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

Transcription

1 Pre-Launch Characterization and In-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)

2 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

3 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 : Optical multi-channel observation for RADIATION BUDGET and CARBON CYCLE using SGLI (GLI follow on) GCOM-W (WATER) AMSR2 GCOM-C (CLIMATE) SGLI GCOM-W was launched on May 18, GCOM-C was launched on Dec. 23, 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 IGARSS

4 1. Overview of GCOM-C satellite and SGLI (2) GCOM-C satellite SGLI IRS ELU SGLI VNR ELU +Y deep space +X flight direction + Z earth SGLI IRS SRU 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 Orbit Parameters Mission Life Orbit Type Local sun time Altitude above equator Inclination GCOM-C sun-synchronous, ground track repeat, nearcircular orbit 10:15 10:45 at descending node 798 km at Equator 98.6 degrees > 5 years IGARSS

5 1. Overview of GCOM-C satellite and SGLI (3) SGLI (Second Generation Global Imager) Non Polarized Observation Telescopes (24deg FOV x 3) Solar Diffuser Earth View Window Polarized Observation Telescopes (55deg FOV x2) Sun Cal. Window About 1.4m About 1.3m About 1.7m About 0.6m Deep Space Window Visible and Near Infrared Radiometer (SGLI-VNR) Sensor Unit Infrared Scanning Radiometer (SGLI-IRS) features SGLI VNR SGLI IRS Non Polarized Observation (11ch), IFOV 250m, Swath 1150km Polarized Observation(2ch), IFOV 1km, Swath 1150km Shortwave Infrared (SWI 4ch), IFOV 250m/1km, Swath 1400km Thermal Infrared (TIR:2ch), IFOV 500m, Swath 1400km IGARSS

6 1. Overview of GCOM-C satellite and SGLI (4) SGLI specifications 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 Sun-synchronous Orbit (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 Polarization 3 polarization angles for P Along track Nadir for VN, SW and T, direction +45 deg and -45 deg for P On-board calibration VN: Solar diffuser, LED, Lunar cal maneuvers, 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 CH 250m over the Land or coastal area, and 1km over offshore SGLI channels L std L max SNR at Lstd IFOV VN, P: VN, P, SW: VN, P, SW: nm W/m T: m 2 /sr/ m SNR m T: Kelvin T: NE T VN VN VN VN VN VN Multi-angle VN obs. for VN and VN / nm VN VN P P SW SW SW SW T /1000 T /1000 IGARSS TIR: 500m resolution is also used 6

7 2. GCOM-C operation status GCOM-C SHIKISAI was successfully launched on Dec. 23 rd, SGLI checkout operation started on Jan. 1 st, 2018 (VNR and SWIR bands) and on Jan. 22 nd (IRS-TIR bands). SGLI first images were released on Jan. 12 th. IRS- As a result of the three-month activities for SGLI in-orbit checkout, all the SGLI functions are operating properly and SGLI maintains the predicted performances obtained by the pre-launch characterization tests. We moved on to the nominal operation phase on Mar. 28 th and keep the continuous global observation. SGLI calibration and validation activities have been carrying out towards the SGLI products release to public on Dec IGARSS

8 2. GCOM-C operation status SHIKISAI (=colorful) Earth Gallery Vegetation distribution of the middle of Japan JAXA Coral reefs in the Bahamas JAXA JAXA Namibia coast and Namib desert IGARSS Morning glow of Kamchatka peninsula JAXA 8

9 3. SGLI pre-launch characterization (1) SGLI characterization Flow Device/Component Test - Optical components - Detectors - Calibration devices - Electronic components -etc. <VNR> <IRS> NP and PL telescope Test - Radiometric test - Geometric test NP and PL Sub-unit Test - Radiometric test - Geometric test - Thermal vacuum test SGLI Proto-flight Test Initial Performance Test (IPT) - Initial radiometric test - Initial geometric test <IRS> SRU-ELU integration Test SRU Environment Test - Vibration test - Acoustic test - Thermal vacuum test -EMC test Final Performance Test (FPT) - Final radiometric test - Final geometric test <IRS> GCOM-C system Proto-flight Test Initial Performance Test (IPT) Environment Test - Vibration test - Acoustic test - Thermal vacuum test -EMC test Final Performance Test (FPT) End-to-End Test (w/ ground system) Launch-site Final test IGARSS

