Tuesday, June 1, 2004
Improved sensors and integrated night vision systems show helicopter crews a clearer, bigger picture after dark
From the 24-hr. battlefield to tense homeland security missions, helicopter night vision systems are essential warfighting and surveillance tools. Advanced image intensifiers, thermal imagers, television cameras and lasers already show helicopter crews sharper imagery at greater distances to navigate terrain, identify friends and target enemies after dark. As night vision technology improves, greater systems integration will fuse multiple sensors with digital maps and other avionics to put the cockpit pictures in context.
Airborne night vision systems for military and law enforcement still differ in price and performance, but better technology for both markets expands the helicopter operating environment and enhances mission effectiveness. Lockheed Martin is replacing the Common Module thermal imagers on U.S. Army Apaches with second-generation Forward Looking Infrared technology that acquires targets at twice the range.
FLIRSystems Inc. has integrated tri-sensor gimbals that enable British Sea Kings to conduct extended range surveillance day or night. L3 WESCAM has introduced multi-sensor gimbals with infrared laser area illuminators on Memphis Police Department JetRangers to assist ground units operating with night vision goggles.
Image Intensifying (I2) Night Vision Goggles amplify ambient light thousands of times to help pilots navigate. For the Army, the current state of art is ITT's AN/AVS-6(V)3 Aviators Night Vision System (ANVIS). Goggle performance and U.S. government export restrictions are defined by the I2 figure of merit.
While early ANVIS tubes had a figure of merit around 580, new AVS-6(V)3 tubes for the U.S. military exceed 2000. Close U.S. allies can buy tubes rated 1,600, but goggle sales to other nations are capped at 1,250.
ITT is the sole AVS-6(V)3 supplier under the current Omnibus VI contract as the Army upgrades all its goggles to (V)3 intensifier tubes. Deliveries started in February 2003 will continue through Fiscal 2006. Though all ANVIS goggles use third-generation I2 tubes, the AVS-6(V)3 introduces Pinnacle thin film technology and gated power supplies to provide clear imagery despite overcast nights or bright urban environments.
NVG Head-Up Displays from Elbit, CMC, and other manufacturers have long injected flight symbology into the pilot's Field Of View on the Bell Boeing V-22 tilt rotor and a range of helicopters. In trials last November, a pilot from the National Research Council of Canada's Institute for Aerospace Research (NRC-IAR) flew a Bell 205 to a night landing following a computer-generated flight path superimposed on his goggles. A GPS/inertial navigator and terrain model matched the aircraft position to a flight plan composed on a digital map. A precision laser-based head tracker from Ascension Technologies linked the NVG field of view to the computer-generated flight path. The Canadian government tests are aimed at commercial development.
The Thales TopOwl Integrated Helmet Mounted Display Sighting System going aboard Bell UH-1Y and AH-1Z helicopters for the Marine Corps superimposes flight, navigation, and targeting symbology over day or night scenes. The TopOwl system currently incorporates ITT Omnibus IV tubes, and though the AH-1Z has no pilotage flir yet, the same helmet will enable German Tiger pilots to view I2 imagery from helmet tubes or thermal imagery from the Pilot Visionics System on the nose.
Advanced Army Flirs
Thermal imagers register infrared (IR) energy from objects in the environment, and second-generation Forward Looking Infrared technology uses larger, more sensitive scanning infrared detector arrays to see more. The U.S. Army killed the Boeing Sikorsky RAH-66 Comanche before the new armed reconnaissance helicopter could prove its full Lockheed Martin Electro Optical Sensor System (EOSS). However, Comanche second-generation flir technology lives on in the Arrowhead Modernized Target Acquisition and Designation Sight (M-TADS) and Modernized Pilot Night Vision Sensor (M-PNVS) for the Boeing AH-64 Apache.
Remanufactured Block I AH-64D Longbow Apaches retained the Common Module thermal imagers, day TV, Direct View Optics, and Hellfire laser designator of the AH-64A. However, AH-64D Block II modernization enables the Army to replace first- generation Common Module TADS/ PNVS FLIRs with second-generation technology. Like their predecessors, the M-TADS/PNVS FLIRs are long-wave (eight to 12 micron) thermal imagers favored by the Army for their performance in dust, smoke and other battlefield obscurants. They nevertheless exploit higher-resolution 640 by 480 pixel focal plane arrays to double range and enhance image clarity. The M-PNVS with its sharper flir and integrated image intensifier should help Apache pilots spot cables and other subtle hazards. M-TADS with flir and I2 TV meanwhile affords greater target acquisition and recognition range and is cued by the Longbow radar to help positively identify targets automatically classified by the millimeter wave sensor. The M-TADS/PNV upgrade S also introduces improved stabilization, automatic boresighting, and reliability improvements to cut operating and support costs.
M-TADS first flew in November 2003 and should be fielded in Block II AH-64Ds by June 2005. The U.S. government looks to buy 704 systems for all modernized AH-6Ds and early AH-64As; however, another round of modernization makes it possible to incorporate even more Comanche technology in the Block III Longbow Apache. Block III M-TADS fuses flir and I2 imagery to reveal targets invisible to either sensor alone. It applies Northrop Grumman Assisted Target Detection and Recognition algorithms to cue the crew to targets hidden in clutter. The M-TADS laser in Block III offers tactical, eye-safe, and MILES training modes, and a color television camera replaces today's monochrome TV sensor. Apache Block III flirs may also mix long- and mid-wave (three- to five-micron) IR detectors to see through any atmosphere, and improved daylight elements may better spot tracers and laser markers on the ground. The further-modernized Apache may also lose its monocular Integrated Helmet Display and Sighting System for the biocular Rockwell Collins Helmet Integrated Display and Sight System from the Comanche.
