1 NPP VIIRS Pre-Launch Performance and SDR Validation- IGARSS 2011.pptx

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1 NPP VIIRS Pre-Launch Performance and SDR Validation- IGARSS 2011.pptx

  1. 1. NPP VIIRS Pre-Launch Performance and SDR Validation<br />Frank De Luccia, The Aerospace Corporation, El Segundo, CA<br />Bruce Guenther, NOAA - Joint Polar Satellite System, Goddard Space Flight Center, Greenbelt, MD<br />Chris Moeller, University of Wisconsin, Madison, WI,<br />XiaoxiongXiongand Robert Wolfe , NASA’s Goddard Space Flight Center, Greenbelt, MD<br />2011 IEEE International Geoscience<br />and Remote Sensing Symposium (IGARSS)<br />24-29 July, Vancouver, Canada<br />
  2. 2. Topics<br />Instrument Background<br />Pre-Launch Performance <br />Comparisons to MODIS Aqua as reference<br />Spectral characteristics<br />Spatial characteristics <br />Radiometric sensitivity - SNR and NEdT<br />Polarization sensitivity<br />Performance summary and issues <br />SDR Validation <br />Calibration and Validation (Cal/Val) team<br />Cal/Val plans and task structure<br />Principal activities per Cal/Val phase<br />Summary <br />2<br />
  3. 3. Instrument Background<br />
  4. 4. Instrument Background<br />NPP VIIRS manufactured by Raytheon under subcontract to Northrop Grumman for NPOESS<br />NPP instruments now under JPSS program management<br />VIIRS design draws on MODIS heritage<br />MODIS also built by Raytheon (SBRS)<br />On-board calibrators and calibration strategy very similar<br />4<br />
  5. 5. Instrument Background – cont’d<br />5<br />
  6. 6. Environmental Data Products (EDRs) Derived from VIIRS Sensor Data Records (SDRs)<br />*<br />* Key Performance Parameter (KPP)<br />** Intermediate Product (not an EDR)<br />6<br />
  7. 7. Pre-Launch Performance<br />
  8. 8. VIIRS Spectral Characteristics<br />VIIRS has 22 bands from 0.4 m to 12.5 m (8 dual gain)<br />7 moderate resolution, 2 imaging resolution and 1 broadband day/night band in 0.4 to 1.0 m range<br />6 moderate resolution and 2 imaging resolution bands in 1 to 5 m range<br />3 moderate resolution and 1 imaging resolution bands in 5 to 15 m range<br />8<br />
  9. 9. VIIRS Spatial Characteristics<br />16 moderate resolution bands with 750 m footprint at nadir<br />5 imaging resolution bands with 375 m footprint at nadir<br />1 DNB with 750 m footprint constant across scan.<br />Pixel aggregation used to control footprint growth across scan. <br />9<br />
  10. 10. VIIRS Radiometric Sensitivity<br />VIIRS SNR and NEdT are comparable or superior to MODIS SNR and NEdT when normalized to the same spatial scale and the same radiance level<br />10<br />
  11. 11. VIIRS Polarization Sensitivity<br />VIIRS polarization performance is generally better than that of MODIS. <br />Unlike MODIS, NPP VIIRS polarization sensitivity varies strongly with field angle resulting in detector dependence. <br />VIIRS pre-launch characterization provides high-quality, per-pixel characterization of polarization sensitivity and phase for use in data product processing. <br />11<br />
  12. 12. Performance Summary and Issues<br />VIIRS performance is comparable or superior to that of MODIS Aqua in corresponding bands in all key performance areas except crosstalk and out-of-band spectral response. <br />NPP VIIRS has optical crosstalk in the VisNIR (0.8% average) due to high angle scattering in the spectral filters<br />May impact Ocean Color/Chlorophyll and Aerosol data products. <br />NPP VIIRS out-of-band (OOB) spectral response somewhat higher than MODIS Aqua due to same scattering mechanism in filters<br />Second and subsequent VIIRS flight units will have reduced optical crosstalk and OOB response due to improved spectral filters. <br />VIIRS polarization sensitivity is lower than that of MODIS Aqua but is detector dependent<br />Requires per-pixel correction in Ocean Color processing<br />Banding effects in SDRs displayed as images<br />In other key performance areas not addressed here, such as band-to-band registration, near-field response and stray light response, VIIRS performance compares favorably with that of MODIS Aqua. <br />12<br />
