code: def _calibrate_vis(radiance, k):
          
          logger.debug('Calibrating to reflectance')
          refl = 100 * k * radiance
          return refl.clip(min=0)
docs: Convert VIS radiance to reflectance
  
          Note: Angle of incident radiation and annual variation of the
          earth-sun distance is not taken into account. A value of 100%
          corresponds to the radiance of a perfectly reflecting diffuse surface
          illuminated at normal incidence when the sun is at its annual-average
          distance from the Earth.
  
          TODO: Take angle of incident radiation (cos sza) and annual variation
          of the earth-sun distance into account.
  
          Reference: [VIS]
  
          Args:
              radiance: Radiance [mW m-2 cm-1 sr-1]
              k: pi / H, where H is the solar spectral irradiance at
                 annual-average sun-earth distance, averaged over the spectral
                 response function of the detector). Units of k: [m2 um sr W-1]
          Returns:
              Reflectance [%]