The EO-1 Hyperion Imaging SpectrometerIEEE Aerospace Conference

Jay Pearlman, Carol Segal, Pamela Clancy, Neil Nelson,Peter Jarecke, Momi Ono, Debra Beiso, Lushalan Liao,Karen Yokoyama, and Steve Carman, TRWAndBill Browne, Lawrence Ong and Stephen Ungar, GSFC

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Hyperion Hyperspectral Imager

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Earth Orbiter - 1 Mission

Three revolutionary land imaginginstruments on EO-1 will collectmultispectral and hyperspectralscenes over the course of theEO-1 mission in coordinationwith the Enhanced ThematicMapper (ETM+) on Landsat-7.Detailed comparisons of theEO-1 and ETM+ images will becarried out to validate theseinstruments for follow-on missions.

Breakthrough technologies in lightweight materials, high performanceintegrated detector arrays and precision spectrometers will bedemonstrated in these instruments.

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Hyperion Imaging Spectrometer

Convex Gratingspectrometers with CCDVNIR and HgCdTe SWIRdetectors (60µm pixels)

Multiple calibration options:lamps, lunar, solar, groundimaging and laboratory

Hyperspectral ImagingCapability to addresstechnology and EarthObservation applications

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Advanced Land Imager (ALI)

•Objective is to validatepushbroom technologies forLandsat applications•Pushbroom MultispectralSensor - 9 multispectral (MS)channels and a pan channel•Spectral coverage enhancesLandsat ETM+ but excludesLWIR channel•Swath width is 37km and MSground resolution is 30m.•S/N is 100 or better

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LEISA Atmospheric Corrector

Correction of multispectral surfaceimagery for atmospheric variability(water and aerosols).

High spectral, moderate spatialresolution (250m), large swath(180km) hyperspectral imager usingwedge filter technology

Spectral coverage of 0.89 - 1.6mm,bands selected for optimalcorrection of high spatial resolutionimages.

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EO-1 Instrument Overviews

Parameters ALI HYPERION AC

Spectral Range 0.4 - 2.4 µm 0.4 - 2.5 µm 0.9 - 1.6 µm

Spatial Resolution 30 m 30 m 250 m

Swath Width 36 Km 7.5 Km 185 Km

Spectral Resolution Variable 10 nm 6 nm

Spectral Coverage Discrete Continuous Continuous

Pan Band Resolution 10 m N/A N/A

Total Number of Bands 10 220 256

EO-1

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HSA, HEA and CEA locations on the EO-1 nadir deck

Hyperion Spacecraft Accommodation

HyperionElectronicsAssembly

(HEA)

Hyperion Sensor Assembly(HSA)

CryocoolerElectronicsAssembly

(CEA)

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EO-1 Spacecraft Prepared for Launch

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Hyperion Swath

N

Landsat 7ETM+

EO-1ALI

EO-1Atmospheric

CorrectorEO-1

Hyperion

Swath is 7.5km wide; standard “image cube” is 20km long by 7.5km wide

Hyperspectral and Multispectral SceneCharacterization

Wavelength

Mea

sure

d R

efle

ctan

ce

Band 3

Band 4

Band 2

Band 1

Wavelength

Mea

sure

d R

efle

ctan

ce

Wavelength

Ref

lect

ance

Spectral characteristic of scene

Hyperspectral ImagingHundreds of bands

Multispectral ImagingFew bands

Hyperspectral Imaging Applications & Benefits

Existing SatelliteCapabilities (SPOT,

Application LandSat) Potential for HSI Perceived Benefits

Mining/Geology Land cover classification More Detailed mineral More Accurate remotemineral mapping exploration

Forestry Land cover classification Species ID Forest health/infestationsDetail stand mapping Forest productivity/yieldFoliar chemistry analysisTree stress Forest inventory/harvest

planning

Agriculture Land cover classification Crop differentiation Yield prediction/commoditiesLimited crop mapping Crop stress crop health/vigorSoil mapping

Environmental Resource meeting Chemical/mineral Contaminant MappingManagement Land use monitoring mapping & analysis Vegetation Stress

