Patriot’s Heart: The MPQ-53 Radar

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 Theater Anti-Missile System, the now famous MIM-104 Patriot. Night after night, the vaunted weapon was launched in an attempt to intercept Iraq’s unsophisticated and terrible inaccurate Scud mid range missile. The image of America’s missile intercepting an incoming object captured the attention of almost anyone. 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 defense platform, the Army decided to develop the Air Defense System (AADS). More than thirty summers has passed since the first blue print for the MIM-104 was submitted for initial review. Baptized under fire in the gulf and in many other theaters, the Patriot has become America’s top defensive weapon. Multiples upgrades were performed since that summer. Changes that had 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 advance targeting array in the world, the now famous MPQ-53V. The 53V is a phased array radar and associated processor that control 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 Center. For target identification, the 53V used the powerful Hazeltine (TPX-46-7) Target Identification Friend or Foe (IFF). A self-contain data link is use 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 utilized a top tier lens array which operated an free optical feed. Sum and difference patterns are individually optimized with a monopulse feed optimizing its efficiency. The aperture is round and utilized around 5000 ferrite phase shifter. A four bit, flux driven, non-reciprocal ferrite phase shifter and waveguide radiators are located at both 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 divided the antenna almost in half, with access boxes. Two slight larger planar arrays are for the command-guidance and it’s receiving its links directly for the missile.

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

The radar utilized a Track-via-Missile (TVM) System in order to suppress 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 optimums 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 use 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 Defense 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 Defense 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

RADAR: The German Side of the Story

Radio detection and ranging (radar) is viewed by most as one of the quintessential technological accomplishments of the Twentieth Century. Radio detection finding or RAD, as it was known in Great Britain, was perhaps the single biggest piece of technology, aside the atom bomb, that came out of the ashes of World War II. The employment of RAD made the defense of Britain more plausible to plan for. The Royal Air Force (RAF) enjoyed a major technological advantage during the Battle of Britain because most of the times they knew where was headed the bulk of the Luftwaffe force. It could be argue that without radar, the fierce battle that ranged over the skies above the British country side would had been lost. Radar also warned the Americans at Pearl Harbor of a massive airborne formation heading towards them. Unfortunately for the United States forces at Hawaii, misinterpretation of the radar data lead to the surprise of the attack. Radar was used extensively by the Americans in their Pacific and Atlantic campaigns. Today, many facts about the development of radar is widely known. What is seldom mentioned by historians and researchers alike is the fact that in the beginning, it was Nazi Germany, not Britain, which was leading the way in the field of radio detection.

On a the clear morning of September 26th 1935, a group of high German naval officers, including the overall commander of the German Fleet, Admiral Erich Raeder and various Nazi party leaders; visited the new Funkmessgerat station (radar finder device) at Pelzerhaken near Neustadt in the Bay of Lubeck. At top of the forty feet tower, the visitors, for the first time, were able to see in action Germany’s new technological marvel: the radar. The rudimentary equipment, which included sets of transmitters, receivers, turntables, monochrome screens and two electrical generators; was designed to located a ship up to a distance of five nautical miles outside the field of view, quiet an accomplishment for the day. As it was setup, the transmitter would send out a radio pulse signal to all directions which would proceed to bounce off the searched platform and return to the receiver. Then the receiver would send a signal to the monochrome display projecting a one dimensional image revealing the platform’s present. To the stunned VIP audience, the demonstration was an eye opener. But to those who knew radio technology it was but just one step towards a bigger goal. Almost a year early, American inventor Robert Morris Page had demonstrated the feasibility of a radar system with his December 1934 experiment near Washington DC. Three months later, Robert Watson Watts, known to many as the father of the radar; made his first active experiment. From there, radar was well on its way. The first German active radar experiment took place on March 1935. A rudimentary set of transmitters and receivers were able to pickup a faint signal bouncing from a German warship one mile away. Similar efforts were also taking place in France, Italy, the USSR and, on a somewhat more limited scope, in Japan.

