Marine optical buoy moby support for ocean color sensor vicarious calibration
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Marine Optical Buoy (MOBY): Support for Ocean Color Sensor Vicarious Calibration. Presented by Menghua Wang. Requirement, Science, and Benefit. Requirement/Objective Ecosystems Protect, restore and manage the use of coastal and ocean resources through ecosystem-based management

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Marine optical buoy moby support for ocean color sensor vicarious calibration

Marine Optical Buoy (MOBY): Support for Ocean Color Sensor Vicarious Calibration

Presented by

Menghua Wang

Requirement science and benefit
Requirement, Science, and Benefit Vicarious Calibration


  • 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


  • How to provide accurate water optical, biological, and biogeochemical property data in coastal and inland regions from satellite measurements?


  • 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

Satellite ocean color remote sensing
Satellite Ocean Color Remote Sensing Vicarious Calibration

  • 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.

Lunar calibration for characterization of sensor degradation
Lunar Calibration for Characterization Vicarious Calibrationof Sensor Degradation


SeaWiFS Looks at the Moon

Sensor Degradation


On orbit vicarious calibration
On-Orbit Vicarious Calibration 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.

Simulation results with vicarious calibration
Simulation Results with Vicarious CalibrationVicarious Calibration

a’()= a()

Inverse of Rayleigh Scattering

After VC, calibration errors a’() for the visible bands are significantly reduced.

Vicarious calibration requires accurate water leaving radiance measurements
Vicarious Calibration Requires Accurate Vicarious CalibrationWater-leaving Radiance Measurements

Computed (Rayleigh)

Predicted using models (Aerosols)

Computed (Whitecap)

Measured at vicarious calibration site, e.g., MOBY

Sensor-measured TOA Reflectance (or Radiance):

t = r + a + ra + twc + tw

  • 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.

Marine optical buoy moby vc facility for ocean color sensor
Marine Optical Buoy (MOBY)-VC Facility Vicarious Calibrationfor Ocean Color Sensor

From D. Clark

Radiance time series for modis ocean color bands
Radiance Time Series for MODIS Vicarious CalibrationOcean Color Bands

From D. Clark

Noaa support moby operation
NOAA Support MOBY Operation Vicarious Calibration

  • 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.

Challenges and path forward
Challenges and Path Forward Vicarious Calibration

  • 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).