GNSS‐TEC Driven E‐CHAIM for Enhanced PALSAR Ionospheric Tomography

Abstract The computerized ionospheric tomography (CIT) has long been implemented in Global Navigation Satellite System systems. Recently, Phased Array L‐band Synthetic Aperture Radar (PALSAR) CIT has demonstrated unique advantages, particularly achieving spatial electron density reconstruction without ground‐based receivers. However, the inherent ill‐posedness of tomography limits PALSAR‐CIT reconstruction accuracy. To address this challenge, we calibrate the E‐CHAIM by adjusting the IG parameter under the constraint of GNSS‐TEC data. This integration yields a high‐precision initial background field for PALSAR‐CIT, effectively mitigating the ill‐posedness and significantly enhancing the overall reconstruction precision. Verifications show the improved E‐CHAIM (IE‐CHAIM) electron density profile matches ionosonde data better than alternative methods. Simultaneously, the proposed method based on the corrected initial value is validated using three PALSAR data sets near Poker Flat, Alaska. The data measured by the incoherent scatter radar (ISR) at the corresponding time nearby are regarded as true values. The results demonstrate that introducing the IE‐CHAIM as the initial background for PALSAR‐CIT significantly improves the reconstruction accuracy at ISR locations compared with using the E‐CHAIM, with decreases of 10.1%, 29.94%, and 26.65% in root‐mean‐square error (RMSE), respectively. Meanwhile, the Average Deviation (AD) values are decreased by 3.83%, 26.88%, and 35.74%, respectively. The results validate the significant role of the IE‐CHAIM driven by GNSS‐TEC in PALSAR‐CIT. By providing optimized initial constraints, the model enables PALSAR‐CIT to effectively improve the reconstruction accuracy of electron density profiles within the study area. Overall, the proposed IE‐CHAIM integration acts as a critical enabling layer that transforms spaceborne SAR data into reliable 3D ionospheric insights, especially in data‐sparse regions.