Presentation on theme: "GOCI: Early In-Orbit Performances"— Presentation transcript:
1 GOCI: Early In-Orbit Performances 2011 IGARSS TH3.T05GOCI: Early In-Orbit PerformancesJuly 28, 2011 Vancouver, CANADAHan-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
2 Agenda Introduction of COMS Introduction of GOCI Current Status of COMS and GOCIGOCI In-Orbit PerformancesConclusion
3 Introduction of COMS (1) COMS: Communication, Ocean and Meteorological SatelliteGeostationary satelliteMass at Launch: 2460 kgOrbital Location: 128.2oEDesign Life time: 10 yearsOperational Life: 7.7 yearsLaunch: June 26, 2910, 21:41 (UTC)Launcher: Ariane 5 ECACOMS MissionsA meteo mission (MI)*An ocean imager mission (GOCI)**An experimental Ka band telecommunication mission* MI: Meteorological Imager** GOCI: Geostationary Ocean Color Imager
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 forMI/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 period55µrad (N/S and E/W) peak to peak over 120s period
5 Introduction of GOCI (1) Overviewworld’s 1st geostationary ocean color imager, jointly developed by EADS Astrium and KARI8 channels/spectral bands (6-Visible and 2-NIR)provides multi-spectral data regarding coastal ocean environment for marine science research and application purposespectral 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)Spectral band selection is ensured by a 9-position filter wheel: 8 positions correspond to the 8 wavebands, and the ninth one is used for detector dark current measurement by providing a full occultation view.
6 Introduction of GOCI (2) Performance requirement specificationItemsTechnical requirementsGround Sample Distance (GSD) 500m 500m at the center of the target areaTarget area2500km 2500kmcentered on (36N , 130E)Spectral coverage412 nm ~ 865 nm(8 channels)Bandwidth10 nm ~ 40 nmSNR750 ~ 1200System MTF0.3 on all bands(after ground processing)Dynamic rangeNEdR ~ Maximum cloud radianceRadiometric calibration accuracy4 %Digitization12 bitSpectral band selection is ensured by a 9-position filter wheel: 8 positions correspond to the 8 wavebands, and the ninth one is used for detector dark current measurement by providing a full occultation view.
7 Introduction of GOCI (3) Key Design Features (i)(Z+ Earth)Five Key Elements: Three mechanisms (SCM, FWM, POM), Telescope Assembly and FPA.Functional chain, in the order of: SCM, POM, Telescope Assembly, FWM, FPACalibration mechanism: SD & Diffuser Aging Monitoring Device (DAMD), a smaller aperture diffuser using identical material to SD (QVD), to be used infrequently and suffer virtually no degradation due to contaminant buildup and polymerization from solar exposure, which allows maintaining the calibration accuracy.GOCI Main Unit (w/o MLI protection)
8 Introduction of GOCI (4) Key Design Features (ii)Spectral band selection is ensured by a 9-position filter wheel: 8 positions correspond to the 8 wavebands, and the ninth one is used for detector dark current measurement by providing a full occultation view.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) pixels2 sub-arrays: 1415 x 715 pixels2 lead-out channels for each sub-arrayLow noise amplification of 4 lead-out channel signals of the detector by FEESpectral band selection is ensured by a 9-position filter wheel: 8 positions correspond to the 8 wavebands, and the ninth one is used for detector dark current measurement by providing a full occultation view.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 effectsSpectral band selection is ensured by a 9-position filter wheel: 8 positions correspond to the 8 wavebands, and the ninth one is used for detector dark current measurement by providing a full occultation view.
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 slotpositionsSpectral band selection is ensured by a 9-position filter wheel: 8 positions correspond to the 8 wavebands, and the ninth one is used for detector dark current measurement by providing a full occultation view.
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.Spectral band selection is ensured by a 9-position filter wheel: 8 positions correspond to the 8 wavebands, and the ninth one is used for detector dark current measurement by providing a full occultation view.
13 Current Status of COMS & GOCI (1) COMS launch and mission timeline
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 ingood health.- Performance checks are completed andsubsystems are showing excellent performances.Payload IOT- All functional checks are completed and all threepayloads are in good health.- Radiometric performance checks and radiometriccalibration have been completed.- Geometric calibration has been completed with thefocus on INR tuning.
