radiometric performance of second generation...

Radiometric performance of

Second Generation Global Imager (SGLI) using integrating sphere

Taichiro Hashiguchi, Yoshihiko Okamura, Kazuhiro Tanaka, Yukinori Nakajima

Japan Aerospace Exploration Agency

Koichi Suzuki JASTECS Corporation

Takashi Sakashita, Takahiro Amano NEC Corporation

SPIE Remote Sensing 2016 at Edinburgh, United Kingdom Sep. 26, 2016 1

Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK

Contents

GCOM overview SGLI specification Strategy of SGLI radiometric test Traceability of SGLI radiometric test SGLI VNR radiometric test SGLI IRS radiometric test Summary

2


Long-term observation of the earth’s environment 5 years of each satellite's mission life and 13 years in total.

Two satellite series; GCOM-W : Microwave observation for WATER CYCLE using AMSR2

(AMSR-E follow on) GCOM-C : Optical multi-channel observation for RADIATION BUDGET

and CARBON CYCLE using SGLI (GLI follow on)

GCOM-C (CLIMATE)

Sensor Advanced Microwave Radiometer 2 (AMSR2) Passive Microwave Observation Water vapor, soil moisture etc

Sensor Second-generation Global Imager (SGLI) Optical Observation 380nm – 12 micron Cloud, Aerosol, Vegetation, Chlorophyll etc

GCOM-W (WATER)

AMSR2

SGLI

Global Change Observation Mission(GCOM) overview

GCOM-W1 “SHIZUKU” was launched on May 18, 2012.

3


SGLI IRS ELU

+ X flight direction

+Y

+ Z earth

deep space

SGLI VNR ELU

SGLI IRS SRU SGLI VNR

SRU

SGLI Second-generation Global Imager VNR Visible and Near Infrared Radiometer IRS Infrared Scanning Radiometer SRU Scanning Radiometer Unit ELU Electronic Unit

GCOM-C

Orbit Parameters

Orbit Type sun-synchronous, ground track repeat, near-circular orbit

Local sun time 10:15 – 10:45 at descending node

Altitude above equator 798 km at Equator

Inclination 98.6 degrees

Mission Life > 5 years

4

GCOM-C overview


Second-generation Global Imager (SGLI) Overview

Polarized Observation Telescopes (55deg FOV x 2)

Non Polarized Observation Telescopes (24deg FOV x 3)

Solar Diffuser

About 1.5m

About 1.4m

Infrared Scanning Radiometer (SGLI-IRS)

Sun Cal. Window

Earth View Window

Deep Space Window

About 1.5m

About 0.7m

Sensor Unit features

SGLI VNR Non Polarized Observation （11ch）, IFOV 250m, Swath 1150km Polarized Observation（2ch）, IFOV 1km, Swath 1150km

SGLI IRS Shortwave Infrared （SWI 4ch）, IFOV 250m/1km, Swath 1400km Thermal Infrared （TIR:2ch）, IFOV 250m, Swath 1400km

Visible and Near Infrared Radiometer (SGLI-VNR)

5


SGLI Specification

• The SGLI features are 250m (VNR-NP & SW3) and 250/500m (TIR) spatial resolution and polarization/along-track slant view channels (VNR-PL), which will improve land, coastal, and aerosol observations.

GCOM-C SGLI characteristics

Orbit Sun-synchronous (descending local time: 10:30) Altitude 798km, Inclination 98.6deg

Mission Life 5 years

Scan Push-broom electric scan (VNR) Wisk-broom mechanical scan (IRS)

Scan width 1150km cross track (VNR-NP & VNR-PL) 1400km cross track (IRS-SWI & IRS-TIR)

Digitalization 12bit Polarization 3 polarization angles for VNR-PL Along track direction

Nadir for VNR-NP, IRS-SWI and IRS-TIR, +45 deg and -45 deg for VNR-PL

On-board calibration

VNR-NP, VNR-PL: Solar diffuser, LED, Lunar cal. maneuvers, and dark current by masked pixels and nighttime obs.

