OAWL System Development Status C.J. Grund, J. Howell, M. Ostaszewski, and R. Pierce Ball Aerospace & Technologies Corp. (BATC), 1600 Commerce St. Boulder, CO Working Group on Space-based Lidar Winds Wintergreen, VA June 17, 2009 Agility to Innovate, Strength to Deliver Ball Aerospace & Technologies Corp.

Page_2 Acknowledgements The Ball OAWL Development Team: Jim Howell – Systems Engineer, Aircraft lidar specialist, field work specialist Miro Ostaszewski – Mechanical Engineering Dina Demara – Software Engineering Michelle Stephens – Signal Processing, algorithms Mike Lieber – Integrated system modeling Kelly Kanizay – Electronics Engineering Chris Grund – PI system architecture, science/systems/algorithm guidance Carl Weimer – Space Lidar Consultant OAWL Lidar system development and flight demo supported by NASA ESTO IIP grant: IIP OAWL: Optical Autocovariance Wind Lidar Ball Aerospace & Technologies

Page_3 Aerosol Winds  Lower atmosphere profile Addressing the Decadal Survey 3D-Winds Mission with An Efficient Single-laser All Direct Detection Solution Integrated Direct Detection (IDD) wind lidar approach:  Etalon (double-edge) uses the molecular component, but largely reflects the aerosol.  OAWL measures the aerosol Doppler shift with high precision; etalon removes molecular backscatter reducing shot noise  OAWL HSRL retrieval determines residual aerosol/molecular mixing ratio in etalon receiver, improving molecular precision  Result: ─ single-laser transmitter, single wavelength system ─ single simple, low power and mass signal processor ─ full atmospheric profile using aerosol and molecular backscatter signals Ball Aerospace patents pending Telescope UV Laser Combined Signal Processing HSRL  Aer/mol mixing ratio OAWL Aerosol Receiver Etalon Molecular Receiver Molecular Winds  Upper atmosphere profile Full Atmospheric Profile Data Ball Aerospace & Technologies

Page_4 Purpose for OAWL Development and Demonstration  OAWL is a potential enabler for reducing mission cost and schedule ─Similar to 2-  m coherent Doppler aerosol wind precision, but requires no additional laser ─Accuracy not sensitive to aerosol/molecular backscatter mixing ratio ─Tolerance to wavefront error allows heritage telescope reuse and reasonable optics quality ─Compatible with single wavelength holographic scanner allowing adaptive targeting if there is need ─Wide potential field of view allows relaxed tolerance alignments similar to CALIPSO ─Minimal laser frequency stability requirements ─LOS spacecraft velocity correction without needing active laser tuning  Opens up multiple mission possibilities including multi- HSRL, DIAL compatibility  Challenges met by Ball approach ─ Elimination of control loops while achieving 10 9 spectral resolution ─ Thermally and mechanically stable, meter-class OPD, compact interferometer ─ High optical efficiency ─ Simultaneous high spectral resolution and large area*solid angle acceptance providing practical system operational tolerances with large collection optics Ball Aerospace & Technologies

Page_5 Optical Autocovariance Wind Lidar (OAWL) Development Program  Internal investment to develop the OAWL theory and implementable flight-path architecture and processes, performance model, perform proof of concept experiments, and design and construct a flight path receiver prototype.  NASA IIP: take OAWL receiver as input at TRL-3, build into a robust lidar system, fly validations on the WB-57, exit at TRL-5. Ball Aerospace & Technologies

Page_6 Ball Flight-path, Multi-wavelength, Field-widened OA Receiver IRAD Status Ball Aerospace & Technologies

Page_7 OAWL Receiver IRAD Objectives  Develop and implement a practical flight-path OAWL receiver with minimal calibration requirements and free of active spectral control systems, suitable for aircraft operation  Develop/implement an OA receiver suitable for simultaneous multi-  winds and HSRL  Develop/demonstrate permanent, flight-compatible, stable high precision interferometric optical alignment and mounting methods and processes  Develop appropriate radiometric and system integrated models suitable for predicting OAWL airborne and space-based performance Ball Aerospace & Technologies

