The Ascendancy of AEW

This was airborne early warning and surveillance nearly 200 years ago, but the art was hardly in its infancy even then.

Kite was the first AEW platform

Kites preceded balloons as airborne platforms; being so used by the Chinese and Japanese during the 11th century. Man’s first aircraft, the kite itself was actually invented by the Chinese some 2000 years earlier. Flown by young and old as a sport, it was later adapted by oriental warlords for signalling, elevating whistles and lights at night to frighten an enemy, and for raising military observers.

“Man-lifters”, as these large kites were called, were rarely if ever, used for pleasure flying. Indeed, dangling from a kite on the end of a long thin rope was quite dangerous and there are reports of enforced kite-flying having been used as punishment by the Chinese.

Used through the centuries to carry messages, drop leaflets, and even tow torpedoes, man-lifting kites for the military were refined by Samuel F. Cody, a Texas-born aviation pioneer, in 1901.
His huge cellular canvas kites with extended wings, flown one above the other in a train, carried observers hundreds of feet above the ground. In 1911, the US Navy found that kites could raise lookouts higher than the tops of battleship masts. And the German Navy used kites to fly observers from submarines during both World Wars.

Napoleon took the balloon corps to Egypt

The use of balloons as observation posts also proliferated after the French Republic added the first air arm to its forces. Napoleon used balloons to send observers aloft during his siege of Mantua in Italy and took a balloon observer corps to Egypt in 1798.

During the American Civil War, Thaddeus Lowe, a balloon-flying meteorologist from New Hampshire, so impressed President Abe Lincoln with the world’s first air-to-ground telegraph message that Lincoln authorised the creation of an army balloon corps in the Union Army with Lowe in command. Lowe later claimed that his aerial surveillance of Confederate troop movements during the battles of Fair Oaks and Richmond helped to avert Union disasters. Lowe’s hot-air balloons also took him to Bull Run and Fredericksburg as a high-flying Union scout.

Despite these early successes, the size, awkwardness, and vulnerability of the hot-air balloons limited their military use, and they soon became part of the nostalgic past.
But the evolution of aerial surveillance continued – and accelerated – with the triumph of the Wright brothers at Kitty Hawk.

The military value of their flying machine “for scouting and carrying messages” did not escape the Wright brothers. Eventually, the War Department also saw the value- after two years of disinterest and procrastination – and awarded the Wrights a contract for a machine “capable of carrying two men (a pilot and observer) and sufficient fuel supplies for a flight of 125 miles, with a speed of at least 40 miles an hour.” Thus, with flimsy fabric-covered wings, wooden frames, and sputtering engines surveillance begins to ascend the “higher ground” military tacticians have sought traditionally.

During World War I, both sides first used the “Aeroplane” to observe enemy positions, preferring slow, stable craft from which to study and photograph the ground. The German Army persisted in its use of balloons for battlefield observations, but the use of hydrogen gas inevitably resulted in many falling in flames before the chattering machine guns of Spads, Nieuports, and other Allied aeroplanes.

With the advent of more reliable aircraft, warning time – always a factor in military engagements and strategies- began to assume critical significance. Higher altitudes and 100-mile-an-hour speeds provided unprecedented opportunities for earlier detection of, and quicker response to, an enemy threat often spelling the difference between victory and defeat.

Ground radar is limited by the horizon.

It was during the Second World War that the role of the aerial observer became more than a nice-to-have adjunct to basic military defence, as spy glasses and binoculars gave way to radar.
The development of ground-based radar came first, and it was a revolutionary military advance. But it soon became evident that, because of the curvature of the earth, even this electronic marvel was severely limited in that it couldn’t see beyond the horizon or behind a hill. Like man-carrying kites and balloons, radar had to be airborne to be effective. The evolution continued.

Early radar was too heavy to be carried in aircraft.* But then, in 1945, the US Navy put an AN/APS-20 radar in the TBM-3W Avenger, a torpedo bomber designed by the Grumman Aircraft Engineering Corporation. A few years later, an improved radar was installed in the Grumman AF-2W Guardian, which extended its detection capability to both air and surface targets.

