NPP VIIRS Pre-Launch Performance and SDR Validation Overview
This presentation covers the pre-launch performance evaluation and SDR validation of the NPP VIIRS instrument, highlighting comparisons with MODIS Aqua, spectral and spatial characteristics, radiometric and polarization sensitivities, as well as calibration and validation strategies. It discusses the design background of NPP VIIRS, its similarities with MODIS, instrument specifications, and environmental data products derived from VIIRS SDRs.
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NPP VIIRS Pre-Launch Performance and SDR Validation Frank De Luccia, The Aerospace Corporation, El Segundo, CA Bruce Guenther, NOAA - Joint Polar Satellite System, Goddard Space Flight Center, Greenbelt, MD Chris Moeller, University of Wisconsin, Madison, WI, Xiaoxiong Xiong and Robert Wolfe , NASA s Goddard Space Flight Center, Greenbelt, MD 2011 IEEE International Geoscience and Remote Sensing Symposium (IGARSS) 24-29 July, Vancouver, Canada
Topics Instrument Background Pre-Launch Performance Comparisons to MODIS Aqua as reference Spectral characteristics Spatial characteristics Radiometric sensitivity - SNR and NEdT Polarization sensitivity Performance summary and issues SDR Validation Calibration and Validation (Cal/Val) team Cal/Val plans and task structure Principal activities per Cal/Val phase Summary 2
Instrument Background NPP VIIRS manufactured by Raytheon under subcontract to Northrop Grumman for NPOESS NPP instruments now under JPSS program management VIIRS design draws on MODIS heritage MODIS also built by Raytheon (SBRS) On-board calibrators and calibration strategy very similar VIIRS MODIS Orbit 824 km, sun-synchronous, near-polar 705 km, sun-synchronous, near-polar Scan Rate 33.6 rpm, cross-track 20.3 rpm, cross-track Swath Dimensions 3000 km across track by 13 km along track at nadir 2330 km across track by 10 km along track at nadir Size 1.3 m x 1.4 m x 0.9 m 1.0 m x 1.6 m x 1.0 m Weight 263 kg 250 kg Power 154 W 225 W Data Rate 10.4 Mbps (peak) 11 Mbps (peak) Quantization 12 bits 12 bits Design Life 7 years 5 years 4
Instrument Background contd Separately Mounted Electronics Module MODIS Solar Diffuser MODIS Blackbody MODIS derived Solar Diffuser Stability Monitor (SDSM) 3-Mirror Anastigmat (TMA) All reflective Rotating telescope 4-Mirror Anastigmat (FMA) All Reflective Aft Optics Imager Flat-panel Cryoradiator Cold FPA Dewar Assembly Half-angle Mirror 5
Environmental Data Products (EDRs) Derived from VIIRS Sensor Data Records (SDRs) Product Group EDRs/OtherProducts Imagery Imagery* * Surface Temperatures Sea Surface Temperature Land Surface Temperature Ice Surface Temperature Clouds Cloud Base Height Cloud Top Height Cloud Cover/Layers Cloud Top Pressure Cloud Particle Size Cloud Top Temperature Cloud Optical Thickness Cloud Mask** Aerosols Aerosol Optical Thickness Aerosol Particle Size Ocean Biosphere Ocean Color/Chlorophyll Land Biosphere Vegetation Index Albedo Vegetation Type Snow & Sea Ice Snow Cover Sea Ice Characterization Fire Fire Detection Other Soil Moisture Suspended Matter Net Heat Flux Geolocation** * Key Performance Parameter (KPP) ** Intermediate Product (not an EDR) 6
VIIRS Spectral Characteristics VIIRS and MODIS Spectral Coverage: 1 m to 5 m VIIRS has 22 bands from 0.4 m to 12.5 m (8 dual gain) 7 moderate resolution, 2 imaging resolution and 1 broadband day/night band in 0.4 to 1.0 m range 6 moderate resolution and 2 imaging resolution bands in 1 to 5 m range 3 moderate resolution and 1 imaging resolution bands in 5 to 15 m range MODIS - 1000 m MODIS - 500 m MODIS - 250 m VIIRS - 750 m VIIRS - 375 m H2O N2O H2O H2O H2O, CO2 H2O H2O CO2, N2O Atmospheric Transmission (Mid-latitude Summer) Wavelength (microns) VIIRS and MODIS Spectral Coverage: 0.4 m to 1.0 m VIIRS and MODIS Spectral Coverage: 5 m to 15 m MODIS - 1000 m MODIS - 1000 m MODIS - 500 m MODIS - 500 m MODIS - 250 m MODIS - 250 m VIIRS - 750 m VIIRS - 750 m VIIRS - 375 m VIIRS - 375 m H2O H2O H2O O3 H2O CO2 Atmospheric Transmission O2 H2O H2O (Mid-latitude Summer) O2 Wavelength (microns) Wavelength (microns) 8