Page_8 OAWL IRAD Receiver Design Uses Polarization Multiplexing to Create 4 Perfectly Tracking Interferometers Mach-Zehnder-like interferometer allows 100% light detection on 4 detectors Cat’s-eyes field-widen and preserve interference parity allowing wide alignment tolerance, practical simple telescope optics Receiver is achromatic, facilitating simultaneous multi- operations (multi-mission capable: Winds + HSRL(aerosols) + DIAL(chemistry)) Very forgiving of telescope wavefront distortion saving cost, mass, enabling HOE optics for scanning and aerosol measurement 2 input ports facilitating 0-calibration Ball Aerospace & Technologies patents pending

Page_9 What’s So Special About the Cat’s-eye Interferometer? Ball Aerospace & Technologies  Allows use of heritage telescope designs (e.g. Calipso) for space system - cost, mass, risk ─ highly tolerance to wavefront errors ─ Very large field of view (>>4mR) capable while maintaining high spectral resolution (~10 9, similar to coherent detection systems)  Allows use of Holographic Optical Element beam directors and scanners even for high resolution aerosol 355nm wind measurements - cost, mass, pointing agility (other missions?)  Relaxes receiver/transmitter alignment tolerances - cost, performance risk ─ Practical on-orbit thermal tolerances ─ Enables single material athermal interferometer design  Enables wind and multi- aerosol missions with common transmitter and receiver - cost, sched. ─ Simultaneous multi-wavelength capable interferometer suitable for HSRL and winds  Enables very high resolution passive and active imaging interferometry – potential for new earth and planetary science instruments with enhanced performance

Page_10 OAWL Receiver A few simple components Detector housings Monolithic interferometer Covers and base plate mount to a monolithic base structure. Detector amplifiers and thermal controls are housed inside the receiver. Ball Aerospace & Technologies

Page_11 OAWL Receiver In Assembly 10 9 Class Spectral Resolution Without Active Stabilization Flowtron stand will also be used to hold the complete lidar system rotated to point up for ground testing Ball Aerospace & Technologies Interferometric stability tests in progress

Page_12 Cat’s Eye Interferometer : Successful Primary Mirror Bond Tests Current (Final) Bond Test (PhaseCam image) Reference Test Mirror 1/4 Wave 633 nm difference Start: 24°C Middle: 41°C End: 23°C Thermal Tilt Test Recovery Reference Test Mirror Ball Aerospace & Technologies Reference mirror Test mirror Achieving 10 9 spectral resolution without active control systems is feasible!

Page_13 Receiver Development: Schedule Impacts and Status  Vendor could not deliver aluminum interferometer mirrors with promised wavefront precision. ─ Solution: new fused silica mirrors produced; bonded to aluminum holders. ─ Status: Resolved. Optics: good; Interferometric optic bond to aluminum: good ─ Impacts: 3 month delay for optics; athermalization less but OK since IIP system operates at the same fixed temperature used during alignment (30-35 C)  Vendor could not deliver cube beamsplitters to promised specs WRT splitting ratio and wavefront quality at 355nm. ─ Solution: cube beamsplitters replaced by plates; structure/holders modified to accommodate ─ Status: Resolved. Optics: good; structure/holders modified ─ Impacts: 5 month delay for optics and mods  Excess shrinkage during cure, and insufficient thermal stability of interferometric potting ─ Solution: experiment with lower cure shrinkage materials, improved application process ─ Status: Resolved, test results: good. Final optic will have 10 nm level compensation for any residuals from all other components. ─ Impacts: 3.5 months of spiral development Ball Aerospace & Technologies

