Proto Flight Model (PFM) performance and development
status of Visible and Near Infrared Radiometer (VNR) on
the Second-generation Global Imager (SGLI)
9264-27

October 14, 2014
SPIE Asia‐Pacific Remote Sensing in Beijing
Tatsuya Uchikata*a, Kazuhiro Tanakab, Yoshihiko Okamurab,
Shunji Tsuidaa, Takahiro Amanoa
a NEC Corporationb Japan Aerospace Exploration Agency (JAXA)
Page 1© NEC Corporation 2014

Contents
GCOM mission and GCOM-C1 satellite
SGLI performanceVNR Optics and focal plane assembly
VNR spectral performance
Measurement accuracy of polarization rate and direction
Current development statusConclusion

Page 2© NEC Corporation 2014

Global Change Observation Mission (GCOM) Global observation satellite system as JAXA’s GEOSS contribution.
 2 satellite series for 5 years, total 13 years observation.
 GCOM-W Microwave radiometer observation for WATERCYCLE using AMSR2 (AMSR-E follow on)
 GCOM-C Opticalmulti-channel
observation
for
RADIATION BUDGET and CARBON CYCLE using SGLI(GLI follow on)
GCOM-C(CLIMATE)

AMSR2

SGLI
GCOM-W(WATER)

SensorPage 3

Advanced Microwave Radiometer 2(AMSR2)
Passive Microwave Observation
Water vapor, soil moisture etc© NEC Corporation 2014

SensorSecond Generation Global Imager (SGLI)
Optical Observation 380nm – 12 micron
Cloud, Aerosol, Vegetation, Chrolophl etc

SGLI on GCOM-C1 satellite
SGLI IRSELUSGLI VNR
ELU+X+Y
deep
space

flightdirection+Z earth

SGLI VNR
SRU

SGLI IRS
SRU

Mission Life> 5 years

Solar Paddle> 4000w （End of Life）

Mass

about 2,000kg

Page 4© NEC Corporation 2014

SGLI Second Generation Global Imager
VNR Visible and Near Infrared Radiometer
IRS Infrared Scanning Radiometer
SRU Scanning Radiometer Unit
ELU Electronic UnitSGLI (Second Generation Global Imager)
External View
Non Polarized
Observation Telescopes(24deg FOV x 3)

SolarDiffuser

Polarized
Observation
Telescopes(55deg FOVx 2)

EarthView Window

Sun Cal.
Window

About
1.4m

About
1.7m

About
1.3m

Visible and Near Infrared Radiometer(SGLI-VNR)
Sensor Unit

Page 5

DeepSpace
Window

About
0.6m

Infrared Scanning Radiometer(SGLI-IRS)
Features

SGLI VNR

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

SGLI IRSShortwave Infrared （SWI 4ch）, IFOV 250m/1km, Swath 1400km
Thermal Infrared （TIR:2ch）, IFOV 500m, Swath 1400km© NEC Corporation 2014

SGLI Performance• The SGLI features are 250m (VNR-NP & SW3) and 500m (TIR)
spatial resolution and polarization/along-track slant view
channels (VNR-PL), which will improve land, coastal, and aerosol
250m over the Land or coastal
observations.
area, and 1km over offshore
SGLI channels

GCOM-C SGLI characteristics

Orbit
Mission Life
Scan
Scan widthDigitalization
Polarization
Along trackdirection

Sun-synchronous(descending local time: 10:30)
Altitude 798km, Inclination 98.6deg
5 years (3 satellites; total 13 years)
Push-broom electric scan (VNR)
Wisk-broom mechanical scan (IRS)
1150km cross track (VNR: VN & P)
1400km cross track (IRS: SW & T)
12bit
3 polarization angles for P
Nadir for VN, SW and T,+45 deg and -45 deg for P

Multi-angle
obs. for674nm and869nm

On-board
calibration

VN: Solar diffuser, LED, Lunar cal maneuvers,and dark current by masked pixels andnighttime obs.
SW: Solar diffuser, LED, Lunar, and darkcurrent by deep space window
T: Black body and dark current by deepspace window

Page 6© NEC Corporation 2014

CHVN, P, SW: nm
T: m

VN1
VN2
VN3
VN4
VN5
VN6
VN7
VN8
VN9
VN10
VN11
P1
P2
SW1
SW2
SW3
SW4
T1
T2

380
412
443
490
530
565
673.5
673.5
763
868.5
868.5
673.5
868.5
1050
1380
1630
2210
10.8
12.0

1010
1010
20
20
2020
1220
20
20
20
20
20200
50
0.70.7

Lstd

Lmax

VN, P:
W/m2/sr/m
T: Kelvin
60210
75
250
64400
53120
413503390
236225210
40
350
83030300
2525030
300
57
248
8103
350
1.9
20300
340
300
340

SNR at Lstd

IFOV

VN, P, SW:SNRmT: NET
250
250
400
250
300
250
400
250
250
250
400
250
400
250
250
250
250/1000
1200
400
250
200
250
250
1000
250
1000
500
1000
150
1000
57
250
211
1000
0.2
250/500
0.2
250/500
optionVNR Optics• 24deg (total 70deg) FOV for three NP sensors.
• 55dev FOV and +/-45deg tilting mechanism for two PL sensors.
• Three NP sensors and two PL sensors have been assembled already.
• Optical test such as integrating sphere test or parallel light test isongoing.

