pre-launch characterization and in-orbit calibration of gcom...

IGARSS 2018July 26, 2018

Japan Aerospace Exploration Agency Yoshihiko Okamura

Pre-Launch Characterization and In-orbit Calibration of GCOM-C/SGLI

T. Hashiguchi, T. Urabe, K. Tanaka (JAXA)J Yoshida, T Sakashita, and T Amano (NEC)

IGARSS 2018 @Jul. 26 2018

Contents

2

1. Overview of GCOM-C satellite and SGLI2. GCOM-C operation status3. SGLI pre-launch characterization4. SGLI in-orbit calibration5. Summary and future plans

IGARSS 2018 @Jul. 26 2018 3

GCOM mission: Long-term observation of the earth’s environment Two satellite series;

GCOM-W “SHIZUKU”: Microwave observation for WATER CYCLEusing AMSR2 (AMSR-E follow on)

GCOM-C “SHIKISAI”: Optical multi-channel observation forRADIATION BUDGET and CARBON CYCLE using SGLI (GLI follow on)

GCOM-C(CLIMATE)

SensorAdvanced MicrowaveRadiometer 2 (AMSR2)

Passive Microwave ObservationWater vapor, soil moisture etc

SensorSecond Generation Global Imager(SGLI)

Optical Observation 380nm – 12 micronCloud, Aerosol, Vegetation, Chlorophyll etc

GCOM-W(WATER)

AMSR2

SGLI

1. Overview of GCOM-C satellite and SGLI(1) Global Change Observation Mission(GCOM)

GCOM-W was launched on May 18, 2012.

GCOM-C was launched on Dec. 23, 2017.

IGARSS 2018 @Jul. 26 2018 4

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

SGLI IRSELU

+ X

flight direction

+Y

+ Z earth

deepspace

SGLI VNRELU

SGLI IRSSRU SGLI VNR

SRU

SGLI Second Generation Global ImagerVNR Visible and Near Infrared RadiometerIRS Infrared Scanning RadiometerSRU Scanning Radiometer UnitELU 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 EquatorInclination 98.6 degrees

Mission Life > 5 years

IGARSS 2018 @Jul. 26 2018 5

1. Overview of GCOM-C satellite and SGLI(3) SGLI (Second Generation Global Imager)

PolarizedObservationTelescopes(55deg FOVx 2)

Non PolarizedObservation Telescopes(24deg FOV x 3)

SolarDiffuser

About1.7m

About1.3m

Infrared Scanning Radiometer(SGLI-IRS)

Sun Cal.Window

EarthView Window

DeepSpaceWindow

About1.4m

About0.6m

Sensor Unit featuresSGLI VNR Non Polarized Observation （11ch）, IFOV 250m, Swath 1150km

Polarized Observation（2ch）, IFOV 1km, Swath 1150kmSGLI IRS Shortwave Infrared （SWI 4ch）, IFOV 250m/1km, Swath 1400km

Thermal Infrared （TIR:2ch）, IFOV 500m, Swath 1400km

Visible and Near Infrared Radiometer(SGLI-VNR)

IGARSS 2018 @Jul. 26 2018 6

1. Overview of GCOM-C satellite and SGLI(4) SGLI specifications

SGLI channels

CH

Lstd Lmax SNR at Lstd IFOV

VN, P, SW: nmT: m

VN, P: W/m2/sr/m

T: Kelvin

VN, P, SW: SNR

T: NETm

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

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

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

GCOM-C SGLI characteristics

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

Mission Life 5 years (3 satellites; total 13 years)

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

Scan width 1150km cross track (VNR: VN & P)1400km cross track (IRS: SW & T)

Digitalization 12bitPolarization 3 polarization angles for PAlong track direction

Nadir for VN, SW and T, +45 deg and -45 deg for P

On-board calibration

VN: Solar diffuser, LED, Lunar calmaneuvers, and dark current by masked pixels and nighttime obs.

