Albedo

Definition

The albedo of a surface is a measure of its reflectivity. The albedos of planetary surfaces depend on their compositions and physical properties. Two types of albedo are often used in connection with planetary surfaces. One is the geometric albedo in a particular photometric band (normally denoted by p, with a subscript for the photometric band, e.g., p_V for visual geometric albedo), which is the ratio of the body’s brightness at zero solar phase angle (i.e., as seen from the direction of the Sun) to the brightness of a perfectly diffusing (Lambertian) disk with the same apparent size and at the same position as the body. The visual geometric albedo is useful for most observational work because it is relevant to the visual brightness of the object. Values of p_V for a selection of bodies are given in Table 1. The second is the bolometric Bond albedo, which is the ratio of the total reflected radiation, summed over all wavelengths and directions, to the incident solar...