15 Current Status of COMS and GOCI (3) GOCI Status SummaryNormal Operation for the service to the end userhas set forth at the completion of IOT (FAR),from April 2011.Current GOCI Status- GOCI is in good health with all functions in goodcheck.- Radiometric calibration is exhibiting good trace ofperformance, calibration and stability.- Geometric correction is exhibiting good landmarkmatching and excellent INR performance metric.
16 GOCI In-Orbit Performances (1) Functional chain architecture of Data Processing
17 GOCI In-Orbit Performances (2) Radiometric Performances (1)Radiance ResponseGOCI radiometric model has been validated through ground testS: Output (Digital count), L: Incident RadianceG: Linear gain, b: Nonlinear gain, Tint: integration timeO: Dark current offset parameter, F: Fixed offset parameter2D mapping parameter O2D mapping parameter FIn orbit offset parameter Ground offset parameter
18 GOCI In-Orbit Performances (3) Radiometric Performances (2)Radiance Response (ii)GOCI radiometric model has been validated through ground testDigital count image of Sun diffused by SDGround Measured Radiometric ResponseIn-orbit radiometric responsivity G & b , PRNU (Pixel Response Non-Uniformity) On-ground measured values
19 GOCI In-Orbit Performances (4) Radiometric Performances (3)Radiometric calibration and stability (i)GOCI radiometric calibration using Sun light through Solar diffuser Covering whole imaging chain (telescope and video chain) for Earthobservation (SD is located in front of pointing mirror) Covering full pupil Monitoring of Solar diffuser aging using secondary solar diffuserIn orbit calibration method using two images has been verified through IOT duration.SD image forlong integration timeSD image for short integration timeGain matrix
20 GOCI In-Orbit Performances (5) Radiometric Performances (4)Radiometric calibration and stability (ii)Gain matrix calculationLineargainNon-lineargainwhere Es : solar irradiance,: sun images: measurement parameter for sun imagingSD: diffusion factor of SD, SD: solar incident angle, TSD: integration timeUsing two measurement points SA, SB (two images): image with long integration time & image with short integration timeUsing solar irradiance ES calculated from the solar spectrum model (Thuillier 2004) provided by GOCI user groupUsing diffusion model SD of SD characterized on-groundUsing solar incident angle SD calculated from Ephemeris data and telemetry20
21 GOCI In-Orbit Performances (6) Radiometric Performances (5)Radiometric calibration and stability (iii)Radiance image calculation using in-orbit gain matrixwhere : raw data after offset correction: Gain parameters calculated through in-orbit solar calibration08/09/2010, 00:15:00 UTCL0 image(raw digital image, slot 7, B8)L1A image(radiance image, slot 7, B8)
22 GOCI In-Orbit Performances (7) Radiometric Performances (6)Radiometric calibration and stability (iv)Evolution of mean gain over 5 months: about 2% degradation(Stabilization after 3 months)
23 GOCI In-Orbit Performances (8) Radiometric Performances (7)SNRSNR has been assessed indirectly by using in orbit gain matrix.IOT SNR measurement > SpecificationNominal sideRedundant side
24 GOCI In-Orbit Performances (9) MTFMTF has been assessed by KEF image for Band 7 and Ban 8.IOT MTF measurement > SpecificationExample of E/W MTF measurement (KEF)
25 GOCI In-Orbit Performances (10) Geometric Performances (1)GSDGSD 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 payloadmodels and hence can avoid any indispensiblemodeling and/or prediction error in the process- Acquisition of sufficient number of landmarks ingood quality is key to this design- Excellent landmark matching algorithm and thefine-tuning of newly established landmark databasewith ample landmark sites render such acquisitionof sufficient number of good landmarks
27 GOCI In-Orbit Performances (12) Geometric Performances (3)GOCI INR performances (i)- Accuracy performances on landmarks have been checkedon KORDI GOCI operational platform (1FEB2011 to 7FEB2011)- GOCI INR performances have been re-checked after thefinal adjustment (15FEB2011 to 21FEB2011)
35 ConclusionThe 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.