Relative Global Positioning System/ Inertial Navigation System (GPS/INS) Innovations for Autonomous Unmanned Air Systems (UAS)

The Navy Unmanned Combat Air System (N-UCAS) is a carrier-based, autonomous combat air vehicle designed to conduct long-endurance strike and ISR operational missions. Due to its very nature, the N-UCAS requires the ability to perform precision navigation in a variety of roles. To accomplish this, a commercial differential GPS (DGPS) augmentation service is used, improving precision but failing to meet current DoD regulatory directives. Additionally, the current precision approach to support automated aerial refueling (AAR) relies on a Precision GPS (P-GPS) technique utilizing relative GPS-INS positioning. This method depends on the tanker and the Unmanned Aerial System (UAS) tracking common GPS satellites, then compares the relative pseudorange and carrier-phase differences to determine their precise relative positioning. This approach results in highly accurate relative navigation (~10 cm) when sufficient GPS satellites are in common view, however, the solution’s robustness can degrade when satellites are obstructed by either aircraft. Under this Phase II SBIR effort, NAVSYS will develop an alternative P-GPS architecture, termed Precision RELNAV (P-RELNAV) where the tanker and the N-UCAS are able to independently navigate to a high degree of precision using Precision GPS Ephemeris (PGE) updates. This architecture will meet current DoD guidance and will demonstrate improved robustness of the P-GPS AAR solution by allowing all satellites in view of either vehicle to be included in the navigation solution. Anticipated Benefits/Potential Commercial Applications of the Research or Development The NAVSYS PGE architecture, integrated with the InterNav filter on board the aircraft’s navigation computer will provide a very precise independent navigation solution for the N-UCAS and tanker vehicles during automated air refueling. This will simplify the calculation of the relative navigation solution while at the same time meeting the DoD regulatory requirements for use of differential GPS.