Supporting NOAA and NASA high-performance space-based DWL measurement objectives with a minimum cost, mass, power, and risk approach employing Optical

Supporting NOAA and NASA high-performance space-based DWL measurement objectives with a minimum cost, mass, power, and risk

approach employing Optical Autocovariance Wind Lidar (OAWL)

Christian J. Grund, Mike Lieber, Bob Pierce, Michelle Stephens, Amnon Talmor, and Carl Weimer

Ball Aerospace & Technologies Corp (BATC)

February 6, 2008

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BATC Objectives and Rationales

OAWL, OA-HSRL─ To offer broadened trade space for wind and aerosol profiling technologies addressing NOAA and NASA goals as

outlined in the NRC Decadal Survey (3D-winds, ACE, and GACM missions)─ OA approach saves mass, cost, volume, complexity, number of lasers, technical risk (e.g. can reuse

CALIPSO/MOLA/GLAS telescope design), and mission performance risk (in conjunction with an etalon receiver) Why is Ball investing in new receiver technology?

─ We believe this is an enabling approach to achieve a space mission─ Target NASA missions start in 2012 (aerosols), but the decisions for the final 3D-wind technology will probably occur in

2010 time frame. Time is now to demonstrate viability of alternatives.─ Belief: Cost, weight, power, complexity, and performance issues of current baseline need addressing.─ Community vetting and acceptance: OAWL is new, but other technologies have 15-30+ year history.

2006 internal investment Built proof of concept OAWL system and demonstrated atmospheric windReferences: Grund, ” Lidar Wind Profiling from Geostationary Orbit using Imaging Optical Autocovariance Interferometry”, WG on space-based lidar winds 7/2007, Snowmass,

COGrund, et al, “Optical Autocovariance Wind Lidar and Performance from LEO”, 7/2007 Coherent Laser Radar Conference, Snowmass, CO.

2007 internal investment Designed and modeled an achromatic, field-widened, high-resolution interferometer (1m OPD), suitable for autonomous

aircraft operation - successfully completed─ Prove OA HSRL with Proof of Concept (POC) hardware, in progress

Built comprehensive space-based OAWL radiometric performance modeling capability

2008 internal investment Fabrication of the robust, multi-wavelength OA receiver design

OAWL: Optical Autocovariance Wind Lidar - Doppler wind profilesOA-HSRL: Optical Autocovariance-High Spectral Resolution Lidar - Calibrated Aerosol Profiles

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OAWL Combines/Augments the Best Traits of Both Coherent and Incoherent Lidar Methods

Yes

Yes

Yes (UV laser)

Yes (Simple ROIC)

Maybe / Yes

Maybe

Yes (UV laser)

Yes (Difficult ROIC)

No

Some

No (IR laser)

N/A

Multi-mission Compatibilities

HSRL (calibrated aerosols/clouds)

DIAL (chemical species)

Raman (Chemical species, T, P)

Photon counting potential (GEO??)

Yes

Maybe

YesYes (integrated with etalons)

Yes / Yes

Yes

No

Maybe

Yes

No

Yes

No

Phenomenology

Measure Aerosol

Measure Molecular

Independent of Aer / Mol mixing ratio

Full precision 0-20 km profile

Yes

4 (time independent)

Yes

Yes

Yes

~4 / 15 CCD accum.

Yes

No,Maybe

No

1

No

No

Receiver

Does not need a stable reference laser

Detector elements per profile

Single multi-speckle averaging/shot

Eliminates orbital velocity correction hardware

Single/hopping OK

Yes

Single, -stable

No

Single/stable

No

Transmitter

Laser Mode

Free of absolute optical frequency lock

Direct Detection OAWL

Direct DetectionEtalons (edge/image)

Coherent Detection

Challenges

Green=positive, Red=negative, yellow=qualified Ball Aerospace & Technologies

2007 Phase 3:Design a Robust , Field-widened, Achromatic

Receiver Suitable for Airborne Testing

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Proof of Concept (POC) OAWL System Demonstrated 1 m/s Precision in Atmospheric Tests

