1. Lessons from MODIS Calibration and Characterization
Xiaoxiong (Jack) Xiong
NASA Goddard Space Flight Center (GSFC)
Acknowledgements:
MODIS Characterization Support Team (MCST)
NPP Instrument Calibration Support Team/Element (NICST/E)
GSICS Joint Research and Data Working Group Meeting, NSMC, CMA, Beijing, China (March 5-8, 2012)

2. Examples presented at AMS 92nd Annual Meeting, New Orleans, LA, 2012
Outline
Introduction
MODIS Calibration and Characterization
Pre-launch and on-orbit
Performance Overview
Lessons
Terra MODIS to Aqua MODIS
MODIS to other sensors (e.g. VIIRS, ABI)
Summary
Examples presented at AMS 92nd Annual Meeting, New Orleans, LA, 2012
Paper: 18SATMET 5B.4
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3. Introduction Moderate Resolution Imaging Spectroradiometer (MODIS)
Developed based on the requirements from the science community for the NASA’s EOS missions
Designed with improvements over heritage sensors, such as AVHRR, CZCS, HIRS, and Landsat TM
Built by Raytheon Santa Barbara Remote Sensing (SBRS)
Managed and operated by NASA GSFC
NPP VIIRS built with strong heritage to MODIS
Benefits from Lessons
Design and performance
Science applications
Schedule and cost
AMS in Jan 2012
CALCON in Aug 2012
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4. MODIS Calibration and Characterization
MODIS Calibration Program or Approach
Pre-launch
Project and Science Team
CVWG (Calibration and Validation Working Group)
Sensor Vendor
Government Led Calibration Support Team
On-orbit
Science Team
Disciplinary Cal/Val scientists
MsWG (MODIS sensor Working Group)
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5. Pre-launch Calibration and Characterization
Solar Reflective Regions
Radiometric
Calibration source: SIS-100 (NIST traceable) at multiple radiance levels (lamp configurations)
Calibration parameters: gain, nonlinearity, SNR, dynamic range, gain dependence on the instrument temperatures
Three instrument temperatures for thermal vacuum test
Primary and redundant electronics
Solar diffuser BRDF calibration (NIST traceable)
Others (all system level)
Spectral: relative spectral response (RSR)
Spatial: pointing, band-to-band registration (BBR)
Response versus scan angle (RVS)
Polarization sensitivity
“Similar” calibration activities thermal emissive calibration
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6. On-orbit Operation and Calibration
SRCA:
Radiometric: monthly
Spatial: bi-monthly
Spectral: quarterly
SD/SDSM:
Weekly to tri-weekly
Solar
Diffuser
SRCA
SDSM
Blackbody
Scan
Mirror
Space
View
BB: quarterly
Spacecraft maneuvers:
Yaw (SD BRF, VF)
Roll (Moon)
Pitch (only applied to Terra)
Moon: monthly (nighttime orbits)
0-20o spacecraft roll maneuvers
55o phase angle
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7. Performance Overview Sensor and OBC Operation and Performance
Instrument and focal plane
Blackbody and solar diffuser
Radiometric
Reflective solar bands
Thermal Emissive bands
Spatial
BBR in along-scan and along track directions
Spectral
Reflective spectral response (CW, BW)
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8. Instrument Temperatures
Terra MODIS: less than 3.5 K increase over 12 years
Aqua MODIS: less than 2.0 K increase over 9 years
Similar trends for the VIS and NIR FPA temperatures
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9. Cold Focal Plane Assembly (FPA) Temperatures
Terra MODIS: SMIR LWIR
Aqua MODIS: SMIR LWIR
Small increase of CFPA temperatures in recent years (0.4K)
No impact on TEB scan-by-scan calibration
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10. Blackbody Temperatures (nominal operation)
Terra MODIS: less than 30 mK increase over 12 years
B-Side
Aqua MODIS: extremely stable
On-board BB used for Thermal Emissive Bands (TEB) calibration
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11. Solar Diffuser (SD) Degradation
Larger degradation at shorter l
Increased SD degradation
due to SD door fixed at “open”
Terra MODIS
Further reduction of Aqua MODIS SD calibration frequency to be considered
Aqua MODIS
On-board SD used for Reflective Solar Bands (RSB) calibration
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12. Reflective Solar Band Responses (VIS) Band Averaged, Mirror Side 1
Larger changes at shorter l
Terra MODIS
Terra/Aqua difference, wavelength, AOI and mirror side dependent
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13. Lessons
Calibration team (e.g. MCST), in support of science team and project, needs to work closely with instrument vendor (e.g., SBRS)
pre-launch calibration and characterization
Calibration team needs to work closely with science team
Early post-launch performance assessment
Vicarious calibration and validation effort
Calibration effort needs to be sustained over the entire mission
Track and correct sensor on-orbit changes or degradation, especially as instrument gets “older”
Documentation and test data records
Operation Concept Document (OCD), ATBD, User Guide
Test data/reports, technical memos, conference /journal papers
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14. Lessons Pre-launch Calibration On-orbit Calibration
