Pre-Launch Characterization andIn-orbit Calibration of GCOM-C/SGLI
IGARSS 2018
July 26, 2018
Japan Aerospace Exploration Agency
Yoshihiko Okamura
T. Hashiguchi, T. Urabe, K. Tanaka (JAXA)J Yoshida, T Sakashita, and T Amano (NEC)Contents

1. Overview of GCOM-C satellite and SGLI
2. GCOM-C operation status
3. SGLI pre-launch characterization
4. SGLI in-orbit calibration
5. Summary and future plans

IGARSS 2018 @Jul. 26 20182

1. Overview of GCOM-C satellite and SGLI(1) Global Change Observation Mission(GCOM) GCOM mission: Long-term observation of the earth’s environment Two satellite series;
 GCOM-W “SHIZUKU”:
Microwave observation for WATER CYCLE
using AMSR2 (AMSR-E follow on)
 GCOM-C “SHIKISAI”:
Opticalmulti-channel
observation
for
RADIATION BUDGET and CARBON CYCLE using SGLI (GLI follow on)

GCOM-C(CLIMATE)AMSR2GCOM-W(WATER)

SGLI

GCOM-W was launchedon May 18, 2012.

Sensor

GCOM-C was launchedon Dec. 23, 2017.

Advanced Microwave
Radiometer 2 (AMSR2)
Passive Microwave Observation
Water vapor, soil moisture etcSensorIGARSS 2018 @Jul. 26 2018

Second Generation Global Imager(SGLI)
Optical Observation 380nm – 12 micron
Cloud, Aerosol, Vegetation, Chlorophyll etc3

1. Overview of GCOM-C satellite and SGLI(2) GCOM-C satellite
SGLI VNR
ELU

SGLI IRS
ELU+X
flightdirection+Y
deep
space+ Z earth

SGLI IRSSRU

SGLI VNR
SRU

SGLI
VNR
IRS
SRU
ELU

Second Generation Global Imager
Visible and Near Infrared Radiometer
Infrared Scanning Radiometer
Scanning Radiometer Unit
Electronic Unit

GCOM-C
Orbit
Parameters

Mission LifeOrbit TypeLocal sun timesun-synchronous, ground track repeat, nearcircular orbit
10:15 – 10:45 at descending node

Altitude above equator

798 km at Equator

Inclination

98.6 degrees> 5 years
IGARSS 2018 @Jul. 26 20184

1. Overview of GCOM-C satellite and SGLI(3) SGLI (Second Generation Global Imager)
Non Polarized
Observation Telescopes(24deg FOV x 3)

SolarDiffuser

EarthView Window

Polarized
Observation
Telescopes(55deg FOVx 2)

Sun Cal.
Window

About
1.4m

About
1.3m

About
1.7m

About
0.6m

Infrared Scanning Radiometer(SGLI-IRS)

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

DeepSpace
Windowfeatures

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 500m, Swath 1400km
IGARSS 2018 @Jul. 26 20185

1. Overview of GCOM-C satellite and SGLI(4) SGLI specifications
 The SGLI features are 250m spatial resolution and polarization/along-trackslant view channels (VNR-PL), which will improve land, coastal, and aerosol
250m over the Land or coastal
observations.
area, and 1km over offshore
GCOM-C SGLI characteristics
Sun-synchronousOrbit(descending local time: 10:30)
Altitude 798km, Inclination 98.6deg
Mission Life 5 years (3 satellites; total 13 years)
Push-broom electric scan (VNR)
Scan
Wisk-broom mechanical scan (IRS)
1150km cross track (VNR: VN & P)
Scan width
1400km cross track (IRS: SW & T)
Digitalization 12bit
Multi-angle
Polarization 3 polarization angles for P
obs. for673.5 andAlong track Nadir for VN, SW and T,
868.5nmdirection+45 deg and -45 deg for P

