Ultra-short-term prediction of LOD using LSTM neural networks

Abstract

<p>The Earth Orientation Parameters (EOP) are fundamentals of geodesy, connecting the terrestrial and celestial reference frames. The typical way to generate EOP of highest accuracy is combining different space geodetic techniques. Due to the time demand for processing data and combining different techniques, the combined EOP products often have latencies from several days to several weeks. However, real-time EOP are needed for multiple geodetic and geophysical applications, including precise navigation and operation of satellites. Predictions of EOP in ultra-short time can overcome the problem of latency of EOP products to a certain extent.</p><p>In 2010, the Earth Orientation Parameters Prediction Comparison Campaign (EOP PCC) collected predictions from 20 methods, which were mainly based on statistical approaches, and provided a combined solution. In recent years, more hybrid and machine learning methods have been introduced for EOP prediction.</p><p>The rapid expansion of computing power and data volume in recent years has made the application of deep learning in geodesy increasingly promising. In particular, the Long Short-Term Memory (LSTM) network, one of the most popular variations of Recurrent Neural Network (RNN), is promising for geodetic time series prediction. Thanks to the special structure of its cells, LSTM network can capture the non-linear structure between different time epochs in the time series. Therefore, it is suitable for EOP prediction problems.</p><p>In this study, we investigate the potential of using LSTM for the prediction of Length of Day (LOD). The LOD data from a combination of space geodetic techniques are first preprocessed in order to obtain residuals. For this step, we experiment with the application of Savitzky-Golay filters, Singular Spectrum Analysis and the Gauss Markov model. We then employ LSTM networks of different architectures and its variations such as bidirectional LSTM networks to predict the LOD residuals in ultra-short time. Furthermore, we study the impact of Atmospheric Angular Momentum (AAM) and its forecast data on the predictions. The performance of this method is compared with other results of EOP PCC in a hindcast experiment under the same conditions. In addition, we assess the performance of LOD predictions using longer time series than for the EOP PCC to consider improvements of EOP products over the last decade.</p>

Geophysically Informed Machine Learning for Improving Rapid Estimation and Short‐Term Prediction of Earth Orientation Parameters

“…Since the rapid EOPs are the basis of many prediction algorithms for EOPs (Gou et al., 2023; Kiani Shahvandi & Soja, 2022a, 2022b; Kiani Shahvandi, Schartner, & Soja, 2022), the results presented in this paper can be used to further enhance the prediction of EOPs, particularly in short‐term horizons.…”

“…In order to evaluate the prediction accuracy, we use the mean absolute error (MAE) metric, which is commonly used in EOP prediction studies (Gou et al., 2023; Kalarus et al., 2010; Kiani Shahvandi, Schartner, & Soja, 2022; Kur et al., 2022; Modiri et al., 2018). This is done for each day individually.…”

“…Regarding the EAM data, both the observations and forecasts are used, since forecasts can help significantly to improve the EOP prediction performance (Gou et al., 2023; Kiani Shahvandi, Schartner, & Soja, 2022; Modiri et al., 2020). Since the horizon of the forecasts is also a determining factor (Kur et al., 2022), we use 14‐day forecasts of ETH Zurich (Kiani Shahvandi, Gou, et al., 2022; Kiani Shahvandi, Schartner, et al., 2023) since they are both accurate and cover a reasonable forecasting horizon for short‐term EOP prediction (i.e., suitable for accurate real‐time purposes).…”

“…There have been successful applications of machine learning for the analysis and prediction of EOPs (Dill et al., 2021; Gou et al., 2023; Kiani Shahvandi & Soja, 2022a, 2022b; Kiani Shahvandi, Schartner, & Soja, 2022). Here, however, we need to consider the specific aspects of the problem and develop a new machine learning algorithm.…”