A unitless measure of the ratio of outgoing to incoming solar radiation created by converting a radiometrically calibrated image observed from orbit to the apparent reflectance of the planet being observed (assuming the planet is acting as a perfect Lambertian reflector). Conversion to planetary albedo assumes knowledge of the solar irradiance for a specific spectral band, distance from the Sun and solar zenith angle. Also see reflectance and bidirectional reflectance.