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Upgrades Give Antimissile System the Upper Hand

June 2003
By Robert K. Ackerman
E-mail About the Author

It was not your father’s Patriot in the Iraq War.

More than 10 years of hardware, software and signal processing upgrades have transformed the Patriot missile system into an effective defensive shield against short-range and theater tactical missiles. The original system that achieved partial success in the 1991 Gulf War became a bulwark in the Iraq War, effectively neutralizing Saddam Hussein’s theater ballistic missile threat.

Several advances helped achieve this standard. The original proximity-detonation warhead missile was improved on by two radically different types of interceptors. Constant software upgrades improved the effectiveness of the missile’s interception system. And, the system’s radar has evolved over the years into a more advanced version with increased detection, targeting and guidance capabilities.

The new Patriot system could choose from three different missiles to intercept ballistic threats. Of these three, the Patriot Advanced Capability (PAC)-2 missile bears the closest resemblance to its progenitor. However, the new version features a better guidance system and a proximity-explosion warhead designed to obliterate enemy missile warheads. Signal processing and software advances gave it a much better ability to discriminate between a missile warhead and its fuselage. During the 1991 war, many of Iraq’s customized Scuds would break up during the descent phase. In some cases, the old Patriots mistakenly locked onto the fuselage fragments as the warhead fell untouched to Earth to explode on impact. The PAC-2 is neither fooled by a missile breakup nor defeated by a fast-moving warhead.

Sgt. Harold Huff, USA, who is with Charlie Company in the 5-52nd Airborne Defense Artillery Patriot Battery, originating from Fort Bliss, Texas, explains that the PAC-2’s improved interception capability became so precise that the explosive feature of its warhead became almost second nature. Experts realized that this system had effectively achieved hit-to-kill capability. This in turn led to another version of interceptor, the PAC-3.

The PAC-3 is radically different from the PAC-2. It is designed as a kinetic-kill vehicle that obliterates an incoming warhead on contact. The most significant difference from the rest of the Patriot missile family is size. The kinetic-kill PAC-3 is much smaller in diameter than the traditional Patriot configuration. Four PAC-3s fit into the launcher box used to launch a single PAC-2. An outside observer might not be able to discern the difference between a PAC-2 launcher box and one containing four PAC-3s.

The third, and newest, version of the Patriot is called the guidance enhanced missile, or GEM. This missile bears closer resemblance to the PAC-2 in that it is a proximity-warhead interceptor, as opposed to the PAC-3’s kinetic-kill approach. It also is similar to the PAC-2 in size and configuration.

Sgt. Huff describes the GEM as the best of the Patriot class. It is used as a Patriot battery’s silver bullet to intercept and destroy targets that might prove tougher kills for the PAC-2 and PAC-3.

These three different interceptors beg the question, Who decides which Patriot to hurl at an incoming ballistic missile? The answer is the system itself. When a particular Patriot battery is activated to intercept an incoming target, its radar system calculates speed, trajectory and potential target footprint of the attacking missile. It then selects the version of the Patriot to launch to destroy the target. Battery crew members can implement a manual override, if they choose.

The battery’s phased-array radar has similar roots with those of the U.S. Navy’s shipborne Aegis system. However, as with Aegis, it has undergone considerable upgrades over the years.

The system’s software and signal processing upgrades have come at a steady pace over the past decade. Sgt. Huff relates that a Patriot system upgrade significant enough to require personnel to attend classes occurs about every 18 months—the same time frame for computer generation leaps expressed in Moore’s Law.