On-board
calibration

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

SGLI channels
Lstd
Lmax SNR at Lstd IFOV
VN, P, SW:
VN, P:VN, P, SW: nm
SNRm
W/m2/sr/m
T: m
T: Kelvin
T: NET
380
1060
210
250
250
412
1075250400
250
443
1064400
300
250
490
1053120400
250
530
2041350250250565203390400
250
673.5
202362400
250
673.5
2025210250250763
12403501200
250/1000
868.5
20830400
250
868.5
2030
300
200
250
673.5
2025250
250
1000
868.5
2030300
250
1000
1050
2057248
500
1000
1380
208103
150
1000
1630
200
35057250
2210
50
1.9202111000
10.80.7300
340
0.2
250/1000
12.00.7300
340
0.2
250/1000


CH
VN1
VN2
VN3
VN4
VN5
VN6
VN7
VN8
VN9
VN10
VN11
P1
P2
SW1
SW2SW3
SW4
T1
T2

IGARSS 2018 @Jul. 26 2018

TIR: 500m resolution is also used6

2. GCOM-C operation status GCOM-C “SHIKISAI” was successfully launched on Dec. 23rd, 2017.
 SGLI checkout operation started on Jan. 1st, 2018 (VNR and IRSSWIR bands) and on Jan. 22nd (IRS-TIR bands).
 SGLI first images were released on Jan. 12th.
http://suzaku.eorc.jaxa.jp/GCOM_C/index.html
 As a result of the three-month activities for SGLI in-orbit checkout, all
the SGLI functions are operating properly and SGLI maintains thepredicted performances obtained by the pre-launch characterizationtests.
 We moved on to the nominal operation phase on Mar. 28th and keep
the continuous global observation.
 SGLI calibration and validation activities have been carrying out
towards the SGLI products release to public on Dec. 2018.
IGARSS 2018 @Jul. 26 20187

2. GCOM-C operation status“SHIKISAI (=colorful)” Earth Gallery

©JAXA

©JAXA
Vegetation distribution of the middle of Japan

Coral reefs in the Bahamas

©JAXA

©JAXA
Namibia coast and Namib desert IGARSS 2018 @Jul. 26 2018

Morning glow of Kamchatka peninsula8

3. SGLI pre-launch characterization(1) SGLI characterization Flow
Device/Component Test
- Optical components- Detectors- Calibration devices- Electronic components- etc.
<IRS>

SGLI Proto-flight Test

Initial Performance Test (IPT)- Initial radiometric test
- Initial geometric test <IRS>
SRU-ELU integration Test

<VNR>

NP and PL telescope Test
- Radiometric test
- Geometric test

NP and PL Sub-unit Test
- Radiometric test
- Geometric test
- Thermal vacuum test

SRU Environment Test
- Vibration test
- Acoustic test
- Thermal vacuum test
- EMC test

GCOM-C system
Proto-flight Test
Initial PerformanceTest (IPT)
Environment Test
- Vibration test
- Acoustic test
- Thermal vacuum test
- EMC test
Final Performance
Test (FPT)
End-to-End Test
(w/ ground system)

Final Performance Test (FPT)- Final radiometric test
- Final geometric test <IRS>
IGARSS 2018 @Jul. 26 2018

Launch-site Finaltest
93. SGLI pre-launch characterization(2) SGLI Radiometric tests (VNR and IRS-SWIR) Three integrating spheres (ISs) were used for the pre-launch radiometrictests of reflective solar bands (VNR and IRS-SWIR).
 Barium sulfate IS and Spectralon IS for VNR
Spectralon Gold-coated IS for IRS-SWIR Radiometric performances were characterized
and satisfied the requirements.
 SNR, gain, dynamic range, stability,PRNU, linearity etc.
Gold-coatedIntegrating Sphere
IRS-SRU[Ref] Hashiguchi et. al. “Radiometric performance of Secondgeneration Global Imager (SGLI) using integrating spheres,"Proc.
IGARSS 2018 @Jul.
26SPIE2018 10000, 1000007 (2016)10

3. SGLI pre-launch characterization(2) SGLI Radiometric tests (VNR and IRS-SWIR) Traceability scheme from the national standard

IRS

SGLI

VNR

Gold‐coatedBarium sulfate

Spectralon

IntegratingSphere

IntegratingSphere

IntegratingSphere
RelativeradianceIntegrating SphereStandard Spectral Radiometer
Radiometer

SGLI sensors are calibrated byintegrating spheres of working standard.

