Electronic Combat

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Flying low, six F/A-18s approach their target: a crit­ical enemy supply and communications center. For five minutes, they flew an irregular course over an area known to have a dense network of coordinated sur­face-to-air missile sites. The course was altered once by an advisory from a high-flying “friendly” some miles behind them. So far, few missiles have been fired, and the few that were seemed poorly directed.

The normally reliable ground-based enemy early warning radars display only a broad sector of noise in the general direction of the attackers. The ground-con­trolled intercept system and the ultrahigh frequency cross-telling network do not seem to be doing their job today because of an unusual interference. (Two EA-6Bs are flying in slow orbits some distance behind the attacking flight.)

Suddenly the radar noise fades, only to be replaced on the radar scopes by several hundred targets flying attack patterns. Which are the real targets?

As the strike objective appears ahead, the flight leader and his wingmates prepare for the final run-in and weapons release. Knowing that he is nearing burn-through range for the EA-6Bs’ stand-off jammers, each pilot glances at a small red indicator on his con­trol panel. Good, the light is on, indicating all is well. Now, there are terminal threat warnings on their radar warning indicators, followed by pinpoints of fire and light smoke trails rising from several surface-to-air missile sites. In a series of maneuvers, the aircraft jink and make their weapon passes. Seven missiles are seen streaking toward the flight. As each missile approaches, it seems to divert course, and pass several hundred yards away before the warhead detonates.

Only light puffs of smoke remain to mark the former threats as the flight heads for the carrier.

The scene changes. An antiship missile is skimming 20 feet above the waves at 450 knots toward its target— °^ne °f four U. S. guided missile destroyers in the outer ^screen of a task group. The missile is running on a Preset course determined at launch and maintained by ^{lts se}lf-contained navigation system. The missile was launched about six minutes earlier by a high-flying wrcraft. Detection of the destroyer was made by a °ⁿg-range surface search radar on board the launch- ^lng aircraft. A single sweep of the aircraft’s radar ^Screen revealed multiple targets.

The missile had been launched on an approximate ^earing on one of the four targets that appeared in the ^1n,fial scan. Its 600-kilogram warhead and unspent fuel ^w‘ll probably disable or sink the ship if it hits on the P°^rt stern quarter where the radar return centroid ^aPPears to be for the particular direction of missile’s ^aPproach. At a 12-mile range from the destroyer, the Missile’s terminal guidance radar switches on and scans for the target. Forty-eight seconds later, the ship’s superstructure and upper hull appear above the missile’s radar horizon. Instead of a single target, however, there are six. The scanning stops as the mis­sile’s seeker logic selects the largest and alters course slightly to starboard to center the target in its flight path. Now, only 40 seconds to impact, the range rate memory circuit is locked on as a counter-countermea­sure against introduction of false targets or momentary loss of detection. A slight change in range rate now causes the missile to compare its radar information with its backup infrared detection system to confirm, by its heat radiation pattern, that the target is real. Every­thing checks out, and the missile skims the sea from port to starboard 200 yards aft of the destroyer head­ing for a chaff cloud and infrared decoy 300 yards away. The warhead explodes; splashes in the water mark the spot. A few fragments strike the ship but cause no serious damage.

These scenarios are idealized. In the real world, many things can go wrong. The sinking of HMS Sheffield in the Falklands Conflict testifies to that. The British, who were the leaders in electronic combat in World War II, were not prepared this time. The missiles described in the scenarios offered here were export ver­sions used by third party nations and their technical char­acteristics were well known. Newer generations of higher speed missiles will give little time for warning and reac­tion, and will contain sophisticated target discrimination techniques coupled with automatic computers that will be more difficult to deceive.

If the U. S. Navy is to survive in this new world, it must be prepared for “electronic combat.” For the purposes of this discussion, electronic combat is the organized exploi­tation and defeat of all forms of enemy radiation, includ­ing communication, weapon guidance signals, and radar or other surveillance and their radiation-dependent passive counterparts. This can include any frequency from acous­tics through microwave and infrared and higher. Often, the techniques used for electronic combat are similar to those employed by the threat. This is the key to under­standing the power of electronic countermeasures (ECM).

When only “dumb” ballistic weapons existed, once the weapon had been fired there was little that could be done to avoid a properly aimed hit other than to maneuver and hope. Precisely because the new weapons are guided, there are ways to divert them once we figure out how they are guided.

ECM Technology and Methods: Types of ECM usually employed against radars include noise jamming across a wide band of frequencies to mask actual target returns. Deception jamming creates false targets that can deceive the victim’s radar in range, bearing, size, and number of targets. Physical decoys such as chaff clouds consist of thousands of short aluminized strips that drift in the air and simulate or screen large targets by reflecting radar signals. Flares can simulate the infrared heat output of a ship or aircraft and thus deceive a heat-seeking missile.

The active electronic deception techniques may be very subtle—so much so that the victim may not realize that he has been deceived until it is too late. Anti-radiation mis­siles (ARM) like Shrike, HARM (high-speed anti-radia­tion missile), and Standard ARM that home on enemy- radiated signals can be used to destroy enemy radar anten­nas if they remain on for a sufficient period.

