prism, avnir-2, palsar · panchromatic remote-sensing instrument for stereo mapping three...

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PRISM, AVNIR-2, PALSAR- ALOS’s Major Mission Instruments -

at ALOS Symposiumon

27 March 2001

Yuji OsawaAssociate Senior Engineer

ALOS Project Team

NASDA

Y.Osawa, NASDA/ALOS, 27 March 2001 2

OUTLINE

Ø Heritage of Japanese Earth Observation Instruments

Ø Overview and Characteristics of Three Mission InstrumentsØPRISMØAVNIR-2ØPALSAR

Ø Current Status of Sensors

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Japanese Earth Obs. Satellite Series

Marine/ Atmosphere

Obs. Sat. MOS-1

MOS-1b

Land Obs. satellite series

1987 200388 89 90 91 92 93 94 95 96 97 98 99 00 01

1987/2/19

1990/2/7

1992/2/11

1996/8/17

2002

2003/6

Marine Observation Satellite - 1

Earth Resources Satellite - 1 JERS-1

Advanced Earth Observation Satellite ADEOS

Advanced EarthObservation Satellite - II

Advanced Land ObservngSatellite ALOS

02

1995/11/29

1996/4/17

1997/6/30

1998/10/12

ADEOS-II


Japanese Earth Obs. Sensors

SWIR Res.: 18m

AVNIR Res.: 8m

OCTS Ch.: 12 Res.: 800 m

ADEOSMOS-1, 1b JERS-1

GLI Ch.: 34 Res.: 250m

AMSR 8 band, 2 pol. Res.: 5 km

ADEOS-II

AVNIR-2 Res.: 10m

PRISM Res.: 2.5m

PALSAR Res.: 10m

ALOS

'90 '95 2000'87 '05

VTIR Ch.: 4 Res.: 900m

MSR 2 band, 1 pol. Res.: 23km

MESSR Res.: 50m

VNIR Res.: 18m

SAR Res.: 18m

CY

Optical sensor (VIS, NIR)

Active microwave sensor

Optical sensor (VIS - TIR)Passive microwave sensor

Hig

h R

es.

Wid

e S

wat

h

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Heritage of Japanese High Res. Optical Sensor

MOS-1/MESSR: 50 m,100 km, 4 bands (VIS - NIR)

JERS-1/OPS(VNIR): 18 m, 75 km, 3 bands (VIS - NIR)

ADEOS/AVNIR: 8 m, 80 km, 1 band (Pa)16 m, 80 km, 4 bands (VIS - NIR)

ALOS/PRISM: 2.5 m, 70 km, 1 band (Pa)

ALOS/AVNIR-2: 10 m, 70 km, 4 bands (VIS - NIR)


Mapping Requirements (1)

1) Providing 3 to 5 m altitude accuracy Digital Elevation Model (DEM):

(a) 2.5 m resolution panchromatic image,(b) triplet stereoscope image with nadir, forward and

backward sensors,(c) base to height ratio between fore and aft telescopes is

equal to 1.0.

2) Providing “mapping without any ground control points” capability:

(d) exact satellite position information within 2.5 m accuracy,

(e) exact satellite attitude information within 0.0002 degree accuracy,

(f) absolute time information for each pixel within 370 µsec accuracy.

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Mapping Requirements (2)

3) Providing “distortion free image”:(g) Long term attitude stability shall be within 0.0002

degree/sec.

4) Requirement for 1), 2) and 3):(h) to minimize thermal distortion among three

telescopes’ optical axes, and between telescope’s optical axes and attitude sensors (Star Tracker, Inertial Reference Unit) in orbital period (100 minutes).


“Mapping without any GCPs”

lGround Control Point (GCP):– GCP is used for determining exact location of each pixel

and/or compensation of distorted image.– Sharp-edged objects (artificial or natural) are desirable

for GCPs,ü building, bridge, airport runway, cape,…

– Five to ten GCPs are required in each scene.

lNot applicable for unmapped region when ground surveying is not available.

– 69% of the world is unmapped in 1/25,000 scale. (United Nations’ statistics, 1995)

l “Mapping without any GCPs” is at the top of Surveyor’s wish list.lALOS is the first satellite to achieve this goal.

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PRISM FeaturesPanchromatic Remote-sensing Instrument for Stereo Mapping

Three independent telescopes Better stereoscope capability (B/H=1) Gathering global data promptly (along track/ one-orbit stereo)

Three mirror optics Wide FOV No chromatic aberration Good image quality

Moderate swath width and high resolution up to 70 km 2.5 m


PRISM Characteristics(nominal)

Item Characteristics RemarksWavelength 0.52 - 0.77 µmField-of-View 7.6 deg Swath Width 70 km Nadir

> 35 km Fore and AftInstantaneous FOV 3.61 µradSpatial Resolution 2.5 m NadirScanning Method Push broom using multiple CCDsBase-to-Height Ratio 1.0 between fore and aftMTF 0.27 (cross-track) @Nyquist freq.

