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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK
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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK
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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK
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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK
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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK
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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 9
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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 10
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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 11
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 performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 12
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.
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 13
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.
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK
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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 15
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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 16
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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK
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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 18
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
SW020.3Lstd 1Lstd 1Lmax
0.8
0.9
1.0
1.1
1 2 3 4 5 6 7 8 9 1011121314151617181920
PRN
U
Pixel
SW030.3Lstd 1Lstd 1Lmax
0.8
0.9
1.0
1.1
1 2 3 4 5
PRN
U
PRNU
SW040.3Lstd 1Lstd 1Lmax
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 19
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[%
]
Radiance[W/m2/str/μm]
SW02 Lmax
Lstd
0.3Lstd
-5-4-3-2-1012345
0 10 20 30 40 50
Line
arity
Err
or[%
]
Radiance[W/m2/str/μm]
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[%
]
Radiance[W/m2/str/μm]
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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 20
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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 21
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[%
]
Radiance[W/m2/str/μm]
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
Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 22
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.