3-Beam Interferometer

Assembly

3 Detector Assembly

Laser Transmitter Assembly

Laser Controller

Alignment Camera and Monitor

PC Data System

COTS Newtonian Receiver Telescope

0-Range, 0-Velocity Sampling Assembly

Receiver Field Stop

Channel Splitting Mirror

Stepped Mirror

Field Stop

Interferometer

Detector/ Amp 2

Detector/ Amp 3

Detector/ Amp 1

Windows PC-based Data System

(Labview) 6” dia., f/8 Newtonian Telescope

Display

3-D Sonic Anemometer

Separator Mirror

Beam Sample

Interferometer quality

Pulse Laser 100 J/pulse,

1 kHz rate

Beam Expander

IM1

IM2

Transmitter

3 physical steps

Ball Aerospace & Technologies patents pending

Demonstrated: ~1m/s precision with 0.3 s averaging and 3m range resolution in atmospheric tests at 60 m, agreeing with model predictions

POC Limitations:• Rooftop range safety limited to 100m• Low power COTS laser limits range• 50% light measured by 3 detectors: simple for POC, but not efficient• Hard to calibrate due to specific 0-phase sampling implementation

Red: OAWL (L); Anemometer-OA cross correlation (R)White: sonic anemometer (L); anemometer autocorrelation (R)Blue: cross correlation for pure Gaussian noise distributions

Brassboard system: 3 parallel interferometer architecture:

Overview of Previous Work

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New OAWL Design Uses Polarization Phase Delays and Multiplexing to Implement 4-Phase-Delay Interferometers with the Same Optical

Path

• 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 (ALADIN needs ~5 R alignment,Coherent requires telescope and <3.8Ralignment (3dB loss))

• Receiver is achromatic, allowing simultaneous multi- operations (multi-mission capable: Winds + HSRL(aerosols) + DIAL(chemistry))

• Very forgiving of telescope wavefront distortion saving cost, mass, enabling HOE optics for high resolution aerosol measurement

• 2 inputs allowing easy calibration

Ball Aerospace & Technologies patents pending

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Solid Model of Receiver (detector module covers removed)

- All aluminum construction minimizes T, cost - Athermal interferometer design

- Factory-set operational alignment for autonomous aircraft operation - ≈100% opt. eff. to detector

- multi- winds, plus HSRL and depolarization for aerosol characterization and ice/water cloud discrimination

Detectors:1 532nm depolarization1 355nm depolarization4 532nm winds/HSRL4 355nm winds/HSRL10 Total

CDR complete Dec. ‘07

Ball Aerospace & Technologies

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NASTRAN FEA Evaluation Suggests Interferometer is Robust to WB-57 Vibe Environment

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EOSyM Representation of the OA Receiver System

Coupled disturbance/ structure/ optics model built up inside EOSyM (End-to-end Optical System Model) environment.

Time simulation and frequency domain cross-checking for vibration results. Seismic mass input of disturbances in 3 directions. Structure outputs 6 optics displacements in 6 DOF to optical model. Optical model ray trace and sensitivity matrices.

Fringes & phase noise


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Integrated Model Process Developed at BATC

Goals:─ <6 nm (0.11 rad

phase error) vibration induced noise), 12 nm accep.

─ <5% visibility reduction due to thermoelastic distortions.

Main system modeling outputs

─ Fringe visibility─ Phase noise

Code V SolidWorks

NASTRAN

Aircraft PSD

6

References:

M. Lieber, C. Weimer, M. Stephens, R. Demara, “Development of a validated end-to-end model for space-based lidar systems”, in SPIE vol 6681, U.N.Singh, Lidar Remote Sensing for Environmental Monitoring VIII, Aug 2007.

M. Lieber, C. Randall, L. Ayari, N. Schneider, T. Holden, S. Osterman, L. Arboneaux, "System verification of the JMEX mission residual motion requirements with integrated modeling", SPIE 5899, Aug 2005.

M. Lieber, C. Noecker, S. Kilston, “Integrated system modeling for evaluating the coronagraph approach to planet detection”, SPIE V4860, Aug 2002


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Example Effect of Vibration and Thermoelastic Structural Distortion

Single pixel detection measures sum of the pupil field intensity (proportional to visibility).

Full transmission,

in phase

Zero transmission, out of phase

E=1 E=0

E=0.72 E=0.28

Visibility constant, but phase varies

Visibility degraded (integral over pupil)

+

Piston due to Doppler signal and vibration

Tilts due to Thermoelastic distortion and misalignment


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Visibility and Phase Noise

Visibility loss means decrease in aerosol velocity measurement optical efficiency, and HSRL aerosol/molecular signal separation.

