The ability to package electronics and sensor payloads into small
unmanned aircraft will determine 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
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.
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 payload. 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
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 Longbow Apache helicopters
and Abrams and Bradley armored vehicles are based on long-wave 8
to12 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
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 provide 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
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 provides
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
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
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
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 provide 1-meter and 0.3-meter SAR resolution
and image a 500-meter wide strip.
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 outfit 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.