At about the same time, an early-warning version of the Douglas AD Skyraider was placed in production, mounting a large radar antenna beneath the fuselage. In addition to the pilot, it carried two radar system operators. These were the first applications of radar for airborne early warning and the beginning of a sophisticated technology that is the backbone of air defence today.

After the war, the British installed an APS-20 radar under the nose of the four-engine Avro Shackleton bomber for AEW operations. This aircraft, which carries eight tactical crew members, and a three-man flight crew, still remains in service.

Overhead rotodome set the new look

In the mid-1950s, a large external radome was installed atop the fuselage of a modified Grumman S-2 antisubmarine warfare aircraft termed the E-1B Tracer, establishing the AEW look of the future. The fixed radome housed a rotating 18-foot dish antenna which, together with the AN/APS-82 radar, gave the Tracer nearly twice the detection range of the earlier Guardian. A height-finder was also added to determine the altitude of airborne targets.

The Tracer was the first early warning aircraft to integrate all electronic system elements so they “played” as one for total effectiveness. Included were a new S-band radar sensor, video displays and controls, communications, and navigation equipment.

However, with the advent of the Naval Tactical Data System (NTDS), which provides a task force commander with information on the disposition of all ships and aircraft in his area so he can more effectively control and deploy his forces, the need soon arose for an AEW aircraft with expanded means for detecting, tracking, and reporting. The evolution continued.

For early warning, higher is better

In 1961, Grumman introduced the twin-turboprop E-2A Hawkeye, the first aircraft ever designed specifically for the early warning mission, and one of the largest to be operated from an aircraft carrier. Upon entering fleet service in the mid-1960s, the Hawkeye was the most advanced system of its kind, built around an AN/APS-96 UHF radar with pulse compression to reduce surface and weather clutter. Now, overwater targets can be detected and tracked automatically, even in the presence of heavy clutter, greatly reducing crew workload. Also, by flying at 30,000 feet, the E-2A could see much further than the Tracer, which had a 12,000-foot ceiling. In the world of early warning, higher is definitely better … and the high-flying Hawkeyes were to become literally the “eyes of the fleet”.

The E-2 was equipped with a new streamlined 24-foot-diameter overhead radome, a “rotodome” that rotated a full 360 degrees along with the radar antennas it enclosed. The fuselage was sized to accommodate three radar operators, a pilot, and co-pilot … and nearly five tons of electronics and data processing equipment.

In Vietnam, E2As established a new level of tactical flexibility, detecting low-flying enemy aircraft attempting to avoid our surface radar screen, and relaying information between our naval task forces and their strike aircraft. Control of major Allied air strikes was thus greatly improved in terms of safety, access to heavily defended targets, and assisting Allied attack planes to carry out missions even in marginal weather, Enemy MiG fighters appearing over Vietnam were frequently cut off through advance detection by E-2s which then vectored F-4 fighters into position for the intercept.

Hawkeyes grow progressively sharper

Combat experience showed not only the key value of Hawkeye’s early warning and command-and-control functions but also ways to make the system even more effective.

The first improvements in the E-2A were to replace its hardwired, drum-memory digital computer- that necessitated hardware modifications whenever a tactical program had to be changed – with a solid-state, core-memory dual processor which could be quickly reprogrammed by simply changing magnetic tape. The changes made it an entirely new generation of Hawkeye: automatic, far-seeing, and now a lot more flexible, too. And they called it the E-2B.

Up to this time, effective E-2 radar detection was primarily limited to overwater operations. But the increasing threat of limited-war scenarios which involved crossing enemy coastlines and operating well inland brought with it the need for radar detection of low flyers over land. Since the APS-96 lacked sufficient clutter rejection capability to detect aircraft over land, a new radar was required. Again, the Navy gave Grumman the go-ahead to upgrade the Hawkeye.

