A novel method for ionospheric monitoring using stellar occultation

The ionosphere is an important region that directly affects human activities. Existing ionospheric space-based detections are limited by airspace coverage, whereas ground-based observations are constrained by geographic environments, making observational deployment in oceans and deserts impractical. Direct measurements via satellite are restricted by orbital paths and cannot fully cover the ionosphere. Although global positioning system (GPS) ionospheric occultation enables global monitoring of the ionosphere, it relies on the availability of navigation satellites. Stellar occultation, using stars as light sources for the detection of planetary atmospheres and the advantages of GPS radio occultation, allows for observation constellations to achieve comprehensive global monitoring. In this study, we validate the feasibility of the ionospheric stellar occultation technique. First, 141 ultraviolet sources were selected based on the spectral absorption characteristics of 303.31 Å and signal-to-noise ratio requirements of the observation spectrum. Second, the 24-h distribution of ionospheric occultation events was forecast through satellite orbits and stellar positions. Third, a forward projection model was built based on the predicted occultation events, and the International Reference Ionosphere (IRI) model was used to simulate the transmission of ionospheric occultation observations. Finally, the simulated transmittance was used as an input to retrieve the ionospheric electron density profiles by the onion-peeling inversion method, with errors calculated against the IRI model. Results showed that stellar occultation provides five times more events than GPS radio occultation under identical orbital conditions. The inversion error at the electron density peak remained below 2%, with even smaller errors at heights below the peak. These results confirm the feasibility and practicability of the ionospheric stellar occultation technique, offering a method for a deeper understanding of ionospheric physical processes, the development of ionospheric space weather forecasting, and long-term, stable global observations of the ionosphere.