Phase noise emulates wind-induced phase shift of return signal; unimportant to HSRL

max min

max min

I IV

I I

Pre-flight calibration goal Imax (envelope)

= Visibility = Contrast

Change due to thermoelastic distortion

Change of phase error due to structural vibration during time-of-flight

Flight operating point (slowly drifting)Long period

Short period


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Integrated Model – Design Iteration:Vibration-Induced Phase Noise Convergence on Specification

1 2 3 4 50

0.5

1

1.5

2

2.5

3

3.5

Lo

g O

PD

(n

m)

1900 nm, initial hard mount

40/ 20 nm, 20 Hz isolators added, WC/ nom

8.5/ 6 nm, redesigned structure, WC/ nom

WC = Worst case

Requirement:<1m/s/shot/100 sRandom dynamic error with WB-57 excitation

Final design Prediction Feb. 2008 : 6nm RMS jitter, exceeding spec and meeting goal, suggests performance dominated by SNR not environment

Thermal results: model verifies design is athermal wrt average temperature


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In Progress and Proposed Efforts to Raise TRL to 5,6

2008 Internally Funded Objective: Fabricate OA Receiver Suitable for aircraft flight testing In-Progress

Status: Optical design PDR - complete Sep. 2007 Receiver CDR - complete Dec. 2007 Receiver design /performance modeled - complete Jan. 2008 Major components to fabrication – in progress Feb. 2008 System Assembled/ preliminary testing - planned Aug. 2008

Proposals submitted: NASA ROSES Instrument Incubator Program:

─ PI Grund (Ball), OA winds. Raise TRL for winds from WB-57, complete OA as a system, flight plan to pass over many wind profiler network sites, potential ground lidar near Boulder, land and ocean

─ PI Hostetler (NASA LaRC), OA HSRL. Alternative interferometer approach for multi-wavelength HSRL, data collected could be processed for winds, no special corroborative winds in current plan

LOOKING FOR OTHER INTERESTS and POSSIBILITIES


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FUTURE CRAD-Proposed Implementation for WB-57

6’ Pallet(WB-57 form factor)

Pallet Cover

Custom Pallet-Mounting Frame

Telescope

Custom Window

IRAD-Built Receiver

Laser Source


Practical OA performance from Space

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Comprehensive LEO Performance Model Implemented for Realistic Components

LEO Model Parameters:

Wavelength 355 nm

Pulse Energy 550 mJ

Pulse rate 50 Hz

Receiver diameter 1m (single beam)

LOS angle with vertical 450

Vector crossing angle 900

Horizontal resolution* 70 km (500 shots)

System transmission 0.35

Alignment error 5 R average

(NOTE: ~50 R allowed)

Background bandwidth 35 pm

Orbit altitude 400 km

Vertical resolution 0-2 km, 250m

2-12 km, 500m

12-20 km, 1 km

Phenomenology CALIPSO model

10-8

10-7

10-6

10-5

10-4

0

5

10

15

20

backscatter coefficient at 355 nm m-1 sr-1A

ltitu

de, k

m

aerosol

molecular

Validated CALIPSO Backscatter model used.

Model calculations validated against short range POC measurements.


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OAWL Daytime Space-based Performance OPD 1m, optimized for aerosols

Waveform signal processing and 4-channel architecture implemented

0

2

4

6

8

10

12

14

16

18

20

0.1 1 10 100Projected Horizontal Velocity Precision (m/s)

Alt

itu

de

(km

)

355 nm

532 nm

Demo and Threshold

Objective

“Objective” Margin

“Thres/Demo” Margin

Cloud free LOS


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Evaluating Cloud Impacts on OA Wind Accuracy: 1st Cut

No biases due to aerosol to molecular backscatter mixing ratio clouds induce no velocity biases Sliding range gate feasible independence from range-backscatter weighting errors Every shot 0-referenced no dependence on changes in laser spectrum over shot averaging time Gradual degradation as signals decrease due to opaque cloud fraction or translucent cloud OD:

If ODmargin = ODcloud that degrades velocity precision to the available margin then, for OAWL:─ ODmargin for “objective” performance is ~0.46─ ODmargin for “demo/target” performance is ~0.81

Conclusions: for the OA model assumptions, if the LOS cloud attenuation over profile integration time averages to: OD<0.46, then objective requirements are still met 100% in the PBL OD<0.81, then demo/threshold requirements are still met 100% in the PBL For OD>0.81, performance degrades slowly with effective cloud OD as per above equation

Running an OSSE would be a good next step to include global statistics.

