Non-Lambertian reference panel effect on spectral reflectance measurements of freshwater ice

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Abstract
Airborne measurements of the spectral reflectance of freshwater ice types on Saginaw Bay (Lake Huron) were used as ground data for satellite (AVHRR) interpretation of the ice cover. These were corrected for the non-Lambertian character of the spray-painted barium sulphate reference panel whose radiance data, measured on the ground, were used in the calculation of reflectance factors. The reflectance measurements were previously corrected for dark current, transmittance of the radiometer optics, and atmospheric attenuation and path radiance from the measurement altitude of 300m. The correction for the non-Lambertian response of the reference panel at the wavelengths and Sun zenith angle at which the panel radiance was measured, resulted in an average decrease in reflectance of 8·3 per cent in the visible band and 3-6 per cent in the near-infrared band for the ice types measured.