Neither the modernized Boeing CH-47F Chinook nor the Sikorsky MH-60M Black Hawk are slated to receive flirs, but the Army is again in the market for an armed reconnaissance helicopter, potentially based on the AH-6 Special Operations Little Bird. Special Operations helicopters, and many other aircraft, have long used the Raytheon AN/AAQ-16B first generation, long-wave flir for navigation, surveillance, and targeting. Follow-on versions with second-generation, long-wavelength flir provide multiple fields of view and a laser designator. The latest version on order for MH-47s, MH-60s, and MH/AH-6s is tentatively designated the AN/ZSQ-1(V) with flir, I2 television, and laser designator, tracker, or pointer. On the MH-47E/G and MH-60K/M, the navigation flir is integrated with a Raytheon APQ-174B terrain-following/terrain avoidance radar to penetrate deep into hostile airspace at low altitudes under cover of darkness and adverse weather.
While long-wave thermal imagers are the Army's preference for dusty desert environments, mid-wave infrared detectors generally provide greater sensitivity in hazy, humid maritime applications. The choice is nevertheless up to the customer, and the Navy's sophisticated new MH-60R Seahawk uses the Raytheon AN/AAS-44(V) sensor set with a long-wave, second-generation FLIR. Compatible with the Seahawk's 1553B databus, the AN/AAS-44(V) provides real-time image processing with contrast enhancement for targeting. It incorporates day TV and a dual-mode video tracker with provides multiple fields of view. Mounted on the nose of the Seahawk, the AAS-44 with six-axis stabilization has a designator for Hellfire missiles and other laser-guided munitions.
The Marine Corps opted for the Raytheon AN/AAQ-27 on the MV-22 Osprey. The amphibious assault tilt rotor sensor uses a mid-wave third-generation staring array for exceptionally clear imagery in humid environments. It has a 30- by 40-degree field of view at unity and a 5- by 6.7-degree FOV at 6X magnification. The same flir is integrated with a Raytheon AN/APQ-186 radar on the Air Force Special Operations Command CV-22. The similar AN/AAQ-29 with three fields of view equips Sikorsky CH-53Es of the Marine Corps and the Kaman SH-2Gs and Sikorsky S-70Bs of the Royal Australian Navy.
Marine Corps Bell UH-1N scout/ utility/command-and-control helicopters flying in Operation Iraqi Freedom have the FLIRSystems Inc. Brite Star flir. The sensor gimbal packages a 320 by 240 pixel mid-wave flir with a day television, 1.06 micron tactical laser, and an eye-safe laser rangefinder. The modernized UH-1Y now in testing introduces a Block II Brite Star with a 640 by 480 pixel array.
The upgraded AH-1Z attack helicopter is due to receive the Lockheed Martin Hawkeye XR or Target Sight System (TSS) with a large-aperture mid-wave flir, color TV, laser designator/ rangefinder, and laser spot tracker. The TSS is moving into Low Rate Initial Production, and two Engineering and Manufacturing Development units have so far exceeded expectations. It is competing in Turkey to equip the locally-produced Bell King Cobra and may be a viable upgrade for AH-1Fs still in service with many nations.
Until the AH-1Z replaces the last AH-1Ws in Marine Reserve light attack helicopter squadrons, the current SuperCobra Night Targeting System (NTS) will remain in service. Kollsman Inc., now part of Elbit, completed NTS deliveries last year and is working on upgraded NTS-U systems for 40 AH-1Ws in the Marine Reserve. The NTS-U replaces the long-wave, first-generation scanning flir now in service with a mid-wave, third-generation staring array.
Sharp Eye of the Law
Though airborne law enforcement continues to buy lighter, less costly sensor packages than those sought by the military, the performance and reliability requirements of both communities are converging. FLIRSystems, for instance, follows a Commercially Developed/Military Qualified path for all its products. The Block I Star SAFIRE III system used by U.S. Customs and the U.S. Forest Service evolved into a Block II version that fuses third-generation flir and I2 imagery on Australian P-3 patrol aircraft. A Star SAFIRE III electro-optical payload will be integrated into the Bell Eagle Eye Vertical Takeoff and Landing UAV (VUAV) planned for the U.S. Coast Guard Deepwater modernization.
The L3 WESCAM MX-15 gimbals flying on the Bell 412 of a major U.S. police department and the MD Explorer of the Manchester U.K. police use the same large 640- by 480-focal plane arrays found in military systems. The entire MX- gimbal family from 12 to 20 in. diameter uses common cameras, common control electronics, and, where possible, common optics.
More sophisticated systems can exploit entirely different helicopter sensors. BAE Systems Solutions and the U.S. Army Aviation Applied Technology Directorate plan to demonstrate a Radar-Enhanced Vision System (REVS) on a CH-47 Chinook this summer to try the fused sensors in brown-outs and other obscured-visibility conditions. REVS will use a millimeter wave radar and an uncooled infrared camera. While the thermal imager generally provides better image resolution than the 94 GHz radar, the millimeter wave picture is unaffected by dust that degrades an optical sensor. Test pilots will see optical, radar, or fused imagery on a cockpit display. A productionized helicopter REVS might include laser radar for cable detection and the BAE TERPROM digital map to provide terrain following cues on a helmet display.
Farther off, commercial and military night vision systems may benefit from uncooled FPAs and sophisticated image fusion algorithms. Raytheon engineers suggest distributed aperture systems in which several fixed sensors replace a stabilized gimbal to reduce cost and weight and improve reliability. With multiple sensors and systems working together, the power of night vision sensors may be greater than the sum of the parts.