Unblinking Eye

By Frank Colucci | August 1, 2009
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All-round radar, electro-optics and electronic support measures will transform the U.S. Air Force Global Hawk Unmanned Aircraft System (UAS) into the U.S. Navy’s Broad Area Maritime Surveillance (BAMS) system.

The Navy intends to network the large, autonomous air vehicles built by Northrop Grumman to provide persistent maritime Intelligence, Surveillance and Reconnaissance (ISR) data to fleet users. Plans now call for Initial Operational Capability (IOC) with four RQ-4N aircraft to sustain round-the-clock orbits from a single operating location in 2015.

Full Operational Capability around 2019 puts 20 unmanned aircraft at five operating locations. The fleet ultimately will grow to 68 RQ-4Ns to augment piloted P-8 Multimission Maritime Aircraft (MMA) in the Navy’s Maritime Patrol and Reconnaissance Force.

According to Capt. Robert Dishman, the Navy’s program manager for Persistent Maritime Unmanned Aircraft Systems, "The key for BAMS is to complement the P-8 and not compete. It’s an adjunct off-board sensor, so you can cover more territory."

A 300-knot platform with better than 34 hours of endurance, cruising altitude above 60,000 feet, and a choice of satellite and line-of-sight datalinks can cover broad expanses of open ocean and littoral territory. The BAMS air vehicle is based on the Global Hawk Block 20 growth platform, with the same 3,200-pound payload and identical payload power and cooling provisions.

However, unlike the Air Force RQ-4A, with its side-looking radar and electro-optics, the Navy RQ-4N will integrate sensors with a 360-degree Field of Regard. "That’s a key piece for a maritime scenario in a constrained geographic formation like the Straits of Hormuz or Straits of Malaga," said Dishman.

The Air Force’s Global Hawk "looks" +/-45 degrees to either side with its Synthetic Aperture Radar, or +/-15 degrees with high-resolution, still-imaging electro-optics. While Air Force mission planners offset flight tracks to accommodate their sensor windows, Navy missions must sometimes follow tight corridors. "You can’t just move the airplane and fly adjacent to the strait," Dishman said. "International law prohibits that. You have to fly ‘feet wet.’"

Walter Kreitler, Northrop Grumman director of BAMS UAS business development, also differentiates Navy surveillance from Air Force reconnaissance: "You’re going after things where it isn’t clear where they’re going to be," he noted.

To search with an all-round Field of Regard, the Increment One RQ-4N will integrate a new, electronically scanned Multi-Function Active Sensor (MFAS) radar with a Multi-Spectral Targeting System (MTS-B) electo-optical/infrared sensor taken from the Air Force MQ-9 Reaper UAS, and a Merlin electronic support measures (ESM) suite from the Navy EP-3E intelligence aircraft.

A dedicated air-to-air radar still to be defined will provide Due Regard of conflicting air-traffic as the UAS changes altitude and course to give mission sensors their best look.

Like Global Hawk, the BAMS UAS will be keyboard-operated by separate crews in dedicated Launch and Recovery and Mission Control Elements built by Raytheon. Sensor imagery will be sent beyond line-of-sight to the Mission Control Element or other networked users via the new Global Wideband Satcom network, in addition to commercial Inmarsat satellites. "There’s not a whole lot of market for commercial bandwidth in the middle of the ocean where we operate," said Dishman. A Common Data Link will likewise carry sensor imagery at 45 megabits/second to Tactical Operations Centers and other theater users sharing a Common Operational Tactical Picture.

L-3 Communications Systems-West, based in Salt Lake City, is responsible for the airborne and ground portions of the BAMS datalinks.

BAMS Increment Two will introduce airborne relay functions and even more robust communications links that are still to be defined by the Navy networking and intelligence communities. Increment Three adds comprehensive Signals Intelligence (SIGINT) capability to the baseline Communications Intelligence (COMINT) package.