VIIRS Spatial Characteristics 16 moderate resolution bands with 750 m footprint at nadir 5 imaging resolution bands with 375 m footprint at nadir 1 DNB with 750 m footprint constant across scan. Pixel aggregation used to control footprint growth across scan. Agg = 1 : 1 Agg = 2 : 1 45 deg < |SA| < 56 deg 32 deg < |SA| < 45 deg Agg = 3 : 1 |SA| < 32 deg 742 m 1104 m 1600 m 262 m 630 m 786 m 1260 m 1600 m SA = Scan Angle Agg = Aggregation VIIRS and MODIS Along-Scan Spatial Sampling VIIRS and MODIS Along-Track Spatial Sampling 2.5 7 VIIRS 375 M VIIRS 375 M Along-Track Ground Sampling Interval (km) 6 Along-Scan Ground Sampling Interval (km) VIIRS 750 M VIIRS 750 M 2 MODIS 250 M MODIS 250 M 5 MODIS 500 M MODIS 500 M 1.5 4 MODIS 1000 M MODIS 1000 M 3 1 2 0.5 1 0 0 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Scan Angle (deg) Scan Angle (deg) 9
VIIRS Radiometric Sensitivity Comparison of VIIRS and MODIS Aqua Reflected Solar Band SNR 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 VIIRS 2200 2000 1800 better 1600 1400 MODIS Substitute 1200 SNR VIIRS Band Spectral Range (um) Nadir HSR (m) MODIS Band(s) Range HSR 1000 DNB 0.500 - 0.900 8 9 0.405 - 0.420 0.438 - 0.448 0.459 - 0.479 0.483 - 0.493 0.545 - 0.565 0.546 - 0.556 0.620 - 0.670 0.662 - 0.672 0.673 - 0.683 0.743 - 0.753 0.841 - 0.876 0.862 - 0.877 0.841 - 0.876 SAME 1.360 - 1.390 1.628 - 1.652 1.628 - 1.652 2.105 - 2.155 3.660 - 3.840 SAME 1000 1000 500 1000 500 1000 250 1000 1000 1000 250 1000 250 500 1000 500 500 500 1000 1000 M1 M2 0.402 - 0.422 0.436 - 0.454 750 750 800 600 M3 0.478 - 0.498 750 3 10 400 M4 0.545 - 0.565 750 4 or 12 200 1 I1 0.600 - 0.680 375 0 M5 0.662 - 0.682 750 13 or 14 M1/8 M2/9 M3/3 M3/10 M4/4 M4/12 I1/1 M5/13 M5/14 M6/15 I2/2 M7/2 M7/16 M8/5 M9/26 I3/6 M10/6 M11/7 MODIS Aqua PL MODIS Aqua On-Orbit VIIRS PL VIIRS PL Scaled 15 2 M6 I2 0.739 - 0.754 0.846 - 0.885 750 375 Comparison of VIIRS and MODIS Aqua Thermal Emissive Band NEdT 16 or 2 I4/20 M12/20 M13/21 M13/22 M14/29 M15/31 I5/31 I5/32 M16/32 M7 M8 M9 I3 M10 M11 I4 M12 0.846 - 0.885 1.230 - 1.250 1.371 - 1.386 1.580 - 1.640 1.580 - 1.640 2.225 - 2.275 3.550 - 3.930 3.660 - 3.840 750 750 750 375 750 750 375 750 1 5 26 6 6 7 20 20 better 0.1 3.929 - 3.989 3.929 - 3.989 1000 1000 NEdT (K) M13 3.973 - 4.128 750 21 or 22 29 SAME 1000 M14 8.400 - 8.700 750 0.01 31 10.780 - 11.280 1000 M15 10.263 - 11.263 750 10.780 - 11.280 11.770 - 12.270 1000 1000 I5 10.500 - 12.400 375 31 or 32 M16 Dual-gain Band 11.538 - 12.488 750 32 11.770 - 12.270 1000 0.001 10 MODIS Aqua PL MODIS Aqua On-Orbit VIIRS PL VIIRS PL Scaled
VIIRS Polarization Sensitivity Polarization Sensitivity vs. Detector Index VIIRS polarization performance is generally better than that of MODIS. Unlike MODIS, NPP VIIRS polarization sensitivity varies strongly with field angle resulting in detector dependence. VIIRS pre-launch characterization provides high-quality, per-pixel characterization of polarization sensitivity and phase for use in data product processing. 5.0% 4.5% 4.0% Polarization Sensitivity (%) 3.5% 3.0% VIIRS HAM A, - 8 deg SA 2.5% VIIRS HAM B, -8 deg SA 2.0% MODIS MS 1, 0 deg SA MODIS MS 2, 0 deg SA 1.5% 1.0% 0.5% 0.0% 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Detector Index VIIRS VisNIR Polarization Sensitivity MODIS Aqua VisNIR Polarization Sensitivity 6% 6% Max. Polarization Sensitivity (%) 5% 5% Max. Polarization Sensitivity (%) 4% 4% -55.5 deg -45 deg -22 deg -8 deg +20 deg +45 deg +55.5 deg -45 deg 3% 3% -22.5 deg 0 deg +22.5 deg 2% 2% +45 deg 1% 1% 0% 0% 300 400 500 600 700 800 900 1000 300 400 500 600 700 800 900 Band Center Wavelength (nm) Band Center Wavelength (nm) 11