The system demonstrated at Pelzerhaken on September 26th was the direct result of the research done by the brilliant German physicist, Rudolf Kuhnold. In the mid 1930s Kuhnold was the owner of a small new corporation named Gesellschaft fur Elektroakustische and Mechanische Apparate (GEMA) which specialized in the development of sophisticated transmitters and receivers mechanisms. GEMA had close ties with Germany’s Naval Research Institute. From the mid 1935 onward, GEMA, although not officially linked to Germany’s military industrial complex, was an integrated part of the Fatherland’s war effort. Before the war ended, the small 1935 company would had grown in size and scope. By early 1945, GEMA employed more than 6,000 skill workers, a far cry from the days of a seven staff operation. But although GEMA began the radar revolution, it had by no means a monopoly on the new technology. Within three years, Siemens, Telefunken and Lorenz would push their own radar system programs.

Beside the enormous potential the Pelzerhaken experiment showed, it also seeded a deep distrust between the Navy and the most powerful Luftwaffe. Because the experiment was first showed to the top brass of the navy, many of them resentful of the treatment they had been receiving from the Luftwaffe leadership, wanted it to keep the news of the system in the dark.

No radar story could be develop without mentioned the extraordinary efforts of one man, British physicist Robert Watson Watt. At forty two, Watson Watt, the head of Britain’s National Physicist Laboratory’s Radio Research Station, was summoned in 1934 by the Air Ministry to explore the possibility of developing a transmitting, damaging radiation platform to be employed against possible enemy air incursions, mainly from Germany. He began his research in earnest focusing on utilizing radio signals for early detection of incoming objects. On February 26th 1935, Watson Watt and his trusted fiend and colleague, AP Rowe, turned on the world’s first true radar mechanism at the British Broadcasting Company’s short wave radio station in Daventry, Northamptonshire, almost seven months ahead of the Germans. Watson Watt’s system operated at a 164′ wavelength spectrum. It employed a basic receiver set that gather signals generated from a high frequency alternating current (the number of cycles per second is known as frequency). Radio emissions or waves are electromagnetic radiation similar to light waves, but they have a longer wavelength range. When utilizing radio signals for detection of objects, a beam is emitted, the waves scatter all over the “target” to later return as an echo which the receiver picks up at the point of origin. Radio wavelength are, by definition, large, and those utilized by radio transmitters are measured in feet or meters. A smaller wavelength is require in order to make a much accurate profile of the targeting object. This was the first problem encounter by Watson Watt and the others radar pioneers of the times. The generation of wavelengths less than a feet, also known as microwaves, required massive amounts of raw energy in order to travel long distances. Any mechanism capable of generating such a force was bound to be big. Then the process would be complicated. The mechanism needed to be reduced to its smallish form in order to be fitted on an aircraft’s bay. On Watson’s experiment at Daventry, a heavy bomber flew over the BBC’s radio towers and on the second pass, radar operators saw “beats” on their monochrome displays screens for just over two minutes. They were able to track the bomber flying pattern for up to eight miles.

Although early successes on both sides of the Channel were promising, they by no means were error-free. Mistakes in developing the new technology was a common trend on both, Germany and England. In Germany, the most costly error made was ceasing research into the development of an magnetron, which German physicists tested and later on, discarded for obscure reasons. A fact attributed to the rigid Nazi political system. In February 1953, while giving a lecture on the birth of radar, Watson Watts stated that “I believe that British and American success in radar depended fundamentally on the informed academic freedom which was accorded, in peacetime radio research, to my colleagues and myself…I believe the most valuable lesson from radar history is that of the intellectual organizational environment from, and in, which it grew”. Renowned German historian, Harry von Kroge disagree “The aspect of the German effort that seems to have differed from the Allied was the degree to which corporate rivalry affected the course events. The numerous agreements that had to be made concerning licensing and post-war rights I order to smooth production will certainly seem remarkable to American and British readers”, he went on to said that “a puzzling aspect of German radar research was the delay imposed by severe secrecy in drawing on the many excellent universities and polytechnic institutes until late in the war”. His claim was that the British and, to a lesser extend, the American radar effort ran more smoothly because its was under the auspices of the military with full access to all of the academic and civilian sources of expertise.