N

i

iRODcloudeN

V

1

),(2 error(R) velocity Ensemble Where N is the number of shots in the profile average,

ODcloud is the optical depth of the cloud in each shot above the altitude of interest, and V is the cloud free velocity error. (might apply to all direct detection lidars if SNR behaves)


Integrated Direct Detection (IDD) Lidarfor Aerosol and Molecular Backscatter Winds

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Aerosol WindsLower atmosphere profile

A Single-laser All Direct Detection Solution: Couple OAWL and Etalon receivers

Integrated Direct Detection (IDD) wind lidar approach: OAWL uses most of the aerosol component, rejects molecular. OAWL HSRL retrieval determines residual aerosol/molecular mixing ratio Etalon backend processes molecular backscatter winds, corrected by HSRL 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 WindsUpper atmosphere profile

1011101100Full

Atmospheric Profile Data


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IDD Receiver vs. ALADIN

ALADIN Approach:

Common Rec/Trans Telescope

355nm Laser

Shutter Fizeau Fringe-Imaging Aerosol Receiver

Double-Edge Etalon

Molecular Receiver

CCD Accumulation

Profiling Detectors

Proposed OAWL/Etalon IDD Approach:

Very small FOV and high receiver /transmitter alignment tolerance are drivenby Fizeau resolution and background light accumulation in detectors. High wavefront quality needed to support small FOV. Precludes HOE scanner/telescope.

QE advantage but signal accumulation precludes per-shot corrections; frequency stability of laser must extend over shot accumulation time.

Receiver Telescope

355nm Laser

Field-widened OAWL Aerosol Receiver

Double-Edge Etalon

Molecular Receiver Per-shot profiling Detectors

Per-shot profiling Detectors

Field-widening supports:• CALIPSO quality telescope • HOE scanner/telescope• Wide rec/trans. alignment tolerance

Shot-resolved detectors support:• Simplified laser• minimized background light• photon-counting, sliding range gate• software-only LOS velocity correction• detector system redundancy


Preliminary Mission Technology Assessment

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Assumptions: Telescope and Scanner

Coherent Detection

Double-Edge Direct

Det.Hybrid

Fringe-Imaging

OADD IntegratedOA+ Double-

edge

Telescope1m, CALIPSO-like 3 7 2 7 7 7

RMS WF (632 nm) 0.3 4 4 4 4 4Mass(kg) ~60 for WF 35 60 35 35 35

TRL 3 7 3 7 7 74 fixed telescopes/optics

Mass(kg) 208 150 208 150 150 150TRL 7 5 7 5 5 5

1.4m mirror+driveMass(kg)/Vol(L) +65 for WF 40 65 40 40 40

TRL 3 3 3 3 3 3HOE Scanner/telescope

TRL not feasible 3(4) NA 3(4) 3(4) 3(4)Mass (kg) not feasible 20 NA 20 20 20

Electrical power(W) not feasible 25 NA 25 25 25

Component

Scanner

WAG’s: Seeking opportunities to work with others on refinementsPerhaps publicizing ISAL’s would be useful


Note: Entries in red are chosen for optimal architecture comparisons

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Assumptions: Laser

Coherent Detection

Double-Edge Direct Det.

HybridFringe-Imaging

OA

Integrated DD

OA+ Double-edge

TRL 3 3 3 3 3 3Injection seeding needed yes maybe yes yes no maybe

Frequency lock yes maybe yes yes no maybeComplexity high low-med high med low low-med

number of SS lasers 4 2-4 6-8 2-4 2 2-4Mass(kg) 15 25 40 25 25 25

Electrical Power

360* (2 m) (10Hz,0.25J,WPE:1.4%)

1100* (355nm)(50Hz, 0.55J,WPE: 3.2%) 1460 1100 1100 1100

Component

Technology

Laser

WAG’s: Seeking opportunities to work with others on refinementsPerhaps publicizing ISAL’s would be helpful

* Laser performance based on Azita Valinia “Discussion of DWL Airborne Campaigns” on the LWG site


Note: Entries in red are chosen for optimal architecture comparisons

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Assumptions: Receiver and Misc, Overall Risks

Coherent Detection

Double-Edge Direct

Det.Hybrid

Fringe-Imaging

OA

Integrated DD

OA+ Double-edge

TRL 4 4(5) 4(5) 4 3(4,5) 3(4,5)mass(kg) 15 10 30 15 15 25

power (W) 30 15 45 20 15 25Calibration complexity low low low high low low

OtherStructure Mass(kg) 20 20 40 20 20 25

Overall RisksCost risk high low high med med low*

Schedule risk med low med low low low*Technical risk med low med med med low*

Component

Technology

Receiver(+data system)

WAG’s: Seeking opportunities to work with others on refinementsPerhaps publicizing ISAL’s would be useful

*presumes OA receiver under construction performs as expected


Notes: Entries in red are chosen for optimal architecture comparisons.