  13. 13. SDR Validation<br />
  14. 14. VIIRS SDR Cal/Val Team<br />14<br />
  15. 15. Evolution of VIIRS Calibration and Validation Plans <br />On-orbit cal/val tasks were defined in an intensive government-contractor team collaboration<br />Cal/val strategies draw heavily on MODIS experience<br />Inputs on specific activities distilled into 54 tasks <br />VIIRS SDR Calibration Plan produced and peer reviewed in 2009<br />Comprehensive description of VIIRS calibration program<br />Describes team, team interactions, tasks, tools and ground truth resources<br />Maps cal/val activities into cal/val phases<br />Provides metrics for evaluating SDR product maturity<br />VIIRS SDR Calibration/Validation Operations Concept (OPSCON) Document developed in 2011 <br />Infrastructure support definition<br />Data flow and process definition to support cal/val rehearsals <br />Managerial leadership has transitioned to Changyong Cao of NOAA STAR<br />Roles and responsibilities have evolved to reflect increased participation of NOAA STAR<br />15<br />
  16. 16. Six Broad Categories of On-Orbit Cal/Val Tasks<br />Functional Performance and Format Evaluation (FPF 1-7)<br />FPF tasks involve evaluating instrument functions and verifying the correctness of data formats. Performed early in the mission, and will not be repeated unless the instrument suffers a catastrophic event.<br />Calibration System Evaluation (CSE 1-6)<br />CSE tasks evaluate the performance of the onboard calibration system and update the calibration algorithm databases accordingly.<br />Image Quality Evaluation (IMG 1-4)<br />IMG tasks evaluate the quantitative and qualitative spatial performance characteristics of the instrument. <br />Radiometric Evaluation (RAD 1-25)<br />RAD tasks evaluate the radiometric performance of the data product algorithm. Radiometric evaluation will include evaluation of spectral characteristics since changes in these characteristics relative to the pre-launch baseline will mainly manifest themselves as in-band radiometric errors. <br />Geolocation Evaluation (GEO 1-7)<br />GEO tasks evaluate the geolocation accuracy of the data product.<br />Performance and Telemetry Trending (PTT 1-5)<br />PTT tasks evaluate long-term changes in the performance of both the instrument and the data product.<br />16<br />
  17. 17. Pre-Launch Activities<br />Continued analysis and refinement of performance baseline based on test program<br />Verification of at-launch SDR algorithm look-up tables (LUTs)<br />Improvements where warranted<br />Operational code review and error checking<br />Cal/val tool development<br />RDR and SDR readers, LUT readers/writers<br />Custom tools for cal/val analysis tasks<br />Practice and training in operation of VIIRS SDR operational code<br />Algorithm Development Library (ADL) version of code allows cal/val team to modify and test LUT updates and potential algorithm improvements<br />Task rehearsals to demonstrate readiness for on-orbit cal/val<br />17<br />
  18. 18. Early Orbit Checkout (EOC)<br />Verify instrument operability and functionality<br />Signal <br />Noise<br />Scan rate<br />Compare signal and noise characteristics to pre-launch baseline<br />Verify RDR, SDR and intermediate product formats and validity of content<br />Early use of Solar Diffuser Stability Monitor<br />Critical for beginning time series to trend change in Solar Diffuser reflectance<br />18<br />
