Albedo formula_5 (also called blue-sky albedo) can then be given as: Directional-hemispherical reflectance is sometimes referred to as black-sky albedo and bi-hemispherical reflectance as white-sky albedo. These terms are important because they allow the albedo to be calculated for any given illumination conditions from a knowledge of the intrinsic properties of the surface. The albedos of planets, satellites and minor planets such as asteroids can be used to infer much about their properties. The study of albedos, their dependence on wavelength, lighting angle ("phase angle"), and variation in time comprises a major part of the astronomical field of photometry. For small
Surface-to-surface missile bomb was the first operational surface-to-surface missile. Contemporary surface-to-surface missiles are usually guided. An unguided surface-to-surface missile is usually referred to as a rocket (for example, an RPG-7 or M72 LAW is an anti-tank rocket whereas a BGM-71 TOW or AT-2 Swatter is an anti-tank guided missile). Examples of surface-to-surface missile include the MGM-140 ATACMS, the Ground-Launched Small Diameter Bomb (GLSDB) and the Long Range Precision Fires (LRPF). Surface-to-surface missiles are usually broken down into a number of categories: Different parties break down missile type by the range differently. For example, the United States Department of Defense has no definition