Performance Summary and Issues 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. NPP VIIRS has optical crosstalk in the VisNIR (0.8% average) due to high angle scattering in the spectral filters May impact Ocean Color/Chlorophyll and Aerosol data products. NPP VIIRS out-of-band (OOB) spectral response somewhat higher than MODIS Aqua due to same scattering mechanism in filters Second and subsequent VIIRS flight units will have reduced optical crosstalk and OOB response due to improved spectral filters. VIIRS polarization sensitivity is lower than that of MODIS Aqua but is detector dependent Requires per-pixel correction in Ocean Color processing Banding effects in SDRs displayed as images 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. 12
VIIRS SDR Cal/Val Team Organization Key Personnel NOAA/NESDIS Center for Satellite Applications and Research (STAR) Changyong Cao - VIIRS SDR Cal/Val Management Lead Fuzhong Weng JPSS SDR Cal/Val Chair Mark Liu, Tim Chang The Aerospace Corporation Frank De Luccia - VIIRS SDR Cal/Val Technical Lead David Moyer, Scott Houchin, Kameron Rausch, Christopher Florio, Jason Cardema, Evan Haas, Patrick Yuen, Allen Raines, Jeff Lipeles, Aaron Myrick, Zaven Petrosyan NASA GSFC NPP Instrument Characterization Support Team (NICST) NPP Instrument Calibration and Support Element (NICSE) Jack Xiong and Kurt Thome - Instrument Scientists Hassan Oudrari, Robert Wolfe, Robert Barnes, Gene Eplee, Fred Patt NICST: Jeff McIntire (Lead), Ning Lei, Thomas Schwarting, Junqiang Sun, Alin Tolea, Shihyan Lee, Aisheng Wu NICSE: Vincent Chiang (Lead), Mash Nishihama, Gary Lin University of Wisconsin Chris Moeller MIT Lincoln Laboratory Juliette Costa, Ed Bicknell Northrop Grumman Airborne Systems Lushalan Liao 14
Evolution of VIIRS Calibration and Validation Plans On-orbit cal/val tasks were defined in an intensive government- contractor team collaboration Cal/val strategies draw heavily on MODIS experience Inputs on specific activities distilled into 54 tasks VIIRS SDR Calibration Plan produced and peer reviewed in 2009 Comprehensive description of VIIRS calibration program Describes team, team interactions, tasks, tools and ground truth resources Maps cal/val activities into cal/val phases Provides metrics for evaluating SDR product maturity VIIRS SDR Calibration/Validation Operations Concept (OPSCON) Document developed in 2011 Infrastructure support definition Data flow and process definition to support cal/val rehearsals Managerial leadership has transitioned to Changyong Cao of NOAA STAR Roles and responsibilities have evolved to reflect increased participation of NOAA STAR 15
Six Broad Categories of On-Orbit Cal/Val Tasks Functional Performance and Format Evaluation (FPF 1-7) 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. Calibration System Evaluation (CSE 1-6) CSE tasks evaluate the performance of the onboard calibration system and update the calibration algorithm databases accordingly. Image Quality Evaluation (IMG 1-4) IMG tasks evaluate the quantitative and qualitative spatial performance characteristics of the instrument. Radiometric Evaluation (RAD 1-25) 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. Geolocation Evaluation (GEO 1-7) GEO tasks evaluate the geolocation accuracy of the data product. Performance and Telemetry Trending (PTT 1-5) PTT tasks evaluate long-term changes in the performance of both the instrument and the data product. 16
Pre-Launch Activities Continued analysis and refinement of performance baseline based on test program Verification of at-launch SDR algorithm look-up tables (LUTs) Improvements where warranted Operational code review and error checking Cal/val tool development RDR and SDR readers, LUT readers/writers Custom tools for cal/val analysis tasks Practice and training in operation of VIIRS SDR operational code Algorithm Development Library (ADL) version of code allows cal/val team to modify and test LUT updates and potential algorithm improvements Task rehearsals to demonstrate readiness for on-orbit cal/val 17
