Vicarious Gains

• The top of the atmosphere (TOA) radiances for each band measured by MODIS or SeaWiFS are compared with MOBY (Marine Optical Buoy) insitu match-up radiance values that have been propagated to the TOA using the current atmospheric correction parameters.
  
  
• It is assumed that the values at MOBY have only small uncertainties and predict what the values measured at the satellite should be. Therefore the difference between the satellite values and the MOBY values gives us the calibration gains.
  
  
• Every time a change is made to the data processing methodology, the vicarious gains have to be updated. Once calculated, the gains are then utilized in the data processing stream.
  
  

  This diagram demonstrates how SeaWiFS (or MODIS) and MOBY data are used to compute the vicarious gains from ratios of TOA radiances.

  The current vicarious gain coefficients used in the processing can be found here: Vicarious Gains For more complete information about the vicarious gains, download the following pdf: Algorithm Updates for the Fourth SeaWiFS Data Reprocessing.

  
  
  

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