ETL 1110-3-456
16 Aug 94
significant errors in bomb delivery because a stable bombing
platform is needed for the few seconds between the initial
tracking point and the bomb release point.
d. Sensors. Sensors provide imagery during orientation
feature identification, target recognition, and target acquisi-
tion, and laser sensors are used as range finders and target
designation devices. The most predominant sensor wavebands are
the radar, long wave infrared (LWIR), middle wave infrared
(MWIR), near infrared (NIR), and visual wavebands shown in figure
A-2. The thermal infrared waveband includes both the LWIR and
MWIR wavebands. The effect of various atmospheric conditions on
sensors operating on various wavebands is shown in table A-I.
Sensor systems can be classified as active or passive. Active
systems rely on beam propagation and reflection; typically a
radar or laser beam. Passive systems produce imagery without
beam propagation and typically use thermal infrared or visual
light signals. Passive systems cannot be detected because there
is no propagated beam to detect.
(1) Radar. Radar beam reflection depends on the surface
orientation, the surface roughness, and the surface dielectric
constant or conductivity. For example, a steel plate has a high
dielectric constant and low roughness and will reflect almost all
of the radar beam without scatter. A radar sensor in a low
altitude attack aircraft will detect a vertical steel plate as a
distinct white area because almost all of the radar beam is
reflected back to the aircraft sensor. A horizontal steel plate
will be detected as a black area because almost all of the beam
is reflected away from the aircraft sensor. Most radar produces
a low resolution image that requires training for effective
interpretation. The exception is the recently developed millime-
ter wave radar or high resolution radar.
(2) Thermal Infrared. Thermal infrared sensors produce
an image from surface heat emissions. Surface areas that have
highly contrasting heat emission properties such as water next to
the shoreline, pavement next to grass, and hot vehicle engines
will produce clear and obvious images.
(3) Visual. Visual images are produced from light in
the visual waveband. Low light systems such as low light
television produce images from small light sources such as
starlight and are used for night viewing.
(4) Lasers. Lasers are used for range finders and
target designation devices. Various laser wavebands and laser
types are shown in figure A-3. The average detection ranges
A-4
Previous Page
