Bridging The Surveillance Gap

The E-2C may be called on to detect a fast, hedge-hopping, hostile intruder or track a high-flying spy plane. Perhaps it will be asked to conduct an air/sea search and rescue mission; but whatever the E-2C’s job, accurate, reliable and timely extraction of specific target information is required. Operating several miles above the earth, the Grumman E-2C Hawkeye, with its powerful radar and passive detection sensors, sees well beyond the horizon, enabling it to monitor covert enemy activities. Surface-based radar can provide adequate warning of high­ altitude aircraft but, due to its line-of­ sight limitations, cannot detect targets on or close to the ground, below the radar horizon. The E-2C can continue its detection and tracking even in the presence of enemy jamming. It is capable of retaining a quite respec­ table detection capability in a multiple­ jammer environment.

The Hawkeye’s central processing system is designed to handle a large volume of air and surface traffic – in both military and civilian applications. It can automatically maintain track data on more than 600 targets derived from its own active and passive sensors, manual entries by the operator, or via data link from external sources such as other E-2Cs, ground control networks, surface vessels, or supporting fighters. The computer-calculated intercepts pair each available fighter to the intruder.

Friendly fighter armament, fuel state and performance are weighed against the target speed and position to op timise pairing and select desired in­tercept geometry. Over 40 simultaneous air-to-air and air-to­ ground aircraft missions can be automatically controlled via data link. These same track/control capabilities may be applied to peacetime uses, such as emergency control of military and civilian air traffic or support of search and rescue activities.

Australia is a large country of ap­proximately the same size as the United States with only about six percent of its population. Most of the Australian population is situated along the east and southeast portions of the country; the remaining parts of the country, for the most part, are thinly populated. It is completely surrounded by water and has an extremely long coastline. Most of the civilised world lies to the north of her. Because of this geography, a potential enemy threat would, most likely, approach from the north, hoping to avoid detection along the sparsely populated coast. If a threat does develop to a point where there is any action against Australia, it would cer­tainly strain the current defence resources whose size, in terms of armed forces and military assets, are limited because of its population.

The armed forces and military assets must be technologically at the state of the art and have the capability to be positioned quickly at forward bases from which they can counter enemy threats. Early warning of an enemy approach or intentions is a prerequisite for providing this force mobility and allows adequate time to bring your forces to maximum readiness.

Although fully capable of independent airborne warning and control operation if necessary, the E-2C nor­ mally operates as an extension of ex­isting ground defence systems. It is data links that allow the E-2C surveillance-type aircraft, friendly fighters, surface vessels and ground stations in addition to data derived from its own sensors. This data can be completely correlated by Hawkeye’s computer and transmitted to a ground-based command centre for display, evaluation and decision by the military commanders. Similarly (and simultaneously), the E-2C can receive data updates from the ground terminal, permitting fully integrated operation of the defence system.

The Hawkeye can automatically track targets derived from its own sensors, manual entries by the operators or, via data link, from other E-2Cs. It can also maintain tracks relayed from supporting fighters, surface vessels, or ground networks. Target course, speed, altitude and status (ie friend, foe or unknown) are continually maintained in the computer file and displayed to the operators or transmitted to the ground, in real-time. The ground-based commander, therefore, has at his disposal the most complete tactical picture and can manage his defensive assets for greater efficiency.

With full visibility of the tactical picture, as it develops and access to highly efficient computer capability, the Hawkeye can play a significant role in fighter control. Computer-calculated intercept solutions, using target and asset parameters, determine the optimum pairing and intercept geometry. Once an assignment is made, the E-2C automatically computes fighter speed, altitude, and bearing for optimum convergence with the target. Fighter control is effected through either standard UHF voice communications or, with suitably equipped fighters, through fully automatic digital data link in either one-way or two-way modes. These capabilities permit effective E- 2C/fighter inter-operations with any fighter currently in inventory or planned for future operations.

Use of the Hawkeye for airborne control will thus significantly increase the number of successful intercept missions and boost the number of potential kills. The Hawkeye is a force multiplier.

A typical scenario involving the north coast of Australia could be a potential threat caused by a changing political environment, or perhaps the increased activity of a foreign fleet in the Indian Ocean. Whatever the reason, the unusual activity to the north of Australia is sufficient reason to gather intelligence to permit the response of positioning forces most effectively should a threat materialise.