A new radar system and its related computer processing and display components represented a major change, so drastically improving the performance and reliability of the overall Hawkeye system so as to constitute a third generation of the original. This one was designated the E-2C.

To provide an overland detection capability immediately, the initial “C”s were produced with the AN/APS-120, an available radar with built-in ground-clutter-rejection circuits. But it had to be operated manually to detect targets overland.

More recently, a new radar – the APS-125 with advanced digital signal processing – was installed, giving the E-2C the latest surveillance technology in the air today. This latest Hawkeye automatically detects airborne and surface targets over land or water at ranges up to 250 miles. It is this total coverage at long range – the ability to look deeply into hostile territory – that provides enough warning for a timely response to a potential threat. From 30,000 feet, for example, the E-2C can detect an intruding aircraft (or cruise missile) three times sooner than ground-based radar … even if the intruder is flying just above the surface.

The key to the E-2C’s effectiveness is its computer …an advanced radar processing system that can distinguish land masses and detect and track fighter-sized targets against any background, land or sea. Using digital processing techniques that display moving targets only, the radar automatically eliminates stationary land noise, clutter, and other false target reflections. As a result, the E-2C can track 250-300 targets and handle more than 40 intercepts simultaneously.

Maritime surveillance of moving or anchored surface vessels is achieved at a range of several hundred miles (line-of-sight), depending on the target size. In actual operations, the E-2C has detected small patrol boats at ranges beyond 100 nautical miles.

The system detects without being detected

One of the problems with any radar system, of course, is that you must transmit a signal in order to get a return you can analyse. But, by radiating energy, you’re telling the other side where you are and thus making yourself a target or, at the very least, subject to jamming.

Supplementing the Hawkeye radar, therefore, is a passive detection system, or PDS, that can pick up and identify other emitters at ranges well beyond that of the radar without transmitting any signals of its own. Available only in the E-2C, the system automatically compares signal characteristics to an onboard file of known radars for positive identification.

The active radar and PDS systems, which together increase the number of targets the E-2C can monitor at one time to more than 600, are keyed directly to a dual-processor computer and display system. With an 80,000-word memory, the computer makes detailed information available to the three E-2C radar operators at the touch of a button. The information can then be sent over a secure data link to an air-defence ground station … automatic, two-way transmission of track data in real-time.

Because of its compact size and well-refined automatic systems, the E-2C requires minimum operating and support personnel. The strength built into its fuselage and beefy landing gear to take repeated carrier takeoffs and arrested landings enables it to operate from short, forward airstrips. The Hawkeye’s folding wings – another adaptation to fit in the crowded environment of the aircraft carrier – can be of significant benefit to land-based operations as well. With wings folded back along its fuselage, the E-2C measures just 30 by 60 feet overall, which makes it feasible to house in protective revetments.

Soviet AEW platform is called “Moss”

The tactical advantages of an airborne early warning and control system have not been lost on the Russians. During the 1971 and Pakistani War, Indian strike aircraft repeatedly succeeded in making low-level penetrations deep into Pakistani air space, locating and attacking targets with great precision at night. Calling the signals a safe distance from the Pakistan border was a lone aircraft flying at about 20,000 feet under cover of Indian surface-to-air missiles. The aircraft was the Soviet TU-126 airborne warning and control system. It bears the NATO code name Moss.

The four-turboprop Moss, which went into service in 1970, carries its surveillance radar in a 36-foot diameter overhead radome. Its radar range is assumed to be about 300 nautical miles, but the tracking performance is said to be only limited over water and ineffective over land. It’s generally agreed that the Moss surveillance technology doesn’t measure up to that of the Hawkeye. However, improved systems are expected in the IL-76 and IL-86 jet transports that are being produced as AEW follow-ons to the TU-126.

