def _calibrate_vis(radiance, k):
        """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 [%]
        """
        logger.debug('Calibrating to reflectance')
        refl = 100 * k * radiance
        return refl.clip(min=0)
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 [%]