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GOCI: Early In-Orbit Performances Han-Dol KIM*, Gm-Sil Kang*, Joo-Hyung Ryu** Pierre Coste †, Philippe Meyer † *Korea Aerospace Research Institute (KARI)

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Presentation on theme: "GOCI: Early In-Orbit Performances Han-Dol KIM*, Gm-Sil Kang*, Joo-Hyung Ryu** Pierre Coste †, Philippe Meyer † *Korea Aerospace Research Institute (KARI)"— Presentation transcript:

1 GOCI: Early In-Orbit Performances Han-Dol KIM*, Gm-Sil Kang*, Joo-Hyung Ryu** Pierre Coste †, Philippe Meyer † *Korea Aerospace Research Institute (KARI) **Korea Ocean Research and Development Institute (KORDI) † EADS Astrium July 28, 2011 Vancouver, CANADA 2011 IGARSS TH3.T05

2 Agenda Introduction of COMSIntroduction of COMS Introduction of GOCIIntroduction of GOCI Current Status of COMS and GOCICurrent Status of COMS and GOCI GOCI In-Orbit PerformancesGOCI In-Orbit Performances ConclusionConclusion 2

3 Introduction of COMS (1) COMS: Communication, Ocean and Meteorological Satellite Geostationary satellite Mass at Launch: 2460 kg Orbital Location: o E Design Life time: 10 years Operational Life: 7.7 years Launch: June 26, 2910, 21:41 (UTC) Launcher: Ariane 5 ECA COMS Missions A meteo mission (MI)* An ocean imager mission (GOCI)** An experimental Ka band telecommunication mission * MI: Meteorological Imager ** GOCI: Geostationary Ocean Color Imager 3

4 Introduction of COMS (2) The main characteristics of COMS - Operational lifetime: 7.7 years - Design lifetime: 10 years - Orbital position: 128.2°E - Launch mass: 2460 Kg - Payload mass: 316 Kg - Payload power: 1077 W - Power generation: 2396 W by GaAs cells solar array - Pointing performance: * better than +/- 0.05°absolute pointing error in roll and pitch for MI/GOCI * better than 0,11°(half cone) error for Ka band RF beam pointing * pointing stability; 10µrad (N/S and E/W) peak to peak over 8s period 55µrad (N/S and E/W) peak to peak over 120s period 4

5 Introduction of GOCI (1) Overview world’s 1st geostationary ocean color imager, jointly developed by EADS Astrium and KARI 8 channels/spectral bands (6-Visible and 2-NIR) provides multi-spectral data regarding coastal ocean environment for marine science research and application purpose spectral band selection is ensured by a 9- position filter wheel: 8 positions correspond to the 8 wavebands (the ninth one for detector dark current measurement) 5

6 Introduction of GOCI (2) Performance requirement specification 6Items Technical requirements Ground Sample Distance (GSD)  500m  500m at the center of the target area Target area  2500km  2500km centered on (36  N, 130  E) Spectral coverage412 nm ~ 865 nm (8 channels) Bandwidth10 nm ~ 40 nm SNR750 ~ 1200 System MTF0.3 on all bands (after ground processing) Dynamic rangeNEdR ~ Maximum cloud radiance Radiometric calibration accuracy 4 % Digitization12 bit

7 Introduction of GOCI (3) Key Design Features (i) 7 (Z+ Earth) GOCI Main Unit (w/o MLI protection)

8 Introduction of GOCI (4) Key Design Features (ii) 8 GOCI Main Unit (w/o MLI protection) during integration phase

9 Introduction of GOCI (5) Key Design Features (iii) - FPA (Focal Plane Assembly) GOCI Detector & FEE (Front End Electronics)  2-D array, COMS detector: 1415(EW)x1432(NS) pixels  2 sub-arrays: 1415 x 715 pixels  2 lead-out channels for each sub-array  Low noise amplification of 4 lead-out channel signals of the detector by FEE 9 GOCI CMOS Detector

10 Introduction of GOCI (5) Key Design Features (vi) - Telescope Assembly: * Three Mirror Anastigmat (TMA) design, providing good MTF performance over the field of view on focal plane array, with all mirrors made of SiC to lower weights and minimize thermal effects 10

11 Introduction of GOCI (5) Key Design Features (v) - FWM (Filter Wheel Mechanism) * 1-D rotation, Filter Wheel * 8 spectral filters * 1 Dark plate for offset measurement - POM (Pointing Mechanism) * An High accuracy pointing assembly, used to select slot positions 11

12 Introduction of GOCI (6) Key Design Features (vi) - SCM (Shutter & Calibration Mechanism) Shutter wheel (1-D rotation) * For the earth view when opening and for closing instrument cavity when it is inactive * SD (Solar Diffuser): for the sun view. effectively insensitive to radiation degradation over mission life time (made of Quasi Volumic Diffuser (QVD)). * DAMD (Diffuser Aging Monitoring Device): for the sun view. a smaller aperture diffuser using identical material to SD, to be used infrequently and suffer virtually no degradation, which allows maintaining the calibration accuracy. 12

13 Current Status of COMS & GOCI (1) COMS launch and mission timeline 13

14 Current Status of COMS and GOCI (2) COMS lOT Summary (July 2010~ Feb 2011) Bus IOT - All functional checks are completed and Bus is in good health. - Performance checks are completed and subsystems are showing excellent performances. Payload IOT - All functional checks are completed and all three payloads are in good health. - Radiometric performance checks and radiometric calibration have been completed. - Geometric calibration has been completed with the focus on INR tuning. 14

