Beam-riding, also known as Line-Of-Sight Beam Riding (LOSBR) or beam guidance, is a technique of directing a missile to its target by means of radar or a laser beam. The name refers to the way the missile flies down the guidance beam, which is aimed at the target. It is one of the simplest guidance systems and was widely used on early missile systems, however it had a number of disadvantages and is now found typically only in short-range roles. Basic concept Beam riding is based on a signal that is pointed towards the target. The signal does not have to be powerful, as it is not necessary to use it for tracking as well. The main use of this kind of system is to destroy airplanes or tanks. First, an aiming station (possibly mounted on a vehicle) in the launching area directs a narrow radar or laser beam at the enemy aircraft or tank. Then, the missile is launched and at some point after launch is “gathered” by the radar or laser beam when it flies into it. From this stage onwards, the missile attempts to keep itself inside the beam, while the aiming station keeps the beam pointing at the target. The missile, controlled by a computer inside it, “rides” the beam to the target. Radar beam riding Beam riding is one of the simplest methods of missile guidance using a radar. It was widely used for surface-to-air missiles in the post-World War II era for this reason. An early example was the British Brakemine, first tested in 1944, as was the first commercially available SAM, the Oerlikon Contraves RSA. Early tracking radars generally use a beam a few degrees wide, which makes it easy to find the target as it moves about. Unfortunately, this makes the beam too wide to accurately attack the target, where measurements on the order of of a degree are required. To perform both operations in a single radar, some additional form of encoding is used. For WWII-era systems this was either lobe switching, or more commonly by the second half of the war, conical scanning. Conical scanning works by splitting the single radar beam in two, and comparing the return strength in the two beams to determine which is stronger. The radar is then rotated towards the stronger signal to re-center the target. The antenna is spun so that this comparison is