guidance (missiles), and evaluation (intercept and
Figure 1-23 illustrates the fire
control problem sequence.
DETECTION.In this phase, the radar looks for
a target. After the radar (usually a search radar) detects
a target, the system obtains precise target position
information. This information can be provided by the
same source that detected the target, or it can be
provided from some other source, such as another
radar. In the majority of the cases, a second radar, a fire
control radar, is used.
The search radar establishes the targets initial
position and transmits this information to the
designated fire control system.
ACQUISITION AND TRACKING.During
this phase, the fire control radar director/antenna is
aligned with the search radars target position
information until it locks on the reflected target signal
Either an operator or an automatic
control circuit maintains that alignment (track) while
the ship and target are moving.
In this way,
continuous, accurate target position information is
available to the weapon system for processing. Not
only is the continuous present position of the target
obtained, but its movement (course and speed) is also
Data other than target data is equally important for
weapon flight path (trajectory) determination. Wind,
for example, could blow the weapon off its flight path.
Appropriate corrections would require that wind
direction and velocity be determined. The course and
speed of the launching ship and its motion, because of
t h e s e a ( p i t c h a n d r o l l ) , a r e a l s o i m p o r t a n t
considerations. If this type of data is not included in
the flight path determinations, it could cause large
errors in the flight path (trajectory).
Data of this nature, along with target data, is
transmitted to the fire control systems computer. The
computer performs the necessary calculations for
computing the launcher or gun mount position angles
and the weapons flight path.
After target detection and target acquisition have
occurred, the fire control system provides three
operations for the tracking, computation (prediction),
and positioning functions.
The first operation tracks the target and provides
all necessary data on the target. The fire control radar
performs this function by establishing a tracking Line
Of Sight (LOS) along which it receives the returned or
reflected energy from the target.
It also provides
accurate range data.
Since the speed of the propagated RF energy is
about 186,000 miles per second (the same as the speed
of light), and since the target ranges involved are
relatively small, the time for the energy to travel to and
from the target can be considered as instantaneous.
Therefore, the radar indications of the target can be
considered as instantaneous, present-target positions.
PREDICTION.The second operation of the
fire control problem that must be performed is the
computation of the gun/launcher positioning angle
(line of fire) and the weapon flight path trajectory. This
operation consists of two parts.
First, the system
processes received data into a usable form. Then the
fire control computer performs arithmetic operations
to predict the future position of the target.
Figure 1-22.Typical fire-control radar.