Radiometric performance of Second Generation Global Imager (SGLI) using integrating sphere

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

Contents GCOM overview SGLI specification Strategy of SGLI radiometric test Traceability of SGLI radiometric test SGLI VNR radiometric test SGLI IRS radiometric test Summary Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 2

Global Change Observation Mission(GCOM) overview 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-W (WATER) GCOM-W1 SHIZUKU was launched on May 18, 2012. AMSR2 GCOM-C (CLIMATE) SGLI 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 Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 3

GCOM-C overview 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, near-circular orbit 10:15 10:45 at descending node 798 km at Equator 98.6 degrees > 5 years Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 4

Second-generation Global Imager (SGLI) Overview Non Polarized Observation Telescopes (24deg FOV x 3) Solar Diffuser Earth View Window Polarized Observation Telescopes (55deg FOV x 2) Sun Cal. Window About 1.5m About 1.4m About 1.5m About 0.7m Deep Space Window Visible and Near Infrared Radiometer (SGLI-VNR) Sensor Unit features Infrared Scanning Radiometer (SGLI-IRS) 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 250m, Swath 1400km Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 5

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 Sun-synchronous Orbit (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 Multi-angle obs. for 673.5nm and 868.5nm 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 Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 250m over the Land or coastal area, and 1km over offshore SGLI channels λ λ L std L max SNR at Lstd IFOV VNR-NP, VNR-PL, VNR-NP, VNR-PL, VNR-NP, VNR-PL, CH IRS-SWI IRS-SWI: nm :W/m IRS-TIR: µm IRS-SWI : SNR /sr/µm IRS-TIR: NE T IRS-TIR: Kelvin 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 TIR: 500m resolution is also used 6

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 7

Strategy of SGLI radiometric test - Specifications of integrating spheres - Monitor detector 200mm 1000mm Monitor detector 1000mm Monitor detector 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) Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 8

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. 1,000 VNR Barium sulfate integrating sphere It has good characteristics (stability, reproducibility) in the visible region. Used to characterize the absolute performance of VNR Spectralon was briefly measured by FieldSpec 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 IRS 3.00 2.50 Radiance [W/m^2/Str/um] 100 10 1 VN01 VN03 VN05 VN07 VN08 PL01 VN10 VN11 PL02 Gold 2.98A(50W)x4 SW02 2.00 1.50 1.00 0.50 0.00 VN02 VN04 VN06 VN09 SW01 SW03 300 500 700 900 1100 1300 1500 1700 1900 2100 2300 Wavelength [nm] Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 9 SW04 Spectral response

Strategy of SGLI radiometric test - Uniformity of the spectral radiance at the aperture in VNR test- 2.00% Radiance uinformity [%] 1.00% 0.00% -1.00% -2.00% -4.0-3.0-2.0-1.0 0.0 1.0 2.0 3.0 4.0 Angle [degree] BaSO4 VN01 BaSO4 VN02 BaSO4 VN03 BaSO4 VN10 Spectralon VN01 Spectralon VN02 Spectralon VN03 Spectralon 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 10

Strategy of SGLI radiometric test - VNR test case - Barium sulfate integrating sphere Spectralon integrating sphere (a) Lamp set VN01 VN02 VN03 VN04 VN05 VN06 VN07 VN08 VN09 VN10 VN11 PL01 PL02 Lamp set 90.0V x 12 (b) Xenon Halogen VN01 VN02 VN03 VN04 VN05 VN06 VN07 VN08 VN09 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 :Lmax level 17.3V x 12 :Lstd level 16.0V x 12 :0.3Lstd level 14.5V x 12 12.5V x 12 10.1V x 12 VN10 VN11 PL01 PL02 On 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 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). 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 11

Strategy of SGLI radiometric test - Matrix of SGLI radiometric test - VNR IRS Radiometric characterization Barium sulfate Spectralon Gold-coated integrating sphere integrating sphere 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 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 12

Traceability of SGLI radiometric test 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 Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 13

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 VNR-SRU Integrating Sphere Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK

VNR PRNU (Photo response non-uniformity) results - preliminary - PRNU PRNU 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) 105 100 95 90 85 (b) 105 100 95 90 85 Lmax VN01 right telescope (before correction and connecting) 0 250 500 750 1000 1250 1500 Pixel Lstd VN01 right telescope (before correction and connecting) 0 250 500 750 1000 1250 1500 Pixel +10 +5 0-5 -10 +10 +5 0-5 -10 PRNU PRNU (c) 105 100 95 90 85 (d) 105 100 95 90 85 Lmax VN01 right telescope (after correction and connecting) 0 250 500 750 1000 1250 1500 Pixel Lstd VN01 right telescope (after correction and connecting) 0 250 500 750 1000 1250 1500 Pixel +10 +5 0-5 -10 +10 +5 0-5 -10 (e) PRNU error [%] 4.0 3.0 2.0 1.0 0.0-1.0-2.0-3.0-4.0 This band is 0.4 %p-p PRNU error VN01 right telescope 0 250 500 750 1000 1250 1500 Pixel Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK

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 VN08 right telescope Linearity Error [%] 4.0 3.0 2.0 1.0 0.0-1.0-2.0-3.0-4.0 0.3Lstd Lstd Linearity by change the lamp set Linearity by CCD electrical shutter Linearity by attenuator function 0 500 1000 1500 2000 2500 3000 3500 4000 [DN] Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 16 Lmax

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

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 1.1 SW01 0.3Lstd 1Lstd 1Lmax 1.1 SW02 0.3Lstd 1Lstd 1Lmax PRNU 1.0 0.9 PRNU 1.0 0.9 0.8 1.1 1 2 3 4 5 Pixel SW03 0.3Lstd 1Lstd 1Lmax 0.8 1.1 1 2 3 Pixel 4 5 SW04 0.3Lstd 1Lstd 1Lmax PRNU 1.0 0.9 PRNU 1.0 0.9 0.8 1 2 3 4 5 6 7 8 9 1011121314151617181920 Pixel 0.8 1 2 3 4 5 PRNU Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK

IRS Linearity results 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 Linearity Error [%] Linearity Error [%] 5 4 3 2-1 01-2 -3-4 -5 0.3Lstd 5 4 3 2-1 01-2 -3-4 -5 0.3Lstd Lstd SW01 Lmax 0 50 100 150 200 250 Radiance[W/m2/str/μm] SW03 Lmax Lstd 0 10 20 30 40 50 Radiance[W/m2/str/μm] Linearity Error [%] Linearity Error [%] 0.3Lstd 5 4 3 2-1 01-2 -3-4 -5 5 4 3 2-1 01-2 -3-4 -5 SW02 Lmax Lstd 0 20 40 60 80 100 Radiance[W/m2/str/μm] 0.3Lstd SW04 Lmax Lstd 0 2 4 6 8 10 12 14 16 18 20 Radiance[W/m2/str/μm] Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 19

IRS final radiometric test environment Transfer radiometer of 1380nm [V] 0.0534 0.0533 0.0532 0.0531 0.0530 0.0529 0.0528 0.0527 0.0526 0.0525 0.0524 10:00:00 12:00:00 Time 14:00:00 Transfer Radiometer of 1.38μm Transfer radiometer of 1380nm [V] Humidity[%] 55.0 54.5 54.0 53.5 53.0 52.5 52.0 51.5 51.0 50.5 50.0 Humidity[%] 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 Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 20

IRS final radiometric test preliminary result Temperature [ ] Absolute Humidity [g/m^3] IRS-SRU Gold-coated Integrating Sphere Temperature Humidity 24.5 24.0 23.5 23.0 22.5 22.0 21.5 21.0 20.5 6:00 9:00 12:00 15:00 18:00 21:00 0:00 2016/9/20~21 Time(JST) 10.0 9.5 Absolute Humidity 48 46 44 42 40 Humidity [%] This linearity data was measured on 21 Sep. Detailed evaluation is ongoing. Linearity Error [%] Linearity Error [%] 5 4 3 2 1 0-1 -2-3 -4-5 5 4 3 2 1 0-1 -2 0.3Lstd Lstd SW01 0 50 100 150 200 250 Radiance[W/m2/str/μm] 0.3Lstd Linearity Error [%] SW02 5 0.3Lstd Lmax 4 3 2 1 0-1 -2-3 -4-5 Lstd 0 20 40 60 80 100 Radiance [W/m2/str/μm] -3-3 9.0-4 -4 8.5-5 -5 Lstd Lstd 0 10 20 30 40 50 0 2 4 6 8 10 12 14 16 18 20 8.0 Radiance [W/m2/str/μm] Radiance [W/m2/str/μm] 6:00 9:00 12:00 15:00 18:00 21:00 0:00 2016/9/20~21 Radiometric Time(JST) performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 21 SW03 Lmax Lmax Linearity Error [%] 5 4 3 2 1 0-1 -2 0.3Lstd SW04 Lmax

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. Radiometric performance of SGLI using integrating sphere @SPIE RS 2016, Edinburgh, UK 22