Perform a complete/comprehensive set of calibration and characterization (different levels and phases)
Eliminate “undesirable features” if possible, otherwise, fully characterize them
Test as it flies (End-to-End test)
On-orbit Calibration
Calibrate with different approaches and methodologies (OBC and ground targets, calibration inter-comparisons)
Establish, review, and update sensor operation and calibration procedures
Expect the “unexpected”
Calibrate, calibrate, and calibrate, …
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15. Lessons Terra MODIS to Aqua MODIS MODIS to NPP VIIRS
Eliminated PC optical leak
Reduced SWIR thermal leak and electronic crosstalk
Performed TEB response versus scan-angle (RVS) characterization
MODIS to NPP VIIRS
Improved SD attenuation screen (block earthshine)
Improved SDSM design (eliminated design error in MODIS SDSM)
Performed SD screen and SDSM screen transmission characterization
Experimented with the E2E RSB calibration
Improved polarization characterization
Test data analysis tools and calibration methodologies
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16. No PC optical leak in Aqua MODIS
PC Bands Optical Leak
Terra B35
Before correction
After correction
Aqua B35
No PC optical leak in Aqua MODIS
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17. Comparison of Terra and Aqua MODIS Surface Reflectance Product
Bands 1, 2, 3 (RGB)
Band 7 (2.1mm)
Aerosol Optical Depth
Terra MODIS
Aqua MODIS
Smaller Xtalk, More Effective Correction, and Better Performance in A-MODIS
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18. TEB RVS Characterization (Terra versus Aqua MODIS)
Terra (South Pacific ) 1 2
Pre-launch RVS
On-orbit RVS
Area 1
Area 2
Area 1
Area 2
Aqua (Baja, CA ) 3 4 1 2
Pre-launch RVS
Area 1
Area 2
Area 3
Area 4
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19. Improved Design of VIIRS SDSM
Large ripples in MODIS SDSM Sun View responses were due to a design error
MODIS SDSM design error was eliminated in VIIRS (thus better performance)
MODIS SDSM SD View Responses
VIIRS SDSM SD View Responses
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20. VIIRS/MODIS SNO Reflectance Trends
( to )
VIIRS and MODIS reflectance ratio trends are derived from a number of SNO events (MODIS C5 LUT with VIIRS LUT V )
VIIRS VIS/NIR spectral response degradations (%) over the trending period (relative to Aqua MODIS) I1 I2 M1 M2
-2.3
-13.5
1.8
1.7 M3 M4 M5 M7
1.0
-0.9
-3.3
-14.0
Normalized VIIRS-to-MODIS
reflectance ratios
VIIRS NIR degradation (especially in M7, I2, M6, and M5)
Methodologies and tools developed for MODIS supported VIIRS NIR degradation anomaly investigations
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21. Summary An overview of MODIS operation and calibration
Calibration activities
Examples of instrument performance
Lessons from MODIS calibration
Dedicated Calibration Team
Sustained calibration effort
Comprehensive pre-launch and continuous on-orbit calibration
Importance of documentation and data records
Benefits from MODIS lessons to future sensors
Improved design with better overall performance
Calibration experience (methodologies and tools)
Calibration results (reference)
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22. Instrument Performance Summary (1)
Both instruments continue to operate normally
Changes of instrument and warm FPA temperatures are less than 3.5K for Terra MODIS over 11 years; less than 2K for Aqua MODIS over 9 years
Terra MODIS cold FPA temperatures remain stably controlled at 83K
Gradual decrease of Aqua MODIS cooler margin has led to small increase (up to 0.30K), orbit-to-orbit and seasonal variations of its cold FPA temperatures
A workshop on Aqua MODIS CFPA performance and operation was held on May 7, 2010 (decision reached to maintain current operational configuration unless there is an evidence that the current CFPA performance has a negative impact on science data product quality)
All on-board calibrators continue to provide key design functions
BB temperatures remain extremely stable for both Terra and Aqua MODIS, short- and long-term
Terra MODIS SD door has permanently fixed at the “open” position since July 2, 2003, which has led to increased SD degradation rates
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23. Instrument Performance Summary (2)
Radiometric (36 spectral bands with 490 individual detectors)
There are no new noisy and inoperable detectors since last STM
45 noisy detectors (30 from pre-launch; 35 at launch) and no inoperable detectors for Terra MODIS
6 noisy detectors (2 from pre-launch; 3 at launch) and 15 inoperable detectors (13 in band 6) for Aqua MODIS
Spectral (VIS/NIR bands only)
Changes in center wavelengths and bandwidths are less than 0.5 and 1.0 nm, respectively, for most spectral bands (only a few exceptions)
Spatial (all bands)
On-orbit band-to-band registrations (BBR) have been stable for both Terra and Aqua MODIS
Large BBR offsets in Aqua MODIS between cold FPA and warm FPA band pairs (a known problem since pre-launch)
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