Early Orbit Checkout (EOC) Verify instrument operability and functionality Signal Noise Scan rate Compare signal and noise characteristics to pre-launch baseline Verify RDR, SDR and intermediate product formats and validity of content Early use of Solar Diffuser Stability Monitor Critical for beginning time series to trend change in Solar Diffuser reflectance 18
Intensive Calibration & Validation (ICV) Radiance match-ups Ground sites Inter-satellite comparisons Comparisons with Cross-Track Infrared Sounder (CrIS) Aircraft underflights Geolocation match-ups Ground Control Points (GCPs) from Landsat Feedback on SDR quality from EDR validation efforts Maneuvers Exploitation of lunar data SDR algorithm tuning and LUT updates Continued performance and telemetry trending Objective is achievement of stable, validated/calibrated SDRs by end of ICV. 19
Long-Term Monitoring (LTM) Routine performance of reflective band off-line calibration Periodic measurement and trending of key instrument characteristics Operability Noise/SNR Gains Critical temperatures, voltages, currents in telemetry Periodic repetition of ICV tasks to maintain calibration and SDR quality Radiometry Geolocation 20
VIIRS Cal/Val Activities by Phase Sensor Functional Checkout Radiance Match-Ups Radiance Match-Ups Characterization Performance & Telemetry Trending Baseline Data Geolocation Geolocation Inventory Performance & Telemetry Trending Performance & Telemetry Trending RDR/SDR Verification SDR Cal/Val Plan Development SDR Algorithm Initialization & Update Capability SDR Algorithm Tuning SDR Parameter & LUT Updates SDR Parameter & LUT Updates Cal/Val Tool Development Launch Early Orbit Checkout (EOC) Phase Intensive Calibration & Validation (ICV) Phase Pre-Launch Phase Long Term Monitoring (LTM) Phase L + 50 days L + 180 days 21
SDR Product Maturity Levels Beta Early release product, initial calibration applied, minimally validated and may still contain significant errors Available to allow users to gain familiarity with data formats and parameters Product is not appropriate as the basis for quantitative scientific publications studies and applications Provisional Product quality may not be optimal Incremental product improvements are still occurring as calibration parameters are adjusted with sensor on-orbit characterization 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 Users are urged to contact NPP Cal/Val Team representatives prior to use of the data in publications Validated/Calibrated On-orbit sensor performance characterized and calibration parameters adjusted accordingly Ready for use by the Centrals, and in scientific publications There may be later improved versions 22
Inter-Satellite Comparisons Analysis of Simultaneous Nadir Overpass (SNO) data from VIIRS and other satellites will reveal relative biases Off-nadir inter-satellite comparisons will be exploited also, particularly to evaluate Response vs Scan Angle effects Leverages validation performed for other satellite systems VIIRS/MODIS comparisons expected to be particularly useful MODIS instruments well validated Many similar bands with similar radiometric performance MODIS Terra/AVHRR 11 m Band Comparison (Xiong et al., CEOS-IVOS 2004) 23
CrIS-VIIRS Cal/Val (heritage AIRS-MODIS) Abundant matchups on every Aqua orbit. 14 orbits per day (>10E6 matchups/day) Radiometric performance as function of scene temperature AIRS footprints overlain on MODIS image. Filter the sample to retain spatially uniform scenes. Radiometric performance as function of scan mirror angle 24