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Hyperion12 months from order to delivery

Hyperion Hyperspectral Imager

The Hyperion is a push-broom imagerwith:

• 220 10nm bands covering thespectrum from 400nm - 2500nm

• 6% absolute radiometric accuracy• Image swath width of 7.5 km• IFOV of 42.4 microradian• GSD of 30 m at 705 km altitude• 12-bit image data• Power: 51W orbit avg.,

126W peak• Mass: 49kg• On year Life (2 year Goal)

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Hyperion Subassemblies

HyperionElectronicsAssembly (HEA)

CryocoolerElectronicsAssembly(CEA) Hyperion Sensor Assembly (HSA)

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Parameter HyperionVolume (L x W x H, cm) 39x75x66Weight (Kg) 49Avg Power (W) 51Peak Power (W) 126Aperture (cm) 12IFOV (mrad) 0.043Crosstrack FOV (deg) 0.63Wavelength Range (nm) 400 - 2500Spectral Resolution (nm) 10No. Spectral Bands 220Digitization 12Frame Rate (Hz) 225Typical SNR 65 - 130

Hyperion Characteristics

Performance Characterization –Pre-Launch

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Properties Characterized

Radiometric CalibrationFPA Rectilinearity

• Spatial Co-Registration of Spectral Channels• Cross-Track Spectral Alignment

Image Quality• Cross-track and Along-track MTF• Spectral Slit Profile

Spectral ResponseSpectral CalibrationScene SimulationVNIR Noise BifurcationSWIR FPA Dark Field StabilityEcho CorrectionPolarization

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Hyperion Specifications (1)

Specification Item Performance MeasurementsGSD 29.88 mSwath 7.5 km (0.61 degrees TFOV)Spectral coverage VNIR: 400 - 1000nm

SWIR: 900 - 2500nmImaging aperture 12.4968 cm (4.92 in.)VNIR SNR 550 - 700nm 144 - 161SWIR SNR 1000 - 1050nm 90SWIR SNR 1200 - 1250nm 110SWIR SNR 1550 - 1600nm 89SWIR SNR 2100 - 2150nm 40On-Orbit lifeIFOV 42.4 µrad

1 year

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Specification Item Performance MeasurementsVNIR MTF @ 450nm 0.27 - 0.30VNIR MTF @ 630nm 0.27 - 0.31VNIR MTF @ 900nm 0.25 - 0.27SWIR MTF @ 1050nm 0.25 - 0.29SWIR MTF @ 1250nm 0.24 - 0.29SWIR MTF @ 1650nm 0.23 - 0.27SWIR MTF @ 2200nm 0.24 - 0.27Number of spectral channels 220SWIR spectral bandwidth 10.08 -10.09 nmVNIR spectral bandwidth 10.11 - 10.13 nmVNIR Cross-track spectral error 2.8 nm @ 655nm

Hyperion Specifications (2)

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Hyperion Specifications (3)

Specification Item Performance MeasurementsSWIR Cross-track spectralerror (typical)

0.6 nm @ 1700nm

Spatial co-registration of pixel (typical)

VNIR18% pix @ FOV Pix #126

SWIR21% pix @ FOV Pix #131

Absolute radiometricaccuracy (1 sigma) <6%.

12-bitData Quantization

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Hyperion Radiometric Characterization

Lamp Image Relay (Light Pipe)

Monochrometer

SteeringMirror

Off-AxisParabola

FoldMirror

Detector

Off AxisParabolaPrecision

Aperture

Transfer Radiometer or Hyperion

PrecisionPinhole

SpectralonPanel

Two modes of Operation:

1) Pinhole, slit and/or KnifeEdge at end of light pipe putat focus of Off-axis Parabola(OAP)

2) End of light pipe is re-imaged onto Spectralonpanel. Both are shownsimultaneously in chartwithout re-imagingoptics

• Transfer radiometer is removable box for calibration ofsource

• Radiometer uses chopped pyroelectric detector

• Accurate AΩ is calculated from precision apertures andOAP focal length

Steering mirror is a twoaxis, fine pointing mirror( ± 1-2 mrad) for sub-pixelscanning in spatialdimensions