SW02‐04

Zn

VN06‐11

SW01

Cu

VN01‐05

Transfer
Radiometer

Integrating spheres of working
standard are traceable to each FPBB.

Pt‐C

FPBBs of primary standard aretraceable to the national standard.

Fixed‐Point Black Body
NationalStandard

Ref: Hashiguchi et. al. “Radiometric performance of Secondgeneration Global Imager (SGLI) using integrating spheres,"Proc. SPIE 10000, 1000007 (2016)
IGARSS 2018 @Jul. 26 2018113. SGLI pre-launch characterization(3) SGLI Radiometric tests (TIR) Radiometric characterization of thermal infrared (TIR) bands wasperformed in the thermal-vacuum test using dedicated high emissivity
blackbody (BB) instruments;
 Temperature variable BB on earth view port
 Cold BB on space view port

IGARSS 2018 @Jul. 26 201812

3. SGLI pre-launch characterization(4) Pre-launch Calibration summary IRS-SWIR VNR
CenterWavelength

ChBandwidthnmNPN
NPLNPR

Signal Level
LstdSaturation(Spec.)
Level
W/m2/str/µm60
240-241

SW21.3920.1

Ch624-675

379.9

10.6

VN02

412.3

10.3

75305-318

786-826

VN03

443.3

10.1

64457-467

487-531

SW3

1.63

SW4

2.21

VN04

490.0

10.3

53147-150

858-870

VN05

529.7

19.1

41361-364

457-522

VN06

566.1

19.8

3395-961027-1064

VN07

672.3

22.0

23

69-70

988-1088

VN08

672.4

21.9

25

213-217537-564

VN09

763.1

11.4

40351-359

1592-1746

VN10

867.1

20.9

8

37-38

470-510

867.4

20.8

30305-306

471-511295609315707-60293

61460

396

646424763

40075260

PL2SW1Center
Wavelength
µm
1.05

VN01

VN11PL1SNR
at Lstd

00-60

672.2

866.3

20.6

20.3

2530

SWIRSignal Level
Lstd
Saturation(Spec.)
Level
W/m2/str/µm
57
289.2

Bandwidth
nm
21.1

SNR
at Lstd
951.8

8

118.9

347.3

195.0

3

50.6

100.5

50.4

1.9

21.7

378.7

 IRS-TIR

T1

CenterWavelengthµm10.785T2

11.975

ChTIR

Band
width

Signal Levelnm
756

Tstd(Spec.)
K300

759

300

NEdT
at TstdK
0.08
0.13

All the requirements of pre-launch SGLI performances wereconfirmed to be satisfied.
IGARSS 2018 @Jul. 26 201813

4. SGLI in-orbit Calibration(1) VNR Calibration concept Deployable Spectralon diffuser is used for both Solar and LED calibration.
 β angle dependency for solar calibration will be characterized shortly after launchusing satellite yaw maneuver.
LED CAL

Solar CALNP Tele.
Right

NP Tele.
CenterNP Tele.
Left

NP Tele.
Right

NP Tele.
CenterTilt Mechanism

NP Tele.
Left

Sun

Tilt Mechanism
DeployedSpectralon Diffuser

LED and Monitor
BenchDiffuser DeployMechanismwith safety function

Backward Tilting
PL telescopes

IGARSS 2018 @Jul. 26 2018

PL telescope
Tilting Mechanism

14

4. SGLI in-orbit Calibration(2) IRS Calibration concept
 IRS 81rpm rotating for both “Earth Observation” and “Calibration”.
Calibration
Window

Spectralon
Diffuser TIR Calibration : “Black Body” and “Deep Space”
 SWI Calibration :“Diffused Solar Light”, “LED/Lamp”
and “Deep Space”+Z (Earth)

Light
Guide

Earth Observation

SCAN
MIRROR

Light Guide

Diffused
Solar Light+X(Sat. Velocity) +Y(Space)

Deep SpaceSCANMIRROR

LightGuide

ε > 0.98

BLACKBODYHalogenLamp& LED

SWI LED assembly

BLACK
BODY
IGARSS 2018 @Jul. 26 201815

4. SGLI in-orbit Calibration(3) VNR & IRS Lunar Calibration overview
 Moon reflecting solar light is a stable light source as a long term
calibration reference of the optical sensors.
 GCOM-C lunar calibration maneuvers are planned every 29.5 days
during 5 years mission.
 Lunar calibration data is evaluatedusing the GSICS lunar calibration tool
(GIRO).