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Assumptions: Optimal Architecture Comparisons

Note: 2 complete transmitters assumed, no receiver redundancy

Possibly unnecessary

Hybrid

InjectionLaser

TransmiterLaser (2m)

InjectionLaser

TransmiterLaser (355 nm)

Double-edgeEtalon receiver

4 Fixed-pointing Telescopes

0.5m, 0.25 waves

Coherent receiver T/R

Commutator

355

nm

/ 2

m

Bea

m C

om

bin

er

Integrated DD (IDD)Injection

LaserTransmitter

Laser (355 nm)

Double-edgeEtalon receiver

1 HOE Telescope/Scanner1m, 355nm, 2 wavesOAWL

receiver

Fringe Imaging DDInjection

LaserTransmitter

Laser (355 nm)

Fringe-ImagingEtalon receiver

1 HOE Telescope/Scanner1m, 355nm, 2 waves


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Mass, Power, Risk, Relative Cost Comparison

Fringe-Imaging Only

Hybrid (Coherent,Fringe Image or Double-Edge)

Integrated DD OA+ Double-

edge

Relative Mass** 0.31 1 0.33Relative Power 0.78 1 0.78Relative Volume 0.7 1 0.75Relative cost 0.5 1 0.5Technology risk 0.8 1 0.8Cost risk 0.5 1 0.5Schedule risk 0.8 1 0.8Performance risk 1.5 1 1Mission Risk 1.2 1 0.8

Criteria

Best System PerformanceOAWL risk reducers vs. Fringe Imaging:

• 4 Separate detectors redundancy (2 min)

• IDD: separate aerosol and molecular receivers

• immune to loss of laser frequency control

• shot-shot correction immune to spectral shape

• high sensitivity to aerosol when present without needing correction

OAWL risk reducers vs. Coherent:• Laser technology readiness (schedule, cost)• Immunity to loss of laser frequency control• Large optics quality requirements (cost, mass)• No hardware correction for spacecraft LOS V required• Can use HOE telescope/scanner (cost, mass, ~power) • Can also provide multi- HSRL (mission cost or technology development cost share?)


**assumes fully redundant lasers

Conclusions and Plans

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Conclusions: OAWL Progress and Plans

• OAWL has achieved TRL 3 with a proof of concept brassboard system that demonstrated atmospheric wind measurements to ~1 m/s, consistent with expectation.

• A comprehensive model predicting space-based OAWL winds and HSRL performance with realistic components has been built and validated by POC measurements and CALIPSO data.

• The space-based model predicts cloudy and cloud free OAWL performance competitive with the coherent detection component of the hybrid without requiring a separate laser and system.

• A robust, achromatic, field-widened OAWL receiver has been designed and evaluated using Ball’s end-to-end integrated modeling capabilities. The integrated model predicts performance exceeding requirements for aircraft testing in the WB-57

• A 355nm/532nm operable, ruggedized, field-widened OAWL receiver suitable for flexible lidar system integration and high altitude aircraft testing is under construction (planned completion ~Sept. ’08) – we are actively seeking partnerships and funding opportunities to rapidly advance the technology to TRL 5-6.

• IIP proposals submitted for integration and airborne testing and validation of a full OAWL lidar and separately, for an OA-HSRL demonstration (winds testing not supported at this time). If successful, the proposed efforts will bring OA to TRL-5, and support shake and bake receiver testing as well.

• OAWL winds from GEO developments will continue in 2008 with realistic scenario modeling including full geometry.


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Conclusions: Space-based Lidar Winds Architecture

Given:• A clear-air profiling capability is a necessity for meeting 3D-winds availability, requiring:

Rayleigh molecular backscatter measurement with a short wavelength laser a powerful laser transmitter operating in the visible to near UV at a minimum

• 3D-winds precision in the lower atmosphere requires aerosol backscatter measurement

Then:• An OAWL and double-edge Integrated Direct Detection (IDD) wind lidar architecture can meet or exceed hybrid performance with a single laser transmitter while reducing mission cost by ~50%, mass by ~67%, and power by ~22%, and at reduced schedule, cost, and performance risks.

• An OA receiver is potentially suitable for multiple missions specified in the Decadal Survey, offering multiple cost sharing opportunities


Documents

Supporting NOAA and NASA high-performance space-based DWL measurement objectives with a minimum cost, mass, power, and risk approach employing Optical