Electronic Eyes Aid Soldiers and Sailors.

Unmanned aircraft get improved sensors, but some equipment still costs too much

The ability to package electronics and sensor payloads into small unmanned aircraft will deter mine how successfully these vehicles will perform in combat, officials said. Powerful sensors on small aircraft could help, along with other weapon platforms, to strip the confusion from the battlefield.

Both the U.S. Army and Navy are investing in programs to push this technology.

The Army, for example, is considering deploying hunter-killer teams with tactical unmanned air vehicles (TUAVs) to locate and designate targets for the Longbow Apache and Comanche attack helicopters. "I think there's tremendous opportunity for the synergy of TUAVs and helicopters," says Edward Bair, the Army program executive officer for intelligence, electronic warfare and sensors. The crew of an AH-64 Apache controlled the flight path and sensors of a Hunter UAV last July. "A TUAV is not the end-all in itself," he said. "We need to correlate multiple sensor inputs into a relevant picture."

Bair manages the development, acquisition, testing, fielding, support and improvement of TUAV sensor payloads. The Navy's program executive office for cruise missiles and joint unmanned aerial vehicles has responsibility for the sensors in the service's vertical-takeoff UAV, or VTUAV.

The so-called Outrider advanced concept technology demonstration in 1998 showed that one UAV could not satisfy the operational requirements of the Army and the Navy. The 535-pound Outrider was too big for the Army to deploy and launch rapidly in the field. Like the small Pioneer UAV currently used by the Navy, the fixed-wing Outrider would have required clumsy recovery gear and more human labor aboard Navy ships. The two services consequently ordered different vehicles with different sensors.

Two Platforms

To give brigade commanders a responsive reconnaissance asset quickly, the Army plans to buy 44 TUAV systems, integrated by AAI Corp., in Hunt Valley, Md. Each system includes four Shadow 200 air vehicles-- three operational and one spare. The Block I or "threshold" air vehicle is expected to loiter for four hours, 50 kilometers (36 nautical miles) from its launch point with an electro-optical/infrared (EO/IR) payload. Block II introduces an advanced EO/IR payload, multi-mode radar and a basic communications relay payload.

The Army selected the Shadow 200 as its TUAV in December 1999. Initial operational capability is scheduled for July 2002.

The Navy intends to use the Firescout VTUAV system to support aviation-capable ships and Marines ashore. Each system--integrated by the Northrop Grumman Ryan Aeronautical Center, in San Diego, Calif.-- includes three Schweizer Model 379 unmanned helicopters. The rotary winged VTUAV is required to fly from small decks and unprepared shore sites and loiter for six hours, 110 nautical miles (154 kilometers). It will enter service with an EO/IR payload and voice-only communications relay pay load. The Firescout contract calls for 12 Navy and 11 Marine systems to be operational by 2003.

Despite having separate programs, the Army and Navy exchange payload data and seek an open architecture that accommodates future payloads without extensive changes to air vehicles, data-links, ground stations and software. Unlike the highly-integrated sensors in the Army's Comanche armed reconnaissance helicopter, small UAV payloads are largely segregated from their air vehicles with separate software builds and simplified interfaces to minimize integration costs and speed payload changes.

The Army Training and Doctrine Command has prioritized sensors for the brigade TUAV and expects to add a synthetic aperture/moving target indicator radar (SAR/MTI), communications relay payloads, hyper-spectral and ultra-spectral imagers and laser rangefinder/designators.

While the Navy has not yet funded radar or other advanced sensors for the VTUAV, the Firescout is expected to acquire signals intelligence (SIGINT), communications/data relay and other payloads. The Pioneer UAV already has demonstrated toxic chemical agent detectors and mine detectors.

The Defense Department wants sensors to be "affordable" to allow for UAV attrition. More than 20 NATO unmanned aircraft were shot down over Kosovo in 1999. Bair observes, "The problem is if you have a $100,000 'attritable' air vehicle, and you put a million-dollar payload on it, it kind of defeats the purpose of your attritable air vehicle."

