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Predicting Equatorial Ionospheric Total Electron Content Using the Transformer-based Model with Observations From Ground GNSS Receivers and COSMIC-2 Satellites
(2025-01-01)
Mutasov, Gleb
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Supnithi, Pornchai
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Budtho, Jirapoom
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Perwitasari, Septi
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Nishioka, Michi
Ionospheric Total Electron Content (TEC) is a key parameter for monitoring and studying the ionosphere, which induces significant delays in radio signals. Equatorial ionospheric irregularities, such as Equatorial plasma bubbles (EPB), can severely disrupt satellite navigation and communication. Predicting TEC is, therefore, essential for space weather monitoring and high-precision positioning applications. This study employs a Transformer-based model to predict TEC 24 hours in advance for specific satellites based on observations from a ground station and COSMIC-2 satellites. Unlike other approaches, our model directly forecasts TEC values for visible satellites within predefined longitude-latitude ranges. To enhance predictive accuracy, we also integrate additional features: ionospheric pierce points (IPP), geomagnetic (HP60), and solar activity indices, utilizing time-series Transformer architecture, and we consider a long-short-term memory (LSTM) model as a baseline. The proposed approach provides promising results for local TEC forecasting in the specific coverage area, with potential for further enhancements using additional GNSS or TEC measurements.
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Clustering of Ionospheric Irregularities based on Spatiotemporal ROTI Keogram Images
(2024-01-01)
Mutasov, Gleb
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Min Myint, Lin Min
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Supnithi, Pornchai
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Budtho, Jirapoom
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Tongkasem, Napat
Ionospheric irregularities associated with Equatorial plasma bubbles (EPB) can significantly impact navigation and communication systems. Therefore, their occurrences need to be studied and predicted. To solve the prediction problem, it is necessary to identify types of spatiotemporal characteristics as reference points for the predictive model. This work employs unsupervised machine learning algorithms to identify types of ionospheric irregularities due to EPB using the rate of total electron content index (ROTI) keograms. Two machine learning methods: two models, the Gaussian mixture model (GMM), and k-means, are considered. Comparative analysis is performed, and the optimal number of clusters is estimated using one classical, k-means and one additional - repeatability score, introduced in this work metric. The optimal GMM model successfully classifies three types of irregularity patterns offering valuable insights for the development of an effective EPB prediction model and enhancing our understanding of ionospheric behavior.
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Statistical Analysis of Separation Distance Between Equatorial Plasma Bubbles Near Suvarnabhumi International Airport, Thailand
(2018-09-01)
Bumrungkit, Acharaporn
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Supnithi, Pornchai
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Saito, Susumu
Ionospheric disturbances can lead to the major detrimental effects on the availability of ground-based augmentation system. In low-latitude regions, equatorial plasma bubbles (EPBs) frequently arise. They originated from the bottom side of the ionosphere with the electron density inside the plasma bubbles lower than the outside area. It is well known that the EPB causes the strong fluctuation on Global Positioning System signals when passing through the ionospheric disturbed regions. Sometimes the EPBs may have more than one front. To better understand the ionospheric anomaly effect on ground-based augmentation system efficiency, the separation distance between EPBs needs to be studied. In this work, we analyze the slant total electron content from dual-frequency Global Positioning System receivers near Suvarnabhumi International Airport, Thailand, to ascertain the EPB occurrence. The distance between observed EPBs is computed based on the Haversine formula technique. The results found that the estimated separation distances between depletions on disturbed days in 2015 are in the range of 100 to 1,200 km.
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Ionospheric delay gradient monitoring for GBAS by GPS stations near Suvarnabhumi airport, Thailand
(2015-10-01)
Rungraengwajiake, Sarawoot
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Supnithi, Pornchai
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Saito, Susumu
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Siansawasdi, Nattapong
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Saekow, Apitep
Ground-based augmentation system (GBAS) is an important augmentation system that provides the differential corrections and integrity information from the reference stations to the aircrafts for precision approach and landing. It is known that the nonuniform ionospheric characteristics called "ionospheric delay gradient" can cause the errors in differential corrections degrading the accuracy and safety level if they are undetected by the reference stations. Since the characteristics of the ionosphere are different for each region, the ionospheric delay gradient observations in equatorial and low-latitude regions are necessary for developing the suitable ionospheric threat models. The purpose of this work is to analyze the ionospheric delay gradients observed by three GPS stations near Suvarnabhumi airport in Bangkok, Thailand, which is located in the low-latitude region. The ionospheric irregularities in this region are mainly caused by the plasma bubble, which usually occurs after sunset. The GPS data with plasma bubble occurrence during the September equinox 2011 and 2012 are therefore analyzed. In addition, the data analysis procedure utilizing the rate of total electron content change index for this region is proposed. The results show that the ionospheric delay gradients observed in the west-east direction appear higher than the south-north direction, varying from 28 to 178 mm/km during plasma bubble occurrences.
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Latitudinal GRBR-TEC estimation in Southeast Asia region based on the two-station method
(2014-10-01)
Watthanasangmechai, Kornyanat
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Yamamoto, Mamoru
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Saito, Akinori
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Tsugawa, Takuya
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Yokoyama, Tatsuhiro
Total electron content (TEC) is an important parameter for revealing latitudinal ionospheric structures, such as the equatorial ionization anomaly (EIA) in Southeast Asia. Understanding the EIA is beneficial for studying equatorial spread F. To reveal the structures, the absolute TEC as a function of latitude must be accurately determined. In early 2012, we expanded a GNU Radio Beacon Receiver (GRBR) network to provide latitudinal coverage in the Thailand-Indonesia sector. We employed the GRBR network to receive VHF and UHF signals from polar low-Earth-orbit satellites. The TEC offset is an unknown parameter in the absolute TEC estimation process. We propose a new technique based on the two-station method to estimate the offset for the latitudinal TEC estimation, and it works better than the original method for a sparse network. The TEC estimation system requires two iterations to minimize the root-mean-square error (RMSE). Once the RMSE reaches the global minimum, the absolute TECs are estimated simultaneously over five GRBR stations. GPS-TECs from local stations are used as the initial guess of the offset estimation. The height of the ionospheric pierce point is determined from the ionosonde hmF2. As a result, the latitudinal GRBR-TEC was successfully estimated from the polar orbit satellites. The two EIA humps were clearly captured by the GRBR-TEC. The result was well verified with the TEC reconstructed from the C/NOFS density data and the ionosonde bottomside data. This is a significant step showing that the GRBR is a useful tool for the study of low-latitude ionospheric features.
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Drift velocity estimation of ionospheric disturbance using GPS observations
(2014-01-01)
Bumrungkit, Acharaporn
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Rungraengwajiake, Sarawoot
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Supnithi, Pornchai
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Siansawasdi, Nattapong
The Ground-Based Augmentation System (GBAS) based on the global positioning system (GPS) is used for positioning accuracy improvement of the aircraft landing. However, the ionospheric irregularity can cause irregular electron density that affects the accuracy of GBAS system. In this work, we analyze the drift velocity of ionospheric irregularity or plasma bubble phenomenon by using the correlation time of slant total electron content (STEC) from two GPS receivers that are located near Suvarnabhumi airport, Thailand. The data on September 1<sup>st</sup>, 2011 with the plasma bubble occurrence is analyzed. The result shows the drift velocity of plasma bubbles is about 108 meterspersecond (m/s). © 2014 IEEE.

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