Lunar phaseangle

7deg +/-3deg

SGLI lunarobservation

All bands (VNR & IRS)
250m resolution

Satellite
Maneuver
Requirement- Pitch rate of 0.15 deg/s with highstability- Selectable roll angle (lunar image
in SGLI swath)
IGARSS 2018 @Jul. 26 2018

ManeuverCT direction: about 29 pixels
AT direction: about 92 lines

Every 29.5 days(= synodic period of the moon andthe sun)

Lunar
Observation

Pitch Maneuver

Calibrationinterval

MoonEarth16

4. SGLI in-orbit Calibration(4) Calibration operations
Calibration methodology
Onboard calibrator
Solar diffuser
Internal lamp
Dark image
Blackbody

VNR

SWIR

WeeklyWeeklyWeekly

WeeklyWeeklyWeekly-TIR

Calibration Events (*1)

1/10,11,16-18, 26, 2/3, 11, 19, 27, 3/15, 23, 28
Hereafter, every 8 days.
Everyscan
Every scan-

Deep space
Calibration maneuver
Lunar calibration maneuverMonthly
Solar angle correction
Yearlymaneuver90-deg. yaw maneuverYearlyVicarious calibration
Continued activities
Cross calibration

1/31, 2/1, 3/1, 3/2, 4/1, 4/30, 5/30, 6/28
1/4
2/7, 2/17-(*) Except for dedicated checkout condition

 Several onboard calibration devices and calibration maneuvers have beenused for SGLI calibration.
 Combination of calibration results from different methodologies and sources
will provide us with good information for the systematic calibration error.
IGARSS 2018 @Jul. 26 201817

4. SGLI in-orbit Calibration(5) Noise performances (SNR, NEdT) Preliminary
1.00
0.90

Dark Noise NPNVNR(NP)

Pre‐launch

Post‐launch_180110

Post‐launch_180624

0.80

0.80
0.70

Dark Noise [DN]

Dark Noise [DN]

Dark Noise PL

1.00

0.60
0.50
0.40
0.30
0.20

0.60

VNR(PL)

0.40
0.200.10
0.00

0.00
VN01

VN02

Pre‐launch

VN04

VN05

VN06

VN07

Post‐launch_180110 NPN

VN08

VN09

VN10m60

VN11

Post‐launch_180624 NPN

Pre‐launch

1.2

Post‐launch(20180101)

pm0p60m60

PL01

SW1,2,4 Dark Noise (1km resolution)

1.4

0.2

Post‐launch(20180306)

10.8
0.6
0.4

pm0p60

PL02

TIR‐1 NEdT (250m resolution)
Spec .: 0.2 K @500m resolution

0.15

NEｄT

Noise [DN]

VN03

Pre‐launch(@300K)
Post‐launch(@290K)

0.1
0.05

0.2
00IRS(SWIR)
3Pre‐launch

Post‐launch(20180101)

IRS(TIR)
0.2

Post‐launch(20180306)
0.15

21.5
1
0.50NEｄT

Noise [DN]

2.5

SW3 Dark Noise (250m resolution)

TIR‐2 NEdT (250m resolution)

Spec .: 0.2 K @500m resolution

Pre‐launch(@300K)
Post‐launch(@290K)

0.1
0.05
0

SGLI in-orbit noise performances of all bands keep the pre-launch ones
and satisfy the SNR and NEdT
requirements.
IGARSS 2018 @Jul. 26 201818

4. SGLI in-orbit Calibration(6) VNR gain trend
Solar calibration

LED calibration

Preliminary
Lunar calibration

VN03(443nm)VN05(530nm)VN07(673nm)VN10(868nm)

PD
Monitor

865nm
670nm
530nm

865nm
670nm
530nm

412nm

412nm

IGARSS 2018 @Jul. 26 2018(*) Ratio of SGLI observation toGIRO simulation

19

4. SGLI in-orbit Calibration(6) VNR gain trend
NPL

m60

pm0

p60

NPL

PDM

NPN

NPL

m60

pm0

p60

NPL

PDM

1.1

1.1

11

1

0.9

0.8

0.7

Calibration Trend

1.1

Calibration Trend

Calibration Trend

NPN

VNR Lunar Cal. trend (20180628 / 20180201)

VNR internal Lamp Cal. trend (20180624 / 20180203)

VNR Solar Cal. trend (20180624 / 20180203)
NPL

Preliminary

0.9

0.80.7

Solar cal.
350

400

450500550 600 650
Wavelength [nm]

700

750

800

850

900

NPLm60pm0p60PDM

0.90.80.7

LED cal.