Larger, more costly air vehicles can mix sensors. The Air Force RPQ-1A Predator medium altitude endurance UAV (MAE-UAV), built by General Atomics, weighs 2,100 pounds and carries a 450-pound payload. It routinely flies with both the Wescam 14TS EO/IR sensor gimbal and the AN/ZPQ-1 tactical endurance synthetic aperture radar (TESAR) made by Northrop Grumman Corp.

On the same mission, the multi-sensor suite returns color video imagery in daylight, infrared imagery at night and high-resolution radar imagery through thick cloud, day or night.

The Air Force operates the Predator from 5,000-foot runways. The Army Shadow will be shot from a mobile hydraulic launcher. It weighs 325 pounds and has a 60-pound payload, forcing brigade commanders to choose payloads for specific missions. The Navy Firescout is a 2,550-pound helicopter with a 200-pound payload, potentially big enough for two or more sensors.

The Army wants the maneuver brigade commander's TUAV in service quickly to avoid repeating the past disappointments of Aquila and other UAVs. "We overburdened potential air vehicles and tried to get them to do too much, too soon," says Bair.

The TUAV will enter service with an off the-shelf EO/IR payload. The POP (plug-in optronic payload) 200 from the Tamam Division of Israel Aircraft Industries was used in the Outrider demonstration and impressed observers during the TUAV flyoff at Fort Huachuca, Ariz. The stabilized 11-inch gimbal contains both daylight color television and thermal imaging forward looking infrared (FLIR) sensors. Unlike the EO/IR payload of the Predator, the baseline sensor for the TUAV has no laser rangefinder/designator/spotter.

The POP 200 thermal imager uses a 320 by 240 pixel indium antimonide (InSb) focal plane array operating in the 3 to 5 micron portion of the IR spectrum. The bigger, more costly second-generation thermal imagers going on the Army's Comanche and Long bow Apache helicopters and Abrams and Bradley armored vehicles are based on long-wave 8 to 12 micron focal plane arrays with mercury cadmium telluride detectors. Mid-wave 3 to 5 micron thermal imagers offer advantages for a small TUAV flying at 6,000 to 8,000 feet, above most battlefield dust and smoke.

Mid-wave thermal detectors exploit the better atmospheric transmittance of the 3 to 5 micron band in both warm, humid and hot, dry climates. They are also able to pro vide clear imagery at longer ranges given the smaller optical components packed in UAVs. Wavelength alone gives mid-wave thermal imagers 2.5 times better resolution than long-wave sensors with the same size optics. The 3 to 5 micron FLIRs enable $120,000 to $150,000 sensors to detect and identify targets at longer ranges.

The baseline EO/IR sensor meets Army target detection requirements at 3 kilometers. An advanced payload is under development to enable users to detect and recognize targets at greater ranges. Wescam received a contract for the enhanced TUAV EO/IR sensor in February 1999, and the new payload will be tested on a Hunter UAV in June 2001.

Sized for the Shadow 200, the 40-pound EO/IR payload integrates a Sony charge-coupled device television camera and a new thermal imager from BAE Systems with a laser rangefinder/spotter. The new FLIR uses a 640 by 480 pixel InSb focal plane array and pro vides fields between 20 degrees down to 2 degrees to match those of the television camera. Image fusion of infrared and visible light sensors could uncover details invisible to either.

Compared to the analog-to-digital imagery provided by the optical sensors on Pioneer and Predator, the all-digital output of the enhanced TUAV sensor initially promises imagery with greater range and resolution. Assisted target detection/classification (ATD/C) like that performed in the Comanche is not possible today in a small TUAV. Bair explains, "The UAV would be able to have only limited processing capability. If you knew the types of threats you might encounter, it's conceivable that you could have the processing power to identify those threats." Even without on-board ATD/C, high resolution digital imagery down-linked to ground stations or attack helicopters might be processed to uncover and identify targets lost to unaided eyes.

