Technology Readiness Levels of Coherent Doppler Wind Lidar for Earth Orbit by M. J. Kavaya, F. Amzajerdian, J. Yu, G. J. Koch, U. N. Singh NASA Langley Research Center to Working Group on Space-Based Lidar Winds 28 June – 1 July, 2005 Welches, Oregon Coherent DWL TRL Levels - 1

Notional Tropospheric Winds Mission Vertical Profiles of Horizontal Vector Wind 833 km sun-syn. polar orbit, on NPOESS S/C for reduced NASA cost Step-stare conical scan, 30 deg. nadir angle, 4 az., for 2 vector wind lines (4 shown in figure) LaRC unique high-energy 2-micron pulsed laser, 10 Hz pulse rate 0.25 J pulse energy (1.5 J demo’d at LaRC). Derated to extend lifetime & conserve power 120 shots per LOS wind profile (12 sec, 78 km) for better sensitivity 20 cm optics to minimize mass, volume, alignment risk Coherent DWL TRL Levels - 2

Doppler Wind Lidar Measurement Geometry t+6.6 ms, 49 m, 6.8 mrad for return light (t+100 ms, 744 m, 103 mrad for second shot) t + 106 s 7.4 km/s 90° fore/aft angle in horiz. plane 30° 984 km FORE AFT 833 km 17 m (86%) 180 ns (27 m) FWHM (76%) 45° 34.4° 492 km 120 shots = 12 s = 78 km 348 km 1/10 s = 658 m 348 km Coherent DWL TRL Levels - 3

Notional Mission Figures of Merit 2.053 mm fundamental laser wavelength 2.053 mm transmitted laser wavelength 0.2 m physical optical diameter 0.03 m2 physical optical area 0.008 J m2 fund. l optical EAP 0.08 W m2 fund. l optical PAP 3.9 W m2 laser electrical PAP 3.9 W m2 laser orbit ave elect PAP 0.25 J fundamental laser pulse energy ~0.25 J transmitted laser pulse energy 10 Hz laser pulse rep freq, PRF 2.5 W fundamental optical power N/A fund to trans conversion efficiency ~2.5 W transmitted optical power 30 J trans opt energy/LOS wind profile 0.9 J m2 trans EAP/LOS wind profile 12 s time interval/ LOS wind profile 2% laser fundamental l WPE 125 W laser electrical power when on 100% laser pulsing duty cycle N/A laser power when not pulsing 125 W laser orbit average electrical power 60 J trans opt energy/horiz wind profile 1.9 J m2 trans EAP/horiz wind profile 118 s time interval/horiz wind profile 350 km horizontal resolution (repeat dis) 2 vector wind profiles/horiz res. 53 s time interval/horiz res. 3250 attempted vector wind profiles/day (~1700 radiosondes/day) (1 hour=3600s radiosonde time/vector profile) Coherent DWL TRL Levels - 4

Notional Tropospheric Winds Mission Vertical Profiles of Horizontal Vector Wind Courtesy: David Emmitt: Coherent detection yields 1-2 m/s HLOS wind accuracy (RMSE) Earth has 5668 target areas (300 x 300 km) 14.2 orbits per day per S/C 52% of target volumes viewed by single S/C in one day, geometry factor (blue area) Lidar success percent ~ 50% near surface, less with increasing altitude (gray area) Enhanced aerosol model, 2 vector wind lines, vertical resolution as shown Repeat every 53 sec = 350 km = horizontal resolution 3250 attempted vector profiles/day (~1700 radiosondes/day) Successful profiles ~ equals radiosonde network near surface, but different global distribution Each profile covers ~ 118s, 2 x {12 s x 80 km x 25 m} Coherent DWL TRL Levels - 5

Requirements vs. Predicted Performance Requirements – Threshold Requirements - Objective Altitude 2 20 km 100% ~12 50% < 2 m/s, 0.5 km < 3 m/s, 1 km < 3 m/s, N/A km Percentage of 300 x 300 km boxes, 24 hr period < 1 m/s, 0.25 km < 2 m/s, 0.5 km < 2 m/s, 2 km 2 20 km ~12 30 km 100% 50% Background Aerosol Enhanced Aerosol Coherent DWL TRL Levels - 6