  19. 19. Intensive Calibration & Validation (ICV)<br />Radiance match-ups<br />Ground sites<br />Inter-satellite comparisons<br />Comparisons with Cross-Track Infrared Sounder (CrIS)<br />Aircraft underflights<br />Geolocation match-ups<br />Ground Control Points (GCPs) from Landsat<br />Feedback on SDR quality from EDR validation efforts<br />Maneuvers<br />Exploitation of lunar data<br />SDR algorithm tuning and LUT updates<br />Continued performance and telemetry trending<br />19<br />Objective is achievement of stable, “validated/calibrated” SDRs by end of ICV.<br />
  20. 20. Long-Term Monitoring (LTM)<br />Routine performance of reflective band off-line calibration <br />Periodic measurement and trending of key instrument characteristics<br />Operability<br />Noise/SNR<br />Gains<br />Critical temperatures, voltages, currents in telemetry<br />Periodic repetition of ICV tasks to maintain calibration and SDR quality<br />Radiometry<br />Geolocation<br />20<br />
  21. 21. 21<br />VIIRS Cal/Val Activitiesby Phase<br />
  22. 22. SDR Product Maturity Levels<br />Beta<br />Early release product, initial calibration applied, minimally validated and may still contain significant errors <br />Available to allow users to gain familiarity with data formats and parameters <br />Product is not appropriate as the basis for quantitative scientific publications studies and applications<br />Provisional<br />Product quality may not be optimal <br />Incremental product improvements are still occurring as calibration parameters are adjusted with sensor on-orbit characterization<br />General research community is encouraged to participate in the QA and validation of the product, but need to be aware that product validation and QA are ongoing <br />Users are urged to contact NPP Cal/Val Team representatives prior to use of the data in publications <br />Validated/Calibrated<br />On-orbit sensor performance characterized and calibration parameters adjusted accordingly<br />Ready for use by the Centrals, and in scientific publications<br />There may be later improved versions<br />22<br />
  23. 23. Inter-Satellite Comparisons<br />Analysis of Simultaneous Nadir Overpass (SNO) data from VIIRS and other satellites will reveal relative biases<br />Off-nadir inter-satellite comparisons will be exploited also, particularly to evaluate Response vs Scan Angle effects<br />Leverages validation performed for other satellite systems<br />VIIRS/MODIS comparisons expected to be particularly useful<br />MODIS instruments well validated<br />Many similar bands with similar radiometric performance<br />MODIS Terra/AVHRR 11 m Band Comparison<br />(Xiong et al., CEOS-IVOS 2004)<br />23<br />
  24. 24. CrIS-VIIRS Cal/Val (heritage AIRS-MODIS)<br />24<br />Abundant matchups <br />on every Aqua orbit. 14 orbits per day<br />(>10E6 matchups/day)<br />Radiometric performance as function of scene temperature<br />AIRS footprints overlain <br />on MODIS image. Filter the sample to retain spatially uniform scenes.<br />Radiometric performance as function of scan mirror angle<br />
  25. 25. Use of Maneuvers for VIIRS SDR Validation (1)<br />S/C Maneuvers for VIIRS Calibration <br />Scientific benefits and implementation strategies are based on lessons and experience from heritage missions and sensors, such as MODIS and SeaWiFS<br />All 3 types of VIIRS maneuvers have been approved for the NPP mission<br />Roll Maneuvers<br />Near monthly event with lunar phase angles at 55 degree and roll angles less than -14 degrees <br />Provide an accurate and long-term monitoring of VIIRS RSB calibration stability and independent monitoring of SD degradation<br />Yaw Maneuvers<br />Once during initial S/C checkout; could repeat every 3 years depending on the SD degradation rate <br />Validate SD solar attenuation screen (SAS) and SDSM sun view screen transmission as a function of solar illumination angles and assure VIIRS SDR quality for the RSB<br />25<br />
