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)

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 Page 2

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 Page 3

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) Page 4

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 Page 5

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 Page 6

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) Page 7

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 Page 8

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 Page 9

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 Page 10

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 Page 11

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 Page 12

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 Page 13

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, … Page 14

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 Page 15

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 Page 16

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 Page 17

TEB RVS Characterization (Terra versus Aqua MODIS) Terra (South Pacific 2000073.0730) 1 2 Pre-launch RVS On-orbit RVS Area 1 Area 2 Area 1 Area 2 Aqua (Baja, CA 2002194.2050) 3 4 1 2 Pre-launch RVS Area 1 Area 2 Area 3 Area 4 Page 18

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 Page 19

VIIRS/MODIS SNO Reflectance Trends (2011-11-21 to 2012-01-16) VIIRS and MODIS reflectance ratio trends are derived from a number of SNO events (MODIS C5 LUT with VIIRS LUT V1.5.5.0) 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 Page 20

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) Page 21

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 Page 22

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) Page 23