Broad Area Maritime Surveillance Radar Northop Grumman

Northrop Grumman boasts that its bid for the U.S. Navy's Broad Area Maritime Surveillance (BAMS) competition is the only one to actively execute end-to-end testing. Central to the company's proposal for the high-profile program is its Multi-Function Active Sensor (MFAS), a 360-deg. radar capable of identifying and tracking ships. Together with the Boeing P-8A Multi-Mission Aircraft, BAMS will replace the Navy's P-3 surveillance fleet. Aviation Week & Space Technology got a behind-the-scenes look as Northrop Grumman demonstrated its prototype BAMS sensor on a test flight Aug. 17, during which operators collected images and data on specific targets. Information was transferred to a prototype mission control station (MCS) located in Hollywood, Md. The demonstration forms a key part of Northrop Grumman's Head Start risk-reduction effort for the $2-billion BAMS program. Boeing and Lockheed Martin are also competing for the bid, but Northrop Grumman is banking on its Head Start initiative to cut risk significantly and build performance margin as well as confidence, both externally and internally. "As far as we know, no one else is doing end-to-end testing," says Robert Wood, Northrop Grumman's business development director for maritime intelligence, surveillance and reconnaissance systems. From 28,000 ft., the Mojave Desert below was obscured by a thick layer of smoke drifting in from coastal California wildfires, but thanks to the aircraft's electronic eyes, the view of the ground from onboard workstations was a different story. A column of clearly defined tanks was the first image to appear on the tracker display in the aft of Northrop Grumman's Gulfstream GII flying testbed as it flew toward the Pacific coast. Illuminated by the active electrically scanned antenna (AESA) radar hung below the belly in a bucket-like cupola, the synthetic aperture radar (SAR) image captured the targets as they stood in the vast openness of the Navy's China Lake test site, more than 40 naut. mi. away and receding further by the second. BAMS is being developed to provide the Navy with persistent maritime surveillance and reconnaissance capability with worldwide access as a major part of its Sea Power 21 strategic vision. In contrast to the manned GII demonstrator, the BAMS requirement calls for a series of unmanned air vehicles (UAVs) to provide long-endurance coverage of the world's oceans. Operating mostly at altitudes over 40,000 ft., above the weather and most air traffic, the UAVs will be fully integrated into the Defense Dept.'s intelligence, surveillance and reconnaissance (ISR) architecture, providing this information to the joint force in near-real time. Threshold requirements include the ability to maintain, with 80% reliability, an effective time on station (ETOS) of around seven days at 2,000-naut.-mi. mission radius with no more than three air vehicles, as well as a target ETOS of 95% and a 3,000-naut.-mi. mission radius. Northrop Grumman's proposal is based on the RQ-4N, a hybrid combining the structure of the Air Force's Block 20 RQ-4B Global Hawk and systems elements of the later Block 30. Using this, Northrop Grumman believes the threshold requirements are achievable with only two aircraft, and three aircraft will meet the objective of 95% effectivness. "We're convinced this is the right platform because of the simulations we've done," says the company's BAMS Head Start program manager, Bill Beck. "The big deal to us is being able to fly at altitude. It's a good place to be for endurance and fast transit capability," he adds. The RQ-4B Block 20, which entered flight tests Mar. 1, can cruise at 310 kt. and operate up to 65,000 ft. Competing BAMS proposals are the Boeing/Gulfstream G550 -- a variant of the business jet adapted for unmanned operations -- and the Lockheed Martin/General Atomics Mariner medium-altitude UAV, which is derived from the Predator family. The Head Start initiative is broken into four main elements of which the GII flying testbed forms one sub-part. A big focus has been on payload demonstrations, including tests of the Night Hunter II 900-2 electro-optical/infrared sensor on both the company's Beech King Air testbed and NASA's high-altitude WB-57 research aircraft, as well as recently completed tests of the radar and "network-ready" communications systems on the GII. Other elements include MCS prototype and simulation, tests of Navy-specific RQ-4 airframe modifications for higher loads as well as ice and corrosion protection, and actual long-lead manufacturing for early tests under production Lot 7. "We're off to the races, and have bought long-lead items for airframe tests," says Beck, also noting that work is underway to clear modifications designed for the BAMS mission. Bird strike tests have been successfully undertaken on a beefed-up wing leading edge, which has also been fitted with an ice-protection system, he says. The GII was acquired for the BAMS "man-in-the-loop" test role in March 2006, and initially outfitted with multiple narrow-band communications systems, a sensor management unit (SMU) and an advanced mission management system (AMMS) -- the latter unit is a key element of the Northrop Grumman BAMS proposal. The company originally planned to use one of the Block 0 Global Hawk test aircraft, but those were obligated to other priorities. The SMU monitors and controls the sensor payloads, and will ultimately be "absorbed" into the more sophisticated AMMS, says Head Start Flight Test Program Manager Matt Shihadeh. Together the two units represent "the hub of the whole thing," adds Beck. Bristling with antennas in April, though yet not at this stage fitted with either BAMS representative radar or communications suites, the GII conducted 10 hr. of Phase 1 BAMS tests to validate the use of an Internet Protocol (IP)-based wireless network for real-time data transfer. Picking up