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Spectralon Panel Calibration

0.25 meterSpectrometer Panel

FEL Lamp

VacuumChamber Wall

HyperionInstrument

TransferRadiometer

SiO2 Vacuum Window

Removed for HyperionIllumination

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Spectralon Panel AssemblyInstalled

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Spectralon Panel AssemblyInstalled

Black Panel OverWhite ChamberWall

FEL 1000Watt Lamp

ChamberWindowCovered

Back ofSpectralonPanel

Gold PlatedBaffle

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Calibration Flowchart

Lamp Spectralon

AΩPyroelectricReferenceDetector

Silicon PhotodiodeTrap Detector

ComponentMeasurement Data Analytical Model

Hyperion Instrument Instrument SpectralResponsivity

In-flightCalibration

Source

NIST GoldStandard

Black Body

SolidState

SiliconDiode

Physics

1

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Calibration StandardsTransfers are:1. Silicon Photodiode Trap Detector to

Pyroelectric Reference Detector (PRD) inWatts

2. PRD to Lamp in Irradiance

3. PRD/ AΩ Ω Ω Ω to Spectralon plate in Radiance

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Hyperion SNR

550 nm 650 nm 700 nm 1025 nm 1225 nm 1575 nm 2125 nm161 144 147 90 110 89 40

Hyperion Measured SNR

SNR

0

50

100

150

200

400 700 1000 1300 1600 1900 2200 2500Wavelength (nm)

SNR

MeasuredVNIR ModelSWIR Model

Radiometric performance model basedon 60o Solar zenith angle, 30% albedo,standard scene

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Cross Track Spectral Alignment(CTSA)

4nm wide“Monochromatic”

Source

Monochrometer stepped spectrally in2nm increments

Spat

ial D

irect

ion

Spectral Direction

View of the imageon the focal plane array.

751.0

751.5

752.0

752.5

753.0

753.5

754.0

754.5

755.0

0 50 100 150 200 250 300

Spatial Pixel Number

Pix

el 4

0 W

avel

engt

h [n

m

1314.0

1314.2

1314.4

1314.6

1314.8

1315.0

1315.2

1315.4

1315.6

Pix

el 1

26 W

avel

engt

h [n

m

Pixel 40Pixel 126

Wavelength ∆λ∗ Wavelength ∆λ∗& (Pixel No) [nm] & (Pixel No.) [nm]477nm (13) 3.5 2314nm (27) 0.45655nm (31) 2.8 2012nm (57) 0.17753nm (40) 2.9 1711nm (87) 0.57834nm (48) 3.2 1315nm (126) 0.98924nm (57) 2.7 1013nm (156) 0.45* peak to peak value

VNIR SWIR

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Image Quality - MTFKnife Edge Data

0.000.200.400.600.801.00

-4 -2 0 2 4 6Crosstrack Pixel Location

Nor

mal

ized

Inte

nsity

Point Spread Function (PSF)

0.0

0.20.4

0.60.8

1.0

-6 -4 -2 0 2 4 6

Crosstra ck Pix e l Num be r

System MT F (Fourier Transform of PSF)

0.000.200.400.600.801.001.20

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Spatia l Frequency (1/pixe l)

Nyquist frequency at 1/2

Measured using knife-edge MTFtechnique:

• Knife-edge positioned at imagerelay focus with edgeperpendicular to the slit ofspectrometer

• Knife-edge illuminated withbroadband light source

• Over-sampling by tilting steeringmirror in fractional-pixel steps

• Fourier transform of the PointSpread Function (PSF) producesCross-track MTF (CT-MTF)

• Along-track direction MTFequals of the cross trackvalue π

2

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0.0000.100

0.2000.3000.400

0.5000.600

300 500 700 900 1100

VNIR MeasurementModel calculation (LLS fit with 4 parameters)

