Detection and simulation study of a Mars intersatellite atmospheric radio occultation constellation

Mars atmospheric research and meteorological support for future surface operations require radio occultation observations with broader spatial and local-time coverage. In this study, we propose a conceptual Mars intersatellite atmospheric radio occultation constellation based on representative orbital configurations of China’s Tianwen-1, the future Tianwen-3 Mars orbiter and Earth return orbiter, and international Mars orbiters including TGO and MEX. The constellation is designed to reduce the local-time blind zones, sparse sampling, and long propagation-path limitations associated with conventional spacecraft-to-Earth radio occultation. Based on the assumed orbital configuration, we simulated the spatiotemporal distribution of valid intersatellite occultation events over one Martian year. The results show that the constellation can provide 110,576 valid occultation opportunities per Martian year, with sampling distributed across different longitudes, latitudes, and local times. A representative MEX-TGO occultation event was further used for U- and X-band forward simulation and retrieval tests. The representative event further demonstrates that intersatellite U/X-band radio links can be used to simulate occultation observables and retrieve Martian atmospheric and ionospheric parameter profiles. These results demonstrate the potential of intersatellite U/X-band radio occultation for complementary sounding of the Martian ionosphere and neutral atmosphere, and provide a scientific reference for the future international cooperation on Mars atmospheric and ionospheric occultation constellation.