measurement
4 5-6
Efficient 355 nm photon counting molecular Doppler receiver
4 5-6
Novel UV Holographic Optical Element telescopes and scanning optics
3 5-6
TWiLiTE Direct Detection Wind Lidar Key Technologies
SLWG 2005
Laser (LiteCycles)
• Leverages funding from SBIR + ESTO• 15 W optical power in uv (15 mJ @
1000 pps)• All solid state diode pumped Nd:YAG
laser• Stable, single frequency operation• High conversion efficiency to 3rd
harmonic (355 nm)• Engineered and packaged for aircraft
operation• Heritage: Cloud Physics Lidar
SLWG 2005
• Leverages funding from SBIR + ESTO• 2.5 W optical power (50 mJ@ 50pps)• All solid state conduction cooled design• Stable, single frequency operation• High conversion efficiency to 3rd
harmonic (355 nm)
• HB Laser on vibration test fixture
– Seeding is stable for 0.5 g bench accelerations at frequencies up to 200 Hz
Amplifers
Seeded Oscillator
Harmonic generators
High Brightness Laser (Fibertek)
SLWG 2005
HOE Telescope/Scanner
• HARLIE heritage• Utah State University/Space
Dynamics Lab compact folded design
• UV HOE success – >50% efficiency; <200 µrad spot
Recent laboratory measurements (left) verify performance of 40 cm diam., 355 nm HOEs.
The SDL design features a central port for laser transmission and fiber coupled receiver output.
SLWG 2005
HOE/Scanner Heritage/Contributors
• $3.5M in NASA Investments since 1990• PHASERS lidar (532 nm) 1994-present• HARLIE airborne lidar (1064 nm) 1998-present – extensive field use• UV HOEs (355 nm) 2000-present• 2 NASA patents, 3 USU patents• Contributors: Thomas Wilkerson (SDL/USU), Richard Rallison (Ralcon), David Guerra (St. Anselm)
SLWG 2005
Advanced Molecular Doppler Receiver
IRAD receiver summary • Reduce volume of Zephyr Double Edge receiver design by >85%• Increase throughput by 1.8x• Dynamic range of each channel increased by 2 orders of magnitude• Utilizes Michigan Aerospace etalon technology.• Robust mechanical design suitable for airborne or spaceborne applications
SLWG 2005
SBIR Phase II awarded in Dec 2004
Objectives :
1. Develop lightweight, thermally stable etalon design using SiC
2. Flight qualify the etalon
3. Develop a digital version of the etalon controller
Michigan Aerospace Corporation Advanced Etalon Technology
SLWG 2005
System Block Diagram
Scanner Ctrl
Laser Power
Timing/Control
Data Acq.
Laser
Com
puter
HOE Scanner/Telescope
Laser Cooling
SIGNAL FIBER
ANALOG/PHOTON COUNTS, SYS DATA
Etalon Control
SYNCAUTOFOV TO COMP
Det. Box Temp
PRESSURE VESSEL
ETALON
Bm Exp
RE
CE
IVE
R T
EM
P C
ON
TR
OL
ETALON SPACING/PARALLELISM
A/D SIGNALFIBERWATERPOWER
AUTO TIP/TILT ADJ
INS/GPS Data
Power Dist/Sw
INS
/GP
S
MOLECULAR DE DOPPLER RECEIVER
PRESSURE VESSEL
PRESSURE VESSEL
PRESSURE VESSEL Window
SLWG 2005
Design Concept MechanicalDoppler Receiver
Data System+ Flight Electronics
HOE Telescope/ Scanner
Laser
SLWG 2005
TWiLiTE Schedule• Anticipate September 2005 start• Initial Test Flights in 2008
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