SNAP Data Processors - Radiance-To-Reflectance Conversion Algorithm Specification

Algorithm Specification

The conversion from TOA radiance (L_TOA) to TOA reflectances (R_TOA) done by the following equation:

where E₀ and θ are the solar spectral irradiance and the sun zenith angle, respectively.

The conversion from reflectances to radiances simply follows the inverse of this equation.

For all sensors supported by the Radiance-to-Reflectance Processor, the sun zenith angle is provided per pixel with the L1b products. The solar spectral irradiance values are also provided per pixel in case of OLCI L1b products, whereas for SLSTR MERIS they are taken from auxiliary data.