Minimize Radiometric Scaling

Radiometric processing, applied to the OLCI raw counts, aims to derive calibrated Top Of Atmosphere (TOA) radiance values. The incoming OLCI samples are processed one by one into radiance at TOA. Radiometric processing includes:

  • initialisation
  • non-linearity correction
  • dark signal correction
  • smear correction
  • absolute gain calibration
  • cosmetic pixel filling.

Initialisation

Long term trend corrections are applied to reference radiometric gain to match product time. Smear factors are computed. Non-linearity correction LUTs are built using a cubic interpolation and quality flags are initialised.

Non-Linearity Correction

All instrument counts are corrected for non-linearity, including the smear band.

Dark Signal Correction

All instrument counts are corrected for dark offset, including the smear band. Reference dark offset is corrected for short time temperature effect.

Smear Correction

The smear signal is estimated at each image sample from the smear band values and corrected for.

Absolute Gain Calibration

Instrument counts corrected of all the above instrumental effects are scaled to radiance using absolute gain coefficients corrected for long-term effects.

Cosmetic Pixel Filling

Some missing samples are filled with cosmetic radiance values and flagged as "cosmetic". Radiances of pixels listed in the "dead pixels" map are replaced by an interpolation of their valid neighbours. Empty samples generated during extraction, because of missing packets, are filled if the packet gap is small enough, by values from the previous valid frame.

Logical Flow of Radiometric Scaling