SW: Solar diffuser, LED, Lunar, and dark current by deep space window

T: Black body and dark current by deep space window

Multi-angle obs. for 673.5 and 868.5nm

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

TIR: 500m resolution is also used

IGARSS 2018 @Jul. 26 2018 7

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 IRS-SWIR 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, allthe 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 keepthe continuous global observation.

SGLI calibration and validation activities have been carrying outtowards the SGLI products release to public on Dec. 2018.

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

Coral reefs in the Bahamas Vegetation distribution of the middle of Japan

Morning glow of Kamchatka peninsula

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

8

©JAXA ©JAXA

©JAXA ©JAXA

IGARSS 2018 @Jul. 26 2018

3. SGLI pre-launch characterization(1) SGLI characterization Flow

9

Initial Performance Test (IPT)- Initial radiometric test- Initial geometric test

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

NP and PL telescope Test- Radiometric test- Geometric test

SGLI Proto-flight Test

Final Performance Test (FPT)- Final radiometric test- Final geometric test

Device/Component Test- Optical components- Detectors- Calibration devices- Electronic components- etc.

SRU-ELU integration Test

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

<VNR><IRS>

<IRS>

<IRS>

GCOM-C systemProto-flight Test

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

Initial PerformanceTest (IPT)

Final PerformanceTest (FPT)

End-to-End Test (w/ ground system)

Launch-site Finaltest

IGARSS 2018 @Jul. 26 2018

3. SGLI pre-launch characterization(2) SGLI Radiometric tests (VNR and IRS-SWIR)

10

Three integrating spheres (ISs) were used for the pre-launch radiometric tests of reflective solar bands (VNR and IRS-SWIR). Barium sulfate IS and Spectralon IS for VNR Gold-coated IS for IRS-SWIR

[Ref] Hashiguchi et. al. “Radiometric performance of Second-generation Global Imager (SGLI) using integrating spheres," Proc. SPIE 10000, 1000007 (2016)

Radiometric performances were characterized and satisfied the requirements. SNR, gain, dynamic range, stability,

PRNU, linearity etc.

IRS-SRU

Gold-coatedIntegrating Sphere

Spectralon

IGARSS 2018 @Jul. 26 2018 11

3. SGLI pre-launch characterization(2) SGLI Radiometric tests (VNR and IRS-SWIR)

Traceability scheme from the national standard

VNRIRS

Zn Cu Pt‐C

National Standard

Gold‐coatedIntegratingSphere

Barium sulfateIntegratingSphere

SpectralonIntegratingSphere

SGLI

Integrating Sphere

RadiometerTransfer

Radiometer

Fixed‐Point Black Body

SW02‐04 SW01 VN06‐11 VN01‐05

Relative radiance

Standard Spectral Radiometer

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.

Ref: Hashiguchi et. al. “Radiometric performance of Second-generation Global Imager (SGLI) using integrating spheres," Proc. SPIE 10000, 1000007 (2016)

IGARSS 2018 @Jul. 26 2018

3. SGLI pre-launch characterization(3) SGLI Radiometric tests (TIR)

12

Radiometric characterization of thermal infrared (TIR) bands was performed 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 2018 13

3. SGLI pre-launch characterization(4) Pre-launch Calibration summary

Signal LevelTstd

(Spec.)µm nm K K

T1 10.785 756 300 0.08T2 11.975 759 300 0.13

TIR

Ch

CenterWave-length

Bandwidth

NEdTat Tstd

Lstd(Spec.)

SaturationLevel

-VN01 379.9 10.6 60 240-241 624-675VN02 412.3 10.3 75 305-318 786-826VN03 443.3 10.1 64 457-467 487-531VN04 490.0 10.3 53 147-150 858-870VN05 529.7 19.1 41 361-364 457-522VN06 566.1 19.8 33 95-96 1027-1064VN07 672.3 22.0 23 69-70 988-1088VN08 672.4 21.9 25 213-217 537-564VN09 763.1 11.4 40 351-359 1592-1746VN10 867.1 20.9 8 37-38 470-510VN11 867.4 20.8 30 305-306 471-511