Use of Maneuvers for VIIRS SDR Validation (1) S/C Maneuvers for VIIRS Calibration Scientific benefits and implementation strategies are based on lessons and experience from heritage missions and sensors, such as MODIS and SeaWiFS All 3 types of VIIRS maneuvers have been approved for the NPP mission Roll Maneuvers Near monthly event with lunar phase angles at 55 degree and roll angles less than -14 degrees Provide an accurate and long-term monitoring of VIIRS RSB calibration stability and independent monitoring of SD degradation Yaw Maneuvers Once during initial S/C checkout; could repeat every 3 years depending on the SD degradation rate 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 25
Use of Maneuvers for VIIRS SDR Validation (2) Pitch Maneuvers Once during initial S/C checkout; could repeat depending on scan- angle dependent changes in TEB responses Validate sensor response versus scan angle (RVS) and assure VIIRS SDR quality for the TEB Operation and Data Analysis Support Maneuver implementation working group established to coordinate among different groups (and instruments) VIIRS maneuver data analysis tools developed primarily from MODIS experience 26
Use of Lunar Data for VIIRS SDR Validation (1) Track Changes in Sensor Responses for VIIRS Reflective Solar Bands 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 Provide Independent Monitoring of VIIRS Solar Diffuser Degradation The angle of incidence (AOI) of VIIRS space view, through which the lunar observations are made, is identical to the AOI of SD observations Enable Calibration Inter-comparison with Other Sensors (e.g. MODIS) This is similar to the effort made to inter-compare Terra and Aqua MODIS, MODIS and SeaWiFS 27
Use of Lunar Data for VIIRS SDR Validation (2) SeaWiFS Normalized Lunar Radiance Terra and Aqua MODIS B1 Lunar Irradiance 28
VIIRS Geolocation Matchups Number of Control Point Matchups Example of first 90 days of control point matchups from MODIS/Terra Good (> 60% normalized cross correlation) control point matchups per day: 260 Used to perform initial refinement of instrument to spacecraft alignment and to refine rotating telescope and half angle mirror geometric parameters Track Residuals (nadir adjusted) Scan Residuals (nadir adjusted) 29
Aircraft Campaigns Aircraft underflights can provide high quality radiometric validation across the VIIRS spectrum Direct observations of the integrated upwelling earth scene radiance in nearly same time, space, and geometry as the on-orbit sensor NIST traceable uncertainties for some airborne instruments Approach based upon heritage validation of AIRS, MODIS, IASI. Preliminary plans for aircraft campaigns have been developed but are currently on hold due to funding constraints Platforms: ER-2 and/or WB-57 Instruments desired for VIIRS SDR validation Enhanced MODIS Airborne Simulator (EMAS) 50 channel Vis/IR spectrometer, 50 m resolution, 36 km swath Expected to include reflective solar band (RSB) Hyperspectral Imager (HSI) Scanning High-resolution Interferometer Sounder (SHIS) Scanning M/LWIR 0.5 cm-1 interferometer, 2 km resolution, 32 km swath NIST traceable calibration NPOESS Airborne Sounder Testbed (NAST-I) Scanning MWIR/LWIR interferometer, 2km resolution, 40 km swath NIST traceable calibration Cloud Physics Lidar (CPL) Micropulse dual polarization lidar, 15 m resolution, nadir only 30
Histogram of radiometric matchups Approach based upon heritage efforts for AIRS and MODIS 11.01 um Fly instrumented ER-2 along satellite track Matching geometry of earth scene observations MODIS on Terra/Aqua SHIS, etc. on ER-2 705 km 20 km 31
Summary VIIRS calibration and validation plans draw heavily on MODIS strategies and experience Similar data products Similar on-board calibrators Similar radiometric and geolocation retrieval approaches VIIRS pre-launch performance baseline very well established Extensive instrument characterization provided in test program Independent data analysis by multiple contractor and government teams has provided highly reliable parameter values for SDR algorithm LUTs Experienced, multi-organization calibration/validation team is well prepared to execute VIIRS on-orbit validation 32
