GPS Exploitation for Precision Targeting - Observability Using Synthetic Aperture Radar

Anthony Abbott, Neeraj Pujara and Peter Howe

Abstract:	As the Global Positioning System (GPS) becomes practical for use in conventional munitions, the relative contribution of targeting errors to the total weapon system error budget becomes significant. In addition to reducing the targeting error budget contribution, it is desired to have an accurate targeting capability on the launch platform to accommodate relocatable and other targets of opportunity. Due to its favorable propagation characteristics, the Synthetic Aperture Radar (SAR) is a very effective sensor for targeting. By itself, however, the SAR is subject to observability limitations, which are inherent to the sensitivity of its range and range rate measurements to target position errors. Without supplemental data or special attention to SAR measurement geometry, a unique solution is not possible with only SAR measurements from a simple pass by a target. Unfortunately, supplemental data (e.g., target altitude) is not always of reliable accuracy and supplemental sensors may not operate in all desired conditions with the required accuracy. Without supplemental data, a large target position uncertainty exists in the direction orthogonal to the SAR plane defined by the SAR’s velocity vector and the **** range vector to the target. This uncertainty contributes to the total weapon’s CEP. Even though the weapon’s trajectory will be shaped to minimize the impact of this uncertainty, this capability in the weapon does not come without considerable expense in a wingless, powerless munition. For these reasons, it is very desirable to perform the complete targeting function with the SAR alone. This paper mathematically defines the targeting observability afforded by SAR measurements. It then develops the theory to obtain full target observability from two or more SAR fixes. The solution is presented as a family of conditions that must be satisfied to guarantee observability. Realistic trajectories are presented to achieve the required geometry for each SAR fix. Based on the anticipated use of GPS on the launch/targeting platform and the weapon, the paper then estimates the total weapon system performance that could be achieved by the use of relative GPS navigation techniques.
Published in:	Proceedings of the 49th Annual Meeting of The Institute of Navigation (1993) June 21 - 23, 1993 Royal Sonesta Hotel Cambridge, MA
Pages:	193 - 202
Cite this article:	Abbott, Anthony, Pujara, Neeraj, Howe, Peter, "GPS Exploitation for Precision Targeting - Observability Using Synthetic Aperture Radar," Proceedings of the 49th Annual Meeting of The Institute of Navigation (1993), Cambridge, MA, June 1993, pp. 193-202.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In