Albedo is the fraction of sunlight, which is reflected off a planet. The reflection is assumed to be diffuse. For the albedo the same spectral shape as for sunlight is assumed. The actual albedo spectrum can change, depending on properties of the surface (different materials can lead to absorption in certain wavelength bands and result in a highly variable spectrum). Albedo values are only applicable when the portion of the planet that is seen by the spacecraft is sunlit.