USAF flies a sentry

At about the same time as the Moss development, the US Air Force put out specifications for its own “Airborne Warning and Control System,” or AWACS. Ultimately, the Air Force decided to modify Boeing 707 jet airliners for this mission. Designated the E-3A Sentry, the AWACS carries a crew of 17 (13 system specialists and a four-man flight crew).

In comparison with the E-2C, the AWACS is considerably larger, can stay aloft longer, and can see somewhat further. However, it relies more on manual radar modes than the fully automated E-2C and lacks the latter’s passive detection capability. while the addition of a maritime surveillance capability comparable to that of the E-2C is planned, this will not be available until 1982 at the earliest. Along with other major system improvements, future plans also call for the E-3A to be refitted with a new high-speed computer with increased memory capacity.

While the large size and capacity of the E-3A afford many advantages for airborne warning and control missions, they also impose certain restrictions on the system’s use. For example, the sheer dimensions of the Sentry limit the number and types of bases from which it can operate. Also, in keeping with its much greater size and complexity, the Sentry’s cost is considerable … more than three times that of the more compact Hawkeye.

Airborne and ground radars must work together

As international crises persist and geographic barriers shrink in the face of advanced long-range bombers and cruise missiles, airborne early warning has become an essential supplement to ground-based radar warning networks. In any viable air defence program, of course, both types of systems are required … and must work together.

Though ground radars have by far the edge in power, their detection range is limited by the horizon.

Also, they carn only track low-level targets for short periods of time, necessitating “handover” to second and even third radar systems to continue the track. And, because ground-based radars can’t see behind high terrain features, intruders can fly around hills and through valleys to avoid detection until the last moment, if at all. Being in a fixed location, they are vulnerable to attack and must be protected, which means substantial support and manpower. Still, ground-based radar systems such as the US BMEWS (Ballistic Missile Early Warning System) normally offer continuous and reliable coverage of ICBM and high-altitude bomber threats at considerably lower costs than AEW systems.

While airborne systems detect everything that moves from the ground up and will maintain a constant track on all targets – directing defensive forces to intercept them – it takes a lot to keep one AEW plane on station on a 24-hour basis, or even for shorter periods. Fuel, manpower, number of aircraft, and support are all real constraints. The answer then is to use airborne platforms on a tactical basis, with ground stations as a continuous backup.

AEW to improve NATO defence

Military experts have long urged the acquisition of a modern airborne early warning system for NATO to close gaps in the existing ground-based European defence network. A growing concern over the increasing threat from the East finally led the Alliance to select the Boeing E-3A Sentry, with the first deliveries to be taken in 1982.

Great Britain and France chose not to participate in the expensive AWACS program, electing instead to pursue their own approaches. The British are going with an AEW version of their own Nimrod Mk3, an adaptation of the Comet jet airliner. France currently is exploring other system possibilities, particularly the E-2C Hawkeye.

Nimrod, which has been used for maritime surveillance in the UK for many years, has been under active AEW development since 1975. Fitted with large bulbous radomes in the nose and tail, it uses a multi-mode pulse Doppler radar and has a passive detection system. When it becomes operational in a few years, Nimrod will be completely compatible with both the NATO AWACS and the E-2C through data link.

Backfire poses a threat

France, like most developed countries, has an excellent ground defence radar system. But aircraft like the supersonic Soviet Backfire bomber can fly low enough, and long enough to avoid most radars. Against these targets, ground tracking, at best, is spotty and difficult to correlate. AEW aircraft, however, would furnish continuity of tracking and, most importantly, would detect the intruders much sooner.

For France, the initial evaluation of the E-2C demonstrated the aircraft’s ability to operate with the French STRIDA air-defence network. E-2C data were converted to the format used for transmitting target data in both the STRIDA and NATO’s NADGE defence networks.

Hawkeyes over Israel

While NATO prepared for delivery of the AWACS, the E-2C continues to impress in US Navy and Israeli Air Force operations. Four E-2Cs are currently operating in Israel and four have been purchased by Japan, with additional orders expected from both countries in the future.

