Operational issues for GPS-aided precision missiles

This paper discusses the operational issues associated with combining the NAVSTAR Global Positioning System (GPS) with a low cost Inertial Navigation System (INS) as the primary means to obtain precision accuracy for air-to-ground missiles. The authors' goal is to achieve precision accuracy without the use of a terminal imaging sensor in the missile. Motivation for removing the homing sensor is to significantly reduce the cost of the entire guided missile system. The overall effectiveness of a GPS-aided air launched missile is a strong function of the method and accuracy in determining target coordinates. Methods for determining target coordinates in a relative GPS frame are presented which allow for removal of GPS related system bias errors. Missile accuracy also depends on the missile platform-target geometry and missile flight trajectory. Short range standoff trajectories can stress the time required for the missile's GPS receiver to acquire and track the satellite signals. In addition, the jamming vulnerability of the GPS receiver in an operational environment is of major concern. The paper presents a review of the major jamming parameters such as the defense's effective radiated jamming power, potential GPS anti-jam enhancements, and jamming range to break GPS signal track.