Northrop Grumman eyes IR countermeasures laser systems upgrade

WASHINGTON - A neodymium:yttrium aluminum garnet (Nd:YAG) laser previously demonstrated for the U.S. Army for helicopter avoidance is being considered as an enhancement to the present arc lamp in the AN/AAQ-24(V) directional infrared countermeasures (DIRCM) self-projection suite to be used in fixed and rotary wing aircraft against heat-seeking infrared missiles.

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By John Rhea

WASHINGTON - A neodymium:yttrium aluminum garnet (Nd:YAG) laser previously demonstrated for the U.S. Army for helicopter avoidance is being considered as an enhancement to the present arc lamp in the AN/AAQ-24(V) directional infrared countermeasures (DIRCM) self-projection suite to be used in fixed and rotary wing aircraft against heat-seeking infrared missiles.

Engineers at Northrop Grumman Electronics & Systems Integration International Inc. in Rolling Meadows, Ill., have been under contract since March 1995 to supply the basic DIRCM suite to the British Ministry of Defence.

The $277 million contract covers the first 131 systems, principally for helicopters, Northrop Grumman officials told a briefing at this year`s Association of Old Crows (AOC) conference in Washington. Preliminary work has already begun on the laser upgrade.

The laser, supplied by Fibertek Inc. in Herndon, Va., is a pulsed, Q-switching device operating at a 1.064 micron wavelength, and has also been demonstrated to the German air force. This is a relatively simple add-on to the existing system, say Northrop Grumman officials; it interfaces directly and has built-in test capability. It also increases the weight slightly, from 122.6 to 133.1 pounds, and the transmit power requirement from 2.85 kilowatts to 3 kilowatts.

Given what company officials consider the increased threat of infrared missiles, they are trying to develop the capability for large aircraft such as the U.S. Air Force C-17 airlifter to jam several different kinds of lasers. On these kinds of aircraft, systems mounted under the fuselage could switch from one threat to another. The company is in low rate initial production now on the AAQ-24.

In a presentation to AOC, Northrop Grumman officials stressed the increased threat of second- and third-generation IR missiles, which are deployed with flare rejection circuitry and are thus less susceptible to IR jamming.

Jamming these threats requires high jamming signal levels that must project at all azimuth aspects around the aircraft. Northrop Grumman officials concluded that the broad-beam IR countermeasures of the past can no longer do the job. Today, directional countermeasures are necessary to point a narrow, high-intensity beam at the incoming threat.

This results in a much more complex system that must perform four additional functions not performed in a broad-beam system: (1) detect a missile engaging the aircraft, (2) hand off to a fine-track sensor, (3) track the missile in a clutter background, and (4) direct a narrow beam jamming source at the missile.

There is actually a dual threat, Northrop Grumman experts say. For long-range, short-burn air-to-air missiles, the principal response is in the IR portion of the spectrum. But for the short-range, long-burn IR-guided surface-to-air missiles, company designers propose ultraviolet detectors.

Engineers at the Northrop Grumman Electronic Sensors and Systems Division in Baltimore have developed an ultraviolet passive missile approach warning system, the AN/AAR-54(V), which is in production for all three U.S. services.

Royal Norwegian air force leaders recently agreed to conduct integration and performance demonstrations tests on one of its F-16 mid-life update aircraft. Portuguese air force leaders earlier ordered the system for C-130H aircraft. These systems are built with SEM-E printed circuit cards.

Looking beyond the current threat, Northrop Grumman engineers are working on what they call a distributed-aperture IR system, which would combine six IR sensors for defensive IR search and track, target cueing, and bomb damage assessment.

This system would tie into helmet-mounted displays. Experts at the U.S. Office of Naval Research in Washington have shown interest in this approach for possible use on the future Joint Strike Fighter.

Northrop Grumman experts have been doing some flight testing of the concept with their own BAC 1-111 instrumented test bed aircraft. The system would use SHARC digital signal processors from Analog Devices Inc. of Norwood, Mass.

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The mid-infrared laser from Northrop Grumman Electronic Systems Integration International Inc. in Rolling Meadows, Ill., is in design verification testing and was set for flight tests earlier this year.

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