United States Navy Fire Controlman (FC), USN rating badge.
A
fire-control radar (
FCR) is a
radar which is designed specifically to provide information (mainly target azimuth, elevation, range and velocity) to a
fire-control system
in order to calculate a firing solution (i.e. information on how to
direct weapons such that they hit the target(s)). Such radars typically
emit a narrow, intense beam of
radio waves to ensure accurate tracking information and to minimise the chance of losing track of the target. Some modern radars have a
track-while-scan capability enabling it to function simultaneously as a fire-control radar and a
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 antenna to generate two (or more) discrete radar beams and dividing them between both tasks.
Operational phases
Fire-control radars operate in three different phases:
[1]
- 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 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 problematic, is gaining
high range resolution. To do this in a basic fire-control radar system,
it must operate at smaller pulse width. 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 reduce
the
radar horizon,
depending on which way the RF is bent. Dust particles, as well as water
droplets, cause attenuation of the RF energy, translating into a loss
of effective range. In both cases, a lower pulse repetition frequency
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 NATO 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, was used effectively and extensively by the Allies during
World War II for anti-aircraft gun laying. Since WWII, the U.S. Army has used radar for directing anti-aircraft missiles including the
MIM-23 Hawk, the
Nike series and currently the
MIM-104 Patriot.
Ship based
Examples of fire-control radars currently in use by the
United States Navy:
Aircraft based
After WWII, airborne fire control radars have evolved from the simpler gun and rocket laying AN/APG-36 system used in the
F-86D to the
Active Electronically Scanned Array based
AN/APG-81 of the
F-35.
See also
References
- ^ Donald J. Povejsil (1965). Airborne Radar. Boston Technical Publishers. pp. p101. Retrieved 2009-02-10.
- US Navy, FIRE CONTROLMAN, VOLUME 02—FIRE CONTROL RADAR FUNDAMENTALS (Revised)
External links
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