Heads-Up Display Modes 35 - Metaboli

Sensors 69
called the Pulse Repetition Frequency (PRF). Radars in “searching” modes
generally use larger scan patterns and a lower PRF, letting the radar monitor
multiple targets. Radars in “tracking” combine small scan areas with a high PRF.
The radar then reports significantly more information about one target, and
continually adjusts the scan pattern to maintain focus on the target. This is
commonly called a “lock on.”
Many modern radar systems attempt to bridge the gap between search and track
radar modes with Track While Scan (TWS) modes. TWS modes attempt to provide
detailed tracking information about multiple targets while continuing to scan a
large volume of airspace. On the positive side, this provides a substantially more
thorough picture of the sky. On the downside, the radar must make “educated
guesses” about the tracked targets, since the radar cannot focus attention on any
single target. Based on information collected when the radar beam scans a given
target, the radar predicts the target’s flight path until the beam again scans that
target. While the beam is busy scanning other targets, the radar display shows
the predicted position of the first target. If that makes a sudden, unexpected
maneuver, the radar display continues to show the predicted position until the
radar beam finally returns its attention to the target and finds it gone.
hTWS mode provides details for multiple targets simultaneously, but
relies on estimations of the target’s position, and can therefore be
“tricked” if a target makes an unexpected maneuver.
4.002 Infrared
Engines, especially jet engines, produce a lot of heat. Weapon designers quickly
realized they could detect and track this heat, or Infrared (IR) energy. Early IR
systems could only track targets from behind, with the hot engine exhaust
pointed directly at the seeker. Modern all-aspect heat-seeking missiles can track
the heat emitted from a target from any angle. Further, many aircraft carry Infrared
Search and Track (IRST) systems, which can detect targets many miles away. IRST
systems are passive, meaning they emit no energy of any kind. Unlike radar,
which announces the emitter’s presence to the world, IR systems are completely
“stealthy” and impossible to detect.
hWeather, such as rain and fog, seriously degrades IR performance. In
severe weather conditions, IR systems suffer greatly shortened
detection ranges.
4.003 Laser
Laser systems provide modern combat aircraft with a third major sensor system.
Laser rangefinders calculate distance very accurately by bouncing a laser beam off
the target and measuring how long it takes the beam of laser light to return to the
emitter. Ground-attack systems use lasers to pinpoint specific objects (such as an
individual battle tank or a specific window on a building) to guide air-to-ground
weapons. Since lasers, like radar, emit energy, laser emitters can be detected by
hostile forces.
As with IR systems, laser systems work best in clear weather. Clouds, fog, and
rain seriously degrade laser systems.