text: Although such reflectance properties are different from those of any terrestrial terrains, they are typical of the regolith surfaces of airless Solar System bodies.Two common optical albedos that are used in astronomy are the (V-band) geometric albedo (measuring brightness when illumination comes from directly behind the observer) and the Bond albedo (measuring total proportion of electromagnetic energy reflected).Their values can differ significantly, which is a common source of confusion.In detailed studies, the directional reflectance properties of astronomical bodies are often expressed in terms of the five Hapke parameters which semi-empirically describe the variation of albedo with phase angle, including a characterization of the opposition effect of regolith surfaces.One of these five parameters is yet another type of albedo called the single-scattering albedo.It is used to define scattering of electromagnetic waves on small particles.It depends on properties of the material (refractive index), the size of the particle, and the wavelength of the incoming radiation.An important relationship between an object's astronomical (geometric) albedo, absolute magnitude and diameter is given by: where is the astronomical albedo, is the diameter in kilometers, and is the absolute magnitude.Radar albedo In planetary radar astronomy, a microwave (or radar) pulse is transmitted toward a planetary target (e.g.Moon, asteroid, etc.) and the echo from the target is measured.In most instances, the transmitted pulse is circularly polarized and the received pulse is measured in the same sense of polarization as the transmitted pulse (SC) and the opposite sense (OC).The echo power is measured in terms of radar cross-section, , , or (total power, SC + OC) and is equal to the cross-sectional area of a metallic sphere (perfect reflector) at the same distance as the target that would return the same echo power.