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CoRP Cal/Val Symposium July 13, 2005

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CoRP Cal/Val Symposium July 13, 2005

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  1. MODIS Thermal Band Radiance Cal/Val Chris MoellerCooperative Institute for Meteorological Satellite Studies, University of Wisconsin with contributions from Jack Xiong, MODIS Characterization Support Team (MCST), GSFC Dave Tobin, Cooperative Institute for Meteorological Satellite Studies Simon Hook, Jet Propulsion Laboratory (JPL, NASA) CoRP Cal/Val SymposiumJuly 13, 2005

  2. Outline • Brief MODIS background • Cal/Val procedure • MODIS L1B validation findings • Contributions to Uncertainty • Summary

  3. Instrument Background FM1 Aqua (EOS-PM): Launched on 05/04/02 First light 06/24/02 • 2-sided Paddle Wheel Scan Mirror • (10km by 2330 km swath per 1.478 sec) • Day data rate: 10.6 Mbps, night data rate: 3.3 Mbps (100% duty cycle, 50% day and 50% night) • 3 Nadir Spatial Resolutions • 250m (1-2), 500m (3-7), and 1km (8-36) • 4 Focal Plane Assemblies (FPAs) • VIS, NIR, SMIR, and LWIR • 36 Spectral Bands (490 detectors) • Reflective solar bands (1-19, and 26), thermal emissive bands (20-25, 27-36) • On-Board Calibrators (OBCs): • Solar diffuser (SD) • SD stability monitor (SDSM) • Blackbody (BB) • Spectro-radiometric calibration assembly (SRCA) • Space view (SV) • Science Applications • Land, oceans, and atmosphere • Nearly 40 science products generated and distributed PFM Terra (EOS-AM): Launched on 12/18/99 First light on 02/24/00 Page 3

  4. MODIS TEB Calibration Using Blackbody RVS: Response Versus Scan-angle e: Emissivity L: Spectral band averaged radiance dn: Digital count with background corrected Radiance (TOA), LEV Calibration coefficient, b1, from BB Page 4

  5. MODIS IR Spectral Bands, MAS FWHM

  6. Why are high altitude aircraft useful for Cal/Val work? • Direct observation of integrated upwelling radiance, closely simulating on-orbit sensors. • Uncertainty dominated by airborne instruments • Mobile laboratory. Aircraft meets the satellite at a chosen time/place. • Covers several thousand km2 in 10 minutes (lots of samples).

  7. TX-2002 ER-2 Payload NPOESS Atmospheric Sounder Testbed (NAST-I) Video Imaging System (VIS) Dual RC-10 Camera Scanning High Resolution Interferometer Sounder (SHIS) Cloud Physics Lidar (CPL) MODIS Airborne Simulator (MAS) • MAS- 50 channel VIS/IR spectrometer, 50 m res., 36 km swath • SHIS - Scanning M/LWIR 0.5 cm-1 interferometer, 2 km res, 32 km swath • CPL – micropulse dual polarization lidar, 15 m res, nadir only • NAST-I – Scanning MWIR/LWIR interferometer, 2km res, 40 km swath • RC-10 - b/w and false color IR photo, 1-5 m res., 15 x 15 km coverage • VIS video imaging system - color video CCD camera; continuous

  8. MODIS on Terra MAS, SHIS on ER-2 705 km 20 km q 2. Transfer SHIS calibration to MAS MODIS Emissive Band Cal/Val from the ER-2 Platform 1. Collect MODIS and ER-2 co-incident data MODIS Footprint 36 km 3. Co-locate MODIS FOV on MAS

  9. 2000 2001 2002 Terra MODIS Aqua MODIS SAFARI-2000 WISC-T2000 TX-2002 CLAMS TX-2001 2004 2005 2003 THORpex-2003 Tahoe-2004

  10. MAS and SHIS data sets collected on the NASA ER-2 aircraft have been key for directly assessing Terra and Aqua MODIS L1B accuracy. Terra MODIS CO2 11 12 4 wv CO2 MODIS spec. given by box Detector averaged Terra MODIS 11 um 04/01/01 Along Track Profile

  11. April 9, 2004 0544 UTC Terra MODIS SHIS SHIS MAS_SHIS - MODIS (K) Predicted – Measured Brightness Temperature (K) MODIS Observed BT (K) Vertical bars represent radiometric accuracy spec. Wavelength (um) MAS_SHIS Simulated MODIS BT (K) MODIS Band Number Buoy Sites The Lake Tahoe 2004 field activity evaluated Terra MODIS radiometric performance. 3.7um 3.9um CO2 4 11 12 CO2 wv 11um 12um Detector averaged

  12. Aqua Nov. 21, 2002 1941 UTC Aqua MODIS MODIS Residual (K) MODIS Band Number Nov 21, 2002 MAS B45 (11 um) TX-2002 Experiment Assess Aqua MODIS Cal/Val Detector dependent (atmospheric bands) CO2 wv 11 12 4 CO2 Detector averaged Detector dependent (window bands)

  13. Uncertainties • SHIS calibration uncertainty • Altitude correction • Geolocation error (spatial mismatch) • Temporal mismatch • Sunglint influence

  14. SHIS Accuracy Blackbody Geometry AERI, NAST, S-HIS, GIFTS Aperture Diameters AERI: 2.7” S-HIS: 1.6” NAST: 1.0”

  15. SHIS Expected Performance TABB = 227K, THBB = 310K SW MW LW

  16. ER-2 Level MODIS B30, 9.6um (Ozone) MODIS B33, 13.3um (CO2) MODIS B35, 13.9um (CO2) MODIS B36, 14.2um (CO2) MAS B43, 9.6um (Ozone) MAS B48, 13.2um (CO2) MAS B49, 13.8um (CO2) MAS B50, 14.3um (CO2) Atmospheric Pressure (mb) Normalized Weighting Function

  17. Influence of Altitude Difference between MODIS and MAS CO2 Atmospheric absorption above the ER-2 altitude (20 km) is important for O3 and CO2 sensitive bands. O3

  18. Spatial Uncertainty

  19. Temporal Uncertainty

  20. Sun Glint:magnifies spatial and temporal uncertainty in 4um region

  21. What Are We Learning? • Cal/Val of MODIS L1B is viable, even necessary, from high altitude aircraft. • MODIS meets spec in almost all bands. • Detector striping is corroborated by Cal/Val. • MODIS radiometric biases can be cautiously applied to L2 products, e.g. CO2 cloud heights.

  22. Back-up Slides

  23. SCAN TRACK The MODIS spatial weighting function was measured in the scan and track directions during prelaunch testing using a 0.1 x 10 FOV slit stepped across the MODIS focal planes. Idealized smearing was added to the scan direction measurements to simulate the effect of the scan mirror motion.

  24. APRIL 01, 2001

  25. November 21, 2002

  26. April 9, 2004

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