Projectile Tracking Device Using GPS

John S. Eicke, George C. Wiles, Brian T. Mays and Andrew Ladas

Abstract:	Significant increases in artillery accuracy and effective- ness can be achieved with the use of projectile tracking and trajectory modeling to predict the point of impact. As part of a U.S. Army cooperative program with the Human Engineering Laboratory and the Ballistics Research Laboratory, the Harry Diamond Laboratories is developing a Global Positioning System (GPS) based transponder capable of providing projectile tracking data. This effort includes development of both the projectile-mounted GPS transponder and the special- ized receiver equipment needed to determine projectile position data. The Harry Diamond Laboratories has been performing the research into the design and implementation of the GPS transponder and the receiver equipment. Transla- tor design issues included careful consideration of interference signals, antenna design requirements, minimization of components, and high-g factors in the design. The extremely high system gain (120 dB) made self-interference issues of prime concern. System fre- quency selections were made to minimize the potential for interference from principal or harmonic frequencies. Frequency selections were also driven by the need for a simple hardware implementation of the system. Survivability in the high-g environment was also a priority in the translator design. The selection of a suitable master oscillator was heavily influenced by characteristics of various oscillators under the 16,000 g (maximum) gun-launch environment. Tradeoffs were made between frequency accuracy and its effects on system power and bandwidth requirements and oscil- lator behavior under high-g conditions. The translator design was breadboarded and evaluated, and then two prototype projectile units were fabricated and fired in October 1991. The translator receiver equipment was required to process the translated GPS signals and provide posi- tion data. The correlation, tracking and position solu- tion are performed in software. The short mission time (less than 2 minutes) made a random access memory (RAM)-based data storage system possible. This unique approach significantly reduced the complexity of the data recording system compared to existing systems. A breadboard of the translator receiver hardware has been fabricated and used to process the data at the field test.
Published in:	Proceedings of the 1992 National Technical Meeting of The Institute of Navigation January 27 - 29, 1992 Catamaran Resort Hotel San Diego, CA
Pages:	89 - 94
Cite this article:	Eicke, John S., Wiles, George C., Mays, Brian T., Ladas, Andrew, "Projectile Tracking Device Using GPS," Proceedings of the 1992 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1992, pp. 89-94.
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