An EC-2 squadron assigned to a forward base in Darwin for the term of that emergency, patrols the northern coast from Learmonth to Townsville, Their purpose is to gather intelligence about any unusual assembly and movement of possible hostile assets. Their mission is to detect low-flying aircraft and surface vessels beyond the line-of-sight limitations of ground-based radars. By virtue of its ability to operate at an altitude above 25,000ft, a typical station altitude, can effectively see low-flying aircraft and surface vessels out to about 200 nautical miles.

In comparison, Ground Control Intercept (GCI) Radar can effectively see low-flying aircraft and surface vessels out to approximately 40 nautical miles. While on patrol the E-2C detects hostile low-flying aircraft and surface vessels approaching within 200 nautical miles of Australia. Through its multi-purpose digital data links, target reports are sent via UHF or HF data link to a surface command post for display and decision. Air and surface track information and associated ECM data are displayed and evaluated on the ground in real time. In turn, command directives for force and weapons control are transmitted to Hawkeye for implementation against the air hostiles. The E-2C assumes control and vectors friendly fighters from Combat Air Patrol stations or ground alert status. Similarly, command directives from surface command posts are implemented by friendly surface assets.

Ground-based GCI radars are severely limited in terms of their ability to detect surface and near-surface targets. The cost of creating an airborne surveillance “barrier” that would be effective against low-flying attack aircraft would be unacceptable except for limited emergency or “terminal defence”. Where extensive areas must be monitored, especially for long periods of time, other alternatives must be investigated. The solution appears to be a combination of a fixed over-the-horizon backscatter (OTH-8) radar and a mobile AEW system, the OTH-B to provide coarse resolution of targets suitable for stationing and an AEW system to provide the fine resolution for vectoring friendly assets to the target Jindalee and the E-2C Hawkeye.

It should be noted that the full capabilities of the Jindalee installation are difficult to project since the research and development are scheduled well into the 1980s.

The Jindalee radar is basically a high-resolution, bistatic HF skywave radar system. It differs from the normal conception of radar because it does not have to be within the line-of-sight of a target to be able to detect. Jindalee uses the HF portion of the electromagnetic spectrum. The radar waves are refracted by the ionosphere to provide a transmission path over the target to the radar receiver via refraction by the ionosphere, which is processed like standard line-of- sight radars.

Jindalee and the E-2C are complementary. The limitations of one system are satisfied by the strengths. Jindalee will provide the day­ to-day large area surveillance so that it is not necessary to maintain E-2C air­ borne, but the E-2C will provide raid count and combat command and control unavailable from Jindalee.

In a tactical situation, unknown targets were detected by Jindalee. Since targets are first detected at extremely long range, sufficient time exists to put an E-2C on-station to identify the target, and, if necessary, the E-2C will provide close control to an interceptor for visual verification, attack and re­ attack. The E-2C will provide target altitude and raid size to con­ serve reaction forces.

The communication network for a combined Jindalee/E-2C system is relatively simple. A low data rate com­munication system is all that is required for the Jindalee radar to position the E- 2C for detecting a threat. Once in posi­tion, the E-2C uses its high data rate communications for commanding friendly forces. The finer grain of the E- 2C radar permits control of interceptors against specific aircraft in the raid and reassignment after initial intercept.

The Airborne Early Warning System (E-2C Hawkeye) is presently operational with the US Navy. Its basic function is to provide detection and tracking of surface and air targets together with the generation and relay of command and control data. The E-2C uses a UHF radar, Identification-Friend or Foe (I FF) and a Passive Detection System (PDS) as its primary sensors. The computer-assisted command and con­trol coordination functions, super­vised by three operators, are ac­complished through UHF line-of-sight and HF long-range voice or data links. The E-2C’s·radar and IFF are capable of automatic detection, correlation, and tracking at ranges in excess of 200nm. The PDS provides lines of bearing to RF sources together with emitter iden­tification and triangulation (for location).

Operating at UHF frequencies and a scan rate of six per minute the E-2C radar provides high-resolution 360-degree line-of-sight coverage and fast reaction to a developing threat. The radar system automatically detects and tracks both large and small air or sur­ face targets, over land and water.

