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ectronic countermeasures (ECM) :*!'e ‘nter>ded primarily to (1) detect
hib63^ t0 friendly ^orces ar>d (2) in- elt: 0r degrade the effectiveness of ^erny w^apons and sensors. Most sur- k e warships, submarines, and com- aircraft have ECM systems to help
an jteCt C^em afia‘nst hostile detection cj attack. In addition, there are spe- ai^ ECM aircraft that assist other fendV *n Penetrat‘n8 heavily de-
^Early ECM efforts were use<j in q °f ^ar I when the British and Co rrnans *nterfered with the other’s Ft()lrnUn*Cat*ons al°ng fhe Western had^' at sea the Royal Navy
Ce tma^°r eff°tts under way to inter-
erman naval radio transmissions
in ' nere were also efforts at send- Sta(.. a se radio signals, having shore shin °nS Send transmissions using tad’S Ca^ S‘Sns’ and jamming enemy Ecm° s‘8nals. By World War II, the sp0of6 °rtS ‘nc*uded jamming and and radat and navigation signals,
°Ped 6r War’ m‘ssdes were devel- tfar, t0 home in on enemy radar ^missions.
againferent ECM techniques are used tjc 'Afferent enemy electromagne-
three i[eatS’ ^or example, there are kctiv aS'C methods of reducing the ef- Int e?eSS an enemy’s radar. enCQtr*ere u'dh the radar: This activity decepJ^aSSes most radar jamming and shipPor°n W/ith jamrninfi> one’s own satUrr aircraft produces signals to noisg”6 enemy’s radar with it Canat a sufficiently high level that enerr, n0t ^etect the objects which the transrnifS SCekin8- The jammers must the e *r enerfiy continuously while Pulsesra^ar transmits energy in largehus> tdle iarnmer requires power. Because the as ls 0n the same radar azimuth
a‘rctaftiCtUa* tarfiet (°ne’s own ship or the jamming can highlight
the target’s presence and direction, but, if successful, will deny the enemy radar the target’s range, an important factor. There are several methods of jamming.
Deception jamming, in contrast to noise jamming, tries to mimic the radar echo so that the enemy radar will see an incorrect echo, masking the actual target. Deception jamming is generally accomplished by repeater jammers and transponders. Basically, the target ship receives the enemy radar signal and quickly plays back a false replica of the signal. The transmitted signal is very close to the original, but is sufficiently different, speeded up, or delayed to provide false target information. Here again, there are several means of deception jamming, some of which give incorrect target bearing information, false targets, and enlarge the echo (to make a small target appear as a larger one).
Change electrical properties of the air: The electrical properties of the air between the radar and its target can be changed to reduce radar effectiveness. Chaff consists of small aluminum strips designed to resonate at radar frequencies. Typical dimensions for strips or dipoles for use against a 10 GHz radar would be 0.6 inches long, 0.01 inches wide, and 0.001 inches thick. Only 0.1 pound of such chaff creates the echo equal to the size of a large bomber. Thousands of such dipoles are compressed into small packages that are dropped from aircraft dispensers.
Rapid “blooming” off-board chaff (RBOC) can also be fired from shipboard launchers. As the chaff opens it can decoy or break the track of a missile with active radar guidance. Those missiles with infrared guidance can be spooked by firing infrared flares which decoy or confuse the guidance systems.
Change the reflective properties of the target: This ECM concept includes primarily radar-absorbing materials or paint applied to ships and aircraft, and both electronic and mechanical echo (blip) enhancers for decoys.
Although the above discussion concentrated on ECM techniques against radar, to some extent the concepts are usable against electromagnetic communications and sonar. For example, the properties of shipboard noise can be reduced. Modern U. S. surface warships use the PRAIRIE and Masker* systems of creating small air bubbles around a ship’s hull and wake to reduce her acoustic signature. Advanced submarine hull designs (e.g., the Al- hacore [AGSS-569] "tear drop” configuration) reduces noise created by submarine movement while special mountings reduce propulsion and auxiliary machinery noises.
Of course, surface ships and, especially, submarines can slow or stop to reduce their self-generated noises. Decoys are also available, especially the Aerojet General SLQ-25 Nixie, a towed torpedo decoy for surface ships, and acoustic jammers and decoys that can be fired from the three-inch-diameter signal-launching tube in submarines. U. S. attack submarines have been said to carry acoustic device countermeasures (ADC) Mk-23 which will decoy homing torpedoes. U. S. ballistic missile submarines also can launch the Mk-70 MOSS (mobile submarine simulator) from torpedo tubes to simulate a full-size submarine to hostile sonar.
There are a large number of threat
•PRAIRIE (an acronym for propeller air ingestion and emission) feeds air through the shaft and propeller, while Masker consists of air "belts’' around the ship.
ero0(
The Navy plans to provide each cai
rrief
munications for by doing so one nies communications intercept to
decef* :ti>y
warning and countermeasure systems in U. S. surface ships and submarines, mostly numbered in the SLQ and WLR series. The latest surface ship ECM equipment is the highly publicized Raytheon SLQ-32 “design-to-cost” EW suite. Variations of this system are scheduled to be installed in most Navy surface ships in the 1980s.
There are four variants of the SLQ-32 with modular “building blocks” for different types of ships. The VI variant, intended for frigates, some amphibious ships (LSD, LPD, LST), and auxiliary ships (AE, AF, AFS), provides warning, identification, and bearing of radar-guided cruise missiles and
their launch platforms.