IRS-SWI: Solar diffuser, LED, Lunar, and dark current by deep space window

IRS-TIR: Black body and dark current by deep space window

SGLI channels

CH

λ ∆λ Lstd Lmax SNR at Lstd IFOV

VNR-NP, VNR-PL, IRS-SWI: nm IRS-TIR: µm

VNR-NP, VNR-PL, IRS-SWI

:W/m2/sr/µm IRS-TIR: Kelvin

VNR-NP, VNR-PL, IRS-SWI : SNR IRS-TIR: NE∆T

m

VN1 380 10 60 210 250 250 VN2 412 10 75 250 400 250 VN3 443 10 64 400 300 250 VN4 490 10 53 120 400 250 VN5 530 20 41 350 250 250 VN6 565 20 33 90 400 250 VN7 673.5 20 23 62 400 250 VN8 673.5 20 25 210 250 250 VN9 763 12 40 350 1200 250/1000 VN10 868.5 20 8 30 400 250 VN11 868.5 20 30 300 200 250 P1 673.5 20 25 250 250 1000 P2 868.5 20 30 300 250 1000

SW1 1050 20 57 248 500 1000 SW2 1380 20 8 103 150 1000 SW3 1630 200 3 50 57 250 SW4 2210 50 1.9 20 211 1000 T1 10.8 0.7 300 340 0.2 250/1000 T2 12.0 0.7 300 340 0.2 250/1000

Multi-angle obs. for 673.5nm and 868.5nm

250m over the Land or coastal area, and 1km over offshore

TIR: 500m resolution is also used 6

Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 7

Strategy of SGLI radiometric test

Objectives To confirm that SGLI was integrated radiometrically as designed To characterize radiometric performance To obtain the parameters of Level 1 ground processing

Test Methods

Use three integrating spheres for each wavelength range and radiance level in SGLI radiometric test

【VNR】 0.38 – 0.87 μm Barium sulfate and Spectralon integrating spheres

• Take advantage of the performance of the each integrating sphere

【IRS】 1.05 – 2.21 μm Gold-coated integrating sphere

• To control the humidity by clean booth


Strategy of SGLI radiometric test - Specifications of integrating spheres -

8

Barium sulfate

integrating sphere Spectralon

integrating sphere Gold-coated

integrating sphere Inner diameter 1000 mm 500 mm 1000 mm Aperture diameter 280 mm 200 mm 300 mm Sphere coating on inner wall Barium sulfate PTFE Gold lamp configuration lamp number of halogen 12 (500W) 3 (220 W) and 1 (150 W) 8 (50 W) and 8 (10 W) Max voltage per halogen lamp 100V 22V 12V lamp number of xenon none 2 none Attenuator none Mechanical attenuator none Lamp control voltage control current control current control Thermal cooling Air circulation with fan Air circulation with fan Air circulation with fan Monitor detector Silicon photodiode Silicon photodiode InGaAs

Used black body to calibrate Fixed-point black body of Copper (1358K) Fixed-point black body of Pt-C (2011K) - Fixed-point black body of Copper (1358K)

Fixed-point black body of zinc (692K)

Monitor detector

Monitor detector

Monitor detector

1000mm

200mm

1000mm


0.00

0.50

1.00

1.50

2.00

2.50

3.00

1

10

100

1,000

300 500 700 900 1100 1300 1500 1700 1900 2100 2300 Spec

tral

resp

onse

Radi

ance

[W/m

^2/S

tr/u

m]

Wavelength [nm]

VN01 VN03 VN05

VN07VN08PL01

VN10VN11PL02

VN02 VN04 VN06 VN09 SW01

SW02

SW03

SW04

Gold 2.98A(50W)x4

VNR IRSSpectralon was briefly measured by FieldSpec

Strategy of SGLI radiometric test - Representative radiance level -

【Spectralon integrating sphere】・To achieve the high radiance in the short wavelength by turning on the xenon lamp.

