Analysis of complementary LEO-PNT and Radio Occultation observations for Ionospheric reconstruction.

Reconstructing the ionosphere with high precision is critical for understanding space weather and its impacts on satellite communications, navigation, and radar systems. Traditionally, ionospheric studies rely on ionosondes and radar measurements as well as ground based Total Electron Content derived from GNSS (Global Navigation Satellite System) as local measurements, but also GNSS Radio Occultation (RO) and insitu electron density from Low Earth Orbiting Satellites (LEO) as global measurements. While GNSS RO has been instrumental in advancing ionospheric modeling, it is limited by its dependence on GNSS satellite orbits and geometry, leading to gaps in spatial and temporal coverage.

This study explores the integration of slant TEC from LEO-PNT (Position Navigation and Timing) satellites, focusing on the potential of ground-to-LEO signal paths to complement GNSS RO observations. LEO satellite constellations, characterized by their dense, global coverage and low orbital altitudes, offer a promising opportunity for enhancing ionospheric reconstruction in both the altitudes between ground and LEO and altitudes between LEO and GNSS. Ground-to-LEO links provide a unique observational perspective, capturing slant total electron content (TEC) across diverse geometries that are inaccessible to GNSS RO. By incorporating these measurements into tomographic reconstruction frameworks, we demonstrate improved spatial resolution and accuracy in modeling ionospheric structures using synthetic data from well-established models such as IRI-2020.

We perform a series of ionospheric electron density reconstructions. The input data includes synthetic slant TEC from ground to GNSS, LEO to GNSS, LEO-RO, and LEO-PNT. We compare the full solution with LEO-RO and LEO-PNT to solutions, where either one or both of these inputs are omitted. Preliminary results highlight the added value of ground-to-LEO measurements in reproducing the IRI-2020 values and extending coverage in regions with sparse GNSS RO sampling. This approach is further validated using synthetic datasets and real-world orbits from existing LEO satellite constellations, such as Swarm, GRACE-FO, Sentinel, COSMIC-2, Jason-3, Sentinel, Spire, ...

Our findings underscore the transformative potential of leveraging LEO satellites in ionospheric science, paving the way for next-generation ionospheric monitoring systems. This contribution aims to stimulate discussion on future directions in multi-platform ionospheric research, emphasizing the synergies between GNSS RO and emerging ground-LEO link observations.