His claim has some merit. Germany’s first radar array was sorely developed by a private company with the encouragement of a major naval research institution. This contrasted with Germany’s other top scientific programs such as missile development. Engineers assigned to rocket and propulsion development usually drew freely on the expertise of others, specially on the universities ranks, to achieve their goals. Again, there’s evidence to support the theory. Its true that the British main radar problem, the development of a workable and reduce microwave-based system was enormously enhanced by the program’s ability to recruit the best talent from any source. This, pluralistic effort will eventually find its way to a central research program and thence to full production. In Germany on the other hand, there were not enough collaborative diversity, instead, a series of modern era monopolies worked under the cover of secrecy, not for military purposes but to protect their intellectual rights. This problem was compounded by Germany’s leaders preferences for offensive weapon systems instead of purely defensive ones such as a radar array. This one set mind would have a devastating effect on the overall German war effort. But what is more puzzling about the whole program was the lack of understanding of what a radar system could achieve by the very top political and military leadership. A clear example of this was the Luftwaffe’s technology chief, General Ernst Udet, who objected from the very beginning the massive amounts of money the radar program were being allocated on the bases that if it works “flying won’t be fun anymore”.

Despite all those factors, Germany could had matched or even surpassed Britain’s radar program if its was not for Watson’s obsessive determination. The prominent scientific historian David Zimmerman put it simple, “Much of the rapid early progress in the early years was a direct result of the drive, energy and leadership of Watson Watt”, but “paradoxically, it would be Watson’s erratic, almost manic behavior and lack of administrative skills which would be a significant factor in the failure to mount effective night defenses ready in time for the Blitz”.

– Raul Colon

More information:
The Paperclip Conspiracy: The Battle for then Spoils and Secrets of Nazi Germany, Tom Bower, London 1987
What Little I Remember, Robert Frisch Otto, Cambridge 1979
Quantum Generations: A History of Physics in the Twentieth Century, Helge Kragh, Princeton 1999

The Graceful EC-121 Early Warning Star

Embed the most advanced electronic detection systems within the slick airframe of a Lockheed Super Constellation and you will have one of the most beautiful-looking aircraft that ever graced the sky: the Lockheed EC-121 Airborne Radar System. Between the early years of the 1950s thru the mid 1960s, the 121 guarded the United States coastline against a surprise enemy air incursion. It saw extensive action in Vietnam where its advanced electronic detection systems provided US force commanders with an in-depth look at the enemy’s movements, not only in the air, but also on the ground and on the seas. The 121 program had its roots at the end of the Second World War, when US military planners were facing what they thought would be an overwhelming Soviet Air Force superiority and they would need as much warning as possible to deploy their air and naval assets. Following the normal development path, the 121 entered full production mode in the early 1950s. The Warning Star, as the EC-121 was officially known – its crew knew it as the “Wily Victor” – first entered front line service with the US Navy in October 1955.

The Warning Star was designed for long and taxing patrols, thus the aircraft retained all the comforts of the airliner on which it was based. The flight deck was roomier than previous military planes, a feature well appreciated by its crew. The pilot and copilot were seated in the front of the aircraft’s cockpit; the flight engineer was seated directly behind them. The radio operator and flight navigator were seated at the end of the cockpit structure. Two rows in the middle of the fuselage were used to house 28 electronic operators who collected and directed information received from the Star’s radar arrays. One of the main reasons Lockheed selected the Constellation airframe to incorporate the most advance airborne radar system designed, was the need to locate the radome on the underside of the airframe. The Constellation had the required ground clearance because of its long undercarriage. The rear part of the aircraft was used to provide the crew with a comfort station. Four bunks and a primitive toilet were placed in the tail end of the 121. A small kitchenette was also installed there. Propelling the aircraft were four 2535-Kw Wright R3350-34 radial piston engines capable of generating 3,400 hp. The 121 could stay airborne for up to thirty five hours without refueling.

Four squadrons of the Warning Star were formed in the mid 1950s. Operating from bases in Scotland and Iceland, Warning Stars performed around-the-clock air patrols over the North Atlantic. They also operated from US Navy bases in Puerto Rico and Cuba. They saw combat action in the sky over Vietnam, offering assistance and relaying electronic information to US aircraft operating in the area. Only one EC-121 was lost during a combat operation. One 121 was shot down near North Korean territorial waters in 1969. The aircraft was lost along with its complementary crew. In the early 1970s, the US Air Force and Navy replaced its respective fleets of EC-121 Warning Stars with the first truly AWACS system platform: Boeing’s E-3. Today we can still see some Warning Stars gracing the skies above the US. All remaining 121s are privately owned and are flown at air shows all across America.

– Raul Colon

More information:
wikipedia: EC-121 Warning Star