60 295 6090 315 707

-60 293 61460 396 6460 424 763

-60 400 752PL2 866.3 20.3

nm W/m2/str/µm

25

30

Ch

Signal Level

NPNNPLNPR

PL1 672.2 20.6

SNRat Lstd

CenterWave-length

Bandwidth Lstd

(Spec.)Saturation

Levelµm nm -

SW1 1.05 21.1 57 289.2 951.8SW2 1.39 20.1 8 118.9 347.3SW3 1.63 195.0 3 50.6 100.5SW4 2.21 50.4 1.9 21.7 378.7

SWIR

CenterWave-length

Bandwidth

Signal LevelSNR

at Lstd

W/m2/str/µm

Ch

VNR IRS-SWIR

IRS-TIR

All the requirements of pre-launch SGLI performances were confirmed to be satisfied.

IGARSS 2018 @Jul. 26 2018 14

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 launch

using satellite yaw maneuver.

Tilt Mechanism

Sun

NP

Tele

.Le

ft

NP

Tele

.Ce

nter

NP

Tele

.Ri

ght

Diffuser DeployMechanismwith safety function

DeployedSpectralon DiffuserLED and Monitor

Bench

Backward TiltingPL telescopes

Tilt Mechanism

NP

Tele

.Le

ft

NP

Tele

.Ce

nter

NP

Tele

.Ri

ght

PL telescopeTilting Mechanism

Solar CALLED CAL

IGARSS 2018 @Jul. 26 2018 15

4. SGLI in-orbit Calibration(2) IRS Calibration concept

DiffusedSolar Light Deep Space

Earth Observation

BLACKBODY

SCANMIRROR

LightGuide

IRS 81rpm rotating for both “Earth Observation” and “Calibration”.

Light Guide

CalibrationWindow

LightGuide

SpectralonDiffuser

ε > 0.98

BLACKBODY

TIR Calibration : “Black Body” and “Deep Space” SWI Calibration :“Diffused Solar Light”, “LED/Lamp”

and “Deep Space”+Z (Earth)

+Y (Space)

+X (Sat. Velocity)

Halogen Lamp& LED

SCANMIRROR

SWI LED assembly

IGARSS 2018 @Jul. 26 2018 16

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.

Earth Moon

Maneuver

LunarObservation

Calibration interval

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

Lunar phase angle

7deg +/-3deg

SGLI lunar observation

All bands (VNR & IRS)250m resolution

SatelliteManeuver Requirement

- Pitch rate of 0.15 deg/s with high stability- Selectable roll angle (lunar image in SGLI swath)

CT direction: about 29 pixels

AT d

irect

ion:

abo

ut 9

2 lin

es

Pitc

h M

aneu

ver

Lunar calibration data is evaluated using the GSICS lunar calibration tool (GIRO).

IGARSS 2018 @Jul. 26 2018

4. SGLI in-orbit Calibration(4) Calibration operations

17

Calibration methodology VNR SWIR TIR Calibration Events (*1)Onboard calibrator

Solar diffuser Weekly Weekly - 1/10,11,16-18, 26, 2/3, 11, 19, 27, 3/15, 23, 28Hereafter, every 8 days.Internal lamp Weekly Weekly -

Dark image Weekly Weekly -

Blackbody - - Every scan -

Deep space - Every scan -Calibration maneuver

Lunar calibration maneuver Monthly 1/31, 2/1, 3/1, 3/2, 4/1, 4/30, 5/30, 6/28Solar angle correction maneuver Yearly - 1/4

90-deg. yaw maneuver Yearly - - 2/7, 2/17Vicarious calibration Continued activities -Cross calibration

(*) 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 sourceswill provide us with good information for the systematic calibration error.

IGARSS 2018 @Jul. 26 2018

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

18

SGLI in-orbit noise performances of all bands keep the pre-launch ones and satisfy the SNR and NEdT requirements.