The E-2C “Over-The-Horizon” capability is derived from its high altitude, 25,000 to 30,000 feet, vantage point. A thumb rule for computing the radar horizon for airborne line-of-sight type transmissions uses the square root of altitude in feet increased by 22 per cent to give a range in nautical miles. At 27,000 feet this range is 201nm. Conversely for a Hub Cap perched on a 1000-foot hill or a P-3C Orion flying at 1000 feet, this range is 38nm. Where real-world targets normally have some altitude of their own detection ranges may be predicted by adding their “radar horizon” to that of the surveillance radar’s. For example, a forma­tion of fighter bombers approaching Darwin at 1500 feet over the water would be detected by the same Hub Cap at 87nm and by the E-2C at 250nm.

One of the E-2C features is that it is highly mobile. As such it is not a fixed target and it may be deployed in­ dependently to support military operations in any part of the world hav­ ing a suitable commercial -airport or carrier deck.

On-station endurance varies with distance from the base but a six-hour flight (or nine hours in the wet wing version) at a 270kt cruise is accomplished comfor­tably. This means that flights from Darwin to Learmonth or Learmonth to Cocos and return would be suitable for routine training missions.

Two E-2C’s working out of Darwin, one toward Learmonth and the other toward Townsville, would cover the en­tire Northern Coast of Australia once each day. A single squadron of four to five aeroplanes could support this type of operation on a continuous basis. Exten­ sion of routine patrol to Cocos might be accomplished by the addition of one or two more aircraft.

Most radar emissions, data links, and communication nets exhibit characteristics that are unique in terms of their source and function. Continuous monitoring and assessment of the electromagnetic spectrum provides valuable passive intelligence and warning.

The E-2C uses a passive detection system (PDS) to search, identify and locate a large variety of signal sources. This function is unique in that these signals are mostly line-of-sight or highly directional. As such ground monitoring stations are usually ineffective because of horizon blockage. The E-2C’s altitude and the PDS’s sensitivity com­ bine to provide ELINT monitoring over a vast area.

The E-2C data processing system cor­ r eI ates the PDS and radar measurements for display or data link transmission. A command control application of such information has ob­vious implications. For example, the ability to monitor a sequence of several signals might indicate a pending missile launch. Coupled with signal location and missile identification, the signal sequence provides clues as to the in­ tended target, means of intercept, and methods to be used for evasion.

The E-2C normally transmits its full tactical data situation by way of stan­dard Naval Tactical Data System (link 11) digital coding using either UHF or HF radios. It may also receive and retransmit this same type of data from most RAN ships, Orion aircraft or other Hawkeyes. In off-shore applications, along much of Australia’s coast, this data linking requires either line-of-sight UHF receiving stations or “continuous­ly available” HF stations. This ability to transmit tactical data to a military com­mand centre and then to receive or relay the command centre’s response is a vital and essential part of the AEW mission.

Fortunately, reliable continuous com­munication can be maintained without additional costs by using OTH-B HF radar facilities. Assuming that the E-2C is working in a sector covered by OTH­ B radar, each scan of the beam through the E-2C’s position opens a highly reliable two-way radio path through the ionosphere. This is made possible by the fact that the OTH-B radar frequency management system and highly directional (high gain) receiving anten­ nas are designed specifically to prevent spurious path disruptions. The E-2C’s HF radio can track the OTH-B radar frequency and “Burst” transmit at high power ensuring that the path is not only reliable but that it is also imper­vious to normal jamming.

The direct operating costs, logistic support and manpower required to keep an aeroplane airborne can be minimised by E-2C co-ordinating with OTH-B radar. For example, instead of continuous 100 per cent coverage of Australia’s 12,000nm coastline, six E-2C’s could be operated on surveillance/training missions to routinely update all boat, aircraft and radar/comm activities from Townsville through Learmonth to Cocos. In a peacetime application, these scheduled flights and real-time data dumps through Jindalee to the RAAF, Customs or the Coastal Surveillance Centre would help secure the coast against low-level incursion, visibly affirm Australia’s deterrent military posture, and contribute significantly to Air Sea Rescue and the EEZ monitoring.