【Barium sulfate integrating sphere】・It has good characteristics (stability, reproducibility) in the visible region. ⇒Used to characterize the absolute performance of VNR

【Gold-coated integrating sphere】・It has high reflectance and flat in the infrared region. ・It is hydrophobic, no water vapor absorption of the wall in 1.38 μm


Strategy of SGLI radiometric test - Uniformity of the spectral radiance at the aperture in VNR test-

-2.00%

-1.00%

0.00%

1.00%

2.00%

-4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0Ra

dian

ce u

info

rmity

[%]

Angle [degree]

BaSO4 VN01BaSO4 VN02BaSO4 VN03BaSO4 VN10Spectralon VN01Spectralon VN02Spectralon VN03Spectralon VN10

【Barium sulfate integrating sphere】 Amplitude of the non-uniformity in each band is various. Radiance uniformity is less than 0.6% except VN01(380nm). It has good characteristics (stability, reproducibility) in the visible

region. ⇒Used for the absolute performance

Gain, Stability, SNR 【Spectralon integrating sphere】 Amplitude of the non-uniformity in each band is almost same and flat Radiance uniformity is less than 0.5% all band.

⇒ Used to characterize the relative performance of VNR Photo response non-uniformity(PRNU), linearity


Strategy of SGLI radiometric test - VNR test case -

Lamp set VN01 VN02 VN03 VN04 VN05 VN06 VN07 VN08 VN09 VN10 VN11 PL01 PL0290.0V x 12 ○ ○ ○

85.0V x 12 △

79.0V x 12 ○ △ ○

71.3V x 12 □ ○ ◎

62.3V x 12 □ △ ◎ ○

51.9V x 12 □ △ ○

48.7V x 12 ○

45.5V x 12 ○ ◎ ◎ ◎

43.5V x 12 ◎

39.7V x 12 □ ○ ○ ○

38.1V x 12 ○

35.1V x 12 ○ ◎ ◎

32.5V x 12 □ ○ ◎ ○ ○

30.5V x 12 ○ ○

27.7V x 12 □ ○ ○

24.8V x 12 △ ○ ○

19.4V x 12 □ □ □

17.3V x 12 □ ◎

16.0V x 12 ○

14.5V x 12 □

12.5V x 12 △ □

10.1V x 12 □

◎：Lmax level△：Lstd level

□：0.3Lstd level

(a)Xenon HalogenOn x 2 10A x 2 ○*On x 2 9A x 2 ○ ○ ○ ○

- 9.6A x 2 ○ ○ ○* ○*- 9.0A x 2 ○ ○ ○ ○ ○

- 7.0A x 2 ○

- 6.0A x2 ○

○* Only Linearity measurement by CCD electrical shutter

VN10 VN11 PL01 PL02VN09(b) VN05 VN06 VN07 VN08Lamp set

VN01 VN02 VN03 VN04

There are many measurement cases to characterize VNR performance using integrating sphere. Per band, telescope , angle of view

and radiance level The lighting time of lamps becomes longer.

The radiance degradation of integrating sphere occurs compared to calibration by FPBB(Fixed-point black body).

【Barium sulfate integrating sphere】【Spectralon integrating sphere】

The merit of using two integrating spheres is to reduce the lighting time of the lamp. Prevent radiance degradation of the lamp by distributing the load using two

integrating spheres.


Radiometric characterization VNR IRS

Barium sulfate integrating sphere

Spectralon integrating sphere

Gold-coated integrating sphere

Gain ○ ○ Dynamic range ○ ○ Stability ○ ○ Photo response non-uniformity (PRNU) ○ ○ Linearity by change of the lamp set ○ ○ Linearity by CCD electrical shutter ○ Linearity by attenuator function ○ SNR ○ ○

Strategy of SGLI radiometric test - Matrix of SGLI radiometric test -

Absolute performance of VNR are characterized by using barium sulfate integrating sphere. Relative performance of VNR are characterized by using Spectralon integrating sphere.

