A low SWaP implementation of high integrity relative navigation for small UAS

Several aerial platforms rely on decimeter-level relative position accuracy for various applications including automatic takeoff and landing, precision targeting, and airborne refueling. For such applications, a Real Time Kinematic (RTK) GPS system provides a relatively low cost, robust, and reliable solution. Current commercial RTK products are inherently susceptible to jamming and spoofing. The Selective Availability Anti-Spoof Module (SAASM) implementations to date typically relied on relatively large and complicated architectures which would be difficult to port into a small (Groups 1-3) Unmanned Aircraft System (UAS) due to Size, Weight, and Power (SWaP) constraints. This paper describes the architecture, algorithms, and testing approach from Rockwell Collins high integrity relative navigation system including a SAASM-based RTK implementation for small UAS. A variant of the system was implemented for the Navy's Small Tactical Unmanned Aircraft System (STUAS) program. The STUAS system performed its first successful ship-based launch and recoveries on the U.S.S. Mesa Verde using Rockwell Collins high integrity relative navigation system in February of 2013.