Global DORIS Differential Slant Total Electron Content (dSTEC) Products Derived from Dual-Frequency Carrier-Phase Observations

A geometry-free dual-frequency carrier-phase combination is formed, and geometry effects associated with frequency-dependent antenna phase-center offsets at both the satellite and ground beacon are corrected. Because DORIS carrier-phase ambiguities and hardware phase delays cannot be reliably separated, a relative ionospheric observable is used. Within each phase-continuous arc, phase-derived slant TEC at the current epoch is differenced from that at the epoch of maximum satellite elevation.

The resulting dSTEC observable removes arc-constant ambiguity and stable hardware phase-delay terms while preserving relative ionospheric variations along the arc.The dataset is intended for independent validation of Global Ionospheric Maps and other ionospheric models, cross-technique consistency analysis, estimation of weights for ionospheric model combination, and studies of global ionospheric variability. Users should note that dSTEC is a relative slant TEC observable and does not provide an absolute TEC datum.

It represents electron-content variations below the orbit of the DORIS-equipped low-Earth-orbit satellite and does not include the entire plasmaspheric contribution above the satellite. Spatial sampling depends on the DORIS beacon network, satellite ground tracks, and mission availability. Exact file fields, sampling intervals, mission-specific coverage, and missing-data information are documented in the accompanying README, variable dictionary, and file_manifest.csv.