10 3. SGLI pre-launch characterization (2) SGLI Radiometric tests (VNR and IRS-SWIR) 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 Spectralon Gold-coated IS for IRS-SWIR Radiometric performances were characterized and satisfied the requirements. SNR, gain, dynamic range, stability, PRNU, linearity etc. IRS-SRU Gold-coated Integrating Sphere [Ref] Hashiguchi et. al. Radiometric performance of Secondgeneration Global Imager (SGLI) using integrating spheres," IGARSS Proc. 26 SPIE , (2016) 10

11 3. SGLI pre-launch characterization (2) SGLI Radiometric tests (VNR and IRS-SWIR) Traceability scheme from the national standard SGLI IRS VNR SGLI sensors are calibrated by integrating spheres of working standard. Integrating Sphere Gold coated Integrating Sphere Barium sulfate Integrating Sphere Spectralon Integrating Sphere Relative radiance Radiometer Standard Spectral Radiometer SW02 04 SW01 VN06 11 VN01 05 Transfer Radiometer Integrating spheres of working standard are traceable to each FPBB. Zn Cu Pt C Fixed Point Black Body FPBBs of primary standard are traceable to the national standard. National Standard Ref: Hashiguchi et. al. Radiometric performance of Secondgeneration Global Imager (SGLI) using integrating spheres," Proc. SPIE 10000, (2016) IGARSS

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

13 3. SGLI pre-launch characterization (4) Pre-launch Calibration summary VNR Center Signal Level Band SNR Wavelength (Spec.) Level Lstd Saturation Ch width at Lstd nm W/m2/str/µm - VN VN VN VN NPN VN NPL VN NPR VN VN VN VN VN PL PL IRS-SWIR Center Signal Level Band SNR Wavelength (Spec.) Level Lstd Saturation Ch width at Lstd µm nm W/m2/str/µm - SW SW SWIR SW SW IRS-TIR TIR Ch Center Wavelength Signal Level Band Tstd width (Spec.) µm nm K K NEdT at Tstd T T All the requirements of pre-launch SGLI performances were confirmed to be satisfied. IGARSS

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. Solar CAL LED CAL Sun Tilt Mechanism NP Tele. Left NP Tele. Center NP Tele. Right Tilt Mechanism NP Tele. Left NP Tele. Center NP Tele. Right LED and Monitor Bench Deployed Spectralon Diffuser Backward Tilting PL telescopes Diffuser Deploy Mechanism with safety function PL telescope IGARSS Tilting Mechanism 14

15 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 Light Guide +Z (Earth) SCAN MIRROR Earth Observation +X (Sat. Velocity) +Y (Space) Light Guide Diffused Solar Light Deep Space SCAN MIRROR Light Guide BLACK BODY Halogen Lamp & LED SWI LED assembly ε >0.98 BLACK BODY IGARSS

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. Lunar calibration data is evaluated using the GSICS lunar calibration tool (GIRO). Earth Lunar Observation Moon Calibration interval Lunar phase angle SGLI lunar observation Satellite Maneuver Requirement Every 29.5 days (= synodic period of the moon and the sun) 7deg +/-3deg All bands (VNR & IRS) 250m resolution - Pitch rate of 0.15 deg/s with high stability - Selectable roll angle (lunar image in SGLI swath) Pitch Maneuver Maneuver CT direction: about 29 pixels IGARSS AT direction: about 92 lines

17 4. SGLI in-orbit Calibration (4) Calibration operations 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, 28 Internal lamp Weekly Weekly - Hereafter, every 8 days. 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, 6/28 Solar angle correction maneuver Yearly - 1/4 90-deg. yaw maneuver Yearly - - 2/7, 2/17 Vicarious calibration Cross calibration Continued activities - (*) Except for dedicated checkout condition Several onboard calibration devices and calibration maneuvers have been used for SGLI calibration. Combination of calibration results from different methodologies and sources will provide us with good information for the systematic calibration error. IGARSS

