A fire-control radar (FCR) is a

radar Radar is a detection system that uses radio waves to determine the distance ('' ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, we ...

that is designed specifically to provide information (mainly target

azimuth An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north. Mathematical ...

elevation The elevation of a geographic location is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface (see Geodetic datum § Ver ...

range Range may refer to: Geography * Range (geographic), a chain of hills or mountains; a somewhat linear, complex mountainous or hilly area (cordillera, sierra) ** Mountain range, a group of mountains bordered by lowlands * Range, a term used to i ...

and

range rate The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the rate of change of the distance or range between the two points. It is equivalent to the vector projection o ...

) to a fire-control system in order to direct weapons such that they hit a target. They are sometimes known as targeting radars, or in the UK, gun-laying radars. If the radar is used to guide a missile, it is often known as a target illuminator or illuminator radar. A typical fire-control radar emits a

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, intense beam of radio 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-range

search radar This is a list of different types of radar. Detection and search radars Search radars scan great volumes of space with pulses of short radio waves. They typically scan the volume two to four times a minute. The waves are usually less than a meter ...

to fill this role. In British terminology, these medium-range systems were known as

tactical control radar Tactical Control is a term originating in the British Army to refer to a class of medium-range radar systems. They are generally used for controlling the airspace around a set location on the ground, sometimes a dispersed battery of anti-aircraft a ...

s. Most modern radars have a

track-while-scan The track while scan (TWS) is a mode of radar operation in which the radar allocates part of its power to tracking the target or targets while part of its power is allocated to scanning, unlike the straight tracking mode, when the radar directs all ...

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 a

phased-array In antenna theory, a phased array usually means an electronically scanned array, a computer-controlled array of antennas which creates a beam of radio waves that can be electronically steered to point in different directions without moving th ...

antenna to generate multiple simultaneous radar beams that both search and track.

Operational phases

Fire-control radars operate in three different phases: ;Designation or vectoring phase: The fire-control radar must be directed to the general location of the target due to the radar's narrow beam width. This phase is also called "lighting up". It ends when lock-on is acquired. ;Acquisition phase: The fire-control radar switches to the acquisition phase of operation once the radar is in the general vicinity of the target. During this phase, the radar system searches in the designated area in a predetermined search pattern until the target is located or redesignated. This phase terminates when a weapon is launched. ;Tracking phase: The fire-control radar enters into the track phase when the target is located. The radar system locks onto the target during this phase. This phase ends when the target is destroyed.

Performance

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 In meteorology, an inversion is a deviation from the normal change of an atmospheric property with altitude. It almost always refers to an inversion of the air temperature lapse rate, in which case it is called a temperature inversion. Nor ...

, 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 the

radar horizon The radar horizon is a critical area of performance for aircraft detection systems that is defined by the distance at which the radar beam rises enough above the Earth's surface to make detection of a target at low level impossible. It is associ ...

, 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 lower

pulse repetition frequency The pulse repetition frequency (PRF) is the number of pulses of a repeating signal in a specific time unit. The term is used within a number of technical disciplines, notably radar. In radar, a radio signal of a particular carrier frequency is tu ...

makes the radar less susceptible to atmospheric conditions.

Countermeasures

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 the Cold War Soviet fire control radars were often named and

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pilots would be able to identify the threats present by the radar signals they received.

Surface based

One of the first successful fire-control radars, the

SCR-584 The SCR-584 (short for '' Set, Complete, Radio # 584'') was an automatic-tracking microwave radar developed by the MIT Radiation Laboratory during World War II. It was one of the most advanced ground-based radars of its era, and became one of the ...

, was used effectively and extensively by the Allies during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

for anti-aircraft gun laying. Since World War II, the U.S. Army has used radar for directing anti-aircraft missiles including the MIM-23 Hawk, the

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series and currently the MIM-104 Patriot.

Ship based

Examples of fire-control radars currently in use by the

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: *Mk 95 — Continuous Wave Illuminator (NATO Sea sparrow Surface Missile System) *Mk 92 — Combined Antenna System (Mk 75 Gun, formerly SM-1 missiles) *

AN/SPG-62 The AN/SPG-62 is a continuous wave fire-control radar developed by the United States, and it is currently deployed on warships equipped with the Aegis Combat System. It provides terminal target illumination for the semi-active SM-2MR/ ER and ...

— Continuous Wave Illuminator (

AEGIS The aegis ( ; grc, αἰγίς ''aigís''), as stated in the ''Iliad'', is a device carried by Athena and Zeus, variously interpreted as an animal skin or a shield and sometimes featuring the head of a Gorgon. There may be a connection with a d ...

) *

AN/SPQ-9 AN/SPQ-9A, (sometimes pronounced as "spook nine"), is a United States Navy multi-purpose surface search and fire control radar used with the Mk-86 gun fire-control system (MK86 GFCS). It is a two dimensional surface-search radar, meaning it provi ...

B — Pulse Doppler ( Mk 45 lightweight gun)

Aircraft based

After World War II, airborne fire control radars have evolved from the simpler gun and rocket laying AN/APG-36 system used in the

F-86D The North American F-86D/K/L Sabre (initially known as the YF-95 and widely known informally as the "Sabre Dog",) was an American transonic jet fighter aircraft. Developed for the United States Air Force in the late 1940s, it was an interceptor ...

to the Active electronically scanned array-based AN/APG-81 of the

F-35 The Lockheed Martin F-35 Lightning II is an American family of single-seat, single-engine, all-weather stealth multirole combat aircraft that is intended to perform both air superiority and strike missions. It is also able to provide elect ...

References

{{Reflist * US Navy, FIRE CONTROLMAN, VOLUME 02—FIRE CONTROL RADAR FUNDAMENTALS (Revised)

External links

AN/APG Fire Control Systems at GlobalSecurity.org
Military radars