The enhanced TUAV sensor also will provide wide-angle surveillance on a digital battlefield. The Wescam 12DS sensor on the Pioneer UAV rotates at 60 degrees per second, controlled by a ground operator. The new TUAV sensor gimbal rotates automatically at 1,000 degrees per second, imaging one frame at a time, to build a battlefield mosaic. Ground-based and airborne users could zoom in on suspected targets digitally and enhance pictures pixel by pixel.

Sensor stabilization is needed for clear long-range imagery and accurate target location. While the Pioneer and Predator payloads were stabilized within 25 to 35 micro-radians, the enhanced EO/IR gimbal will hold steady within 5 to 10 microradians. The TUAV payload will incorporate a laser rangefinder/designator/spotter to fix locations accurately, designate targets for Hellfire missiles and other guided weapons, and mark targets for ground troops and aircrews wearing night-vision goggles.

Under an Army contract, Northrop Grumman is delivering the last of 82 AN/ZPQ-1 TESARs for the Air Force Predator. TESAR is a Ku-band synthetic aperture radar with 1-foot (0.3 meter) resolution. It can sweep a broad strip or spotlight areas to reveal small targets with striking clarity. The 800-meter wide strip image reveals only stationary objects, but TESAR has demonstrated MTI capability. Flight trials with commercial Power PC microprocessors are scheduled in May.

Northrop Grumman won a contract in April 1998 for a combined SAR/MTI radar to fit the Army TUAV. While the Predator TESAR weighs approximately 165 pounds, a production TUAV-R has to weigh 57 pounds and fit the 7-inch ground clearance under the Shadow 200. A 63-pound version of the TESAR has been flying in an Islander testbed aircraft since November 2000 and is scheduled to fly in a Hunter UAV in March. A radar could be available in 12 to 18 months.

Army cost goals call for the small radar to deliver 60 to 75 percent of the performance of the $800,000 to $1.1 million TESAR for around $400,000. The TUAV-R will pro vide 1-meter and 0.3-meter SAR resolution and image a 500-meter wide strip.

Firescout Eyes

The baseline sensor for the Navy/Marine VTUAV is the Tamam U-MOSP (UAV multi-mission optronic stabilized payload). Tamam, a subcontractor to Northrop Grumman, will deliver the first U-MOSP payloads to the Ryan Aeronautical Center for integration in May 2001. First flight of the VTUAV with its EO/IR payload is scheduled for spring 2002.

The U-MOSP contains a FLIR, TV and laser rangefinder/designator. Tamam considers the high resolution 3 to 5 micron InSb thermal imager a third-generation FLIR with 50 to 100 percent greater range than the first-generation technology flown in early UAVs. The FLIR provides three fields of view from 13.5 to 0.75 degrees while the continuous-zoom TV ranges from 13.75 to 0.75 degrees.

Army sensor requirements for a division level TUAV differ from those of the brigade only in making a hyper-spectral sensor a higher priority than a laser rangefinder/designator.

Unlike thermal imagers working in discrete-IR bands, passive hyper-spectral payloads create a larger number of images from contiguous regions of the electromagnetic spectrum to penetrate heavy foliage. The Army is monitoring work by the Defense Advanced Research Projects Agency (DARPA) on hyper-spectral sensors. According to Bair, "From a capabilities standpoint it's intriguing. From a size and cost standpoint, it's exorbitant."

The Army and DARPA are studying future TUAV sensors. The division TUAV signals intelligence program expects to out fit additional Shadow 200 air vehicles with SIGINT payloads.

DARPA is looking to scale a communications relay payload sized for the big Global Hawk down to the small TUAV. However, relay payloads are still too big to share the 1 cubic-foot payload bay and 1-kilowatt payload power supply of the Shadow 200.