ship tracking information through a ventrally mounted automatic identification system (AIS) antenna, the data was then sent through independent narrow-band UHF and L-band communications links to a truck-mounted ground station based in the parking lot of Northrop Grumman's Camarillo facility close to the coast northwest of Los Angeles. From here, the data was sent in near-real time via Northrop Grumman's company intranet to the prototype MCS in Hollywood, Md. For the Phase 2 mission systems demonstration, the company took the process forward to integrate BAMS representative radar and data link systems, as well as multi-site ground network connectivity. The GII, which is now being modified for another Northrop Grumman project, was fitted with the prototype multifunction active sensor (MFAS) version of the AESA radar, as well as a dual Ku/X-band common data link (CDL). The forward CDL was chin-mounted while the aft was mounted on a ventral fin beneath the tail. The initial CDL data transmission rate was 10 Mbps., "but the finished product will run at 274 Mbps.," adds Beck. To further emphasize its relevance to BAMS, the dual CDL IP system in the testbed was, like the EO/IR system, also identical to that selected for the Boeing P-8A multi-mission maritime aircraft with which BAMS will work. The AIS antenna was retained, as was an upper-fuselage-mounted LN-100 navigation antenna which had been augmented with an air scoop for two heat exchangers. "The radar is a big deal to us," says Beck, who describes the two-dimensional AESA as a direct descendent of the APY-6 X-band, multimode, air-to-ground radar evaluated on the Navy's NP-3C Hairy Buffalo testbed. The APY-6 moving-target-indication (MTI) radar simultaneously overlaid images of terrain and structures with moving targets, and in 2004 the NP-3C testbed was the Navy's only MTI-radar-equipped aircraft. "When it turned into AESA, we picked up where they left off," says Beck. Also being tested on the GII is the liquid radar's cooling system that will be used on the BAMS, says Tom Twomey, business development director for Northrop Grumman's high-altitude long-endurance systems. In its MFAS AESA configuration, the radar was situated in a bulbous housing below on the GII's belly and could be mechanically gimballed in azimuth and elevation. As well as APY-6 heritage, the unit also incorporated elements of the AN/APG-77 F-22 Raptor radar, APG-80 F-16 Block 60 unit and APG-81 F-35 sensor, as well as the MP-RTIP (Multi-Platform Radar Technology Insertion Program) currently being developed for the RQ-4B. The radar is capable of 360-deg. coverage, while the BAMS requirements call for 270 deg. of coverage. Wood says the extended coverage is a clear advantage of his company's proposal over those of competitors. An Aviation Week reporter joined the 10th Phase 2 flight test -- the eighth flight test for the radar -- aimed at further radar and communications systems check-out, part of which involved transmission of data to the MCS. After takeoff from the test team's base in Mojave, Calif., Northrop Grumman BAMS Project Chief Test Pilot Roy Martin brought the aircraft to 28,000 ft. before crossing the coast at Santa Barbara. Several radar calibration spot SAR and ISAR (inverse SAR) images were made of land targets en route, before maritime surveillance, 360 deg. and sector scanning modes were tested. According to officials at the MCS, during a single 2-hr. test flight earlier this year, the radar collected 6,000 ISAR returns. One of the technical challenges for the competition will be developing radar modes capable of distinguishing small targets from "clutter," or false returns from the ocean's surface, Twomey says. Much of the flight-test program for MFAS is focused on exploring tweaks to algorithms for the maritime surface surveillance mode. "Ongoing post-flight data analysis allows us to adjust the maritime search post-processor software," he says. Ships provide AIS data, a passive signal delivering information on vessels at sea, and this was also uploaded and transmitted to the MCS. Attempts to send images of Phantom, a Northrop Grumman ship acting as a cooperative target standing off from the coast near Point Mugu, were frustrated when the testbed developed a hydraulic system fault, forcing an early return to Mojave. Officials at the MCS say that despite the hydraulic problem, at least 40% of the mission's goals were achieved and the radar was operating for about 90 min. Northrop Grumman says its strategy in developing the MCS is to integrate the system into existing Navy ground stations. Twomey says the company doesn't want to build any "prima donna" equipment that will not interface with existing workstations used by the Navy. Another Aviation Week reporter viewed the data at the company's Hollywood, Md., facility, where there is also what Northrop Grumman officials call a "podule," a small portable facilty used to demonstrate various methods of displaying data from the GII. At the podule, operators were able to visually fuse data from the prototype MFAS radar with open source data, including satellite imagery and AIS shipping information. Though the extensive displays are not part of the formal BAMS proposal, Northrop Grumman officials emphasize that improved displays can enhance the Navy's ability to make maritime surveillance more responsive and effective in near-real time. By the time of its final tests in late August, the GII amassed 19 flights and almost 50 hr. of tests in Phase 2. "We're satisfied about our progress to date, particularly with AMMS and how it's glued all the elements together," says Beck. "The radar data is proving to be a gold mine, and everything we're seeing to date is confirming that." Navy officials are expecting to announce a BAMS winner as soon as October. Initial operational capability is set for 2013. Australia, a partner in the development effort, expects to buy up to nine BAMS aircraft.