Rel

ativ

e S

enso

r Res

pons

e

Spectral Wavelength Calibration

Reflectance Spectra of Doped Spectralon

Spec

tralo

n R

efle

ctiv

ity

0.4

0.6

0.8

1.0

1.2

1.4

1.6

200 400 600 800 1000 1200 1400 1600 1800 2000Wavelength (nm)

Erbium (offset by 0.5)

Holmium

Wavelength (nm)

Process:1. Two data frames taken:

• Doped Spectralon• Un-doped Spectralon

2. Ratio of frames removeslamp source wavelength andsensor response variations

3. High resolution scans areconvolved with sensorspectral response function

4. Linear least squaresregression using secondorder fit in λ versus pixelnumber determines sensorwavelength calibration(accuracy ~ 0.02 pixels)

High resolution scans of Holmium and Erbium Oxide doped Spectralon

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VNIR Spectral Response

VNIR Channel Center Wavelengths (nm, accuracy +/- 0.5 nm)Spectral Channel

FOV #13 31 40 48 57

6 477.4 656.5 753.6 834.3 925.471 478.5 657.5 754.1 834.9 925.1

136 478.0 656.8 753.7 834.4 925.3196 476.8 655.7 752.8 833.4 924.4251 475.2 654.6 751.3 831.9 922.8

VNIR FWHM of Spectral Response Functions (nm)Spectral Channel

FOV #13 31 40 48 57

6 11.2 10.5 10.6 11.1 11.171 11.6 10.4 10.9 11.3 11.3

136 11.3 10.3 10.7 11.3 11.3196 11.4 10.2 10.7 11.4 11.3251 11.3 10.2 10.6 11.3 11.2

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SWIR Spectral Response

SWIR channel Center Wavelengths (nm +/- 0.5 nm)Specral Channel

FOV #27 57 87 126 156

6 2314.1 2012.2 1711.2 1314.3 1013.371 2314.2 2012.1 1711.4 1315.2 1013.2

136 2314.0 2012.2 1711.6 1315.1 1013.2196 2313.9 2012.1 1711.6 1315.1 1013.2251 2313.7 1711.1 1314.2 1012.9

SWIR FWHM of Spectral Response Function (nm)Special Channel

FOV #27 57 87 126 156

6 10.4 10.6 11.6 10.6 10.771 10.5 10.8 11.4 10.6 11.1

136 10.4 10.9 11.8 10.8 11.2196 10.5 11.1 11.6 10.8 11.2251 10.2 11.3 10.6 11.1

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Polarization

Polarizer located justoutside of the vacuumwindow

Data taken at 15 degreesteps in polarization angle

Scene response averagedover spatial channels 171-256 for each spectralchannel

Results are in PercentPolarization

Wav

elen

gth

(nm

)

SWIR Response

0 50 100 150 200 250 300

2200

1800

1400

1000-5-4-3-2-1012345

VNIR Response W

avel

engt

h [n

m]

0 50 100 150 200 250 300 350

500

600

700

800

900

1000-5-4-3-2-1012345

Polarizer Angle [degrees]

%Polarization

%Polarization

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Starburst Image (from End to End Test)

Radiometricallycorrected

Uncorrected Data

Image is created bytranslating a“starburst” patternacross the Hyperionslit simulating satellitemotion.

Starburst pattern usedas an alternativetechnique to assessMTF characteristics

Performance Characterization –On-Orbit -- Preliminary Results

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Spectral Calibration using Internal Calibration System

Examples of absorptionlines of the white paint

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Hyperion Image of Fairfax, VA December2000

Golf Course Turf

Athletic Field

Dormant Trees

Image taken by Hyperion shows the relativechlorophyll content of vegetation in Fairfax County.The spectral profiles indicate healthy grass in theathletic field and golf course. The spectral profile ofthe trees indicates dormant vegetation.

Oxygen in the atmosphere is detected by the spectralprofiles in the near infrared wavelength.