18 4. SGLI in-orbit Calibration (5) Noise performances (SNR, NEdT) Preliminary Dark Noise [DN] VNR(NP) Dark Noise NPN VN01 VN02 VN03 VN04 VN05 VN06 VN07 VN08 VN09 VN10 VN11 Dark Noise [DN] VNR(PL) Dark Noise PL Pre launch Post launch_ Post launch_ m60 pm0 p60 m60 pm0 p60 Pre launch Post launch_ NPN Post launch_ NPN PL01 PL02 Noise [DN] SW1,2,4 Dark Noise (1km resolution) Pre launch Post launch( ) Post launch( ) NEdT Spec.: 0.2 resolution TIR 1 NEdT (250m resolution) Pre launch(@300k) Post launch(@290k) IRS(SWIR) Noise [DN] SW3 Dark Noise (250m resolution) Pre launch Post launch( ) Post launch( ) IRS(TIR) NEdT Spec.: 0.2 resolution TIR 2 NEdT (250m resolution) Pre launch(@300k) Post launch(@290k) SGLI in-orbit noise performances of all bands keep the pre-launch ones and satisfy the SNR and NEdT requirements. IGARSS

19 Solar calibration 4. SGLI in-orbit Calibration (6) VNR gain trend LED calibration Preliminary Lunar calibration VN03 (443nm) VN05 (530nm) VN07 (673nm) VN10 (868nm) PD Monitor 865nm 670nm 530nm 412nm 865nm 670nm 530nm 412nm (*) Ratio of SGLI observation to GIRO simulation IGARSS

20 4. SGLI in-orbit Calibration (6) VNR gain trend Preliminary 1.1 VNR Solar Cal. trend ( / ) NPL NPN NPL m60 pm0 p60 PDM 1.1 VNR internal Lamp Cal. trend ( / ) NPL NPN NPL m60 pm0 p60 PDM 1.1 VNR Lunar Cal. trend ( / ) NPL NPN NPL m60 pm0 p60 PDM Calibration Trend Calibration Trend Calibration Trend Solar cal. LED cal. Lunar cal Wavelength [nm] Wavelength [nm] Wavelength [nm] 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.) IGARSS

21 4. SGLI in-orbit Calibration (7) IRS gain trend Preliminary 1.01 SW3 gain trend using LED calibrator SW3 lamp Cal. trend (LED) Ratio to pre launch PIX1 PIX2 PIX3 PIX4 PIX5 PIX6 PIX7 PIX8 PIX9 PIX10 PIX11 PIX12 PIX13 PIX14 PIX15 PIX16 PIX17 PIX18 PIX19 PIX20 Pre launch 2018/1/ /1/ /1/ /2/3 2018/2/ /2/ /2/27 SW1,2,4 gain trend using Halogen lamp (ratio to SW3) Ratio to pre launch SW1 lamp Cal. trend (Halogen lamp, SW3 比 ) 1.01 PIX1 PIX2 PIX3 PIX PIX Ratio to pre launch SW2 lampcal.trend(halogenlamp,sw3 比 ) Ambient test Due to water vapor PIX1 PIX3 PIX5 PIX2 PIX4 Ratio to pre launch SW4 lamp Cal. trend (Halogen lamp, SW3 比 ) 1.01 PIX1 PIX2 PIX3 PIX PIX SWIR Lunar calibration trend (Ratio of SGLI observation to GIRO simulation) In-orbit SWIR observation gain are stable. (less than +- 1%) IGARSS

22 5. Summary and future plans As a result of the three-month checkout activities and preliminary 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 and ice, and other applications.) IGARSS

23 5. Summary and future plans JAXA G-Portal Website IGARSS

24 5. Summary and future plans Vegetation distribution of the middle of Japan JAXA Coral reefs in the Bahamas JAXA Please look forward to using SGLI data!! Thank you. JAXA Namibia coast and Namib desert IGARSS Morning glow of Kamchatka peninsula JAXA 24

25 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