Sam Pullen, Sherman Lo, Isaiah Colobong, Sukrut Oak, Juan Blanch, Todd Walter Stanford University; Mark Crews, Robert Jackson, Stephen Young, Kevin Huttenhoff

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In previous work (Pullen 2022), we introduced the concept of augmenting GPS with six inclined geosynchronous satellites (I-GEOs) that would provide GPS-Block-III-quality military and civil ranging signals along with conveying Satellite-based Augmentation System (SBAS) messages to users. This would create a new means to distribute SBAS messages globally and would support Advanced Receiver Autonomous Integrity Monitoring (ARAIM) for users not equipped to use SBAS. This paper examines multiple configurations of I-GEO satellites augmenting GPS satellites and includes augmentation by satellites in Low Earth Orbit (LEO). For each arrangement of satellites, the Stanford MAAST GNSS simulation software package is used to evaluate the protection levels and the availability of integrity for aviation LPV approaches (to a minimum decision height of 250 ft) for ARAIM users. MAAST computes PLs and availability for a global grid of military (dual-frequency M-code and/or PRS) and civil (dual-frequency L1/L5 or equivalent) user locations separated by 5 degrees of latitude and longitude. Contour plots of LPV availability, Vertical Protection Level (VPL), and Horizontal Protection Level (VPL and HPL) are generated for each combination of I-GEO and other GNSS satellites. In addition, sorted (by magnitude) values of VPL and HPL are plotted for example locations in the user grid to illustrate the sensitivity of VPL and HPL to the poorest satellite geometries before and after I-GEOs or LEOs are included.