The AEW is vulnerable to airborne intercepts and SAM’s unless a fighter escort or standoff tactical positioning is used as a means of protection. If the AEW must be accompanied by fighters on “pure surveillance”, ie: exploratory probing missions, then the range and endurance of the fighter limit the AEW radius of action. Even fighter tanking does not solve the problem if pilot endurance is limited. Again the OTH-B provides an acceptable alternative.

Full 360-degree OTH-B radar coverage around Australia obviates the need to despatch the AEW into the far reaches of surrounding oceans. The tactical versus strategic synergism of E- 2C and Jindalee can be maintained without exposing valuable assets to undue risk and without the need to dilute fighter forces for dedicated protection of the AEW. The Jindalee provides the strategic warning needed for concentrating air and surface forces along the near shore threat axis with the AEW located in a protected or standoff position. But still, the Airborne Early Warning Aircraft is a high-value target for enemy fighters and missiles due to its tactical importance. In Vietnam and during innumerable naval exercises the E-2C has consistently avoided attack by maintaining a standoff location, evading incoming fighters or vectoring friendly fighters for protection. The E-2C used in Australia where extensive fighter protection or standoff locations might not be practical could benefit from the OTH-B radar warning and HF data link by “tracking” targets beyond its normal radar range. This would allow more or less autonomous operation.

If hostilities escalate to the stage where an attack on Australia’s cities or military installations is imminent the E- 2C/OTH-B radar can provide the lead time and tactical targeting precision necessary to make such an event so risky, costly or crippling than an aggressor would be destroyed or seek other alternatives. If an enemy chose to attack by sea, long-range detection of hostile naval forces by OTH-8 radar followed by E-2C positioning along the threat axis would set the stage for active defence using the F111C, A-4, Orion, Mirage aircraft and the selected TFF. At this point reconnaissance, diversionary probes, anti-shipping attack, air defence, fighter intercepts and close air support could be controlled and monitored through the E-2C via the Jindalee link from any command control centre in Australia.

The prime function of the AEW is to provide fighter, bomber, or cruise mis­ sile targeting and efficient intercept control. The information available from the E-2C permits initial fighter engagements at maximum range, optimises the chances of re-attack, and warns against counter-attack.

An article entitled “Eyes Over the Horizon” which appeared in the March 6, 1975 issue of FLIGHT INTERNATIONAL outlines the Hawkeye’s role in Vietnam specifically: “The Hawkeye enabled the Task Force Commander a new level of flex­ibility. In particular, the much greater detection ranges now possible required fewer interceptors to be kept in the air or maintained on alert during darkness. The control of major air attacks against principal military targets in North Viet­nam was greatly improved in several ways including safety, access to the target and the ability of day attack air­craft to carry out missions successfully despite marginal weather. Much of the success in foiling MiG 17 and MiG 21 interceptions was due to advanced detection and tracking by E-2s on patrol, diverting F-4 sections from their heart of any AWACS aircraft, the operations centre where the surveillance bomber escort duties and vectoring them into position for Sparrow and Sidewinder attacks. ”

The payoff in the air war was also significant in terms of lowered attrition, quick rescue of downed crews and “emergency navigation” for disabled aircraft.

In-depth analysis and simulation studies of the AEW interaction in air­ borne combat scenarios show that fighter effectiveness is increased by as much as 250 per cent. All other things being equal, the task of 25 fighters can be accomplished by as few as 10.

The attack against today’s sophisticated Naval targets using visual and conven­tional (close-in) weapons is impractical in terms of survivability and predicted attrition. In general, there are three methods of improving the effectiveness and success in such an attack.

They are:

• Launch-and-leave weaponry (with the associated on-board system capability).
• High-performance jamming; both Standoff – Tactical and On-Board­ Deceptive types.
• Coordinated C3 for low-level at­ tack with a minimum exposure delivery.

