GIST: A tool for Global Ionospheric Tomography using GPS ground and LEO d ata and sources of opportunity with applications in instrument calibration

Ionospheric tomography using GPS data has been reported in the literature and even the application to radar altimeter calibration was succesfully carried out in a recent work. We here present a new software tool, called Global Ionospheric Stochastic Tomography software (GIST), and its powerful capability for ingesting GPS data from different sources (ground stations, receivers on board LEO for navigation and occultation purposes) and other data such as altimetry data to yield global maps with dense coverage and inherent calibration of the instruments. We show results obtained including 106 IGS ground stations, GPS/MET low rate occultation data, TOPEX/POSEIDON GPS data from the navigation antenna and NASA Radar Altimeter with the additional benefit of a direct estimation of the NRA bias. The possibility of ingesting different kinds of ionospheric data into the tomographic model suggest a way to accurately monitor the ionosphere with direct application to single frequency instrument calibration.