The consistency of two integrating spheres in VNR test is confirmed by linearity performance.

IRS performance are characterized using by gold-coated integrating sphere.


VNRIRS

Zn Cu Pt-C

National Standard

Gold-coatedIntegrating

Sphere

Barium sulfateIntegrating

Sphere

SpectralonIntegrating

Sphere

SGLI

Integrating Sphere

RadiometerTransfer

Radiometer

Fixed-Point Black Body

SW02-04 SW01 VN06-11 VN01-05

Relative radiance

Standard Spectral Radiometer

Traceability of SGLI radiometric test

FPBBs of primary standard are traceable to the national standard.

Integrating spheres of working standard are traceable to each FPBB.

SGLI sensors are calibrated by integrating spheres of working standard.


VNR radiometric performance summary

VNR final radiometric test finished in Aug. 2016 We used barium sulfate and Spectralon integrating sphere The performances of each band center pixel were characterized and

satisfied the requirement SNR, gain, dynamic range, stability, PRNU, linearity

All pixel and band performance under calculation

The radiometric parameters will be implemented in ground system

Integrating Sphere

VNR-SRU


VNR PRNU (Photo response non-uniformity) results - preliminary -

859095

100105

0 250 500 750 1000 1250 1500

PRN

U

Pixel

Lmax VN01 right telescope (before correction and connecting)

+10°+5°0°-5°-10°

859095

100105

0 250 500 750 1000 1250 1500

PRN

U

Pixel

Lstd VN01 right telescope (before correction and connecting)

+10°+5°0°-5°-10°

859095

100105

0 250 500 750 1000 1250 1500

PRN

U

Pixel

Lmax VN01 right telescope(after correction and connecting)

+10°+5°0°-5°-10°

859095

100105

0 250 500 750 1000 1250 1500

PRN

U

Pixel

Lstd VN01 right telescope(after correction and connecting)

+10°+5°0°-5°-10°

-4.0-3.0-2.0-1.00.01.02.03.04.0

0 250 500 750 1000 1250 1500

PRN

U e

rror

[%]

Pixel

PRNU error VN01 right telescope

Using the Spectralon integrating sphere The measurements were carried out at Lmax, Lstd level for five angle of

view for VNR-NP The data at Lmax, Lstd level were corrected of the uniformity of radiance

at the aperture and connected The residual of Lmax and Lstd PRNU satisfied the requirement of 1%p-p

(a)

(b)

(c)

(d)

(e)

This band is 0.4 %p-p


VNR Linearity results - preliminary -

Using the barium sulfate and Spectralon integrating spheres The linearity is defined as deviation from the first order polynomial

The requirement is less than ±2% between 0.3Lstd and Lmax The linearity is measured by three methods

The changing lamp set method using barium sulfate integrating sphere The CCD electrical shutter method of VNR function The mechanical shutter method using attenuator function of the Spectralon integrating

sphere The consistency between different methods and spheres were verified

Lmax-4.0-3.0-2.0-1.00.01.02.03.04.0

0 500 1000 1500 2000 2500 3000 3500 4000

Line

arity

Err

or [%

]

[DN]

VN08 right telescope Linearity by change the lamp setLinearity by CCD electrical shutterLinearity by attenuator function