About 75 percent of BAMS Increment One software is re-used from the Air Force Global Hawk, and Northrop Grumman program mangers seek commonality in aircraft handling and other functions. Different missions and sensors will nevertheless give the BAMS air vehicle a somewhat different mission computing system, data handling architecture, and ground processing strategy. RQ-4N enhancements are candidates for Air Force Global Hawk Block 20, 30 and 40 upgrades.

Pending delivery of the first RQ-4N test aircraft, the Navy is flying two RQ-4A Block 10 Global Hawks modified with ESM and maritime radar modes for the BAMS-D demonstration. The demonstrators also carry an off-the-shelf Automatic Identification System (AIS) to interrogate co-operating surface ships.

"It helps you sort out the good guys from the not-so-good guys, and it gives you some situational awareness out in front of the aircraft where you don’t have that field of regard in the sensors," explained Dishman.

The BAMS UAS currently has no requirement for active survivability equipment; the Increment One RQ-4N is expected to maintain its own sanctuary.

One of the BAMS-D aircraft was combat deployed in the U.S. Naval Forces Central Command theater and linked to a Mission Control Element at Naval Air Station Patuxent River, Md. "We are validating the limitations of the sensor but also providing useful information to the support Commander NAVCENT," said Dishman.

The RQ-4N BAMS and P-8A Poseidon ( Avionics, July 2009, page 24) emerged from a common Mission Need Statement for broad area maritime and armed surveillance missions. A Navy Analysis of Alternatives concluded an unmanned system was the best way to do about 30 percent of the ISR tasks performed today by manned P-3 patrol aircraft. At IOC, the new P-8 MMA will exercise Level II control over the BAMS UAS sensors. MMA objective requirements extend manned-unmanned teaming to Level IV control over the BAMS flight path.

BAMS prime contractor Northrop Grumman Aerospace Systems, Redondo Beach, Calif., started work under a System Development and Demonstration contract last August and should deliver three Test and Evaluation air vehicles by mid-2012 — two paid for by the Navy and one sponsored by the manufacturer. Three Low Rate Initial Production (LRIP) aircraft delivered later that year will support BAMS Operational Evaluation. All six test aircraft will have the Increment One mission suite.

The MFAS radar from Northrop Grumman Electronic Systems (NGES) leverages fourth-generation Active Electronically Scanned Array (AESA) hardware derived from tactical fighters and dedicated maritime mode software matured from the Northrop Grumman Head Start demonstration program.

"We’ve done a lot of work with ONR (Office of Naval Research) starting in the early ‘90s to develop the mode suite," said Joe Schuster, NGES director of aerospace programs business development. Maritime modes were demonstrated on a Gulfstream II test aircraft, and Northrop Grumman is considering MFAS risk reduction flights on the same aircraft before the advanced radar flies on the RQ-4N.

The mechanically-scanned radar on the Air Force Global Hawk reaches out to 200 km in Synthetic Aperture Radar (SAR) or 100 km in Ground Moving Target Indicator (GMTI) modes. SAR relies on aircraft motion to generate crisp target imagery over land, but the picture smudges with sea motion. The electronically scanned MFAS adds Inverse Synthetic Aperture Radar (ISAR) functions to classify pitching, rolling sea targets by their "blotology." Said Dishman, "It’s actually a different mode and different skill set for the operator to interpret maritime targets."

Unlike the Global Hawk Mission Control Element, the BAMS MCE will have additional operator space for naval specialists to interpret ISAR. "It will allow us to do a first-pass analysis like what happens in the back of a P-3 today or will happen aboard an MMA," said Dishman.

Auto-classification algorithms are not now part of the BAMS capability, but ISAR returns will also be simulcast to other exploitation facilities.

Unlike the visible light/near-infrared electro-optical payload now on the Air Force Global Hawk, the MTS-B gimbal from Raytheon Space and Airborne Systems, El Segundo, Calif., will enable the RQ-4N to provide streaming video. The Navy BAMS UAS also will introduce Due Regard radar to avoid air-traffic conflicts, either by cuing distant operators or direct interface with the flight controls. "We see telling the ground operator what’s out there and allowing him or her to change the flight path as a stepping stone to a fully autonomous capability," said Dishman.