The third option with the E-2C used to support an A-4 or F-111C strike is presently available and relatively inex­ pensive. It could be accomplished by low-level high-speed minimum ex­posure run-in vectoring for a precisely timed pop-up, minimum target acquisition delays, and a minimum exposure run-out. E-2C Automatic Tracking and positioning accuracy of both airborne and surface targets allow precision vectoring of multiple attack aircraft, such that tactics are controlled to achieve a minimum risk to the strike aircraft, eg; (1) run-ins from several direc­tions are co-ordinated to achieve simultaneous weapon delivery, (2) Deceptive tactics are coordinated for maximum saturation of surface target defences, (3) run-in and run-out routes are programmed to avoid SAM’s and provide fighter cover.

Various forms of Command and Control links are available for directing maritime strikes. A simple voice technique, similar to that used in air-to­ air intercept, may be applicable when limited numbers of aircraft are involved but where multiple aircraft and precise attack coordination are desired, com­ puter-directed data link command becomes mandatory.

The E-2C System, with software control or relayed control. With a sim­ ple on-board system the attack pilot could use cross-pointer type informa­tion programmed to display pit-up and course commands. Installation of this type of equipment involves a data link receiver, decoder, interface box, cockpit display and pilot controls.

The Oberon class submarine equipped with the Harpoon missiles is capable of standoff attack from about 60km but targeting at these ranges is difficult to conceal. A single shot or salvo would necessarily need to be directed selectively since it would most likely give away the submarine’s most valuable defensive asset – its location. Under these conditions, it might be necessary to limit the use of Harpoon to a single, very high probability of kill, and firing in order to minimise the risk of be­ ing detected and attacked by enemy ASW forces. However, a submarine equipped with a Link II Receiver and data terminal could passively assimilate the complete surface and airborne target situation sensed by the E-2C without surfacing. This provides con­tinuous manoeuvring information, Friend and Foe Identification (IFF), and. target value assessment/designation together with surface or airborne attack warning. The sub’s safety and effec­tiveness is greatly enhanced by the use of AEW data.

An Orion equipped with Harpoon is severely restricted by its size, speed and manoeuvrability. As such during an at­ tack against surface shipping the Orion is a relatively easy target for SAM’s and AAM’s. Naval formations are usually structured in such a way that the Orion would necessarily be within SAM firing envelopes before it could launch its Harpoon. A low-level (below the horizon) approach would help protect against surface detection until the Har­ poon could be tired but again targeting and target assessment requires radar line-of-sight. The Orion is capable of interfacing with the E-2C to allow the same kind of low-level coordination available to strike aircraft.

Without diluting the prime AEW mis­sion the E-2C contributes significantly to Orion’s anti-submarine warfare mission by detecting long-range “Pop-up” surface contacts and short burst radar transmissions. The two-way data link compatibility between Hawkeye and Orion aircraft allows automatic data transfer and autonomous Orion operation without burdening the AEW’s primary mission.

The E-2C’s most critical function in any battlefield operation is its contribu­tion to fighter air superiority, but the ability to detect low-flying hostile attack aircraft and to direct friendly strike air­ craft for close air support is equally important and proven capabilities. Enemy movement or helicopters, air­ borne troops, and cargo drops also represent significant battlefield sur­veilancee data. These functions together with the E-2C’s potential for data link and communications relay offers field commanders the ability to monitor their entire area and maintain real-time tactical updates. Detection of enemy gun laying, SAM and anti­ aircraft radars adds significantly to intelligence and safety.

Portable data terminals linked to the E-2C and augmented by relayed central command centre information offer local commanders a highly sophisticated, reliable, valuable and current battlefield picture.

The E-2C, an aeroplane for many mis­sions is truly unique. It has grown from an overwater detection system to aver­ satile effective surveillance and control system capable of providing reliable small target detection and tracking, nearland, overland and overwater. It can be fully interoperable with any fighter-interceptor and air defence ground environment. It can work autonomously but is most effective as part of a command and control network. The E-2C not only fills today’s requirements but also tomorrow’s.

Extended Endurance

In its present configuration, Hawkeye will maintain the station at a distance of some 200 miles for about four hours. Range and endurance capability can be increased by adding:

• Fuel tanks to the outer section of the wings, increasing on-station time to more than 6 hours
• An inflight refuelling probe that will sustain on-station time for indefinite periods.

The E-2C normally carries a pilot, copilot, and three operators, each at an independent operating station. For extended time-on-station, a fourth operator can be accommodated, allowing relief for the rotation of positions.