0.3Lstd Lstd


IRS radiometric performance summary

IRS final radiometric test is ongoing We used gold-coated integrating sphere The performances of initial test were characterized and satisfied the

requirement SNR, gain, dynamic range, stability, PRNU, linearity

The radiometric parameters of final performance are implemented in ground system

Integrating Sphere IRS-SRU


IRS PRNU (Photo response non-uniformity) results

Using the gold-coated integrating sphere IRS PRNU of initial test satisfied the requirement within 10% of the

maximum value

0.8

0.9

1.0

1.1

1 2 3 4 5

PRN

U

Pixel

SW010.3Lstd 1Lstd 1Lmax

0.8

0.9

1.0

1.1

1 2 3 4 5

PRN

U

Pixel


0.8

0.9

1.0

1.1

1 2 3 4 5 6 7 8 9 1011121314151617181920

PRN

U

Pixel


0.8

0.9

1.0

1.1

1 2 3 4 5

PRN

U

PRNU



IRS Linearity results

-5-4-3-2-1012345

0 50 100 150 200 250

Line

arity

Err

or[％

]

Radiance[W/m2/str/μm]

SW01 LmaxLstd0.3Lstd

-5-4-3-2-1012345

0 20 40 60 80 100

Line

arity

Err

or[％

]


SW02 Lmax

Lstd

0.3Lstd

-5-4-3-2-1012345

0 10 20 30 40 50

Line

arity

Err

or[％

]


SW03 Lmax

Lstd

0.3Lstd

-5-4-3-2-1012345

0 2 4 6 8 10 12 14 16 18 20

Line

arity

Err

or[％

]


SW04 Lmax

Lstd

0.3Lstd

Using the gold-coated integrating sphere The linearity is defined as deviation from the first order polynomial

The requirement is less than ±2% between 0.3Lstd and Lmax


IRS final radiometric test environment

SW02 (1.38 μm) data is affected by water vapor variation. The humidity sensitivity experiment was

performed using transfer radiometer of 1.38 μm.

IRS final test and radiance calibration of integrating sphere by FPBB are needed to control same environment (temp. and humi.) in clean booth

50.050.551.051.552.052.553.053.554.054.555.0

0.05240.05250.05260.05270.05280.05290.05300.05310.05320.05330.0534

10:00:00 12:00:00 14:00:00

Hum

idity

[％]

Tran

sfer

radi

omet

er o

f 138

0nm

[V]

Time

Transfer radiometer of 1380nm [V]Humidity[％]

Transfer Radiometer of 1.38μm


IRS final radiometric test preliminary result

IRS-SRU Gold-coated

Integrating Sphere

This linearity data was measured on 21 Sep. Detailed evaluation is ongoing.

40

42

44

46

48

20.521.021.522.022.523.023.524.024.5

6:00 9:00 12:00 15:00 18:00 21:00 0:00

Hum

idity

[%]

Tem

pera

ture

[℃]

2016/9/20~21 Time(JST)

Temperature Humidity

8.0

8.5

9.0

9.5

10.0

6:00 9:00 12:00 15:00 18:00 21:00 0:00Abs

olut

e H

umid

ity

[g/m

^3]

2016/9/20~21 Time(JST)

Absolute Humidity

-5-4-3-2-1012345

0 20 40 60 80 100

Line

arity

Err

or[％

]

Radiance [W/m2/str/μm]

SW02

-5-4-3-2-1012345

0 50 100 150 200 250

Line

arity

Err

or[％

]


SW01

-5-4-3-2-1012345

0 10 20 30 40 50

Line

arity

Err

or[％

]

Radiance [W/m2/str/μm]

SW03

-5-4-3-2-1012345

0 2 4 6 8 10 12 14 16 18 20

Line

arity

Err

or[％

]Radiance [W/m2/str/μm]

SW04

LmaxLstd0.3Lstd Lmax

Lstd

0.3Lstd

Lmax

Lstd

0.3Lstd Lmax

Lstd

0.3Lstd


Summary

The SGLI radiometric tests were carried out in the strategy and traceability using three integrating spheres. The integrating spheres were used depending on the wavelength

range and the radiance level of SGLI.

Preliminary test results indicate to achieve the required radiometric performance. Further detailed evaluation is ongoing. It is necessary to evaluate all the pixel and band characterizations.

The radiometric parameters will be derived from final radiometric

performance.

radiometric performance of second generation...

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