Impact of Existing and Planned GNSS Observation Systems on Global Ionospheric Modeling: Observation System Simulation Experiments

An Ionospheric simulation System for satellite Observations and Global Assimilative Model Experiments (ISOGAME) has been developed at the Jet Propulsion Laboratory based on the Global Assimilative Ionospheric Model (GAIM) and a GNSS-Inferred Positioning System and Orbit Analysis Simulation Software (GIPSY-OASIS). GAIM incorporates a first-principles physics model and data assimilation modules. The physics model computes volume densities of multiple ion species and electron by numerical solving the collisional plasma hydrodynamic equations on a global 3D geomagnetic frame. The data assimilation modules include observation operator, Kalman filter and 4-dimensional variational (4DVAR) approach. Assimilating GNSS-derived total electron content measurements made from ground-based global networks (such as the International GNSS Service - IGS) and low Earth orbiter (LEO) constellation (such as COSMIC), GAIM is capable of modeling and estimating weather conditions of ionospheric state (electron densities) and model drivers, such as electric fields, winds and ionization. During last few years, GAIM has been upgraded with nested-grid and real-time operation capabilities. ISOGAME has been used to conduct observation system simulation experiments (OSSE's) to evaluate the impact of space science satellite missions on global ionospheric specifications. This report will highlight recent OSSE's performed at the Jet Propulsion Laboratory using the existing and planned GNSS observation system.