The Israelis have indicated that they are very satisfied with the E-2C, rarely sending up fighter aircraft unless E-2Cs are up as well. With its Hawkeyes on station, the tiny nation has greatly reduced the likelihood of being taken by surprise by hostile ground or air operations. For example, the coverage provided by the E-2C systems means the Syrian MiGs are constantly under surveillance even while taking off from bases near Damascus.

Overall, the Hawkeyes supplement Israel’s ground-based air defence radars, providing information on the movement of equipment and troops, and helping to tie together the nation’s entire defence network. The compact size of the E-2C with its unique folding wing and ability to operate from forward bases make it an ideal system for the small country with long, exposed borders.

In Japan, the concern is primarily over the continued intrusion of sovereign airspace by Soviet intelligence aircraft. Weakness of the Japanese air defence radar system was dramatically illustrated in 1976 when a defecting Soviet pilot landed his MiG-25 at an airport in northern Japan. The pilot evaded the radar network at low altitude and dodged late-scrambling Japanese fighters on his way in.

With the addition of E-2Cs to the present Japanese Basic Air Defense Ground Environment (BADGE) network early warning coverage will be substantially improved, allowing adequate reaction time against any future low or high-flying intruders.

Australia, which has also expressed an interest in the E-2C, has a huge coastline to defend. It is also faced with the need to control smuggling, protect its offshore resources and fishing rights, detect “boat people” and other illegal aliens, and to coordinate far-flung search and rescue operations.

For missions such as these, the jet-powered AWACS and Nimrod would have significant capability. In contrast, the turboprop Hawkeye, though smaller and considerably less expensive, offers the most advanced AEW system with proven capabilities in maritime surveillance, plus the unique advantage of its passive detection system. It demonstrates, as one observer puts it, that high-performance aircraft are not necessarily needed to carry the latest state of electronics art aloft.

While Hawkeye, Nimrod, and Sentry represent – each in its own way- today’s most advanced state of the art in airborne early warning, new technology improvements are planned which should keep these systems in operation for many years to come. In the US, plans for the E-2C and E-3A extend to at least the year 2000 and more probably to 2010. Nimrod, if it proves to be a viable system, should also be around as long.

In terms of E-2C system growth, the evolution will continue primarily in four major areas: data processing – expand memory capacity and speed up the computer to handle the ever-growing volume of targets to be processed, and add the ability to do parallel processing for greater versatility; radar system – improve tracking capabilities and develop antennas with very low sidelobes to further reduce opportunities for the system to be jammed; passive detection system – expandability to detect and identify new, more exotic emitters and extend frequency coverage; and communications – improve resistance to enemy jamming and add more secure communication modes.

While improvements such as these will keep the electronics of these surveillance aircraft tactically up to date, similar long-term improvements are being planned for the airframes.
These include, in the case of the Hawkeye, rearranging the fuselage to accommodate a fourth operator’s control and display console; adding an aerial refuelling unit to extend the plane’s endurance time; upgrading the engines; and applying phase,antenna-array technology to improve radar performance in a jamming environment.

Future AEW concepts are on track

Eventually, of course, along will come to a new development that may revolutionise the field of airborne surveillance in the way that adapting radars to aeroplanes did in the 1940s. One such development, a new lightweight radar with antennas that conform to an aircraft’s shape, is already firmly on the evolutionary track for the future. Conceived and developed at Grumman, this conformal radar uses electronically scanned phased antenna arrays embedded in the wings, tail, and fuselage to give full 360-degree coverage. It offers the prospect of a surveillance system of increased capability at one-third the weight of conventional ones … and at a lower cost. (See the “on the horizon” feature on page 28 of this issue.)

By eliminating today’s large protruding antenna radomes, the solid-state system greatly reduces aerodynamic drag and weight, making it possible for new generations of small AEW aircraft to do the job of today’s much larger ones. Conformal radar is thus directly in line with the move toward wider distribution of tactical airpower among smaller carriers and other naval vessels and at forward airfields.