Vegetation

0

0.2

0.4

0.6

0.8

1

500 550 600 650 700 750 800

Wavelength (nm)

Rel

ativ

e In

tens

ity

Athletic Field

Dormant Trees

Golf Course Turf

Oxygen Line

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Verrazano-Narrows Bridge, New York

Noteclearlydefinedshadow ofbridge

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Lake Frome Calibration Site

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Applying Calibration:Repeatability

50 % CompleteSolar Calibration DCEs indicate instrument repeatabilityDuplicate ground images may also be used to verify repeatability based on Top ofAtmosphere Radiance, EX: Mt. Fitton, Saharan

Day 362 Day 362 Day 012Day 012

VNIR: 630 nm 549 nm 487 nm SWIR: 2358 nm 2327 nm 2206 nm

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MTF Examples

Port Eglin Day 359

-10 -5 0 5 100

20

40

60

80

100

120

140

160

180

Interlaced bridge images and curve-fit from band 40

line 220 line 225 line 230 line 235 line 240 Curve-Fit

0 1 2 3 4 50

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

MTF from curve-fit: 0.42164

Direct MTF: 0.388

Direct MTF with window: 0.41676

MTF

Normalized Frequency

Crosstrack MTF calculated from Mid-Bay bridge for band 40

Scene crosstrack MTF: 0.41Ground measurement: 0.34 - 0.44

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MTF Examples

Ross Ice Shelf Day 16, Band 28

Scene In-track MTF: 0.28Ground measurement: 0.22 - 0.27

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Active Illumination with 3 Lamps

On the night of December 10,2000 three Xenon lampsspaced linearly 160 metersapart were directed at EO-1from Edwards AFB. Highclouds were present duringthe test.The spotlight spectrum hassharp lines for spectralcalibration and a broadspectrum for spatialcoregistration.This was very early in theEO-1 mission while pointingwas being established.Spotlights were seen byLandsat-7 and ALI.

Predicted Satellite Irradiance

0.00E+001.00E-072.00E-073.00E-074.00E-075.00E-07

350 850 1350 1850 2350wavelength [nm]

Spec

tral

Irrad

ianc

e [W

/m^2

-m

icro

n]

Landsat-7 PAN image ALI PAN image

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Expanded View of ALI data

134

137

140

143

146

149

152

155

158

161

164

167

170

173

176 5799

5807

0

500

1000

1500

2000

2500

3000

300

* Rad

ianc

e

X

Y

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14 Lamp Active IlluminationConfiguration

The expandedconfiguration allowstesting of MTF, spatialcoregistration, spectralaccuracy, GSD andartifact correction.

Experiment wasscheduled for Jan 10,2000 but had to berescheduled due toweather and pointinguncertainty.• Results should be

available by May 2001

Hyperion Swath Width = 7.68 km

1420.001420.00 1420.00 1420.002000.00

14 SpotlightConfiguration

160.00

160.00

160.00 160.00

5.33 GSD

5.33 GSD

5.33 GSD 5.33 GSD

1 GSD = 30 meters

MTF Array Detail

EnlargementOf 3x3 matrix

Hyperion Data Processing

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Final product:level 1 data,

metadata file attached

Overview: Hyperion Data Flow

L0 Science data

TRWHyperion

processing

Raw or GSFC processed data

TRW functionor product

Level 1 Science data

Shipto GSFC

Ancillary data in engineering units

Science Data: Level 0 or Level 1(radiometrically corrected) dataproducts with VNIR and SWIR dataframes combined. Includes solar,lunar calibrations, earth images, darkand light calibrations

Metadata: Data about the sciencedata. Information to support higherlevel processing, e.g., pre-flightcharacterization data

Ancillary Data: Supporting dataderived from spacecraft telemetryduring image collection

GSFC

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X-bandScience

Data

Hyperion Data Flow

• Level-1 ALI & AC Processing

• Science Data Archive• Data Distribution• Image Assessment• Calibration

EO-1 ScienceValidation

Facility

HyperionSupport

• Process to level 1 data• Performance monitoring

Mission Operations Center (MOC)

Data Processing System (DPS)

Tape Handling and Data

Distribution

Mission PlanningOffice

TRW

GSFC

GSFC

GSFC

Long TermArchive?