What Are Technology Readiness Levels (TRLs)? Coherent DWL TRL Levels - 7

TRL Pros and Cons Used by everyone in human quest to express the complex in overly simplistic terms Many common circumstances have no guiding TRL rules for consistency: e.g., if you take a lidar system and fly it successfully on an airplane, are you only up to TRL 4? e.g., if you successfully space qualify a lidar system with thermal/vacuum, vibration, EMI, etc., are you up to TRL 8? e.g., if a side-pumped laser flew successfully in space, but now you want to propose an end-pumped version, what is the TRL? (same for bandwidth, beam quality, stability, cooling technique, etc.) e.g., if a laser flew successfully in space for a 1-year mission, but now you want to proposed a 3-year mission, what is the TRL? e.g., if another agency/country/group of people has a successful space mission, can you take credit for TRL 9 with no guaranteed mechanism to transfer the knowledge to your mission team? Coherent DWL TRL Levels - 8

Space Coherent Doppler Lidar: TRL Levels Technology TRL Now TRL After IIP Completion Comments Pulsed 2 Micron Laser 3-4 4 except lifetime = 3 Pulsed Laser Energy & PRF: 0.25J, 10 Hz 4 Same Demonstrated 1 J (1.5 J double pulse) & 10 Hz1 Pulsed Laser Efficiency: 2% WPE Efficiency demonstrated except for space environment. CALIPSO demo’s power supply effciency Pulsed Laser Beam Quality: ?? Beam quality of 1.2 demonstrated in earlier version of laser Pulsed Laser Packaging: compact, rugged 3 Technology compatible with compact, rugged packaging Pulsed Laser Conductively Cooled Laser Risk Reduction Program is working on this technology Pulsed Laser Pump Laser Diodes 5 Laser Risk Reduction Program is working on this technology2, not IIP Pulsed Laser Lifetime: 3 years Laser Risk Reduction Program is working on this issue, not IIP CW Tunable LO Laser, Crystal Laser 5-6 (JPL working on semiconductor version) CW LO Laser Power: 25 mW 100, 250, & 850 mW delivered by CTI.3 Space tests during SPARCLE CW LO Laser Tuning Range: ±6 GHz Demonstrated ±12.5 GHz by CTI (3/00); demonstrated offset locking to ±10 GHz3 CW LO Laser Linewidth: 0.1 MHz CTI demonstrated < 15 kHz over 4 ms3 Simultaneous Simultaneous Coherent DWL TRL Levels - 9

Space Coherent Doppler Lidar: TRL Levels Technology TRL Now TRL After IIP Completion Comments Detector, 2-Micron, Room Temperature 5 Same Detector Quantum Efficiency at IF Frequency: 80% Demonstrated 80% in VALIDAR3 Detector Bandwidth: 500 MHz Demonstrated 1 GHz in VALIDAR4, 2.4 GHz by UAH Detector Active Area: 75 micron dia. Demonstrated 75 microns diameter in VALIDAR4 Telescope 4 Telescope Diameter: 20 cm 23 cm telescope fabricated during SPARCLE, delivered 11/96 Telescope Wavefront Quality: l/18, RMS, 2 micron, double pass Demonstrated during SPARCLE Telescope Volume: 30 x 34 x 27 cm3 Scanner, Conical, Step-Stare 2-7 Scanner Wedge: 20 cm Fabricated during SPARCLE, 28 cm, 30 deg, 11.5 lbs Scanner Motor: 20 cm Fabricated during SPARCLE by BEI, 23 cm, 36 lbs, available for space? Simultaneous Simultaneous Coherent DWL TRL Levels - 10