V/STOL-type aircraft, which have a notorious weight problem, maybe the first to use conformal radar. But the phased-array technology will probably be applied to AEW long before that. In fact, the next new airborne early warning system will most likely not be flown on an aircraft at all, but on a satellite in outer space.

Space: the ultimate “high ground”?

One might logically (and, to a degree, validly) assume that the evolution of AEW technology has reached its zenith with access to space … the ultimate “high ground”. Satellites have been used since the early 1960s for a variety of surveillance purposes ranging from earth resources studies to early warning of possible ICBM attacks. Infrared detectors and optics have been the primary sensory devices.

Today, the US Air Force’s space early warning system is comprised of several satellites in geostationary orbit, each mounting an array of infrared sensors to detect the rocket engine exhaust trails (or plumes) of large ballistic missiles.

With each revolution of the satellite, the array scans a sector of the Earth. On detecting a plume, the satellite transmits a target signal down to a ground control station.

By monitoring a series of signals, an operator can determine the size and quantity of missiles launched and where they are generally headed. The method has proved effective, but the technology is of 1960s vintage and limited primarily to the detection of intercontinental ballistic missiles, leaving the tracking of airborne targets to other means.

To keep pace with rapid advances in Soviet ICBM technology, future space warning systems may have to contend with dimmer (cooler) plumes, shorter engine burn times, and evasive manoeuvring of the newer weapons. Achieving improved detection sensitivity and faster response will be critical, as will the need to track all missiles well into their flights. Requirements such as these make it clear that space poses some big challenges, as well as unique opportunities, for early warning.

Starers to replace scanners

The Department of Defence is taking steps to meet that challenge by sponsoring the development of a promising new surveillance medium, the mosaic sensor, which is expected to be operational by the mid-1990s.

For the past several years, Grumman Aerospace has been working on a mosaic infrared sensor concept. Instead of a linear array of scanning detectors, our mosaic sensor uses a large number of IR detectors that form the focal plane of a large space telescope.

Motionless in its synchronous orbit, this satellite stares at the entire Earth’s disc continuously with keen, unblinking “eyes” that can instantly detect anything that moves across its vast field of view. Replacing early-warning scanners with such starer satellites would provide both the improved detection sensitivity and faster response needed to cope with advanced ICBMs as well as supersonic bombers, air or sea-launched cruise missiles, and any other type of weapon that radiates a discernible amount of heat.

Space-based radar may be next.

In addition to the mosaic starter, the Defence Department is sponsoring work by Grumman and others on the use of very large radars in space as early-warning systems. The Space Shuttle would make this feasible by easing the payload/volume restrictions and reducing the launch costs of placing a radar of the required size in orbit.

Grumman, a leader in space-based radar technology, has developed a unique concept for a self-deploying antenna of up to 1000 feet in diameter. Resembling a huge wire wheel, the structure can be neatly collapsed for stowing in the cargo bay of the Shuttle orbiter. Once in orbit, an electronic signal triggers the antenna to begin unfurling automatically… the entire process, from stowed condition to fully deployed, takes only several hours.

Unlike conventional radar antennas which are mechanically swivelled to keep their beams focussed on targets, nothing moves in Grumman’s design. Instead, the radar beam is generated by phased arrays of thousands of antenna elements and electronically shifted from point to point to track high-speed targets within widely dispersed surveillance zones.

Of course, the self-deploying antenna concept represents a dramatic advance in the evolution of early warning systems, but it is still at least a decade away. Much technology work remains in proving out the Shuttle system, self-deploying the large structure in space, conducting operational tests in orbit, and finding answers to background clutter and other related problems that may arise as we survey Earth’s surface from this entirely new perspective.

Satellites will co-operate with Hawkeyes

Space-based systems such as the large radar antenna and mosaic starter will provide an important third dimension to early warning, but they will not operate in isolation. For example, the satellites will function co-operatively with E-2Cs and E-3As, using these aircraft as “hand-offs” for responding to very early target detections.

