Patriot’s Heart: The MPQ-53 Radar
Raul Colon
rcolonfrias@yahoo.com

No one who saw the First Gulf War in 1991 was glued to the television set looking at the majestic sight of the United States Army’s newest Theatre Anti-Missile System, the now famous MIM-104 Patriot. Night after night, the well known weapon was launched in an attempt to intercept Iraq’s unsophisticated and inaccurate Scud mid range missile. The image of America’s missile intercepting an incoming object captured the attention of the pubic. As new and sensational as the Patriot looked in that conflict, the system was actually in its third decade of life.

Born during the height of the Cold War (1963) in an attempt by the US to overlap their complex HAWK air defence platform, the Army decided to develop the Air Defence System (AADS). More than thirty summers have passed since the first blueprint for the MIM-104 was submitted for initial review. Baptized under fire in the gulf and in many other theatres, the Patriot has become America’s top defensive weapon. Multiples upgrades have been undertaken since that summer. Changes that have improved dramatically the capability of the system.

One of the most significant modifications came in the spring of 2005 when the Patriot was fitted with the most advanced targeting array in the world, the now famous MPQ-53V. The 53V is a phased array radar and associated processor that controls the missile’s trajectory from its launch. The radar is a multifunctional, electronically scanned array mounted on the M-860 trailer which is towed by an M Engagement Control Centre. For target identification, the 53V uses the powerful Hazeltine (TPX-46-7) Target Identification Friend or Foe (IFF). A self-contained data link is used to communicate with the rest of the missile package.

The Patriot was designed to operate in all weather conditions without losing operational effectiveness. It can destroy aircraft and missiles at all altitudes. It can direct several missiles to engage multiple targets simultaneously even in the toughest electronic jamming environment. For this, the MPQ utilizes a top tier lens array which operates a free optical feed. Sum and difference patterns are individually optimized with a monopulse feed optimizing its efficiency. The aperture is round and utilizes around 5000 ferrite phase shifters. A four bit, flux driven, non-reciprocal ferrite phase shifter and waveguide radiators are located at high and low temperatures. A separate, redundant array for missile guidance and IFF is also part of the overall platform’ profile.

The most recognizable feature of radar is its face. A huge, phased array face dominates the upper part of the antenna unit. The ‘face’ performs as both, surveillance and tracking mechanism. Below the face lays an almost circular, 5000 element phase shifter which has two smaller units (each with 50 elements a piece). A row of 18 rectangular boxes divides the antenna almost in half, with access boxes. Two slightly larger planar arrays are for the command-guidance and it’s receiving links directly for the missile.

Before an engagement is begun, the radar array has to be aligned to cover the expected direction of attack. During the engagement, the radio beam is steered electronically in azimuth and elevation. The system was designed in such a way than it can prioritize a single target from several locations.

The radar utilizes a Track-via-Missile (TVM) System in order to reduce its overall cost. In semi-active systems, the radar illuminates the target and a seeker in the missile’s head tracks the reflecting energy. Then the missile computes the interception pattern based on its bearing to the engaging object. The TVM allows the missile to relay the same bearing data to the engagement control station via the radar. The platform’s powerful processors comb through the information with the absolute position of the target, the missile and the profile (velocity, altitude, bearings) of the engaging object and generate tracking commands to guide the warhead to the optimum interception point. In the terminal phase, the missile’s acquisition system acquires the target and relays the data to the phase array where the final intercepting calculations are performed.

The main advantage the TVM system has over its competitors is that the powerful ground based processors are used mostly for guidance thus allowing more data interpretation time. This processing technique make it’s difficult for countermeasures to jam the Patriot’s targeting trajectory. Even when the Patriot’s targeting radar is receiving jamming strobe, its missile can still maintain missile-to-target bearing data from the TVM system. On top of this, the ground based processors have sufficient computing power to resolve troubling jamming issues such as blinking jamming, where two aircrafts in formation jam alternatively to frustrate home-on-jam modes.

Raytheon, the Patriot’s primary contractor (its have all the Defence Department contracts for the system that surpassed the $ 5 million mark) had produced a reported 128 MPQ-53V units for the US Army and an estimated 26 for Japan’s Self Defence Force (2007 totals). Price for each unit is around $ 2.5 million.

Technical Data

Weight 79,008lb
Length 56.08ft
Height 11.83ft
Width 29.42ft
Frequency 4-6 GHz
Range 68km
Detection Sector 120deg
Engagement Sector 90deg
Target Capacity 50 simulations
Missile Control Capacity 9 in final engagement