Business & GA, Military

Enduring Oversight

By Frank Colucci | March 1, 2009
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Promising endurance of up to 52 hours and operating costs a fraction of those associated with fixed-wing or rotary-wing aircraft, the Polar 400 Remotely Piloted Air Vehicle (RPAV) is an appealing new surveillance platform.

Last November, Guardian Flight Systems (formerly Blackwater Airships) teamed with sensor integrator PSI Origin to demonstrate the optionally-manned blimp with Broad Area Persistent Surveillance technology. The 80 megapixel compound focal plane camera flown on the RPAV images 10 times the area viewed by traditional electro-optical sensors and affords nearly twice the resolution.

"The idea is, let’s not look at something through a soda straw; let’s look at everything all the time," explained John Bastedo, PSI Origin vice president.

Airborne data storage and real-time processing help analysts on the ground search hours of down-linked imagery for select events. "You can see where the bad guys go afterwards, and where they came from," Bastedo said. "That’s a forensic capability never available before."

The Polar 400 Broad Area Surveillance demonstration was sponsored by the Office of the U.S. Secretary of Defense, Advanced Systems and Concepts, and managed by the Air Force Research Laboratory. It included a technical evaluation by the Persistent Maritime Unmanned Aircraft Systems office of the Naval Air Systems Command. The U.S. Army, Air Force, and Defense Advanced Research Projects Agency (DARPA) all have broad area surveillance programs.

The "PSiViSiON" system on the RPAV searched for people and vehicles around the Guardian host facility in Elizabeth City, N.C., and sent imagery to a laptop ground viewer via duplex datalink from Microwave Radio Communications, North Billerica, Mass.

"Right now there is a bandwidth limitation," said Bastedo. "But nominally, somewhere between eight and 12 users could be looking at that data at any point in time."

PSI Origin, with offices in Van Nuys, Calif., and Canada, plans to productionize a lighter, turnkey version of the 400-pound demonstrator for various platforms. The company also has a 500 megapixel sensor in the works.

The Polar 400 RPAV is itself a proof-of-concept demonstrator for the slightly larger Polar 450, due in September. Test flown with a safety pilot and flight test engineer aboard, the ultimately unmanned and autonomous, 4,000 cubic meter (140,000 cubic foot) airship carries 2,600 pounds of fuel and mission equipment at altitudes up to 12,000 feet. Like ordinary airships, the diesel powered RPAV burns less fuel in transit and on station than heavier-than-air vehicles.

Unlike traditional airships, with only rudders and elevators for control, the Polar 400 uses vectoring thrusters to maneuver in all three axes. Landing in wind, the RPAV trims the typical ground crew of 12 to 20 handlers to just three or five people.

"It’s got the lowest cost per hour of basically any comparable system," declared Alan Ram, Guardian’s head of production and business development. "A Predator or similarly capable UAV, from a sensor perspective, can cost upward of three, four, five thousand dollars an hour. Our airship, fully loaded, runs about $800 to $1,200 per hour."


The RPAV also provides a benign sensor environment. The hydraulically-driven thrusters enable the Polar 400 to hover or orbit over a programmed area of interest. Cruising speeds are just 20 to 50 knots to simplify motion compensation in the sensor. In turbulent air, the slow response of the airship provides lower accelerations and pitch rates than experienced by small fixed- or rotary-wing UAVs.

"Accelerations are a lot less," one Guardian engineer observed. "You get more in a car than in an airship." Meanwhile, the helium envelope provides a vibration absorber to isolate sensors from engines and other sources.

Guardian engineers also claim the envelope materials give the large vehicle a small radar cross section. They say the shielded engine, captured exhaust, and water recovery ballast system suppress thermal signature. In applications free of air-to-air threats, Ram said, "anywhere you have a fixed-wing aircraft flying in circles, you should have an airship instead."

PSI Origin did much of its early broad area surveillance work on helicopters and solved the jitter, bumping, and blurring problems associated with rotorcraft and small airplanes. The Polar 400 nevertheless offered a comparatively smooth, spacious carrier for the system.

"It’s a very good platform for this sort of work," Bastedo said.

The RPAV demonstrator hauls up to 1,000 pounds in its cockpit/payload module, and it can accommodate radars or other equipment inside its helium envelope. The PSiViSiON sensor gimbal flew in an aerodynamic fairing previously used on a Cessna Caravan testbed. The system power supply, processing bank, and data storage system filled a 19-inch rack.