According to Kreitler, "Obviously, in one sense, it would be optimal for the airplane to be self-aware or autonomous. The man-in-the-loop, where the information gets down to the ground, is the straightforward, simple way."

Northrop Grumman engineers are still conducting trade studies of existing air-to-air radars, but the Due Regard radar will probably be a purpose-built sensor integrated into the Increment One BAMS. Like a manned aircraft, BAMS also will carry a simplified SRVIVR flight data recorder from L-3 Electrodynamics, Rolling Meadows, Ill., for post-mishap analyses.

The Sierra Nevada Merlin ESM system in the Increment One BAMS may give way in Increment Three to Northrop Grumman’s Airborne Signal Intelligence Payload (ASIP) aimed at the Air Force Block 30 Global Hawk. ASIP will look for a broader range of signals and may itself require a different processing architecture.

Navy leaders are still studying BAMS basing options. Fleet planners may consolidate BAMS ground stations at planned P-8 bases in the continentalUnited States, with RQ-4N air vehicles and Tactical Operations Centers deployed overseas. However the BAMS UAS is used, it promises to extend the reach of the maritime patrol and reconnaissance force.

"It’s the unblinking eye of improved situational awareness for the warfighter," Dishman said. "It allows you to have a persistent knowledge of the maritime domain we don’t enjoy today."

RQ-4N BAMS Major Suppliers

Below is a list of some of the major BAMS suppliers provided by Northrop Grumman

Aurora Flight Sciences V-tail assembly, composite structures

L-3 Communications Communications integration

Northrop Grumman Norden Systems Multi-Function Active Sensor

Raytheon Co. Multi-Spectral Targeting System EO/IR sensor

Rolls-Royce North America AE3007H turbofan

Sierra Nevada Corp. Merlin Electronic Support Measures (ESM)

Vought Aircraft Industries Wings

Aim Aviation Crew storage closet

Arnprior Aerospace Sonobuoy Storage Racks

ART Secure Network Server

Avtech FDIU

BAE SMYD and Flight Deck Panels


BE Aerospace ESM Chiller

Beaver Aerospace EO/IR Actuation System

Boeing Acoustics, MMA Program, SMART Weapons System

Brandywine Comm TDS

Cable Technologies Wiring manufacturing

CFM Propulsion

Com Global Systems ISAT

Cox & Company Icing Heater

Curtiss-Wright Controls VIU

Damar Machine Machine parts, assembly and kiting

Data Link Solutions MIDS

DiCon Fiberoptics Secure Switching Unit

DRS Communications Link 11/22

EDO SLS Ejectors


EMS Technologies INMARSAT, CNX

Firetrace Firetube

Flight Dynamics HUD

Fokker Elmo

GE Aviation FMCS, SMS, Heater Controller, Observer Window Controller

GE Aviation Aerostructures Weapons Pylons

Geven Planning Table, Sleeper Seat

Goodrich FQIS, Inlets, Fans, Cowls

Hamilton Sundstrand ECS Fans, Gate/ECS valves, Primary/Secondary Power


Kiddle Aerospace DBFPS

Kildeer Wiring manufacturing

L-3 Comm CDL

L-3 Comm East NSS/DVR

Marotta Controls BRU compressors

Marshalls Aerospace Auxillary Fuel System

Martin Baker Crew Planning Seats

MD NASA Glenn IRT Icing Tunnel Testing

Monogram Mission Seats

Northrop Grumman EGI, ESM, EWSP, IBI

Nurad CDL and ESM Radomes

Orbit Instruments Ordinance Panel

Palomar Products ICS


Patterson Labs Icing Tunnel Models

Pole/Zero AIU (UHF)

Raytheon Radar

Raytheon Systems Ltd. GAS-1

Rockwell Collins IDFCS, V/UHF, HF, ADF, RTP

Sabritec Breakaway Connector

Spirit Fuselage

Teledyne Controls AHMS

Telephonics IFF

Tenix Systems Ltd.
Data Diode

Terma Elektronik AS

Vermont Composites Oxygen Enclosures

Whittaker Controls
Gate/ECS Valves

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