IEC lends precision guidance to artillery shells with satellite navigation

Sept. 1, 2001
Engineers at Raytheon Missile Systems Co. in Farmington, N.M., seek to use satellite navigation to guide U.S. Army artillery shells to their targets.

By John McHale

ANAHEIM, Calif. — Engineers at Raytheon Missile Systems Co. in Farmington, N.M., seek to use satellite navigation to guide U.S. Army artillery shells to their targets.

To do this, Raytheon experts are installing selective-availability anti-spoofing module (SAASM)-based Global Positioning System (GPS) receivers from Interstate Electronics Corp. (IEC) in Anaheim, Calif., in special Army 155 mm precision-guidance artillery projectiles.

The super-hardened Global Positioning System receiver from IEC helps guide 155 mm howitzer shells to their targets.
Click here to enlarge image

The IEC GPS devices are part of the U.S. Army's Excalibur program. The shipment represents the world's first SAASM-based guidance system able to withstand the 15,000-G acceleration firing from a gun, IEC officials claim.

Raytheon Missile Systems officials have ordered 331 GPS receivers form IEC for testing as part of the engineering, development, and manufacturing phase of the program. The Excalibur program may need more than 200,000 units over the next decade, IEC officials say.

Raytheon Guided Projectiles is the developer of the Excalibur guidance systems, and the Army's Armament Research Development and Engineering Center manages the program. IEC is a wholly owned subsidiary of L-3 Communications.

"The GPS receiver includes government-supplied key data processor (KDP) devices that we incorporated into a tamper resistant coated multichip module (MCM)," says Paul Bricker, director of GPS programs at IEC. "Using proprietary gun-hardening design techniques, the SAASM module is combined with a radio frequency (RF) receiver to form the GPS receiver for the 155 mm projectile. This SAASM GPS receiver is capable of withstanding a gun firing of 15,500 Gs."

IEC test engineers use centrifuge, air gun, rail gun, finite element analysis, as well as component adhesive patterns as gun-hardening validation techniques, says Gary Patterson, a principal engineer at IEC.

The KDP devices included custom designed application-specific integrated circuits (ASIC) and software, Patterson says. The KDP components are flash memory, CINCO II ASIC, a Motorola 68332 processor, and application software, he adds.

Ninety five percent of the components in the IEC design are commercial-off-the-shelf (COTS), Patterson continues. To resolve the obsolescence issues that come with COTS, IEC performs lifetime buys or has the government procure suspect components and maintain government inventory, Patterson adds.

The Army's Excalibur program seeks to improve the accuracy of artillery projectiles from between one quarter and one half mile to between 200 and 500 feet, IEC officials say. The Excalibur guidance system must have a shelf life of more than 20 years, be easily field-loaded with targeting data, withstand the severe gunfire shock, and protect the classified GPS technology if a round falls into enemy hands, company officials say.

Military GPS satellite signals are encoded and military GPS receivers contain firmware to decode the signals, IEC officials say. IEC's design met the government's requirement by protecting the security codes in such a manner that they are destroyed if the chipset in the receiver is tampered with or compromised, company officials say.

The SAASM assembly is an MCM, which contains the core logic devices for a P (Y) code GPS receiver. The SAASM along with RF down converter and I/O logic forms the complete GPS receiver.

For more information on IEC's GPS receivers contact Greg Martz by phone at 714-758-0500, by fax at 714-758-4148, by mail at 602 East Vermont Ave., PO box 3117, Anaheim, Calif. 92803-3117, by e-mail at [email protected], or on the World Wide Web at http://www.

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