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Poisoned arrows: New anti-radar weapons add GPS technology and more to take on integrated air-defense systems.

Mythological gods and monsters generally had some weaknesses that their heroic foes sought to exploit. Vanity or lust, perhaps, or a blind spot from which an approach with raised spear would be unseen. Just as often, the heroes had weaknesses of their own: an Achilles' heel or Herculean rage. The stuff of epics, seeking an enemy's weakness while guarding one's own, is the foundation of strategy and tactics to this day.


Arguably, there is no struggle more epic in scope than the initiation of a modern air campaign. Like thunderbolts thrown by Zeus, strike aircraft swoop in releasing precision weapons, the pilots and their commanders seeking to shock and awe. Like a hydra, integrated air defenses monitor and snap at the attackers from multiple points. Command of the electromagnetic spectrum offers air warriors--for the moment--a vital advantage. To be effective, air defenses must radiate with a multitude of early-warning, tracking, and fire-control radars. But in the modern battlespace, if you radiate, you die. Fully aware of this weakness, makers of air-defense systems incorporate features that enable radar operators to shut down on warning of an anti-radar attack. While shutting down the emitter might result in a sort of mutual blindness, the tactical situation and fielded technologies will reveal which opponent is more discomforted by such a state.

The current standard for anti-radar weapons, for example, the US AGM-88 High-speed Anti-Radiation Missile (HARM), now a couple of decades old, relies on passive radar detection only. As is well known, when enemy air defenses shut off their radar emitters, already-launched HARMs can only fly about without guidance for a time, then run out of fuel and crash to earth uselessly. Furthermore, by interconnecting ground-based radar detectors so that information collected by one can be combined with information collected by others to create a big picture, air-defense operators can avoid leaving any single radar detector on too long, decreasing the attackers chances of destroying not only a given radar but the integrity of the air-defense system as a whole.

The development of such techniques, analyst Jack Spenser of the Heritage Foundation noted, are inevitable, as enemy combatants, wherever they may be, recognize the huge advantage some countries possess with their aircraft fleets and search for some way to neutralize that advantage, at least a bit. The idea, of course, is to find that elusive Achilles heel. Countries with limited means will simply focus their resources on certain niche technologies that give them the most bang for the buck. "It might involve not relying on radar for air defense, because stealth technology is largely counter-radar," Spenser said. "Perhaps it's some sort of passive air-defense system that uses some other sensing technology. Perhaps it is using some technique that does not allow aircraft carriers to come within range of the country in question. There's any number of tactics an adversary could employ to minimize the West's capability to exert violence on them."


Do tactics such as turning radars on and off quickly, or internetworking them, seriously threaten air campaigns by the US, NATO, or other military powers? "I would not say it has seriously threatened them," said Michael O'Hanlon, a senior fellow at the Brookings Institution. Shutting down a radar to evade detection may protect the radar from destruction, but it doesn't necessarily do much good for the radar operator, since they've turned it off. "An enemy would have to keep shutting off radars to prevent current anti-radiation weapons from being lethal. And when that happens, enemy air defenses don't accomplish much." If the enemy is forced to shut down its radar to prevent detection, then that might fairly be said to be suppression. But while the mission of suppression of enemy air defenses (SEAD) has been achieved, warfighters obviously would prefer out-and-out destruction of enemy air defenses (DEAD).

Low Blow

The best-known achievement against the otherwise overwhelmingly powerful Western air campaigns of late was the downing by Serbia of a F-117 aircraft over Kosovo in 1999 using an SA-3 surface-to-air missile (SAM). Though the details are sketchy, the plane may have been brought down using some form of passive detection of the aircraft combined with observations by confederates in Italy regarding the takeoff of the aircraft and its expected flight path. In any case, the shoot-down showed that the use of air attacks in the first hours or days of a military operation is not entirely without danger. If a small country like Serbia was able to score a lucky hit, a much larger military power might actually be able to seriously threaten an air campaign. While the typical type of conflict today tends to be relatively small. Western military planners don't want to rule out the potential for a serious threat to what has lately been their key to military dominance: air power.

Anti-radar weapons are expensive. HARMs, for example, cost more than $300,000 each. So when a more all-purpose--and not least of all, cheaper--missile can be used to knock out enemy air defenses, it will be. If the location of the enemy radar, SAM, or other aircraft threat is definitely known, attacking forces may prefer to use a Tomahawk, Joint Direct Attack Munition (JDAM), or Hellfire missile. In the initial attack against Iraq during the 1991 Gulf War, eight AH-64 Apache helicopters carrying Hellfire missiles were sent to destroy two air-defense radars west of Baghdad, opening up a lane through which other aircraft could then fly without being detected. In the latest war against Iraq, two B-1 bombers reportedly used laser-guided missiles to take out truck-mounted anti-aircraft radar systems. To give attackers more chances of a successful hit, whether the strike be on radars or something else, new missiles in development are being fitted with multiple means of targeting. Lockheed Martin (Orlando, FL), for example, recently announced the successful testing of the Joint Common Missile (JCM)--the replacement for the Hellfire, Longbow, and Maverick air-to-ground missiles--that uses three types of targeting: infrared imaging, semi-active laser, and millimeterwave radar.


