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AVHRR Vicarious Calibration

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The LTDR V5 forward production will be switched from the AVHRR instrument onboard N19 to the same from MetOp-B, in a month, and this will be followed up by a re-processing of all the LTDR records from the beginning of the MetOp-B mission, in V5. (click here for the details)

V5 and V4 LTDR data now available. V3 LTDR has been decommissioned

LTDR AVHRR Calibration

Consistent and accurate calibration is a prerequisite to creating a long-term data record for climate studies. The AVHRR instrument suffers from the lack of onboard calibration for its visible to short wave infrared channels. Various vicarious calibration approaches were employed by users to account for the sensor degradation. For the LTDR REASoN project, we adopted the approach developed by Vermote and Kaufman (1995) that relies on clear ocean and accurate Rayleigh scattering computations to derive the sensor degradation in the red bands. This approach uses high clouds to predict the variation in the near infrared (NIR) to Red ratio and transfer the calibration to the NIR channel. This approach does not require any in-situ or aircraft measurements and is applied consistently across the AVHRR instruments onboard various NOAA satellites. Click on the satellite link to get the calibration coefficients for the corresponding AVHRR (NOAA-7, NOAA-9, NOAA-11, NOAA-14, NOAA-16).


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