  26. 26. Use of Maneuvers for VIIRS SDR Validation (2)<br />Pitch Maneuvers<br />Once during initial S/C checkout; could repeat depending on scan-angle dependent changes in TEB responses<br />Validate sensor response versus scan angle (RVS) and assure VIIRS SDR quality for the TEB<br />Operation and Data Analysis Support<br />Maneuver implementation working group established to coordinate among different groups (and instruments) <br />VIIRS maneuver data analysis tools developed primarily from MODIS experience<br />26<br />
  27. 27. Use of Lunar Data for VIIRS SDR Validation (1)<br />Track Changes in Sensor Responses for VIIRS Reflective Solar Bands<br />Both MODIS and SeaWiFS have used lunar time series to track changes in sensor responses; lunar viewing geometry corrections are made using ROLO lunar model <br />Provide Independent Monitoring of VIIRS Solar Diffuser Degradation<br />The angle of incidence (AOI) of VIIRS space view, through which the lunar observations are made, is identical to the AOI of SD observations<br />Enable Calibration Inter-comparison with Other Sensors (e.g. MODIS)<br />This is similar to the effort made to inter-compare Terra and Aqua MODIS, MODIS and SeaWiFS<br />27<br />
  28. 28. Use of Lunar Data for VIIRS SDR Validation (2)<br />SeaWiFS Normalized Lunar Radiance<br />Terra and Aqua MODIS B1 Lunar Irradiance<br />28<br />
  29. 29. VIIRS Geolocation Matchups<br />Example of first 90 days of control point matchups from MODIS/Terra<br />Good (> 60% normalized cross correlation) control point matchups per day: 260<br />Used to perform initial refinement of instrument to spacecraft alignment and to refine rotating telescope and half angle mirror geometric parameters<br />29<br />Number of Control Point Matchups<br />Track Residuals (nadir adjusted)<br />Scan Residuals (nadir adjusted)<br />
  30. 30. Aircraft Campaigns<br />Aircraft underflights can provide high quality radiometric validation across the VIIRS spectrum<br />Direct observations of the integrated upwelling earth scene radiance in nearly same time, space, and geometry as the on-orbit sensor<br />NIST traceable uncertainties for some airborne instruments<br />Approach based upon heritage validation of AIRS, MODIS, IASI.<br />Preliminary plans for aircraft campaigns have been developed but are currently “on hold” due to funding constraints <br />Platforms: ER-2 and/or WB-57<br />Instruments desired for VIIRS SDR validation<br />Enhanced MODIS Airborne Simulator (EMAS)<br />50 channel Vis/IR spectrometer, 50 m resolution, 36 km swath <br />Expected to include reflective solar band (RSB) Hyperspectral Imager (HSI)<br />Scanning High-resolution Interferometer Sounder (SHIS)<br />Scanning M/LWIR 0.5 cm-1 interferometer, 2 km resolution, 32 km swath<br />NIST traceable calibration<br />NPOESS Airborne Sounder Testbed (NAST-I) <br />Scanning MWIR/LWIR interferometer, 2km resolution, 40 km swath<br />NIST traceable calibration<br />Cloud Physics Lidar (CPL) <br />Micropulse dual polarization lidar, 15 m resolution, nadir only<br />30<br />
  31. 31. 31<br />11.01 um<br />MODIS on <br />Terra/Aqua<br />SHIS, etc.<br />on ER-2<br />705 km<br />20 km<br />q<br />Approach based upon heritage efforts for AIRS and MODIS<br />Histogram of radiometric matchups<br />Fly instrumented ER-2 along satellite track<br />Matching geometry of earth scene observations<br />
  32. 32. Summary<br />VIIRS calibration and validation plans draw heavily on MODIS strategies and experience<br />Similar data products<br />Similar on-board calibrators<br />Similar radiometric and geolocation retrieval approaches<br />VIIRS pre-launch performance baseline very well established<br />Extensive instrument characterization provided in test program<br />Independent data analysis by multiple contractor and government teams has provided highly reliable parameter values for SDR algorithm LUTs<br />Experienced, multi-organization calibration/validation team is well prepared to execute VIIRS on-orbit validation<br />32<br />

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