Geometric albedo node of their orbit, and hence lie on the ecliptic. In practice, measurements at small nonzero phase angles are used to derive the parameters which characterize the directional reflectance properties for the body (Hapke parameters). The reflectance function described by these can then be extrapolated to zero phase angle to obtain an estimate of the geometric albedo. For very bright, solid, airless objects such as Saturn's moons Enceladus and Tethys, whose total reflectance (Bond albedo) is close to one, a strong opposition effect combines with the high Bond albedo to give them a geometric albedo above unity (1.4 in the
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