15 Current Status of COMS and GOCI (3) GOCI Status Summary Normal Operation for the service to the end user has set forth at the completion of IOT (FAR), from April Current GOCI Status - GOCI is in good health with all functions in good check. - Radiometric calibration is exhibiting good trace of performance, calibration and stability. - Geometric correction is exhibiting good landmark matching and excellent INR performance metric. 15

16 GOCI In-Orbit Performances (1) Functional chain architecture of Data Processing 16

17 GOCI In-Orbit Performances (2) Radiometric Performances (1) Radiance Response 17 S: Output (Digital count), L: Incident Radiance G: Linear gain, b: Nonlinear gain, T int : integration time O: Dark current offset parameter, F: Fixed offset parameter GOCI radiometric model has been validated through ground test 2D mapping parameter O2D mapping parameter F In orbit offset parameter  Ground offset parameter

18 GOCI In-Orbit Performances (3) Radiometric Performances (2) Radiance Response (ii) 18 GOCI radiometric model has been validated through ground test Ground Measured Radiometric Response In-orbit radiometric responsivity G & b, PRNU (Pixel Response Non-Uniformity)  On-ground measured values Digital count image of Sun diffused by SD

19 GOCI In-Orbit Performances (4) Radiometric Performances (3) Radiometric calibration and stability (i) 19  GOCI radiometric calibration using Sun light through Solar diffuser Covering whole imaging chain (telescope and video chain) for Earth observation (SD is located in front of pointing mirror) Covering full pupil Monitoring of Solar diffuser aging using secondary solar diffuser In orbit calibration method using two images has been verified through IOT duration. SD image for long integration time SD image for short integration time Gain matrix

20 GOCI In-Orbit Performances (5) Radiometric Performances (4) Radiometric calibration and stability (ii) 20 Using two measurement points S A, S B (two images) : image with long integration time & image with short integration time Using solar irradiance E S calculated from the solar spectrum model (Thuillier 2004) provided by GOCI user group Using diffusion model  SD of SD characterized on-ground Using solar incident angle  SD calculated from Ephemeris data and telemetry Linear gain Non-linear gain : sun images : measurement parameter for sun imaging  SD: diffusion factor of SD,  SD : solar incident angle, T SD : integration time where E s : solar irradiance,  Gain matrix calculation

21 GOCI In-Orbit Performances (6) Radiometric Performances (5) Radiometric calibration and stability (iii) 21 L0 image (raw digital image, slot 7, B8) L1A image (radiance image, slot 7, B8) 08/09/2010, 00:15:00 UTC where : raw data after offset correction : Gain parameters calculated through in-orbit solar calibration Radiance image calculation using in-orbit gain matrix

22 GOCI In-Orbit Performances (7) Radiometric Performances (6) Radiometric calibration and stability (iv) 22 Evolution of mean gain over 5 months: about 2% degradation (Stabilization after 3 months)

23 GOCI In-Orbit Performances (8) Radiometric Performances (7) SNR 23 SNR has been assessed indirectly by using in orbit gain matrix. IOT SNR measurement > Specification Nominal side Redundant side

24 GOCI In-Orbit Performances (9) MTF 24 MTF has been assessed by KEF image for Band 7 and Ban 8. IOT MTF measurement > Specification Example of E/W MTF measurement (KEF)

25 GOCI In-Orbit Performances (10) Geometric Performances (1) GSD 25 GSD at FOV center has been assessed. IOT GSD measurement: OK

26 GOCI In-Orbit Performances (11) Geometric Performances (2) Geometric Correction: INR - A new, noble approach to INR system design - Not directly dependent on system and/or payload models and hence can avoid any indispensible modeling and/or prediction error in the process - Acquisition of sufficient number of landmarks in good quality is key to this design - Excellent landmark matching algorithm and the fine-tuning of newly established landmark database with ample landmark sites render such acquisition of sufficient number of good landmarks 26

27 GOCI In-Orbit Performances (12) Geometric Performances (3) GOCI INR performances (i) - Accuracy performances on landmarks have been checked on KORDI GOCI operational platform (1FEB2011 to 7FEB2011) - GOCI INR performances have been re-checked after the final adjustment (15FEB2011 to 21FEB2011) 27

28 GOCI In-Orbit Performances (13) Geometric Performances (4) GOCI INR performances (ii) 28 MeanStandard Deviation Performance (  rad) EWNSEWNSEWNSEWNS Navigation Band-to-Band Reg

29 GOCI In-Orbit Performances (14) Geometric Performances (5) GOCI INR performances (iii): Example of shoreline matching (B7) 29

30 GOCI In-Orbit Performances (14) Geometric Performances (6) GOCI INR performances (vi): Example of shoreline matching (B7) 30

31 GOCI Sample Images (1) 31

32 GOCI Sample Images (2) 32

33 GOCI Sample Images (3) 33

34 GOCI Sample Images (4) 34

35 Conclusion The newly developed GOCI is demonstrating quite decent performances in orbit, both in radiometric and geometric aspects. It is anticipated that such GOCI image data will bring a new dimension to the geostationary remote sensing and in the related scientific research fields. More in-depth review, thorough analysis and active iteration are desired to define the requirement specification for the next generation GOCI (‘GOCI-2’). It is hoped that GOCI will further be expanded in terms of its design, development, operation and applications, into the next generation of geostationary remote sensing satellites. 35


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