G O D D A R D S P A C E F L I G H T C E N T E R Status of the Tropospheric Wind Lidar Technology Experiment (TWiLITE) IIP Project Bruce Gentry, M. McGill, G. Schwemmer,, M. Hardesty, A. Brewer, T. Wilkerson, R. Atlas, M. Sirota, S. Lindemann, F. Hovis I&T Engineering team: Stan Scott, Roman Machan, Ryan Cargo, Dan Reed, Bill Hart, John Yorks, Dennis Hvlaka June, 2009

G O D D A R D S P A C E F L I G H T C E N T E R 2 Acknowledgments NASA SMD ESD ESTO (G. Komar) NASA SMD ESD (R. Kakar) NASA GSFC IRAD

G O D D A R D S P A C E F L I G H T C E N T E R 3 The TWiLiTE instrument is a compact, rugged direct detection scanning Doppler lidar designed to measure wind profiles in clear air from 18 km to the surface. TWiLiTE operates autonomously on NASA research aircraft (ER-2, DC-8, WB-57). Initial engineering flight tests on the NASA ER-2 in February, 2009 demonstrated autonomous operation of all major systems. TWiLiTE will mount in the DC-8 cargo bay using either the fore or aft nadir port. Tropospheric Wind Lidar Technology Experiment (TWiLiTE) Instrument Incubator Program TWiLiTE system configured for ER-2 QBay TWiLiTE ER-2 Integration February, 2009

G O D D A R D S P A C E F L I G H T C E N T E R DC8 WB57 ER2 Altitude (km) GLOW mobile lidar TWiLiTE configured for DC8 Nadir Port 7 (ROSES07-AITT) TWiLiTE configured for WB57 3’ Pallet (ESTO IIP04) TWiLiTE configured for ER2 Q-Bay (ESTO IIP04) (SMD,NMP,IPO, ARO, ROSES07-WLS) TWiLiTE Airborne Doppler Lidar Direct Detection Doppler Lidar Development Roadmap

G O D D A R D S P A C E F L I G H T C E N T E R 5 Airborne Lidar Wind Measurement Lidar ranging permits determination of wind speed as a function of altitude. Multiple look angles permit determination of vector wind.

G O D D A R D S P A C E F L I G H T C E N T E R 6 Entrance TRL Exit TRL High spectral resolution all solid state laser transmitter 45 High spectral resolution optical filters 45 Efficient 355 nm photon counting molecular Doppler receiver technologies 45 Novel UV Holographic Optical Element telescopes and scanning optics 35 TWiLiTE Direct Detection Wind Lidar Key Technologies

G O D D A R D S P A C E F L I G H T C E N T E R 7 Wavelength354.7 nm Telescope/Scanner Area0.08 m 2 Laser Linewidth (FWHH)150 MHz Laser Energy/Pulse(8 W) pps Etalon FSR GHz Etalon FWHH2.84 GHz Edge Channel Separation6.64 GHz Locking Channel Separation 4.74 GHz Interference filter BW (FWHH)120 pm PMT Quantum Efficiency25% TWiLiTE Instrument Parameters

G O D D A R D S P A C E F L I G H T C E N T E R 8 TWiLiTE Assembly and testing July – November, 2008 Optical bench, telescope and laser alignmentStructure and lidar modules mounted to ER-2 frame Dust covers, heaters, wiring and plumbing added Insulation (1 to 3 inch thick) added

G O D D A R D S P A C E F L I G H T C E N T E R 9 TWiLiTE Assembly and testing November, January, 2009 Laser electronics, Data electronics and power distribution TWiLiTE atmospheric testing using turning mirror & roof hatch (vertical only) TWiLiTE assembly on ground support cart Looking up at 45 degrees into blaze of HOE

G O D D A R D S P A C E F L I G H T C E N T E R 10 ER-2 Engineering Flights Feb 17-27, 2009

G O D D A R D S P A C E F L I G H T C E N T E R 11 ER-2 Engineering Flights Feb 17-27, 2009

G O D D A R D S P A C E F L I G H T C E N T E R 12 Signal strength between Mcounts/Sec in boundary layer Very clean atmosphere – no significant clouds or aerosol Feb Ground Data

G O D D A R D S P A C E F L I G H T C E N T E R 13 Feb. 19, 2009 Flight Just over 7 minutes of lidar data (weak signals due to laser Temp ) Raw data for Edge 1-High Energy Channel shows promising functionality: – Single shot; 30 m range resolution – Skies were primarily clear, but TWiLiTE did detect a contrail – Signal from the surface was also detected at approx 30 km in range

G O D D A R D S P A C E F L I G H T C E N T E R 14 Feb. 19, 2009 Flight – Temps (1 of 2) Pumps carrying coolant fail 20 minutes into the flight causing the laser to overheat (black and blue: top plot) Other components are also affected such as the Heater Block (red: top plot) Etalon sweep 1Etalon sweep 2 Science data Acq2

G O D D A R D S P A C E F L I G H T C E N T E R 15 Etalon Calibration Sweeps

G O D D A R D S P A C E F L I G H T C E N T E R 16 Summary and Future Plans Integrated TWiLiTE into the ER-2 and verified all mechanical, electrical, thermal and control interfaces on the ground and in the air. 2 hour test flight with pump not operating demonstrated key - functions: –Auto alignment system (ground returns form 30 km) –Etalon calibration and alignment sequence completed –Photon counting data acquisition –Laser seeding, thermal interlocks and restart Observed failures were COTS parts (pump, CPU) not lidar components. We are repairing, testing and will deploy for additional flights this summer. Reconfiguring TWiLiTE for integration on the DC-8 (ROSES07-AITT). Proposal submitted for summer 2010 hurricane experiment (GRIP)

G O D D A R D S P A C E F L I G H T C E N T E R 17 Backups

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

G O D D A R D S P A C E F L I G H T C E N T E R 19 ER-2 Flight Test Summary 2/9 - Ship from GSFC 2/17 – TWiLiTE arrives DFRC 2/18 – Integration into ER2 2/19 – First 2 hour test flight. Coolant pumps fail 20 minutes into flight. Instrument performs autonomous turn on and calibration functions normally until laser T interlock turns off laser. Demonstrates key engineering functions 2/20 to 2/22 – Replace pump with heavier duty industrial pump. 2/23 - Warning light prior to take off scrubs flight 2/24 – Ground crew not available. No flights 2/25 to 2/26 – Surface winds exceed safe limits for takeoff. Ground tests of TWiLiTE with ER-2 pushed out from hangar 2/26 – 3 hours of ground testing in hangar to verify software operations. At end of this period the instrument CPU began to reboot repeatedly. 2/27 - Trouble shoot CPU without success. Determine repair or replacement in field is not practical. Pack instrument for return to GSFC

G O D D A R D S P A C E F L I G H T C E N T E R 20 Feb. 19, 2009 Flight - Temps (2 of 2) Despite issues with the pumps, the etalon & receiver temperatures remained relatively stable

G O D D A R D S P A C E F L I G H T C E N T E R 21 Future Plans Thermal system will be modified and tested Data System Electronics Box will be tested and faulty CPU board replaced Return to DFRC for additional flight tests on ER-2 planned in summer, 2009