0

0.05

0.1

0.15

0.2

NEｄ

T

TIR‐1 NEdT (250m resolution)

Pre‐launch(@300K)

Post‐launch(@290K)

Spec .: 0.2 K @500m resolution

0

0.05

0.1

0.15

0.2

NEｄ

T

TIR‐2 NEdT (250m resolution)

Pre‐launch(@300K)

Post‐launch(@290K)

Spec .: 0.2 K @500m resolution

00.20.40.60.81

1.21.4

Noise [D

N]

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

Pre‐launch Post‐launch(20180101) Post‐launch(20180306)

0

0.5

1

1.5

2

2.5

3

Noise [D

N]

SW3 Dark Noise (250m resolution)

Pre‐launch Post‐launch(20180101) Post‐launch(20180306)

Preliminary

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

VN01 VN02 VN03 VN04 VN05 VN06 VN07 VN08 VN09 VN10 VN11

Dark Noise [D

N]

Dark Noise NPN

Pre‐launch Post‐launch_180110 NPN Post‐launch_180624 NPN

0.00

0.20

0.40

0.60

0.80

1.00

m60 pm0 p60 m60 pm0 p60

PL01 PL02

Dark Noise [D

N]

Dark Noise PL

Pre‐launch Post‐launch_180110 Post‐launch_180624VNR(NP)VNR(PL)

IRS(SWIR) IRS(TIR)

IGARSS 2018 @Jul. 26 2018

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

19

Solar calibration

Preliminary

VN03(443nm)

VN05(530nm)

VN07(673nm)

VN10(868nm)

PDMonitor

LED calibration

412nm

530nm670nm865nm

412nm

530nm670nm865nm

Lunar calibration

(*) Ratio of SGLI observation to GIRO simulation

IGARSS 2018 @Jul. 26 2018

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

20

0.6

0.7

0.8

0.9

1

1.1

350 400 450 500 550 600 650 700 750 800 850 900

Calib

ratio

n Tren

d

Wavelength [nm]

VNR Solar Cal. trend (20180624 / 20180203)NPL NPN NPL m60 pm0 p60 PDM

0.6

0.7

0.8

0.9

1

1.1

350 400 450 500 550 600 650 700 750 800 850 900

Calib

ratio

n Tren

d

Wavelength [nm]

VNR internal Lamp Cal. trend (20180624 / 20180203)NPL NPN NPL m60 pm0 p60 PDM

・ 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 is due to degradation of Spectralon diffuser.(Solar light might be partially illuminated to the stored diffuser around south pole.)

0.6

0.7

0.8

0.9

1

1.1

350 400 450 500 550 600 650 700 750 800 850 900

Calib

ratio

n Tren

d

Wavelength [nm]

VNR Lunar Cal. trend (20180628 / 20180201)NPL NPN NPL m60 pm0 p60 PDM

Solar cal. LED cal. Lunar cal.

Preliminary

IGARSS 2018 @Jul. 26 2018

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

21

0.99

0.995

1

1.005

1.01

Pre‐launch 2018/1/10 2018/1/14 2018/1/18 2018/2/3 2018/2/11 2018/2/19 2018/2/27

Ratio to pre‐la

unch

SW3 lamp Cal. trend (LED)

PIX1 PIX2 PIX3 PIX4 PIX5




SW3 gain trend using LED calibrator

In-orbit SWIR observation gain are stable. (less than +- 1%)

Preliminary

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

0.99

0.995

1

1.005

1.01

Ratio

to pre‐la

unch

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

PIX1 PIX2PIX3 PIX4PIX5

0.99

1

1.01

1.02

1.03

Ratio

to pre‐la

unch



0.99

0.995

1

1.005

1.01

Ratio

to pre‐la

unch



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

Due to water vapor

Ambienttest

IGARSS 2018 @Jul. 26 2018 22

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 2018


23

https://gportal.jaxa.jp/

JAXA G-Portal Website

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

Coral reefs in the Bahamas Vegetation distribution of the middle of Japan

Morning glow of Kamchatka peninsula


24

©JAXA ©JAXA

©JAXA ©JAXA

Please look forward to using SGLI data!!Thank you.

IGARSS 2018 @Jul. 26 2018

Acknowledgements

25

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.

pre-launch characterization and in-orbit calibration of gcom...

Documents