Space Coherent Doppler Lidar: TRL Levels Technology TRL Now TRL After IIP Completion Comments Momentum Compensation of Step-Stare Scanner 2-7 Same Addressed briefly by IMDC, 2/02. Previous space missions? Pointing 1. Pre-Shot Pointing Control: ±2 degrees 7 Put Doppler shift within LO tuning range. (GLAS = 145 microradians) 2. Pre-Shot Nadir & Azimuth Pointing Knowedge Error: ±0.2 degrees Depends on azimuth angle and allowed receiver capture bandwidth. Previous space missions? 3. Transmitter/Receiver Misalignment, for 7 ms after each shot: ±8 microradians (~2 microradians/ms) 3? Yields budgeted average SNR loss of 3 dB, combination of instrument and spacecraft. Design - SPARCLE 4. Pointing Stability During Shot Accumulation: ±0.2 degrees/12 sec (~ 0.03 deg/sec) Yields budgeted 0.3 m/s contribution to error. Depends on azimuth angle. Depends on horiz. wind magnitude/dir. (Hubble = 0.05 microrad/24 hrs) 5. Final Nadir & Azimuth Pointing Angle Knowledge Error: ±65 microradians 5 Yields 0.3 m/s contribution to error. Depends on azimuth angles. GLAS demonstration – dedicated spacecraft. Ground return demo’d by SWA/LAHDSSA using TODWL - must scan to work. (GLAS = 7 microradians) Lidar Autonomous Operation 2-5 CTI has coherent Doppler lidars operating autonomously at 2 airports. NASA does not have this capability Pre-Launch Lidar Photon Sensitivity Validation 3 A method was formulated during SPARCLE, but not implemented Coherent DWL TRL Levels - 11 Applies to both coherent and direct detection Doppler wind lidar

Space Coherent Doppler Lidar: TRL Levels Technology TRL Now TRL After IIP Completion Comments Compensation Optics for Nadir Angle Tipping During Round Trip Time of Light Optional? 2 7 microrad. tipping for 833 km orbit. Static compensation? Slaved to scanner position? Array Heterodyne Detector for Alignment Maintenance. Optional? Same Some work done by Rod Frehlich at Univ. of CO. Lidar Survives Radiation Environment Medium effort under LRRP Lidar Survives Contamination Optional: Balanced heterodyne receiver 5 Demonstrated in VALIDAR Optional: Integrated monolithic heterodyne receiver 3 Low funded effort under LRRP at LaRC Optional: Multiwavelength lidar scanner: 1.5 m direct, 0.2 m coherent: HOE SHADOE Geary Schwemmer, GSFC Optional: Semiconductor Version Of Tunable LO Laser Being developed at JPL, Kamjou Mansour Space Integrated GPS/INS (SIGI). Optional? 8 Purchased during SPARCLE, available for use Optional: Ground and Airborne Measurement Validation Fleet ? May “roughly” prove orbiting sensor works, but will not prove velocity error or spatial resolution is satisfactory. Coherent DWL TRL Levels - 12

Conclusions TRL’s don’t cover all circumstances TRL’s are often used in an overly simplistic way It is helpful to do a comprehensive TRL analysis The TRL scores will vary with who is assumed to implement the mission The gap to close for the notional mission is narrowing Are there any suggested changes to the TRL’s shown here? Coherent DWL TRL Levels - 13

Back Up Charts Coherent DWL TRL Levels - 14

Current Wind Observations ~23.4 km Global averages If 2 measurements in a box, pick best one Emphasis on wind profiles vs. height Courtesy Dr. G. David Emmitt Coherent DWL TRL Levels - 15

Supporting References S. Chen, J. Yu, M. Petros, Y. Bai, B. C. Trieu, M. J. Kavaya, and U. N. Singh, “One-Joule Double-pulsed Ho:Tm:LuLF Master-Oscillator-Power-Amplifier (MOPA),” Advanced Solid State Photonics 20th Anniversary Topical Meeting in Vienna, Austria (Feb. 6-9, 2005) F. Amzajerdian, B. L. Meadows, U. N. Singh, M. J. Kavaya, N. R. Baker, and R. S. Baggott, “Advancement of High Power Quasi-CW Laser Diode Arrays For Space-based Laser Instruments,” Proc. SPIE 5659, p. N/A, Fourth International Asia-Pacific Environmental Remote Sensing Symposium, Conference on Lidar Remote Sensing for Industry and Environmental Monitoring AE102, Honolulu, HI (8-12 Nov 2004) C. P. Hale, J. W. Hobbs, and P. Gatt, “Broadly Tunable Master/Local Oscillator Lasers for Advanced Laser Radar Applications,” paper 5086-25, SPIE AeroSense 2003, Orlando, FL (21-25 April 2003) G. J. Koch, M. Petros, B. W. Barnes, J. Y Beyon, F. Amzajerdian, J. Yu, M. J. Kavaya, and U. N. Singh, “Validar: a testbed for advanced 2-micron Doppler lidar,” Proc. SPIE 5412, Laser Radar Technology and Applications IX (12-16 April 2004) Coherent DWL TRL Levels - 16