Albedo 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. The correlation between astronomical (geometric) albedo, absolute magnitude and diameter is: formula_7, where formula_8 is the astronomical albedo, formula_9
Surface-to-air missile than aircraft. Virtually all surface warships can be armed with SAMs, and naval SAMs are a necessity for all front-line surface warships. Some warship types specialize in anti-air warfare e.g. "Ticonderoga"-class cruisers equipped with the Aegis combat system or "Kirov" class cruisers with the S-300PMU "Favorite" missile system. Modern Warships may carry all three types (from long-range to short-range) of SAMs as a part of their multi-layered air defence. SAM systems generally fall into two broad groups based on their guidance systems, those using radar and those using some other means. Longer range missiles generally use radar for early detection