But aircraft will continue to field weapons specially designed to tune into and target radar, given that some air-defense systems may be a lot more sophisticated than simply a couple of older radars mounted on trucks. Recognizing the need to improve the capabilities of anti-radar weapons, US developers of an update to HARM, the AGM-88E Advanced Anti-Radiation Guided Missile (AARGM), are adding geolocation technology and active radar homing to increase the means of targeting enemy radar. Lieutenant Commander Carlos Rippe, team leader of the AARGM program for NAVAIR, said the HARM can guide to a target very, very well--as long as the target cooperates by radiating. "As we use this product more and more, folks have gotten better and better at defeating the HARM, using shutdown tactics, moving, things like that," LCDR Rippe said.

Another type of anti-radiation missile developed a few years after HARM, the Royal Air Force's Air-Launched Anti-Radar Missile (ALARM), uses a parachute to loiter longer over a target area, so if the radio emitter that originally prompted the launch of the ALARM is turned on again, the missile has more time to go back on the hunt. The RAF's web site states that since the ALARM's "original entry into service, radars have become increasingly more sophisticated in their ability to avoid detection and attack by anti-radiation weapons such as the ALARM; consequently, the missile is currently being upgraded and the improved capability ALARM is now entering service with the RAF's Tornado squadrons." One of the planned modifications to Tornado F3s currently in use will be the fitting of an emitter-location system that will allow the aircraft to receive real-time targeting information from other aircraft such as the Sentry AEW1. The UK's next-generation fighter aircraft, the Eurofighter, will also be able to carry ALARMs, among other weapons.

MBDA Missile Systems (Velizy-Villacoublay, France), the current producer of the ALARM, would not comment on work it might be doing to update the missile, but the US Navy and ATK Missile Systems (Minneapolis, MN), which is the prime contractor for AARGM, are openly touting the benefits of adding new technology like the Global Positioning System/inertialnavigation system (GPS/INS) to anti-radar weaponry. With the geolocation abilities of the AARGM--a program that will retrofit some 1,750 HARMs beginning in 2009, with the missiles to be used on US Navy and Marine Corps F/A-18 Hornet and EA-6B Prowler aircraft--information regarding the location of a radar emitter will be loaded into the missile, so that when launched it can head in the proper direction, regardless of whether or not it has a radio signal to home in on. When it gets in the general neighborhood of the target, then the active millimeter-wave-radar terminal seeker, also built into the AARGM, kicks on, guiding the missile onto the target if the radar has in fact stopped emitting signals.

Heat Seeker

Besides the AARGM, the other anti-radiation weapon being widely talked about, Germany's Antiradition Missile with Intelligent Guidance and Extended Range (ARMIGER), which is currently in the research-and-development phase and scheduled for fielding sometime in 2010, also is based on GPS technology. Provided Germany can spare the funding for continued development of ARMIGER--a difficult task given the country's serious budget problems--the missile will be used on Luftwaffe Tornado-ECR defense-suppression aircraft. Unlike the AARGM, which will use active radar for terminal tracking of targets, the ARMIGER will instead use infrared. Klaus-Eberhard Moeller, project manager of the ARMIGER for the missile system's prime contractor, Bodenseewerk Geraetetechnik (BGT) (Ueberlingen, Germany), said the ARMIGER's GPS technology will "bridge the gap" between the time when the passive radar seeker loses track of the radar emitter and the point when the enemy radar is detected by infrared.

Moeller said the German military has developed and tested a new capability to combine GPS information collected by multiple aircraft to find the position of enemy radar, with the information then passed to the missile prior to its launch from the aircraft. "You need the geographic information to fly to a certain point; that was what GPS was intended for," Moeller said. "On the other hand, you could have external targeting in which, for example, you already have a GPS coordinate and the target is not emitting at all. Then it would just send the missile with the GPS data and conduct the final approach with infrared. That's the idea behind it."

The US Defense Advanced Projects Agency (DARPA), meanwhile, is working on a similar concept of networking threat-warning receivers, so that any mix of aircraft would be able to combine information collected by their individual sensors to identify a target within 50 meters, from 50 nautical miles away, and within 10 seconds of the first interception of a signal. By pooling the data, the system would be able to geolocate the threat, and that geolocation information could then be passed along to an aircraft equipped with anti-radar missiles. As a complement to this Advanced Tactical Targeting Technology Program, as it is called, in which information can be quickly transmitted between aircraft, DARPA is also overseeing development of the Tactical Targeting Network Technologies, which aims to lower the latency and improve the bandwidth of the tactical datalink called Link 16.


