JED - May 2013 - 55

EW 101

Infrared Systems and Countermeasures – Part 6

Flares cont’d.
Tracking Window

By Dave Adamy

Target responds
with predictable
ratio of energy
at two wavelengths.

Bloomed oxidizing material
is at temperature of target
but occupies larger area for
increased energy.

Temperature Sensing Trackers
In March, we discussed the two-color sensor
Figure 1: A low-temperature flare blooms smoldering material over a large area to cause
that can determine the actual temperature of
a high-energy response in the missile sensor, seducing the tracker away from its intended
target.
the target and of the flare. The tracker then
tracks only a target at the correct temperature.
As discussed in the March “EW 101” column, the tracker senses
ible and of not setting fires if they hit the ground in forests
at two different wavelengths. If the sensed energy at the two
or cities.
wavelengths has the proper ratio, the tracker will conclude
A second approach is to manufacture flares with two chemithat it is tracking a valid target. If the flare is at a higher
cals that burn at high temperatures but emit with the cortemperature, it will be rejected by the tracker and thus cannot
rect energy ratio at the two wavelengths sensed by the missile
decoy the missile away from its intended target.
tracker. The energy ratio will cause the tracker to accept the
For a flare to be effective against a two-color sensor, it must
flare as a valid target, and the high temperature will create an
create the correct energy ratio. This can be
done by emitting at the proper temperature or
by emitting at a higher temperature, but with
TARGET
the correct ratio between the energy at the two
Energy ratio at two
wavelengths sensed by the tracker.
wavelengths dictated
TRACKER
by temperature (per
Senses at two wavelengths;
As shown in Figure 1, a low temperature
black body characteristics)
qualifies on correct
flare can emit at the correct temperature, but
energy ratio
then it must create higher energy by filling
a larger volume than that of the missile’s intended target. This can be accomplished by
FLARE
dispensing a cloud of small pieces of mateTwo high energy sources at
rial coated with a rapidly oxidizing chemiwavelengths sensed by tracker –
energy ratio meets black body
cal (such as a pyrophoric IR decoy) that will
characteristics at temperature of
spontaneously burn at the correct temperatarget
ture. Igniting a cloud of flammable vapor
can create the same effect. Low-temperature
flares have the advantage of being less visFigure 2: A two-color flare emits energy with the correct ratio to match that of the target.

The Journal of Electronic Defense | May 2013

F

lares are a very effective countermeasure against heat-seeking
missiles because a flare puts more
energy into the tracker than the
target does. Thus, the flare captures the seeker and leads the missile away from its target. However, there are
various techniques that can be employed to
allow the missile tracker to discriminate the
flare from the target. If successful, they allow
the tracker to ignore the flare and continue
toward its intended target. Some of these techniques are chemical, some are temporal and
some are geometrical.

55


http://www.CROWS.ORG

JED - May 2013

Table of Contents for the Digital Edition of JED - May 2013

The View From Here
Conferences Calendar
Courses Calendar
From the President
Letters
The Monitor
The Monitor
The Long Hard Road – EW’s Future in Europe
Technology Survey: Signal Generators
Two Domains Are Better Than One
Preview: AOC 50th Anniversary
EW 101
Book Review
AOC News
Index of Advertisers
JED Quick Look
JED - May 2013 - cover1
JED - May 2013 - cover2
JED - May 2013 - 3
JED - May 2013 - 4
JED - May 2013 - 5
JED - May 2013 - The View From Here
JED - May 2013 - 7
JED - May 2013 - Conferences Calendar
JED - May 2013 - 9
JED - May 2013 - Courses Calendar
JED - May 2013 - 11
JED - May 2013 - From the President
JED - May 2013 - 13
JED - May 2013 - Letters
JED - May 2013 - The Monitor
JED - May 2013 - 16
JED - May 2013 - 17
JED - May 2013 - 18
JED - May 2013 - 19
JED - May 2013 - 20
JED - May 2013 - 21
JED - May 2013 - 22
JED - May 2013 - 23
JED - May 2013 - 24
JED - May 2013 - 25
JED - May 2013 - The Monitor
JED - May 2013 - 27
JED - May 2013 - The Long Hard Road – EW’s Future in Europe
JED - May 2013 - 29
JED - May 2013 - 30
JED - May 2013 - 31
JED - May 2013 - 32
JED - May 2013 - 33
JED - May 2013 - 34
JED - May 2013 - 35
JED - May 2013 - 36
JED - May 2013 - 37
JED - May 2013 - 38
JED - May 2013 - 39
JED - May 2013 - 40
JED - May 2013 - Technology Survey: Signal Generators
JED - May 2013 - 42
JED - May 2013 - 43
JED - May 2013 - 44
JED - May 2013 - 45
JED - May 2013 - 46
JED - May 2013 - 47
JED - May 2013 - Two Domains Are Better Than One
JED - May 2013 - 49
JED - May 2013 - 50
JED - May 2013 - 51
JED - May 2013 - Preview: AOC 50th Anniversary
JED - May 2013 - 53
JED - May 2013 - 54
JED - May 2013 - EW 101
JED - May 2013 - 56
JED - May 2013 - 57
JED - May 2013 - 58
JED - May 2013 - Book Review
JED - May 2013 - 60
JED - May 2013 - AOC News
JED - May 2013 - 62
JED - May 2013 - 63
JED - May 2013 - 64
JED - May 2013 - Index of Advertisers
JED - May 2013 - JED Quick Look
JED - May 2013 - cover3
JED - May 2013 - cover4
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