It is generally believed that fewer aircraft will be needed on early-warning patrol once global coverage is provided by space surveillance systems. But, for the conceivable future, advanced airborne platforms will continue to be relied on for their uniquely detailed and responsive warning and control, as well as ground early-warning facilities. Then, too, space systems offer no assurance of being invulnerable to threats.

In the continuing one-upmanship of electronic surveillance, space-based warning systems have already become targets for anti-satellite measures. The latter may include attack spacecraft that can either destroy or disrupt the electronics of a surveillance satellite. High-energy lasers also pose a potential mean for confusing space sensors, degrading their optics, or even for killing a satellite at a distance.

Finding reliable means for surveillance, or early warning, has challenged military designers throughout the centuries. Kites and balloons were the best men could devise to meet this need in the earliest days. Eventually, with the advent of modern electronics-airborne radar in particular steadily improved series of AEW aircraft and, more recently, space systems evolved. These represent the knowledge and experience that will form the building blocks of future AEW technology… as the evolution continues.

Conformal Radar:

Airborne Surveillance System of the Future

Electronically scanned antenna arrays that conform to an aircraft’s shape may be the next major advance in airborne radar. With future early warning and other types of surveillance aircraft in mind, Grumman Aerospace is developing a lightweight, solid-state system with elements embedded in wings, tail, and fuselage to give full 360-degree coverage. The program is being sponsored by the US Navy.

By eliminating the aerodynamic drag and weight penalties of large protruding antennas, conformal radar would enable small aircraft to do the job of today’s much larger (and costlier) ones – or it would equip large aircraft to take on multiple surveillance roles.

The basic phased-array technique of conformal radar is, of course, not new. However, it took a breakthrough by Grumman in designing a high-gain antenna unit small enough to fit within a wing to make conformal radar a contender for future airborne surveillance systems.

A typical conformal radar installation would include both end-fire arrays in the wings and tail and slotted arrays of antenna elements embedded in the fuselage, each element being fed by its individual solid-state transmitter-receiver module. Using modern data processing technology, the system can be made to perform multi-mode surveillance. Signal processing techniques enable the system to resist electronic countermeasures … even multiple jamming of radar main lobes and sidelobes.

To increase radar performance, you need simply add antenna array modules, which give the conformal system the versatility to fit a range of aircraft sizes and missions. The modular design also assures a high degree of reliability and maintainability.

Radar is multi-mode

The conformal radar lends itself to multi-mode operation. Slowing the beam scan rate puts the radar into an extended-range surveillance mode that can double its normal detection range. The system also operates in a “zoom” mode, a synthetic aperture radar (SAR) processing technique that enables the operator to magnify a potential target area at a very long range. The feature would, for example, enable him to distinguish individual ships in a crowded harbour.

Capabilities such as these, combined with the advantages of reduced weight and drag, should find many future applications. In particular, conformal radar is expected to have a major impact on the design of the next generations of sea and land-based surveillance planes. It offers the prospect of a surveillance system of increased capability at one-third the weight of conventional ones … and at a lower cost.

One of the most promising applications would be a small VISTOL (vertical/short takeoff and landing) aeroplane capable of operating from land bases or from a variety of surface vessels including destroyers and merchantmen equipped with helicopter landing platforms. Conformal radar would enable these future Navy aircraft to serve a range of critical missions, including airborne warning and control, anti-surface warfare, and over-the-horizon- targeting against enemy ships and aircraft.

Of course, the use of conformal radar need not be tied solely to the development of such radically new types of aircraft. Applied to a future carrier-based early warning and control aircraft, the new lightweight radar could give substantially better system performance than that presently attainable … and in a smaller, less expensive aeroplane. As a result of its lower weight, the airplane could carry more fuel to remain on station longer – and, with a higher operating altitude, the radar detection range would be significantly extended.

Similarly, for a variety of existing and planned patrol planes, conformal radar would add an early warning to their other increasing their cost-effectiveness.