Afire-control radar (FCR) is aradar that is designed specifically to provide information (mainly targetazimuth,elevation,range andrange rate) to afire-control system in order to direct weapons such that they hit a target. They are sometimes known asnarrow beam radars,[1]targeting radars,tracking radars, or in the UK,gun-laying radars. If the radar is used to guide a missile, it is often known as atarget illuminator orilluminator radar.
A typical fire-control radar emits anarrow, intense beam ofradio waves to ensure accurate tracking information and to minimize the chance of losing track of the target. This makes them less suitable for initial detection of the target, and FCRs are often partnered with a medium-rangesearch radar to fill this role. In British terminology, these medium-range systems were known astactical control radars.
Most modern radars have atrack-while-scan capability, enabling them to function simultaneously as both fire-control radar and search radar. This works either by having the radar switch between sweeping the search sector and sending directed pulses at the target to be tracked, or by using aphased-array antenna to generate multiple simultaneous radar beams that both search and track.
Fire-control radars operate in three different phases:[2]
The performance of a fire-control radar is determined primarily by two factors: radar resolution and atmospheric conditions. Radar resolution is the ability of the radar to differentiate between two targets closely located. The first, and most difficult, is range resolution, finding exactly how far is the target. To do this well, in a basic fire-control radar system, it must send very short pulses. Bearing resolution is typically ensured by using a narrow (one or two degree) beam width. Atmospheric conditions, such as moisture lapse,temperature inversion, and dust particles affect radar performance as well. Moisture lapse and temperature inversion often cause ducting, in which RF energy is bent as it passes through hot and cold layers. This can either extend or shorten theradar horizon, depending on which way the RF is bent. Dust particles, as well as water droplets, cause attenuation of the RF energy, resulting in a loss of effective range. In both cases, a lowerpulse repetition frequency makes the radar less susceptible to atmospheric conditions.
Most fire-control radars have unique characteristics, such as radio frequency, pulse duration, pulse frequency and power. These can assist in identifying the radar, and therefore the weapon system it is controlling. This can provide valuable tactical information, like the maximum range of the weapon, or flaws that can be exploited, to combatants that are listening for these signs. During theCold War Soviet fire control radars were oftennamed andNATO pilots would be able to identify the threats present by the radar signals they received.
One of the first successful fire-control radars, theSCR-584, was used effectively and extensively by the Allies duringWorld War II for anti-aircraft gun laying. Since World War II, the U.S. Army has used radar for directing anti-aircraft missiles including theMIM-23 Hawk, theNike series and currently theMIM-104 Patriot.
Examples of fire-control radars currently in use by theUnited States Navy:
After World War II, airborne fire control radars have evolved from the simpler gun and rocket layingAN/APG-36 system used in theF-86D to theactive electronically scanned array-basedAN/APG-81 of theF-35 Lightning II.[4]
