A novel method for ionospheric monitoring using stellar occultation

The ionosphere is an important region that directly affects human activities. However, existing ionospheric detection methods are limited by airspace coverage, and ground observation stations are constrained by geographic environments, making deployment in oceans and deserts impractical. Direct measurements via satellite are restricted by orbital paths, and cannot fully cover the ionosphere. While Global Positioning System (GPS) ionospheric occultation enables global monitoring of the ionosphere, it relies on the availability of navigation satellites. Stellar occultation, a technique that uses stars as light sources for the detection of planetary atmospheres, could be combined with the advantages of GPS radio occultation and 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 calculated and selected based on the spectral absorption characteristics of 303.31 Å and signal-to-noise ratio requirements of the observation spectrum. Second, the 24-hour distribution of ionospheric occultation events was forecast using 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 employed to simulate the transmission of ionospheric occultation observations. Finally, the simulated transmittance was used as an input to retrieve the ionospheric electron density profiles using the onion-peeling inversion method, with errors calculated against the IRI model. Results show that stellar occultation provides five times more events than GPS radio occultation, under identical orbital conditions. The inversion error at the electron density peak remains 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, as well as long-term, stable, and global observations of the ionosphere.