Lunar cal.

0.60.60.6

NPN

350

400

450500550 600 650
Wavelength [nm]

700

750

800

850

900

350

400

450500550 600 650
Wavelength [nm]

700

750

800

850

900

・ Output of VNR shorter wavelength bands is decreasing for Solar and LED cal.
・ On the other hand, output of the lunar calibration is almost constant.
⇒ In-orbit VNR observation gains itself are stable.
(less than +- 1%)⇒ Decrease of the Solar and LED calibration output isdue to degradation of Spectralon diffuser.
(Solar light might be partially illuminated to thestored diffuser around south pole.)
IGARSS 2018 @Jul. 26 201820

4. SGLI in-orbit Calibration(7) IRS gain trend

Preliminary

SW3 gain trend using LED calibrator
SW3 lamp Cal. trend (LED)

1.01

Ratio to pre‐launch

1.005

10.995

PIX1

PIX2

PIX3

PIX4

PIX5

PIX6

PIX7

PIX8

PIX9

PIX10

PIX11

PIX12

PIX13

PIX14

PIX15

PIX16

PIX17

PIX18

PIX19

PIX200.99
Pre‐launch 2018/1/10 2018/1/14 2018/1/18

2018/2/3

2018/2/11 2018/2/19 2018/2/27

SW1,2,4 gain trend using Halogen lamp (ratio to SW3)

10.995

0.99

PIX1

PIX2

PIX3

PIX4

PIX5

1.03

SW2 lamp Cal. trend (Halogen lamp, SW3比)

1.02

1.01

10.99

Due to water
vapor
Ambient
test

PIX1

PIX2

PIX3

PIX4

1.01

Ratio to pre‐launch

1.005

SW1 lamp Cal. trend (Halogen lamp, SW3比)

Ratio to pre‐launch

Ratio to pre‐launch

1.01

1.005

1SW4 lamp Cal. trend (Halogen lamp, SW3比)
PIX1

PIX2PIX3

PIX4

PIX5

SWIR Lunar calibration trend(Ratio of SGLI observation to GIRO simulation)

0.995

PIX50.99

In-orbit SWIR observation gain are stable. (less than +- 1%)
IGARSS 2018 @Jul. 26 201821

5. Summary and future plans As a result of the three-month checkout activities andpreliminary calibration trend, All the SGLI functions are operating properly.
 SGLI maintains the predicted performances obtained by
the pre-launch characterization tests.
 Calibration and validation activities are ongoing.
 SGLI scientific products will be released to public on
December 2018 via JAXA G-Portal (data distribution system).
 Level 1 products
 Level 2 and 3 products (more than 28 scientific products
including clouds, aerosols, ocean color, vegetation, snow andice, and other applications.)

IGARSS 2018 @Jul. 26 201822

5. Summary and future plans JAXA G-Portal Website

https://gportal.jaxa.jp/
IGARSS 2018 @Jul. 26 201823

5. Summary and future plans

©JAXA

©JAXA
Vegetation distribution of the middle of Japan

Coral reefs in the Bahamas

Please look forward to using SGLI data!!
Thank you.
©JAXA©JAXA
Namibia coast and Namib desert IGARSS 2018 @Jul. 26 2018

Morning glow of Kamchatka peninsula24

Acknowledgements

 SGLI Lunar calibration data was evaluated using the GSICS lunar
calibration tool (GIRO: GSICS Implementation of the Robotic Lunar
Observatory).
 The authors would like to thank the GIRO implementation agencies
led by EUMETSAT and GSICS lunar calibration community for GIRO
usage and technical assistance.

IGARSS 2018 @Jul. 26 201825