Microwave ECM, as used in Vietnam, can be divided into two broad categories: self-protect and standoff or support ECM. In the former, a strike aircraft or ship car­ries an active jammer to divert an oncoming missile away from only itself. Standoff or third-party jamming is done by an aircraft or ship with the sole mission of covering or protecting groups of other aircraft or ships, usually from a stand-off distance compared with the attackers. Because of their dedicated mission, standoff jammers carry more powerful transmission equipment which covers broad frequency bands and has a wider repertoire of ECM tech­niques than would otherwise be practical and cost-effec­tive on individual strike aircraft.

Electronic combat can also be used to obtain long-range over-the-horizon fixes for strikes on opposing emitters and associated forces and to provide real-time combat infor­mation derived from enemy communications. ECM can be used to disable enemy command links, often the most vulnerable part of a netted weapon system. Similarly, if the enemy surveillance systems cannot initially detect targets at which to fire weapons or, if using third-party targeting, cannot communicate detection data to the remote weapon launch platform, the weapon system is effectively defeated. Many more possibilities exist. Note that each one of these methods can also be used against us. Obvious electronic counter-countermeasures (ECCM) techniques are the use of very short radar on-times, and highly directional or coded communications links that are difficult to jam because they are difficult to detect and relatively invulnerable to the jammer power because of geometry.

ECCM and Limitations of Electronic Warfare: Elec­tronic warfare (EW) is most vulnerable to a surprise. The opponent may have developed a new guidance technique that has not been detected by intelligence. The weapon systems may contain battle modes that are never used in training and, therefore, are unlikely to be detected in advance. Depending on its flexibility and the installed ECM, the new guidance system may or may not be thwarted. Because our forces may encounter such a sur­prise, the requirement remains for the “hard kill” weap­ons which often seem to be emphasized to the disadvan­tage of ECM.

Electronic countermeasures also will do no good against an old-fashioned dumb bomb or straight-running torpedo or ballistic weapon. But these types of weapons imply short standoff distances and therefore great vulnera­bility of the launch platform to modem weapons.

Ground-to-air missiles can be aimed optically if the radar acquisition or guidance system is jammed. ECM in this case would have served its purpose by degrading weapon system effectiveness and forcing it to a clear- weather-only mode.

Timeliness of response can be a limiting factor in ECM. In the event of a technical surprise, it may be necessary to develop a new countermeasure, produce and install it, and develop tactics for its use.

This all takes time. World War II countermeasure response times, from the introduction of a new electronic threat to fielding its countermeasure, varied from about one month to one year. With more complex systems, the time increases. In Vietnam, response times ran from six to 30 months. We cannot afford that kind of delay very often. ECM must be preplanned and flexible to accommodate wide frequency bands and varied signal modulations.

There are also physical limitations. Laws of physics are difficult to evade. The effective broadside radar reflecting area or radar cross section of a medium to large ship can be 100,000 square meters or more. This compares with one to ten square meters for most aircraft. Because the strength of the radar signal returned from the ship is pro­portional to the radar cross section, it takes very large and

sometimes unattainable power for the ECM to defend completely. Effective ECM usually requires that the ECM ^Slgnal at the threat radar be as large or larger than the real target echo. The same limitations can apply to chaff or other decoys that must compete with the true echo for the threat missile’s attention. All countermeasures work best ^when the target itself is made harder to detect in the first place. “Low observable” technology used in the stealth” aircraft aids ECM protection.

One guidance technique that is difficult to defeat by conventional ECM is monopulse radar guidance. Monopulse radars have an angle-tracking scheme that is ^Very robust and cannot be deceived by ordinary counter­measures. Inertial guidance, which relies only on informa- hon preset into the missile, has no known countermeasure other than its physical destruction. Its disadvantage is that ‘t is unsuitable for most naval tactical situations where the relative position of the firing platform and target change ^substantially during the time of flight of the missile, and it ^quires a very precise knowledge of the position of the ^uoch platform relative to the target. gp^^rne'°n-jam is another technique that can reduce M effectiveness. A home-on-jam-equipped missile can _r ,^{Se cer}tain types of jamming and guide on the jamming to ^^{an tar}8^{et return} signal. If the jammer happens the ^C, '^ocated on the target, it may serve only to increase ty ^chance of a hit. This argues in favor of the more subtle jj ^es °f jamming, which are difficult for the missiles to ^Cr|minate against, and for off board ECM.

Finally, as technology advances, the sheer numbers of signals become increasingly difficult to interpret and handle. The effect on the ECM system is to overload it. The result can be that the important threat signal is not detected amidst the other less important signals.

Preparation for Future Naval Electronic Combat: The U. S. Navy can improve significantly its electronic combat capability by taking five actions.

► Increase the investment in electronic warfare based on effectiveness rationale. The average self-protection ECM system installed in U. S. combat aircraft accounts for only about 4.5% of the platform’s cost. For most ships, the ratio is 1.5%. The Navy’s fiscal year 1983 budget included about $1.2 billion for EW of all kinds, including laser, microwave, optical, infrared, acoustic, signal intel­ligence, and command, control, and communications countermeasures. This was about 1.7% of the Navy’s fiscal year appropriation. The numbers are more the result