For the AARGM, the GPS/INS does more than just provide some initial targeting, said Dave Wise, president of the AARGM prime contractor, ATK Missile Systems, which in June 2003 signed a $223-million contract with the Navy for the system-development-and-demonstration phase of AARGM. The GPS/INS also permits the operators to keep the missile out of certain areas. For instance, though the enemy may place its air-defense system, including radar emitters and SAMs, close to schools, churches, or other civil structures in hopes of dissuading attacks or, in the event of attacks that result in "collateral damage," create opportunities for propaganda railing against the heartless aggressors, the GPS can permit missile operators to prevent missiles from straying into designated areas. Thus, commanders of air assaults can be more confident of attacking enemy air defenses without inadvertently hitting innocents. Wise said ATK recently finished a test in which a missile launched in the direction of two radar emitters tracked and struck the radio emitter outside the zone designated as off-limits by the GPS system--even though a radar within the zone continued to emit signals and the target radar did not.

In addition, a technology that sprung out of a sister program to the AARGM called Quick Bolt has now been incorporated into the AARGM program, and will permit the AARGM to transmit geographic information to users after its launch. Though not technically battle-damage-assessment information, the information the AARGM will provide commanders about where it is just prior to impact can be combined with other information to help military forces determine what may have been blown up and where. "About 10 seconds or so prior to impact, it starts transmitting information, saying, 'Here I am, and here's the target I'm about to blow up.'" LCDR Rippe said. "It doesn't tell you when it's blown up, because it's obviously by then too late to send any information. It's more like, 'Here's where I'm going.'"


X Marks the Spot

In updating anti-radar weapons, developers also seek to improve their ability to detect a range of emissions. For instance, older SAMs likely use older radars with simpler designs. The frequency over which they operate the bandwidth they use remain static, in other words, and is, therefore, more predictable and detectable. But newer radars being fielded are phased arrays, so that their beams move around, as well as their frequencies. "The older ones had a kind of constant beam that spun around, but the phased array will poke out of the sky in different locations," LCDR Rippe said. "These new modes help detect targets more quickly, but they have the added benefit of making a harder target. It's essentially a moving target, if you will." So part of the update to the HARM is the addition of capabilities that can read these new frequencies and modes of operating--basically improved receiving and processing software.

Also, anti-radar weapons may not be necessarily mounted just on manned aircraft. Unmanned aerial vehicles (UAVs) have long been used for SEAD, beginning as remotecontrolled aircraft used to draw attention away from attacking aircraft. Israel, Turkey, and other countries use the Harpy, for example, a "loitering" attack weapon that flies around above enemy air defenses and attacks any activated enemy radar. The US Air Force recently chose Raytheon (Tucson, AZ) to develop and demonstrate the Miniature Air Launched Decoy (MALD), an expendable air-launched vehicle that serves as a decoy for fighter aircraft and bombers, mimicking their radar signatures and flight characteristics and, thus, hopefully distracting the attention of enemy air-defense systems. In addition, UAVs are now being fitted with weapons themselves, so that they can attack targets. Among the work being done with UAVs for use in DEAD, DARPA, along with the US Navy and USAF, are together developing Joint Unmanned Combat Air Systems (J-UCAS), in which multiple UAVs will operate in combination to perform missions like SEAD, DEAD, and precision strikes.

A successor to the unmanned combat aerial vehicle (UCAV) program, the J-UCAS program is developing both the Boeing (Palmdale, CA) X-45 and the Northrop Grumman (San Diego, CA) X-47 systems for use in combination for various missions. Among the latest news regarding the program, flight demonstrations of the Boeing X-45A began in November 2003 at Edwards AFB to test communications links with the UAV, as well as its ability to release small smart bombs. Although which specific munitions will ultimately be placed on the J-UCAS has not been determined, one potential candidate is Boeing's 250-pound Small Diameter Bomb (SDB), a near-precision-guided weapon currently under development that, according to the company, will be able to hit targets from more than 40 miles away. A spokesman for Boeing said another version of the X-45, the X-45C, will have two internal weapon bays that will each be able to accommodate four SDBs.

Thus, an unmanned aircraft navigated using GPS technology will be able to drop bombs on enemy air defenses and other targets thanks also to the use of GPS. This falls within today's trend of incorporating geolocation technology into weaponry in general, including new anti-radar missiles like the AARGM and ARMIGER. "Missiles are moving to precision guidance in so many aspects." ATK spokesman Bryce Hallowell said "When you're talking about precision guidance for an infantryman now, all the services recognize the value of eliminating the collateral damage, of having a one-shot, one-kill performance, and it is definitely the wave of the future." But if GPS can be used to target enemy radar, using missiles launched from aircraft or UAVs, why use active or radar homing at all, since the enemy is just going to turn off its radar emitters anyway? Because targets move, making the GPS information obsolete. Additional means of targeting--including GPS, active radar, and (in the case of the ARMIGER) infrared--simply provide anti-radar weapons with additional means of destroying the target, of probing to find its weakness.
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Author:McKenna, Ted
Publication:Journal of Electronic Defense
Article Type:Cover Story
Geographic Code:1USA
Date:Mar 1, 2004
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