GPS Awareness Enabling Algorithms for Theater and Space Environment

ABSTRACT: The Air Force requires accurate knowledge of the ionospheric environment in order to mitigate ionospheric impacts on vital radio-based systems, including communications, navigation, and surveillance systems. Current DoD capability for the specification and forecasting of the ionosphere relies heavily on GPS measurements of ionospheric total electron content (TEC). Currently TEC data is sparse in regions of interest. However there are many GPS receivers that normally only provide position, navigation or timing (PNT) information in these regions. The objective of the proposed work is to develop algorithms that will allow these receivers to compute TEC and other relevant space environment data. To address this objective, we propose to: i) survey typical DoD GPS User Equipment (UE) and identify onboard parameters that are readily available to develop required algorithms for TEC estimation; ii) design, develop and demonstrate algorithms that could potentially be deployed on operational UE to produce TEC, etc, accounting for operational realities for PNT systems iii) feasibility study for algorithm application to operational UE, and assessment of existing hardware At the end of Phase-I, we will deliver results of a feasibility study for algorithm application to GPS receivers in general, and GPS UE in particular. BENEFIT: At the end of the proposed Phase-I work we will have assessed the viability of producing TEC (and other ionospheric parameters) from existing dual-frequency GPS receivers that compute TEC for their internal position corrections, but which do not normally report the TEC directly or make it available as an output from the device. We will have utilized our understanding of GPS and algorithm development to design, develop and demonstrate algorithms that could potentially be deployed on operational equipment. We will have investigated some of these realities using ASTRA"s new CASES dual-frequency receiver, purposefully degrading the CASES data to emulate the inferior performance of other receivers. The main benefit of this work is that TEC and other ionospheric data are currently sparse in regions of interest, and if existing deployed GPS equipment can be used to obtain TEC and other space weather parameters, then data will suddenly be available in large quantities in the regions of greatest interest. The work complements ASTRA"s existing commercial production of science-grade GPS receivers and space weather data, in that these algorithms and ideas can be applied to commercial operations in addition to DoD UE.