U.S. military forces prefer global positioning system (GPS) navigation because of its reliability and ease of use. However, GPS signals are vulnerable to enemy jammers. The Office of Naval Research (ONR) is investigating these vulnerabilities and methods to systematically eliminate these weaknesses to provide the Department of Defense with a robust navigation capability.
GPS vulnerability mitigation: Initial efforts focused on electronically steered GPS antenna systems, featuring antenna that preferentially select the intended satellite source and reject spatially inhomogeneous noise and jammer sources. Present interest involves the development of controlled radiation pattern antennas for specific naval platforms such as ships, airborne platforms, guided munitions, unmanned air vehicles and unmanned underwater vehicles. This thrust also addresses the coupling of GPS with inertial systems.
Precision time and time transfer: Ongoing areas of interest in this technology area are concerned with the development of tactical grade atomic clocks that possess unique long-term stability and precision. Additionally, this thrust explores the capability of: (1) transferring GPS derived 1 pps universal coordinated time via radio frequency links, such as joint tactical information distribution system/link-16; and (2) maintaining a common reference time by tying together existing time standards distributed in the various systems.
Non-GPS navigation: This technology area focuses on the development of a correlation navigation technique using earth maps of high precision (including bathymetric, magnetic and gravitometric data); the development of devices using wide-ranging physical principles and phenomena, such as gravity gradiometers and celestial navigation (CNS); gyroscope development employing compact microelectronic mechanical system (MEMS) devices and fiber optics; and the development of a CNS through the use of improved optical components, approaches and the incorporation of higher resolution CCD focal planes.