1. Center for Satellite Applications and Research (STAR) Review 09 – 11 March 2010 Image: MODIS Land Group, NASA GSFC March 2000 Image: MODIS Land Group, NASA GSFC March 2000 Presented by Menghua Wang Presented by Menghua Wang Marine Optical Buoy (MOBY): Support for Ocean Color Sensor Vicarious Calibration

2. Center for Satellite Applications and Research (STAR) Review 09 – 11 March 2010 2 Requirement, Science, and Benefit Requirement/Objective Ecosystems –Protect, restore and manage the use of coastal and ocean resources through ecosystem- based management Healthy and productive coastal and marine ecosystems that benefit society Advancing understanding of ecosystems to improve resource management A well informed public that acts as a steward of coastal and marine ecosystems Weather and Water –Serve society’s needs for weather and water information Better, quicker, and more valuable weather and water information to support improved decisions Increase lead time and accuracy for weather and water warnings and forecasts Improve predictability of the onset, duration, and impact of hazardous and high-impact severe weather and water events Science How to provide accurate water optical, biological, and biogeochemical property data in coastal and inland regions from satellite measurements? Benefit Protect and monitor our ocean resource Improve water resources forecasting capabilities Protect and monitor water resources Understand the effect of environmental factors on human health and well-being Requirement/Objective Ecosystems –Protect, restore and manage the use of coastal and ocean resources through ecosystem- based management Healthy and productive coastal and marine ecosystems that benefit society Advancing understanding of ecosystems to improve resource management A well informed public that acts as a steward of coastal and marine ecosystems Weather and Water –Serve society’s needs for weather and water information Better, quicker, and more valuable weather and water information to support improved decisions Increase lead time and accuracy for weather and water warnings and forecasts Improve predictability of the onset, duration, and impact of hazardous and high-impact severe weather and water events Science How to provide accurate water optical, biological, and biogeochemical property data in coastal and inland regions from satellite measurements? Benefit Protect and monitor our ocean resource Improve water resources forecasting capabilities Protect and monitor water resources Understand the effect of environmental factors on human health and well-being

3. Center for Satellite Applications and Research (STAR) Review 09 – 11 March 2010 3 Satellite Ocean Color Remote Sensing  Ocean Color Remote Sensing: Derive the ocean water-leaving radiance spectra by accurately removing the atmospheric and surface effects.  Ocean properties can then be derived from the ocean water-leaving radiance spectra.  At satellite altitude usually ~90% of sensor-measured signal over ocean comes from the atmosphere & surface –It is crucial to have accurate atmospheric correction and sensor calibration. –0.5% error in the TOA radiance corresponds to possible of ~5% in the derived ocean water-leaving radiance. –We need ~0.1% sensor calibration accuracy. –On-orbit vicarious calibration is necessary.  Ocean Color Remote Sensing: Derive the ocean water-leaving radiance spectra by accurately removing the atmospheric and surface effects.  Ocean properties can then be derived from the ocean water-leaving radiance spectra.  At satellite altitude usually ~90% of sensor-measured signal over ocean comes from the atmosphere & surface –It is crucial to have accurate atmospheric correction and sensor calibration. –0.5% error in the TOA radiance corresponds to possible of ~5% in the derived ocean water-leaving radiance. –We need ~0.1% sensor calibration accuracy. –On-orbit vicarious calibration is necessary.

4. Center for Satellite Applications and Research (STAR) Review 09 – 11 March 2010 4 Lunar Calibration for Characterization of Sensor Degradation SeaWiFS Looks at the Moon Sensor Degradation SeaWiFS Sea-Viewing Wide-Field-of-view Sensor From http://oceancolor.gsfc.nasa.gov

5. Center for Satellite Applications and Research (STAR) Review 09 – 11 March 2010 5 On-Orbit Vicarious Calibration  For ocean color remote sensing, post-launch vicarious calibration is necessary for visible bands.  Vicarious Calibration: Calibration of whole system: Sensor + Algorithms –Account for (by direct measurement or prediction) all of the components of the TOA radiance and –Compare the results with the sensor-measured radiance.  Sensor-measured reflectance:  t (meas) = [1 + a( )]  t a( )-- Calibration error  After vicarious calibration:  t (V) = [1 + a’( )]  t a’( )-- Calibration error It is found (Wang and Gordon, 2002) that a’( ) depends only on the longest wavelength of a( ) (e.g., 865 nm, a(  )). Thus, a’( ) for the visible bands can be significantly reduced after on-orbit vicarious calibration. Wang, M. and H. R. Gordon, “Calibration of ocean color scanners: How much error is acceptable in the near-infrared,” Remote Sens. Environ., 82, 497-504, 2002.

6. Center for Satellite Applications and Research (STAR) Review 09 – 11 March 2010 6 Simulation Results with Vicarious Calibration After VC, calibration errors a’( ) for the visible bands are significantly reduced. a’(  )= a(  ) Inverse of Rayleigh Scattering

7. Center for Satellite Applications and Research (STAR) Review 09 – 11 March 2010 7 Vicarious Calibration Requires Accurate Water-leaving Radiance Measurements Sensor-measured TOA Reflectance (or Radiance):  t =  r +  a +  ra + t  wc + t  w Computed (Rayleigh) Computed (Whitecap) Predicted using models (Aerosols) Measured at vicarious calibration site, e.g., MOBY  It has been demonstrated that VC is necessary for producing accurate satellite ocean color products.  Post-launch vicarious calibration has been carried out for SeaWiFS and MODIS, and will also be carried out for the MERIS.  We are currently working on implementing the vicarious calibration method for routinely deriving the gains for the MODIS-Aqua data products.

8. Center for Satellite Applications and Research (STAR) Review 09 – 11 March 2010 8 Marine Optical Buoy (MOBY)-VC Facility for Ocean Color Sensor From D. Clark

9. Center for Satellite Applications and Research (STAR) Review 09 – 11 March 2010 9 Radiance Time Series for MODIS Ocean Color Bands From D. Clark

10. Center for Satellite Applications and Research (STAR) Review 09 – 11 March 2010 10 NOAA Support MOBY Operation  MOBY data have been used for vicarious calibration of ocean color satellite sensors SeaWiFS and MODIS, as well as in support for calibration for various other international ocean color sensors.  SeaWiFS and MODIS-Aqua have been producing high quality global open ocean color products.  MOBY data will be needed in support for the on-orbit vicarious calibration for NPOESS/VIIRS for generating global ocean color products.  NOAA will need to build End-to-End ocean color data processing capability, including sensor calibration capability using MOBY data.  MOBY data have been used for vicarious calibration of ocean color satellite sensors SeaWiFS and MODIS, as well as in support for calibration for various other international ocean color sensors.  SeaWiFS and MODIS-Aqua have been producing high quality global open ocean color products.  MOBY data will be needed in support for the on-orbit vicarious calibration for NPOESS/VIIRS for generating global ocean color products.  NOAA will need to build End-to-End ocean color data processing capability, including sensor calibration capability using MOBY data.

11. Center for Satellite Applications and Research (STAR) Review 09 – 11 March 2010 11 Challenges and Path Forward Science challenges –Providing accurate and consistent in situ data measurements for calibration and validation of ocean color products. Next steps –Develop next generation instrument (new MOBY) for satellite sensors calibration. Transition Path –Development of techniques for routine calibration applications for ocean color satellite sensors (both US and international). Science challenges –Providing accurate and consistent in situ data measurements for calibration and validation of ocean color products. Next steps –Develop next generation instrument (new MOBY) for satellite sensors calibration. Transition Path –Development of techniques for routine calibration applications for ocean color satellite sensors (both US and international).