0.21 (along-track) S/N 80 Quantization 8 bits

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PRISM Spectral Response

Spe

ctra

l Res

pons

e [%

]

Wavelength [nm]


PRISM Observation Geometry

PRISM

observable area 70km

Swath 70km/35km

forwardview

nadirview

aftview

ground track

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Geometry of Stereoscope

BaseHeight

= = 1~ 690 km~ 690 km

Direction of Flight

The Earth

Nadir

23.8 deg

Altitude =691.65 km

BaseHeight

ForeAft


PRISM Three-telescope System

Nadir

VelocityOptical Bench

Nadir telescope

Forward telescope

Backwardtelescope

Area for Star Trackers

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PRISM’s On-board Earth Rotation Correctionfor fully overlapped triplet image

N

F

B

ground track

No Correction

ve = 0.46 km/s

45sec

45sec

35km

less overlap

On-board Correction

N

F

B

20km

20km

ground track

ve = 0.46 km/s

full overlap


PRISM’s Bread Board Model

2.0m x 1.0m x 1.0m

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Structure of PRISM

Advantage of Three-Mirror Optics

Wide FOV

No Chromatic Aberration

GoodMTF

Primary Mirror

Tertialy MirrorDetector

Inner TrussOuter Shell

Hood

Outer Truss

Secondary Mirror(not shown here)


PRISM Optics (BBM)

G1 MirrorInner Truss

G3Mirror

Outer Truss

Detector

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Thermal Vacuum Test of PRISMat NASDA’s Space Simulated Chamber


PRISM Simulation Image

DEM Extraction from 2.5 m triplet images.

Simulated image of nadir-looking Generated DEM

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AVNIR-2 FeaturesAdvanced Visible and Near-Infrared Radiometer type 2

Succesor to ADEOS/AVNIR Same observation bands Inherited optics from “space proven” AVNIR

Wide observable area Pointing angle: ±44 degrees Prompt observation of e.g. disaster struck area

Moderate swath width and spatial resolution 70 km 10 m


AVNIR-2 Observation Geometry

AVNIR-2

ground track

Pointing angle ±44deg

Swath

70 km

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AVNIR-2 Characteristics(nominal)

Item Characteristics Remarks Wavelength band1: 0.42 - 0.50 µm

band2: 0.52 - 0.60 µm band3: 0.61 - 0.69 µm band4: 0.76 - 0.89 µm

Field-of-View 5.8 deg Swath Width 70 km Instantaneous FOV 14.28 µrad Spatial Resolution 10m Nadir Pointing Angle ±44 deg. Cross-track Scanning Method Push broom MTF >0.25 @Nyquist freq. S/N >240 Quantization 8 bits


AVNIR-2 Spectral Response(center pixels of each band)

0.0000

0.1000

0.2000

0.3000

0.4000

0.5000

0.6000

0.7000

0.8000

0.9000

1.0000

485

490

495

500

505

510

515

520

525

530

535

540

545

550

555

560

565

570

575

580

585

590

595

600

605

610

615

620

625

630

635

640

645

波長（ｎｍ）

分光

感度

略PN1775Teff80

0.0000

0.1000

0.2000

0.3000

0.4000

0.5000

0.6000

0.7000

0.8000

0.9000

1.0000

390

395

400

405

410

415

420

425

430

435

440

445

450

455

460

465

470

475

480

485

490

495

500

505

510

515

520

525

530

535

540

545

550

波長（ｎｍ）

分光

感度

略PN1775Teff80

Band 1 Band 2

Band 3 Band 4

0.0000

0.1000

0.2000

0.3000

0.4000

0.5000

0.6000

0.7000

0.8000

0.9000

1.0000

550

560

570

580

590

600

610

620

630

640

650

660

670

680

690

700

710

720

730

740

波長（ｎｍ）

分光

感度

略PN1775Teff80

0.0000

0.1000

0.2000

0.3000

0.4000

0.5000

0.6000

0.7000

0.8000

0.9000

1.0000

700

710

720

730

740

750

760

770

780

790

800

810

820

830

840

850

860

870

880

890

900

910

920

930

940

950

960

970

980

990

波長（ｎｍ）

分光

感度略PN1775

Teff80

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AVNIR-2 Mechanical Test Model

1m

1.1m2.3m


AVNIR-2 Optics

Folding Schmidt

Pointing Mirror

Detector

Main ReflectorFolding MirrorAspheric Corrector

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PRISM and AVNIR-2 Dynamic Range

80

70

60

50

40

30

20

10

0 Gain 1 Gain 2 Gain 3 Gain 4

15

25

40

60

20

40

60

80Albedo (%)

ADEOS/AVNIR

ALOS PRISM & AVNIR-2


Phased Array type L-band Synthetic Aperture Radar (PALSAR)

l A Follow-on Sensor of JERS-1 SAR.(L-band)

l Higher Performance and Multi-function– such as spatial resolution, variable off-

nadir capability,– multi-polarization, ScanSAR observation.