NP Telescope

PL Sensor2
PL Sensor1

NP-L Sensor
NP-N Sensor

Tilting motor±45deg

NP-R Sensor

PL Telescope+Z+X

PL sub unit
Page 7© NEC Corporation 2014

+Y

NP sub unit

VNR focal plane assembly (FPA)• 11 lines Band pass filter(BPF) isequipped on the 11 line 6000pix
CCD for NP sensor.
• Polarization filter is equipped on
the same kind of CCD for PLsensor. 3 of 11 lines are used forpolarization outputs(+60deg,0deg, -60deg).

CCD-60゜ POL0゜ POL+60゜ POLPolarization filter

Structure of BPF

A. Kurokawa et al, “High-precision narrow-band opticalfilters for global observation”, ICSOS, Oct. 2012

Page 8© NEC Corporation 2014

11 lines band pass filter

VNR spectral performance
F4/F8 corn optics• Wavelength characteristics are total characteristics
of telescope, CCD sensitivity and BPF.
• F4/F8 corn optics and filter slope is considered
for NP/PL in this characteristics.
• BPF locality is considered by shifting the center wavelength.
NPPage 9© NEC Corporation 2014

PLBPF

Measurement accuracy of polarization• Measurement error caused by SNR is calculated by considering SNR
as 500 which is achieved with enough margin in the PFM test.
• Relative difference of three detectors depends on compensation
error of sensitivity non-uniformity. PFM test has finished and it’sunder evaluation now.
• Mueller matrix compensation is used to realize the polarization
target spec. So its measurement error is important.

Target spec. for measurement accuracy of polarization
Page 10© NEC Corporation 2014

Sensitivity non-uniformity for PL sensor・ Integrating sphere test for two PL sensors have finished.
・ Sensitivity non-uniformity, S/N, linearity, dynamic range havejust been measured.
・ Sensitivity non-uniformity between pixels and between eachpolarized output(+60deg, 0deg, -60deg) will be compensated tomeet distributed specification for relative difference of threedetectors.
Integratingsphere
PL Sensor

・Before the compensation of Integrating sphere brightness
・Pixel data will be integrated.

Page 11© NEC Corporation 2014

Polarization observation test(a) Measure the three outputs of PL sensor I(0°) (θ), I(+60°) (θ) andI(-60°) (θ) while rotating the linear polarization plate on turret2
as shown in Figure below and calculate Mueller matrix.
(b) Change the linear polarization plate to 5% polarization plate onturret2 and measure the three outputs again.
PLF Unit
Test piece

PLF Unit

ParallelLight source
Rotary rack
Test piecesideTurret 1
Turret 2

Page 12© NEC Corporation 2014

Measurement accuracy of polarization rate and direction(c) Calculate the polarization rate and direction by eq.(1),(2),(3)(d) Calculate the accuracy of polarization rate and direction.
These are in the distributed specification as shown below.

<1.3%

<0.7゜

> -1.3%> -0.7゜・・・ (1)・・・ (2)・・・ (3)

Accuracy of Pol rate
Page 13© NEC Corporation 2014

Accuracy of Pol direction

Current status• Three NP sensors have been assembled and parallel light test will
start by the end of this year.
• Two PL sensors are assembled and integrating sphere test havebeen finished already. Parallel light test including polarization
observation test will start from now.
• I-SRU Component assembly and PFT have been done and systemtest will start soon.
Japanese Fiscal Year
GCOM-C1

JFY2013

JFY2014

JFY2015PFT Start

VNR

JFY2016
Launch(TBD)

V-SRU Assy/PFT
V-ELU Assy/PFTIRSI-SRU Assy/PFT
I-ELU Assy/PFTPage 14© NEC Corporation 2014

ASSY,TEST
Sub-Unit ASSY,TESTPFTConclusion
GCOM is JAXA’s GEOSS contribution and SGLI is the opticalsensor on the GCOM-C1 satellite.
VNR spectral performance is measured and calculated.
VNR PL & NP sensor assembly has finished and optical test isongoing. Polarization observation test will start within this year.
Target launch of GCOM-C1 is JFY2016

Page 15© NEC Corporation 2014