JED - October 2017 - 44

TH E H E AT I S O N

H elico pte r E l ec t r o n ic D efe n s e -
H ave I n f r a r e d M i s s i l e Wa r n i ng
S ys tem s Fi n a ll y A r r i ve d?
By Burt Keirstead

I
The Journal of Electronic Defense | October 2017

44

n the opening of Tom Clancy's 1988 novel, The Cardinal
of the Kremlin, he describes a fictional Afghani Mujahid
fighter readying his Strela to target a Soviet helicopter;
Strela being the Cyrillic name for the ubiquitous Soviet
infrared man-portable air defense system (MANPADS),
known in NATO parlance as the SA-7. The book's character is known as "The Archer," and in Cyrillic, Strela means
"arrow," an apt name for the slender weapon that, when loosed
from its shoulder-mounted launch tube, guides in a matter of
seconds toward the heat of an aircraft engine. It is well known
that the US supplied a similar but more advanced anti-aircraft
weapon, the Stinger, to the Mujahideen, which became a game
changer in helping to oust the Soviets from Afghanistan, where
the mountainous terrain meant helicopters were necessary to
ferry troops and equipment. The indigenous Mujahideen shot
down more than 250 Soviet helicopters and small fixed wing
planes, once they were trained to use the Stinger properly.
The interminable US experience in Afghanistan would be
even worse had it not developed missile warning systems to
its aircraft deployed there. In this month's column, we'll examine some of the history of US missile warning development
and some of the key trade-offs involved in choosing the right
technology for warning helicopter aircrews of missile threats
to their aircraft. In particular, we'll focus on the fundamental
trade-off between using infrared (IR) sensors and ultraviolet
(UV) sensors as the "eyes" of the missile warning system.

A MOSTLY UV LEGACY
During US operations in both Afghanistan and Iraq, missile
warning systems have protected aircraft from IR MANPADS by
detecting the incoming missile and cueing a countermeasure.
To date, the predominant missile warning systems for US helicopters, the AAR-47 and the AAR-57, have detected the missile
by using sensors to look for the heat signature from the rocket
motor in the ultraviolet (UV) portion of the electromagnetic
spectrum. This technology has proven effective in balancing
the required high probability of detecting the missile with the
potential for false alarms from other sources in the environment that also have ultraviolet signatures. By using a very
narrow portion of the UV spectrum, this technology has been
effective at filtering out most false sources upon initial detection of an incoming signal. False alarms are further minimized
by using signal processing based on a priori knowledge of the
features that characterize an approaching missile.
The trade-off to using a narrow portion of the UV spectrum
to screen out false sources is the reduction in the overall signal
that gets through the filter for processing. The attenuation to
the missile signal limits the detection range of the system. For
years, the detection range performance has proven adequate
for most helicopters over their mission profiles and against the
array of threats they are likely to encounter. But for larger aircraft that fly at higher altitudes and therefore can be attacked
at longer ranges, the preferred approach for detecting the missile has been to use sensors in the IR portion of the spectrum,
where there is more signal available. The main challenge in
that case has been having enough processing power to
limit the false alarm rate to an acceptable level.

DIRCM DROVE NEW REQUIREMENTS

The AAR-47B(V)2, shown here with an APR-39A RWR on a V-22 Osprey.
The AAR-47 family is the most widely deployed UV MWS across the US
Navy and US Marine Corps. (Jacobst photo)

Of course, detecting the missile is
necessary, but not sufficient, for protecting aircrews who, because of
the missile's speed and agility, have
virtually no chance of evading the
missile by maneuvering the aircraft.
There must also be a countermeasure
that disrupts the missile's seeker and
guidance functions. Countermeasure
flares of different types have been
used to great effect for many



Table of Contents for the Digital Edition of JED - October 2017

The View From Here
Conferences Calendar
Courses Calendar
From the President
The Monitor
Washington Report
World Report
Maximizing EW Capabilities Within the Brigade Combat Team
Homing Senses: Anti-Ship Seekers Show New Diversity
The Heat is On
EW 101
Technology Survey: COMINT/DF Receivers
2018 EW/SIGINT Resource Guide
AOC News
Index of Advertisers
JED Quick Look
JED - October 2017 - intro
JED - October 2017 - cover1
JED - October 2017 - cover2
JED - October 2017 - 3
JED - October 2017 - 4
JED - October 2017 - 5
JED - October 2017 - The View From Here
JED - October 2017 - 7
JED - October 2017 - Conferences Calendar
JED - October 2017 - 9
JED - October 2017 - Courses Calendar
JED - October 2017 - 11
JED - October 2017 - From the President
JED - October 2017 - 13
JED - October 2017 - 14
JED - October 2017 - insert1
JED - October 2017 - insert2
JED - October 2017 - The Monitor
JED - October 2017 - 16
JED - October 2017 - 17
JED - October 2017 - 18
JED - October 2017 - 19
JED - October 2017 - 20
JED - October 2017 - 21
JED - October 2017 - Washington Report
JED - October 2017 - 23
JED - October 2017 - World Report
JED - October 2017 - 25
JED - October 2017 - Maximizing EW Capabilities Within the Brigade Combat Team
JED - October 2017 - 27
JED - October 2017 - 28
JED - October 2017 - 29
JED - October 2017 - 30
JED - October 2017 - 31
JED - October 2017 - 32
JED - October 2017 - 33
JED - October 2017 - 34
JED - October 2017 - 35
JED - October 2017 - Homing Senses: Anti-Ship Seekers Show New Diversity
JED - October 2017 - 37
JED - October 2017 - 38
JED - October 2017 - 39
JED - October 2017 - 40
JED - October 2017 - 41
JED - October 2017 - 42
JED - October 2017 - 43
JED - October 2017 - The Heat is On
JED - October 2017 - 45
JED - October 2017 - EW 101
JED - October 2017 - 47
JED - October 2017 - 48
JED - October 2017 - 49
JED - October 2017 - 50
JED - October 2017 - Technology Survey: COMINT/DF Receivers
JED - October 2017 - 52
JED - October 2017 - 53
JED - October 2017 - 54
JED - October 2017 - 55
JED - October 2017 - 56
JED - October 2017 - 57
JED - October 2017 - 58
JED - October 2017 - 59
JED - October 2017 - 60
JED - October 2017 - 61
JED - October 2017 - 62
JED - October 2017 - 63
JED - October 2017 - 64
JED - October 2017 - 65
JED - October 2017 - 66
JED - October 2017 - 67
JED - October 2017 - 2018 EW/SIGINT Resource Guide
JED - October 2017 - 69
JED - October 2017 - 70
JED - October 2017 - 71
JED - October 2017 - 72
JED - October 2017 - 73
JED - October 2017 - 74
JED - October 2017 - 75
JED - October 2017 - 76
JED - October 2017 - 77
JED - October 2017 - 78
JED - October 2017 - 79
JED - October 2017 - 80
JED - October 2017 - 81
JED - October 2017 - 82
JED - October 2017 - 83
JED - October 2017 - 84
JED - October 2017 - 85
JED - October 2017 - 86
JED - October 2017 - 87
JED - October 2017 - 88
JED - October 2017 - 89
JED - October 2017 - AOC News
JED - October 2017 - 91
JED - October 2017 - 92
JED - October 2017 - Index of Advertisers
JED - October 2017 - JED Quick Look
JED - October 2017 - cover3
JED - October 2017 - cover4
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