Low Probability Intercept/Detect (LPI/LPD) Alternative Navigation System Demonstration

The Long Range Navigation (LORAN) system was a proven and stable navigation aid until it was abandoned because of the success of the Global Positioning System (GPS). However, while being highly successful, GPS has created a single point of failure for many military and civilian applications requiring precise time and position. Therefore, it is now clear that a backup to GPS is required and the enhanced-LORAN (eLORAN) system is being proposed to take over that role. The performance of an eLORAN-aided navigation system under GPS-denied and all-weather conditions was studied during the Phase I effort. The simulated performance of the design indicates that the proposed adaptive eLoran-aided positioning and timing (ADEPT) system will be capable of achieving global GPS-like positioning accuracy under GPS-denied conditions using signals from either GPS pseudolites, eLoran, ADEPT beacons, or alternative signals-of-opportunity (SoOp). In beacon-aided mode, the ADEPT receiver requires only two beacons, rather than the four GPS pseudolite/satellite signals required, and achieves centimeter-level performance for a full 3 D position and time solution, and meets the Joint Precision Approach and Landing System (JPALS) requirements under GPS-denied conditions. In SoOp-aided mode, the system achieves better than 10 m circular error probable (CEP) performance under all-weather conditions.