Page_14 OAWL IRAD Receiver Development Status Receiver Status (Ball internal funding):  Optical design PDRcompleteSep  Receiver CDRcomplete Dec  Receiver performance modeled complete Jan  Designcomplete Mar  COTS Optics procurementcomplete Apr  Major component fabrication complete Jun (IIP begins Jul. 2008)  Custom optics procurementvendor issues Aug ─ Custom optics procurementcomplete Dec ─ Accommodating rework completeJan  Interferometric optics/mount bonding completeFeb  Interferometric alignment bond testsshrinkage / thermal issuesFeb ─ New materials/process/mount designcompleteMay, 2009  Assembly and Alignmentin progress Late Jun  Preliminary testing scheduled Jul  Delivery to IIPscheduled Late Jul 2009 Ball Aerospace & Technologies

Page_15 OAWL System NASA-funded IIP Ball Aerospace & Technologies

Page_16 OAWL IIP Objectives  Demonstrate OAWL wind profiling performance of a system designed to be directly scalable to a space-based direct detection DWL (i.e. to a system with a meter-class telescope 0.5J, 50 Hz laser, 0.5 m/s precision, with 250m resolution).  Raise TRL of OAWL technology to 5 through high altitude aircraft flight demonstrations.  Validate radiometric performance model as risk reduction for a flight design.  Demonstrate the robustness of the OAWL receiver fabrication and alignment methods against aircraft flight thermal and vibration environments.  Validate the integrated system model as risk reduction for a flight design.  Provide a technology roadmap to TRL7 Ball Aerospace & Technologies

Page_17 OAWL IIP Development Process Provide IRAD-developed receiver to IIP: Functional demonstrator for OAWL flight path receiver design principles and assembly processes. (entry TRL 3) Shake & Bake Receiver: Validate system design and test for airborne environment Integrate the OAWL receiver into a lidar system: add laser, telescope, frame, data system, isolation, and autonomous control software in an environmental box Validate Concept, Design, and Wind Precision Performance Models from the NASA WB-57 aircraft (exit TRL 5) Ball Aerospace & Technologies

Page_18 OAWL Validation Field Experiments Plan 1. Ground-based-looking up Side-by-side with the NOAA High Resolution Doppler Lidar (HRDL) 2. Airborne OAWL vs. Ground- based Wind Profilers and HRDL (15 km altitude looking down along 45° slant path (to inside of turns). Many meteorological and cloud conditions over land and water) Ball Aerospace & Technologies Jan 2010 Fall 2010 NOAA HRDL 2  m Coherent Doppler Lidar OAWL System Leg 1 Leg 2 Multipass ** Wind profilers in NOAA operational network Platteville, CO Boulder, CO Houston, TX

Page_19 OAWL IIP System Arrangement in WB-57 Pallet Ball Aerospace & Technologies Laser Power Supply Pallet Frame Custom Double Window Laser Wire Rope Vibration Isolators Lifting Hooks Telescope Primary Mirror Sub-Bench with Depolarization Detector Receiver Telescope Secondary Mirror Chiller Optic Bench Thermal Control Isolation Data Acquisition Unit Power Condition Unit Electronics Rack

Page_20 OAWL Optical System Interferometer Detectors (10) Telescope Laser Zero-Time/OACF Phase Pulse Pre- Filter Ball Aerospace & Technologies

Page_21 IIP Optical System Exploded View Ball Aerospace & Technologies Top Pallet Cover Pallet Base with Window OAWL Optical System Thermal Control Insulation Panels Electronics Rack

Page_22 Data System Overview  Data system architecture ─ Based on National Instruments PXI Chassis ─ Utilizes mostly COTS Hardware ─ Custom (Ball) ADC daughter card on NI FPGA interface card ─ Custom (Ball) FPGA code to implement photon counting channels on NI card ─ Labview code development environment  Challenges & Solutions ─ Reduced air pressure at altitude degrades heat removal ability of stock cooling fans  Upgrade cooling fans, add fans as needed  Test system in altitude chamber ─ Jacket material used in COTS cables is PVC, which is not permitted on WB-57  Utilizing NI terminal strip accessories where possible  Fabricating custom cables made from allowable jacket materials Ball Aerospace & Technologies