PSI Origin is a division of vision systems integrator PV Labs, of Burlington, Ontario. It has culled broad area surveillance expertise from Lawrence Livermore National Laboratory, L3 Wescam and UAV manufacturer General Atomics Aeronautical Systems. (PV Labs counts four of the original 10 Wescam founding investors on its management team.)

The PSiViSiON system is designed to search large areas automatically and cue ground analysts to changes in largely unchanged scenes. "The predominant cost in broad area persistent surveillance is you need analysts to look at it all," said Bastedo.

The 80 megapixel electro-optical sensor in the PSiViSiON system is based on commercial Kodak 16 megapixel imaging chips arrayed in a common focal plane for best image quality in a wide footprint.

"You’re basically taking a bunch of lenses and putting a bunch of cameras behind them, so you can put more than one chip behind one lens," Bastedo said.

Common 1 or 2 megapixel UAV sensors with a relatively wide, 35-degree field of view, image about 6.5 square kilometers with 2 meter resolution from 15,000 feet. The 80 megapixel sensor flown on the Polar 400 has a 90-degree field of view and covers a trapezoid of 65 to 100 square kilometers with 0.75 meter best resolution. PSI Origin developed advanced calibration and matching capabilities to stitch together and rectify the scene in real-time with sub-pixel accuracy.

The current PSI sensor is a day-only electro-optical imager in a three-axis gimbal. "We can go pretty low-light with various photographic techniques," explained Bastedo. "Technically speaking, it’s not a low-light technology camera."

Low light and infrared sensors remain in development, but according to Bastedo, "the dollars per pixel on infrared are dramatically greater."

The current PSiViSiON system stores or downlinks about 1 terabyte of data per hour. "When you’re collecting that much data at such high resolution, you get into a data processing challenge," Bastedo acknowledged.

PSI Origin real-time processing technology reduces the volume of data to be moved and enables analysts to zoom-in on any place in the footprint and rewind to any point in the timeline. Data cubes store 10 to 12 hours of data and can be ganged for longer surveillance.

The demonstration system used a mobile ground unit from CRI, of Kyle, Texas. Analysis stations in a production system would be tailored to the application. Computationally-intense tracking algorithms can now follow cars or other objects. Custom systems would integrate aircraft altitude, speed, and other parameters of the camera, processor, and storage or transmission system to provide desired information.

"You bore down in that massive footprint to what you can actually see," said Bastedo. "It ends up being driven by the environment, the end user."

Guardian Flight Systems began in 2006 to develop affordable, remotely piloted airships with vectored-thrust propulsion for military, police and non-government users. Airships typically have engines and propellers mounted on their gondolas, but Polar 400 engineers put lightweight hydraulic propeller drive motors directly on the reinforced helium envelope. At low airspeeds, when conventional tail surfaces are ineffective, the patented vectored thrust arrangement uses a lateral tail thruster for yaw control and side thrusters for differential pitch and roll control.

The single-engine Polar 400 demonstrator uses electromechanical engine controls and mechanical hydraulic controls. The twin-diesel Polar 450 will integrate digital controls on the variable-speed engines and thruster hydraulics. "It’s a little smoother operation, another layer of integration," said Ram.

The piloted Polar 400 demonstrator first flew in November 2007 and received its remote flight-control hardware in January 2008. The digital control system was adapted from equipment developed by L-3 BAI Aerosystems, manufacturer of the lightweight, fixed-wing Viking UAV. A Controller Area Network (CAN) data bus architecture carries communications between flight sensors and controls. The airship payload uses either the CAN or an Ethernet bus to feed the downlink.

The Polar 400 demonstrator is programmed with autonomous flight plans through an L-3 BAI-specific Ground Control Station (GCS). The Polar 450 will use a generic GCS, according to Ram. "We’re migrating to a more common ground station, whether the [AAI] Army One system or one of those configurations common to the U.S. military and NATO."

Significantly, the Polar 400 demonstrations have also shown potential for customers who may want an optional pilot aboard for some missions. A border patrol operation flying in the continental United States under an FAA Certificate of Authorization, for example, might use an on-board pilot from the factory to eliminate disassembly, shipping and reassembly costs.

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