The U.S. Navy wants to expand the role of its Hawkeye aircraft to include coastal area surveillance and theater air and missile defense (TAMD). This is no small order for an airplane traditionally used for airborne early warning (AEW) and command and control missions in the deep ocean environment. Reinventing Hawkeye for littoral and overland performance will take a much more precise and powerful radar, tied into an existing fleet sensor/fire control network. The new version of the stalwart E-2 aircraft, known as Advanced Hawkeye (AHE), is scheduled to begin deployment in 2011. The service intends to buy 75 AHEs, including two system development and demonstration (SD&D) aircraft.
This expansion of the E-2’s defense mission will be built around an electronically scanned array radar system, feeding target data into a sea-air network known as the cooperative engagement capability (CEC). Already approved for shipboard operation, CEC has been installed on four carriers, six cruisers, six destroyers and one amphibious ship. Airborne CEC was used over Iraq, and the results of an operational evaluation of the system this year on the Hawkeye 2000 (an interim upgrade) are expected in August. The Navy plans to install CEC on 38 ships and four aircraft squadrons by fiscal year 2006.
Advanced Hawkeye, however, also will continue using Link-16 to disseminate, via data link, the “surveillance picture” — CEC, surface and other track data not found in CEC — to platforms without cooperative engagement capability.
AHE will be “one of the four pillars in the ‘Navy integrated fire control combat air’ [concept],” says Tim Farrell, vice president of AEW programs for Hawkeye prime contractor, Northrop Grumman. The others are the SPY-1 surface ship radar, the standard missile and CEC. “If we do our job right, [Hawkeye] will be naval aviation’s server in the sky,” he predicts. “It will be naval aviation’s centerpiece for the chief of naval operations’ vision of ForceNet.”
Electronically Scanned Array
Advanced Hawkeye is being designed to detect, track, classify and identify emerging aircraft and missile threats, says Capt. Robert LaBelle, E-2 program manager for the Naval Air Systems Command (NavAir). The digital radar is expected to detect far more targets than is now possible and to almost double the surveillance volume. It is intended to detect threats in high-clutter, high-electromagnetic interference (EMI) and jamming environments over land as well as over open ocean.
The radar passed its preliminary design review (PDR) in April 2004 and is heading toward critical design review (CDR) in January 2005. The system-level PDR is set for October 2004 and CDR for October 2005.
The radar, under development by Lockheed Martin, Syracuse, N.Y., must be able to pick out low-flying cruise missiles deep inland in order to provide earlier warning to naval battle groups. It will be optimized to remove radar returns from ground terrain and stationary objects that will be mixed in with the returns from moving targets. Improved performance against increased levels of jamming also is planned. Lockheed will provide the radar’s exciter and processor, as well, while Northrop Grumman Electronic Systems in Baltimore and Raytheon in El Segundo, Calif., respectively, will supply the rest of the transmitter and the receiver.
Besides the electronically scanned antenna, the AHE radar will employ higher-speed processors, use advanced digital space-time adaptive processing (STAP) and produce a significantly higher power output. In a moving target indicator (MTI) radar such as this, STAP increases the accuracy of detection by better removing the returns from fixed objects. The radar also is to provide higher-fidelity, more richly detailed, potentially more frequently updated target data into the shipboard CEC network.
Unlike today’s system, the new radar will scan the beam in azimuth electronically as well as mechanically, increasing radar flexibility. The antenna will allow:
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The basic 360-degree, mechanical scan that is done today,
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A simultaneous “mechanical plus electronic scan,” and
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A purely electronic scan conducted while the rotodome is held constant, focusing more energy on a target.
Electronic scanning will be possible because the design will use 18 antenna elements spaced at intervals equal to one-half the system’s UHF wavelength. Today’s radar employs 10 antenna elements spaced at intervals of one times the wavelength, a design that precludes electronic scanning.
Rotary Coupler
Another key enhancement will be a rotary coupler designed by L-3 Communications’ Randtron Antenna Systems for Northrop Grumman’s Integrated Systems sector. The coupler “translates the RF [radio frequency] signals from the rotating antenna down to the stationary cables located in the aircraft fuselage,” explains Jim Day, airborne radar technical director with Lockheed Martin Syracuse.