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PALSAR Observation Mode

Off-nadir : 9.9 deg. - 50.8 deg.(nominal operation : 34.3 deg.)

#1

#18

#1

#5

350km

Off-nadir : 20.1 deg. - 36.5 deg.

870km

90kmIncident : 8 deg. - 60 deg.

Fine mode ( #1 - #18)Direct downlink mode ( #1 - #18)Polarimetric mode ( #1 - #12)

ScanSAR mode (3scans - 5scans)

380km

70km

Sub-satellite track


PALSAR Characteristics

Operation mode Fine Direct downlink ScanSAR Polarimetric

Center frequency L band (1270MHz)

Chirp bandwidth 28MHz 14MHz 14MHz 14MHz, 28MHz 14MHz

Polarization HH, VV HH+HV, HH, VV HH, VV HH+VV+HV+VHVV+VH

Incident angle 8 - 60 deg. 8 - 60 deg. 8 - 60 deg. 18 - 43 deg. 8 - 30 deg.

Range resolution 7 - 44 m 14 - 88 m 14 - 88 m 100 m (multi Look) 24 - 89 m

Observation swath 40 - 70 km 40 - 70 km 40 - 70 km 250 - 350 km 20 - 65 km

Bit length 5 bits 5 bits 3 / 5 bits 5 bits 3 / 5 bits

Data rate 240 Mbps 240 Mbps 120 Mbps 120Mbps, 240 Mbps 240 Mbps

Radiometric accuracy scene : 1 dB / orbit : 1.5 dB

Antenna size Az : 8.9 m / El : 3.1 m

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Noise Equivalent Backscattering Coefficient(Fine mode and ScanSAR mode)

-35

-30

-25

-20

5 10 15 20 25 30 35 40 45 50 55 60 65

9.9

14.0

18.0

21.5

25.8

28.8

30.8

34.3

36.9

38.8

41.5

43.4

45.2

46.6

47.8

49.0

50.0

50.8

-35

-30

-25

-20

15 20 25 30 35 40 45

SCAN#1

SCAN#2

SCAN#3

SCAN#4

SCAN#5

(Pulse width = 40 us)

Off-nadir angle(deg.)

Incident angle(deg.)

(dB)Noise equivalent backscattering coefficient

(Fine mode)

(Pulse width = 40 us) Incident angle(deg.)

Noise equivalent backscattering coefficient(ScanSAR mode)(dB)


Calibration

l Internal (Onboard) calibration– T/R modules: Temperature measurement,

Transmission power monitor– Transmitter: Chirp replica– Receiver: Noise level, Gain monitor

l External calibration and validation– Antenna elevation pattern : Amazon rain forest– Backscattering coefficient:

Corner Reflector, Active Radar Calibrator– Simultaneous air-borne SAR observation

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PALSAR Breadboard Model (BBM)

PALSAR BBM　（～　Dec., 1998）・Mechanical Model　(Deployment, Acoustic, Separation Shock)

PALSAR BBM　（～　Mar., 1999）・Electrical Model　(Electric, Antenna pattern)


Far Field Antenna Pattern Measurementat NASDA/TKSC using PALSAR BBM (Electric model）

Reference Antenna One Antenna Panel of PALSAR(Azimuth Pattern Measurement)

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PALSAR Engineering Model (for mechanical and thermal test)

Four Antenna Panels fully deployed Opposite side(T/R modules and RF Dividers)


Observable Area of ALOS

Obs. area (673km)

Obs.area (1721km)

Obs. area (70km)Obs. area (872km)

Obs. area (1522km)Obs. area (70km)

Obs. area (70km)

AVNIR-2

PALSAR

PRISM

Altitude

691.65km

470km 540km

761km-761km

960km

-761km

-35km 35km

ALOS

44deg-44deg

35km-35km

-2.9deg 2.9deg

8deg60deg

761km

960km

Ground

both AV-2 & PAL

either AV-2 or PAL

88km

88km

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Summary and Conclusion

p PRISM’s, AVNIR-2’s and PALSAR’s specifications are fully met ALOS mission requirements:- mapping,- regional observation,- disaster observation,-Earth resources surveying.

p Several tests of these instruments using engineering models have been done with successful results.

p Calibration/validation plan will be established by the end of this year.

prism, avnir-2, palsar · panchromatic remote-sensing instrument for stereo mapping three...

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