Page_23 Taking an OAWL Lidar System Through TRL 5 NASA/ESTO Funded IIP Plan:  Program start, TRL 3 complete Jul. 2008TRL-3  IRAD receiver delivered to IIPplannedJul  Receiver shake and bake (WB-57 level)planned Aug  System PDR/CDR complete Feb./Mar  Lidar system design/fab/integration complete May 2009  Ground validations completedplannedMar. 2010TRL-4  Airborne validations complete (TRL-5)plannedDec. 2010TRL-5  Receiver shake and bake 2 (launch level)plannedApr  tech road mapping (through TRL7) plannedMay 2011  IIP Complete plannedJune 2011 Ball Aerospace & Technologies

Page_24 Conclusions  All vendor component performance and flight-path process related issues have been overcome for the multi- (355nm, 532nm), field-widened, flight- path receiver.  The receiver is expected to be available to the IIP this August. Late delivery causes slightly delays in ground tests but airborne tests still on schedule.  IIP system development progress:  Optical and mechanical design complete; CDR complete, major procurements underway and fabrication has started.  Aircraft plans in place and flight conops understood.  Ground validation plans in progress  Ground testing moved from December 2009 to in late January  WB-57 flight tests remain on track for Fall 2010 (TRL 5) Ball Aerospace & Technologies

Backups

Page_26 Optical Autocovariance lidar (OAL) approach - Theory  No moving parts / Not fringe imaging  Allows Frequency hopping w/o re-tuning  Simultaneous multi-  operation Optical Autocovariance Wind Lidar (OAWL): Velocity from OACF Phase: V = *  * c / (4 * (OPD)) OA- High Spectral Resolution Lidar (OA-HSRL): A = S a * C aA + S m * C mA,  = S a * C a  + S m * C m   Yields: Volume extinction cross section, Backscatter phase function, Volume Backscatter Cross section, from OACF Amplitude Pulse Laser d 2 d 1 Detector Data System CH 1 CH 3 CH 2 From Atmosphere Phase Delay mirror Beam Splitter Receiver Telescope Prefilter OPD=d 2 -d 1 Simplest OAL (Not the IIP config) Frequency Ball Aerospace & Technologies  = phase shift as fraction of OACF cycle

Page_27 OAWL Optical System Details Pre- Filter Depolarization Detector Module Ball Aerospace & Technologies

Page_28 Ball Space-based OA Radiometric Performance Model – Model Parameters Using : Realistic Components and Atmosphere LEO Parameters WB-57 Parameters Wavelength 355 nm, 532 nm 355 nm, 532 nm Pulse Energy 550 mJ 30 mJ, 20 mJ Pulse rate 50 Hz 200 Hz Receiver diameter1m (single beam) 310 mm LOS angle with vertical ° Vector crossing angle 90 0 single LOS Horizontal resolution* 70 km (500 shots) ~10 km (33 s, 6600 shots) System transmission Alignment error5  R average 15  R Background bandwidth 35 pm 50 pm System altitude400 km top of plot profile Vertical resolution0-2 km, 250m 100m (15m recorded) 2-12 km, 500m km, 1 km Phenomenology CALIPSO model CALIPSO model -scaled validated CALIPSO Backscatter model used. ( -4 molecular, -1.2 aerosol) Model calculations validated against short range POC measurements. Ball Aerospace & Technologies Volume backscatter cross section at 355 nm (m -1 sr -1 ) Altitude (km)

Page_29 OAWL – Space-based Performance: Daytime, OPD 1m, aerosol backscatter component, cloud free LOS Ball Aerospace & Technologies Threshold/Demo Mission Requirements 250 m 500 m 1km Vertical Averaging (Resolution) Objective Mission Requirements

Page_30 Looking Down from the WB-57 (Daytime, 45°, 33s avg, 6600 shots) Ball Aerospace & Technologies