The coupler’s job will be more demanding on the Advanced Hawkeye than on legacy aircraft because the new equipment will have to handle 18 signals — for main-lobe clutter cancellation and electronic counter countermeasures (ECCM, or jamming cancellation) — from the antenna, rather than just two signals today.
The current antenna adds up the 10 signals from the 10 antenna elements and creates a “sum” signal and a “difference” signal. These are used to perform displaced phase center antenna processing for platform motion compensation to improve clutter cancellation in the radar’s main lobe. The two signals—formed as two different combinations of the 10 antenna elements—are then passed through the rotary coupler into the digital signal processing chain. The legacy radar also supports side lobe canceller channels for jamming cancellation in the radar side lobes.
The new system, by contrast, will process all 18 signals from the 18 antenna elements through the coupler, creating the sum and difference patterns through digital processing. Because all 18 signals are coming into the digital processing system, “we essentially allow ourselves to have more degrees of freedom to deal with and help cancel the clutter and jamming,” Day says. The 18 channels passing through the rotary coupler “also are used to facilitate electronic scanning,” he adds.
Radar data will be digitized much earlier in the processing chain than was possible in the legacy system, enabling the use of STAP algorithms. The radar’s STAP processor “senses the signals coming in from the antenna and optimizes the sum and difference patterns to optimally cancel clutter and jamming,” Day explains.
The AHE radar will use modular construction to make upgrades easier and will incorporate ruggedized, commercial off-the-shelf (COTS) elements to hold down costs. The transmitter will be built up from identical power amplifier modules, for example, and the receiver from common down conversion and analog-to-digital conversion modules.
The radar processor also will employ a small number of board designs — not only custom cards, but ruggedized COTS quad-, dual-, and single-board computers running Wind River Systems’ VxWorks commercial real-time operating system.
Cooperative Engagement
A key enabler of AHE’s expanded air defense mission is the cooperative engagement capability, which distributes raw sensor measurement data to participating ships and aircraft in real time over a multimegabit data link. This permits all networked platforms to simultaneously see the entire air picture within their sensors’ surveillance volumes and to cooperatively engage threats. Neither the current nor the future airborne radar, however, has the fidelity of the extremely precise SPY-1 shipboard radar, a major CEC node.
Although the details are classified, AHE’s radar will enhance the CEC picture by means of its improved accuracies, yielding improved detection ranges “with smaller areas of uncertainty, as well as improved track continuity,” says the E-2 program office. Identification will become easier. AHE also will support “more robust engagement solutions.” One observer cites the ability of rotating radars to “fill in the blanks” when shipboard phased array radars lose lock on maneuvering targets.
CEC fuses track measurement data from radars on multiple platforms into a high-quality, real-time composite track picture. A shipboard system, for example, sends raw contact data to Hawkeye. Hawkeye’s CEC system views that data, recognizes that the aircraft is tracking the same target, adds its own associated radar data and sends all the information back to the ship again. The shipboard system, like its airborne counterpart, combines data from the other CEC units with its own radar measurement data — locally, via common CEC data fusion algorithms — to produce a composite track. Data sharing produces better fleet situational awareness — the so-called “common air picture” — and allows more time to counter fast-moving air threats.
CEC is like a Venn diagram, explains Lt. Cmdr. Alex Carr, operations officer for the Navy’s E-2 VAW-117 squadron, which last year flew missions in the Iraq theater using CEC in both the relay and full-up, two-way modes. “If you look at the intersection of four or five different radars—it’s much more precise,” Carr says.
He also notes the range of the data link. “It was interesting [for] battle group commanders and warfare commanders to see that they were having shared track data…hundreds of miles away—much beyond the advertised [CEC] capability.”
Operational tests of aircraft-based CEC took place during January through March this year, using Hawkeyes, CEC- and non-CEC-equipped ships, and unmanned target drones. Although the results are not yet in, a four-hour technical evaluation in 2001 suggests CEC capability. Some 1,100 tracks went through the CEC network during that exercise, involving two airborne, six shipboard and three land-based nodes.
“The concept of CEC is to allow better tracking — not only detection but tracking — of low-observable, highly maneuverable objects, such as cruise missiles,” says Gifford Clegg, director of business development for Raytheon’s Network Centric Systems. With Hawkeye on top, networking the ships together, Clegg says, surface combatants can be distributed over the horizon from each other, expanding the situational awareness picture and extending fleet reaction time.