The V2 variant, for guided-missile destroyers and frigates, and the Spruance (DD-963)-class large destroyers, has the VI capability and expanded Esk capabilities. The V3 configuration, for cruisers, large amphibious ships (LCC, LHA, LPH), and auxiliaries (AOE, AOR) has the VI and V2 capabilities and the means to counter or deceive missile guidance radars. The V3 has a quick-reaction mode that permits the initiation of jamming against a target signal before its characteristics are fully analyzed. This feature could be particularly useful against “pop-up” submarine- launched missiles or those fired by missile craft hiding in coastal shore “clutter.”
The SLQ-32 and other ECM systems are used in conjunction with RBOC or super RBOC launchers that fire either semi-automatically or on manual direction from a ship’s ECM operators. (The infrared decoys and flares can also be fired in response to detections by threat warning devices.) It has been reported that the SLQ-32 has experienced problems during recent fleet exercises, which coupled with maintenance difficulties and questions about its ability to handle high-angle missile attacks, demonstrates the complexity of the ECM situation.
Several older EW sets are in current Navy use. These include: the WLR-1, 6, 8, 9, 10, 11, and 12, and SLR-12 threat warning systems; ULQ-6 deception repeater; and the SLQ-17 and BLR-14 countermeasure systems. The SLQ-17, apparently used mainly in carriers, includes the WLR-8 and provides computer-controlled warning and jamming capabilities. The BLR-14— dubbed the submarine acoustic warfare system (SAWS)—provides an integrated receiver, processor, display,
and countermeasure launch system f°r submarines.
The principal naval ECM aircraft art the EA-6A/B, flown by the Navy an Marine Corps. Both are variants of the excellent Grumman A-6 Intruder all weather/night attack aircraft. The EA-6B is easily identified by the hous ing atop its tail fin and five jammer pods on its wings and fuselage. The pods are ALQ-99 tactical jammers, eaC with an exciter/processor and a min* computer to detect, identify, and jarn a broad spectrum of hostile radars- The aircraft also has the ALQ-10^ multi-band track breaking system ALQ-92 communications jammer. T EA-6B is probably the most capable E aircraft in the West (although Gm111 man is now providing these systems the Air Force’s EF-111A).
The EA-6A/B aircraft are designed provide ECM support for strike airef* attacking defended targets. The stfl aircraft can themselves carry ehai*’ ECM pods, and radar-homing miss* to further enhance their survivabilW wing with four EA-6B Prowle^ while the Marine Corps has one squa ron with about 15 ECM aircta ^ mostly E A-6 As, with Prowlers n° being acquired.
Electronic countermeasures costly, not only in resources (espee1 for research and development), but cause of tactical uncertainties limitations that they impose. For ample, it may be undesirable to ploy ECM against an enemy’s c°
on«’s
own side. Or, firing chaff and to defend against a possible ene^lfl missile attack can degrade one s 0 radar effectiveness. „ jt
Also, ECM produces “soft kills- ^ is not always possible for the
hib
P ~~ **** wiicmy. n.5 in cv^ivi,
Q includes both systems and Perator training. The designer must ^rovide a variety of options that can
theUSe<^ a^a‘nst exPected threats while °Perator must be trained to recog- fe t*le various countermeasures that th^ C use<J‘against him and select e appropriate response with both ^'Pment and tactics.
ere are a number of characteris- Cs °f radar, sonar, and communica
ative to an enemy. As in ECM,
operator to detect or determine if his e °rts are successful. Further, ESM/ Ecm/eccm are a continuous interac- tlQn. Those who allocate resources are n°t always anxious to spend funds on fn ECM system, for example, that may e a counter to a threat the intelligence community predicts may have a certain capability. Somehow, it seems easier to buy a new ship, or missile, or a|rcraft rather than a new “black box.” One approach to solving this prob- ls electronic counter-counter- ^easures (ECCM). This is the art of re- Ew'n^ effectiveness of an enemy h'k't^reat ma^'n8 costs pro-
tions equipment that can be optimized to enhance resistance to enemy ECM efforts. These include such features as the equipment’s power, frequency, pulse length, antenna design, scan pattern, and computer capability. Some systems are naturally more resistant to jamming and deception. For example, Doppler radars operate on the frequency shift caused by moving targets. They automatically filter out pulse returns from non-moving targets and consequently eliminate many unwanted signals, such as those from chaff. Some Doppler radars will even discriminate between returns from objects of different velocities, such as an aircraft in a chaff cloud.
Similarly, phased-array radars, such as the RCA SPY-lA used in the Aegis weapon system, are highly jam resistant because of the manner in which they can modulate the power and frequency of the numerous antenna elements in each antenna “face.”
The operator and supervisor are vital elements in ECCM considerations. An automatic processor can be designed to operate only against those interfering or jamming signals programmed before the action. New jamming situations not designed into the processor might not be readily handled. However, the human operator has the ability to adapt to new and varied situations and is more likely to be able to recognize, interpret, and cope with a new situation than can a machine.
Another key element of ECCM is knowledge of potential enemy EW equipment, doctrine, and tactics. This information can be obtained overtly as well as covertly. The acquisition of this information is as vital as the acquisition of “hard kill” weapons such as guns and missiles.
Indeed, in view of the Soviet quantitative superiority to U. S. naval forces, and in some areas qualitative superiority as well, electronic warfare takes on as great an importance as some “hard kill” weapons. Obviously, the most effective U. S. fleet capability would have the “right” mix of EW and “hard kill” systems.
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