Product Quality Analysis and Correction Modeling of the GIM Produced by UPC in the Antarctic Region

In this study, the high temporal resolution ionospheric product uqrg provided by Universitat Politècnica de Catalunya (UPC) is downsampled into eight products with different temporal resolutions (15, 30 min, 1, 2, 4, 6, 12, and 24 h) in the Antarctic. Then, the accuracy of different products is analyzed using Global Navigation Satellite System (GNSS) total electron content (TEC) from approximately 40 stations’ data between 2015–2016 and 2022–2023. The results indicate that there is little difference in the accuracy of products with time resolution $\le 60$ min, with a difference in root mean square (rms) <0.2 Tecu. Then, as the temporal resolution decreased, the rms of products gradually became larger, from 4.2 to 6.0 Tecu in 2015–2016 and 5.1 to 7.0 Tecu in 2022–2023, respectively. The differential TEC between UPC TEC and GNSS TEC is further used to fit a model for correcting UPC products based on the spherical crown harmonic (SCH) function. The results show that the bias and rms decreased from −1.93 to −0.07 and 4.39 to 2.89 Tecu after the correction, and the correction effect is better in polar day than in polar night. Finally, the polynomial model and the long short-term memory (LSTM) model are used to predict the SCH coefficients, respectively, to obtain the predicted TEC. The results suggest that the polynomial model performs better in short-term prediction, with an accuracy improvement of 20.38% compared with the product before corrected, and the LSTM model performs better in long-term prediction, with an accuracy improvement of 13.3%.

I. Introduction

The ionosphere, an important part of the solar-terrestrial space environment, lies within a range of approximately 60–1000 km above the ground. The ionosphere exhibits long-term stable cyclic variations (solar cycle variations) and short-term unstable perturbation variations [1], [2] owing to various factors such as solar and geomagnetic activities. Perturbations in the ionosphere significantly affect the safety of spaceflights, high-frequency communication, positioning, and navigation. The total electron content (TEC), defined as the line integral of the electron density along the propagation path of a signal from the satellite to the receiver, is of great significance in the theoretical study of ionospheric physics and the applied study of ionospheric wave propagation [3]. Currently, various ionospheric models are available for obtaining the TEC, such as broadcast models, empirical ionospheric models, and global ionospheric maps (GIMs).