Raytheon today has delivered approximately 98 production sets of CEC equipment — for both air and surface combatants — with about 180 to go. Eight Hawkeye 2000s so far have been equipped with CEC, the Navy says. This version of the aircraft also includes voice satcom and a new mission computer.
A ‘Miniterminal’
Airborne CEC can both relay radar data from ship to ship and actively inject its own sensor data into the network. E-2 target information extends the battle group’s threat awareness outward, beyond the shipboard radars’ 17- to 20-nautical mile line of sight, and downward to the surface, below the radars’ horizon. Hawkeye’s current radar contributes long-range detections and contact data to the composite track.
The Hawkeye’s 686-pound (311-kg) CEC suite on the E-2 consists of “black” and “red” processors — part of the data distribution system, or RF network function — the cooperative engagement processor that processes all sensor measurement data, receiver/synthesizer, power converter and transceiver, plus an antenna.
Raytheon is proposing a slimmer, 519-pound (235-kg) version of the CEC avionics for Advanced Hawkeye. This includes a “miniterminal,” combining the radio function, receiver/synthesizer and CEC processor into one unit. Following a COTS mandate from the surface Navy, the miniterminal will meet Level 3 of the Navy Open Architecture computing environment, Clegg says. It will run a version of Wind River System’s VxWorks real-time operating system in both the radio and the CEC processing sections. Raytheon hopes for a production award next year, following an assessment later this year.
CEC benefits the Hawkeye’s command and control mission, as well. Its high-quality track data “makes our tactical data links picture better,” says Carr. “A track — an airplane or a ship — is just more precise in where it’s located.”
Tactical Cockpit, Mission Computer
Advanced Hawkeye (AHE) will feature a glass cockpit with three 17-inch color displays — for tactical as well as flight data — a big change from the current suite of electromechanical flight instrument displays and indicators. The AHE “tactical cockpit” — the main focus of the integrated navigation, controls and displays system (INCDS) upgrade — will enable the front-seaters to see what the backseat operators are looking at. The AHE pilot or copilot will be able to control the tactical display, reducing the workload of the remaining crewmembers.
It’s like adding “an additional virtual workstation [via optical link] up in the front end of the airplane,” says Tim Farrell, vice president of AEW programs for Hawkeye prime contractor, Northrop Grumman. “They’ll be able to go from their flying displays to a tactical display,” with the ability to see the “air picture.” The pilots can see who’s flying out there, whether they’re hostile or not, their direction and speed.
INCDS also will add two control panels for managing the functions on the three landscape-style displays; two backup flight displays; two avionics/flight management computers; two embedded GPS/inertial navigation (EGI) units; a flight data loader to enter, record and retrieve navigation and system maintenance information; two dual-channel air data systems; redundant navigation and communications Mil-Std-1553B buses; and multiple ARINC 429 buses for message traffic.
Northrop Grumman also will upgrade the AHE’s mission computer — a task awarded to Raytheon — using a high-end, commercial off-the-shelf (COTS) server in a “ruggedized” chassis to more rapidly transfer commercial advances to the fleet.
“What we’re challenging folks to do,” Farrell says, “is, instead of ruggedizing or militarizing a commercial architecture, go with a true commercial hardware suite [of cards].” The Hawkeye operates in a hostile environment with humidity, salt/spray, explosive decompression, and 20-g crash load requirements. “So, how many of those requirements can the chassis handle, as opposed to the computing cards?”
The problem with militarizing computer boards is that it takes a lot of time and money. If you could buy a commercial card for $5,000 — based on notional figures — you could ruggedize it for $50,000 and militarize it for $250,000, Farrell says. Each phase in the process not only multiples the board’s cost, but delays its deployment, so that the eventual product is two steps behind what’s available in the commercial market. If these engineering issues can be solved, big savings will follow.
Northrop also has a technology road map, including a set of exploitation and decision aids that are being “developed and matured” for possible introduction into the production program.
The annually updated, seven-year outlook includes things like “multisource integration” of target data coming in from other systems with target data from ownship sensors, to improve detection accuracy. Another item is advanced decision aids for taking on changes to air tasking orders and automatically correlating them with target data. (Air tasking orders provide information such as aircraft descriptions, configurations, target assignments and refueling locations.)