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美军空袭叙基地证明电子干扰难于完全避免巡航导弹打击,需要弹炮拦截
送交者: 古宇庙 2017年04月19日15:36:56 于 [世界军事论坛] 发送悄悄话



Tomahawk cruise missiles proved to be difficult targets for Russian electronic warfare systems

The US Navy hit Syrian air base Al-Shayrat with Tomahawk sea-launched cruise missiles (SLCM) early in April. A leading Russian designer of electronic warfare (EW) equipment has spoken with the Izvestia daily about why the Tomahawk is a very hard target to deal with and how friendly forces, airfields and intercontinental ballistic missile (ICBM) silos may be protected and defended against it.



Tomahawk cruise missiles proved to be difficult targets for Russian electronic warfare systems A Tomahawk Land Attack Missile is launched from an Arleigh Burke-class destroyer. (U.S. Navy photo)



Cruise missiles are very hard targets to hit. Both Russia and the rest of the world lack effective EW gear able to dupe cruise missiles through and through to make them miss the target or to render them inefficient altogether. One can only degrade their guidance or force them to climb to the altitude where it will become theoretically vulnerable to air defense (AD) systems. 

Many an expert says that it is enough to jam the GPS signal to prevent the cruise missile from getting a fix on its own position and veer off the course. Alas, this is far from the fact. ‘Experts’ make such statements due to their ignorance of the operating principles of the Tomahawk’s guidance and navigation systems. The Tomahawk carries a rather sophisticated inertial navigation system (INS) operating in conjunction with the radar altimeter and the electro-optical system. The terrain contour matching (TERCOM) data and the target’s grids are uploaded to the INS that steers the weapon along the route and sets its flight speed and altitude in self-contained mode. 



Tomahawk cruise missiles proved to be difficult targets for Russian electronic warfare systems Tomahawk scale model on Raytheon booth at Paris Air Show 2015. Navy Recognition picture.



If the flight takes several hours, however, the INS accumulates a navigational error. The missile gradually drifts off the course, but this comes unnoticed by the INS. Hence, the latter has to be updated by means of outside data in order to figure out its whereabouts and correct itself. The Tomahawk’s INS relies on waypoints. Waypoints are well discernible terrain features with the characteristic outlines, e.g. mountains, hills, valleys, river bends, etc. When passing waypoints, the missile turns on its electro-optical system. The INS has the master image showing how the terrain the missile is passing through should look like if the missile is on course. Comparing the standard image with the imagery provided by the optics, the INS realizes the degree of its deviation. As a rule, there are several waypoints on the route. 

The Tomahawk flies 30-50 m above the ground. During its navigation correction, it climbs to 100 m for a few seconds but then descends again. The cruise missile climbs sharply once it reaches the target to ensure the best view for its electro-optical system, because the TLAM finds the target by using both its grids and video imagery. The target’s image is stored in its memory. The guidance system analyzes the video, finds the target’s outline, compares it against the memory-stored image and only then steers the weapon to the target. 

On average, the missile’s circular error probable (CEP) is within 10 m. The present-day Tomahawk uses satellite navigation (satnav). However, the GPS system is needed on the last leg of the flight for terminal attack. The weapon’s accuracy has grown from 10 m to 10 cm owing to its satnav capability. This is especially important when the cruise missile is employed against point targets, e.g. ICBM silos. 

If the Tomahawk impacts 10 m away from the silo’s cover that weighs many tons, it will not damage it. Owing to its satnav receiver, the missile will hit the middle of the cover and destroy it. However, it does not need this kind of accuracy when engaging area targets, such as airfields, bunched-up combat vehicles or fighting positions. The Tomahawk’s guidance system also relies on the GPS signal for course updates. Once updated, the INS compares its data with that of the GPS. The Tomahawk will approach its target without satnav anyway.



Tomahawk cruise missiles proved to be difficult targets for Russian electronic warfare systems A Tactical "Tomahawk" Block IV cruise missile, conducts a controlled flight test over the Naval Air Systems Command (NAVAIR) western test range complex in southern California. (U.S. Navy photo)



Russian media have run reports that a Russian-made Rychag-AV EW system jammed several dozen Tomahawks and made them drop to the ground. The Rychag-AV deals mostly with AD missile systems. Hence, only an utter layman can say that the system ‘jammed’ the Tomahawks. 

If the missile is aimed at a point target, jamming its satnav receiver will be enough. For instance, the Zhitel EW system, which is in the Russian military’s inventory, will be just the thing. The accuracy of the Tomahawk’s guidance will diminish, rendering the weapon incapable of hitting its target. 

If the TLAM is employed against an area target, it does not make sense to jam the GPS signal. The missile’s warhead packs several hundred kilograms of high explosives. It will surely destroy the target even if its CEP is 10 m. 

Another option is to overwhelm the Tomahawk’s radalt with heavy electronic countermeasures (ECM). If the radalt fails, the missile will climb to several hundred meters at once to avoid collision with terrain features. Once it has climbed, it will expose itself to the air defenses. However, jamming the radalt is difficult. Its radar return is very weak and aimed vertically to boot. Therefore, the jammer has to cover a huge area. For this purpose, it has to enjoy very high power and be mounted tens of meters above the ground. The higher the jammer, the longer its range. However, such jammers are effective only when they are set up on the cruise missile approaches, i.e. close to where Tomahawks will fly. Otherwise, they are useless. 

A laser may blind the Tomahawk’s electro-optical system, making the missile unable to identify the target’s outline and forcing it to attack using the pre-loaded target coordinates alone. This will reduce its accuracy, but that will be that. The laser’s effectiveness depends heavily on weather conditions and the distance to the target to boot. 

For now, the most effective counter to the Tomahawk is the Pantsir (NATO reporting name: SS-22 Greyhound) anti-air gun/missile system. It has proved to be very effective against such threats in trials and on exercises. There also are advanced anti-cruise missile defense systems in trials, which are based on new physical principles, according to the Izvestia daily.


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