Alison Brown

A hybrid integrity solution for precision landing and guidance

A design was developed for a hybrid integrity solution for precision approach and landing in a GPS jamming environment. The integrity solution described in this paper leverages the capabilities of next generation digital spatial processing and ultra-tightly-coupled (UTC) GPS/inertial integrated military user equipment (UE). A design is also included for a spatial environment integrity monitor, for a GPS/inertial receiver autonomous integrity monitor solution (GI-RAIM) that allows detection of small error drift rates before the inertial solution can be corrupted and an integrity monitoring function embedded within the kinematic carrier phase tracking (KCPT) algorithms which provides a level of confidence on the final KCPT positioning data output. Simulation and test results showing the expected performance of this multi-level integrity monitoring approach are presented. A design for an aircraft GPS/inertial digital spatial processing receiver, the HAGR-A, is also included which will be used as a test bed for implementation and testing of these integrity monitoring techniques.

Architecture and performance testing of a software GPS receiver for space-based applications

Space-based GPS technology presents significant challenges over Earth-based systems. These include visibility issues for rotating platforms and tracking of GPS satellites from spacecraft that are in higher orbits than the GPS, realtime resolution of carrier phase ambiguities, and different dynamics during various mission phases. NAVSYS has developed a software GPS receiver that makes use of 3-dimensional digital beam steering technology and inertial aiding to address these issues. This approach offers several advantages including all round visibility for spinning satellites, tracking of weak GPS signals, reduction of multipath, and reprogrammability to accommodate different mission phases. Additionally, a suite of simulation tools based on the NAVSYS Matlab Toolbox and Advanced GPS Hybrid simulation products have been built to allow testing for simulated space environments. The receiver architecture and test tools are described in this paper.