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Accurate Earth orientation parameter (EOP) predictions are needed for many applications, e.g., for the tracking and navigation of interplanetary spacecraft missions. One of the most difficult parameters to forecast is the length of day (LOD), which represents the variation in the Earth’s rotation rate since it is primarily affected by the torques associated with changes in atmospheric circulation. In this study, a new-generation time-series prediction algorithm is developed. The one-dimensional convolutional neural network (1D CNN), which is one of the deep learning methods, is introduced to model and predict the LOD using the IERS EOP 14 C04 and axial Z component of the atmospheric angular momentum (AAM), which was taken from the German Research Centre for Geosciences (GFZ) since it is strongly correlated with the LOD changes. The prediction procedure operates as follows: first, we detrend the LOD and Z-component series using the LS method, then, we obtain the residual series of each one to be used in the 1D CNN prediction algorithm. Finally, we analyze the results before and after introducing the AAM function. The results prove the potential of the proposed method as an optimal algorithm to successfully reconstruct and predict the LOD for up to 7 days.

This work focuses on the assessment of UT1-UTC estimates from various types of sessions during the CONT17 campaign. We chose the CONT17 campaign as it provides 15 days of continuous, high-quality VLBI data from two legacy networks (S/X band), i.e., Legacy-1 (IVS) and Legacy-2 (VLBA) (having different network geometry and are non-overlapping), two types of Intensive sessions, i.e., IVS and Russian Intensives, and five days of new-generation, broadband VGOS sessions. This work also investigates different approaches to optimally compare dUT1 from Intensives with respect to the 24 h sessions given the different parameterization adopted for analyzing Intensives and different session lengths. One approach includes the estimation of dUT1 from pseudo Intensives, which are created from the 24 h sessions having their epochs synchronized with respect to the Intensive sessions. Besides, we assessed the quality of the dUT1 estimated from VGOS sessions at daily and sub-daily resolution. The study suggests that a different approach should be adopted when comparing the dUT1 from the Intensives, i.e., comparison of dUT1 value at the mean epoch of an Intensive session. The initial results regarding the VGOS sessions show that the dUT1 estimated from VGOS shows good agreement with the legacy network despite featuring fewer observations and stations. In the case of sub-daily dUT1 from VGOS sessions, we found that estimating dUT1 with 6 h resolution is superior to other sub-daily resolutions. Moreover, we introduced a new concept of sub-daily dUT1-tie to improve the estimation of dUT1 from the Intensive sessions. We observed an improvement of up to 20% with respect to the dUT1 from the 24 h sessions.

In 2021, the International Earth Rotation and Reference Systems Service (IERS) established a working group tasked with conducting the Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC) to assess the current accuracy of EOP forecasts. From September 2021 to December 2022, EOP predictions submitted by participants from various institutes worldwide were systematically collected and evaluated. This article summarizes the campaign's outcomes, concentrating on the forecasts of the dX, dY, and dψ, dε components of celestial pole offsets (CPO). After detailing the campaign participants and the methodologies employed, we conduct an in-depth analysis of the collected forecasts. We examine the discrepancies between observed and predicted CPO values and analyze their statistical characteristics such as mean, standard deviation, and range. To evaluate CPO forecasts, we computed the mean absolute error (MAE) using the IERS EOP 14 C04 solution as the reference dataset. We then compared the results obtained with forecasts provided by the IERS. The main goal of this study was to show the influence of different methods used on predictions accuracy. Depending on the evaluated prediction approach, the MAE values computed for day 10 of forecast were between 0.03 and 0.16 mas for dX, between 0.03 and 0.12 mas for dY, between 0.07 and 0.91 mas for dψ, and between 0.04 and 0.41 mas for dε. For day 30 of prediction, the corresponding MAE values ranged between 0.03 and 0.12 for dX, and between 0.03 and 0.14 mas for dY. This research shows that machine learning algorithms are the most promising approach in CPO forecasting and provide the highest prediction accuracy (0.06 mas for dX and 0.08 mas for dY for day 10 of prediction). Graphical abstract

Project “Saptarshi” was initiated by the National Centre for Geodesy, Indian Institute of Technology Kanpur to set up the modern space geodetic infrastructure in the country. This project primarily focuses on the establishment of an Indian Geodetic VLBI network. The purpose of this paper is to anticipate the potential impact of the geodetic VLBI network in India to the national and international scientific products. Saptarshi proposes to establish three VLBI stations along with a correlator at one facility. In this work, we investigate how adding proposed Indian VLBI antennas will affect terrestrial and celestial reference frames as well as Earth Orientation Parameters (EOP). Additionally, we shortly demonstrate scenario of VLBI observations of one of the Indian regional navigation satellite system called Navigation with Indian Constellation (NavIC) to determine its orbit. Two VLBI networks were simulated to observe the NAVIC satellite along with quasars to check how well the orbit of this satellite can be recovered from VLBI observations. To investigate the impact on the terrestrial reference frame, three types of 24-h sessions, IVS-R1 (legacy), IVS-VGOS (next generation VLBI), and IVS-AOV (Asia Oceania VLBI), were studied to examine the gain in precision of geodetic parameters when adding the proposed Indian VLBI antennas. IVS-type Intensive sessions were also investigated with the proposed Indian antennas to assess the improvement in the estimation of dUT1 as one important VLBI product. Furthermore, the u-v coverage of some radio sources of the southern hemisphere was compared utilizing observing networks with and without the proposed Indian antennas. Apart from that, we briefly discuss other benefits of the establishment of Indian geodetic VLBI in the scientific fields of atmosphere, metrology, and space missions.

Predicting Earth Orientation Parameters (EOP) is crucial for precise positioning and navigation both on the Earth’s surface and in space. In recent years, many approaches have been developed to forecast EOP, incorporating observed EOP as well as information on the effective angular momentum (EAM) derived from numerical models of the atmosphere, oceans, and land-surface dynamics. The Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC) aimed to comprehensively evaluate EOP forecasts from many international participants and identify the most promising prediction methodologies. This paper presents the validation results of predictions for universal time and length-of-day variations submitted during the 2nd EOP PCC, providing an assessment of their accuracy and reliability. We conduct a detailed evaluation of all valid forecasts using the IERS 14 C04 solution provided by the International Earth Rotation and Reference Systems Service (IERS) as a reference and mean absolute error as the quality measure. Our analysis demonstrates that approaches based on machine learning or the combination of least squares and autoregression, with the use of EAM information as an additional input, provide the highest prediction accuracy for both investigated parameters. Utilizing precise EAM data and forecasts emerges as a pivotal factor in enhancing forecasting accuracy. Although several methods show some potential to outperform the IERS forecasts, the current standard predictions disseminated by IERS are highly reliable and can be fully recommended for operational purposes.

Growing interest in Earth Orientation Parameters (EOP) resulted in various approaches to the EOP prediction algorithms, as well as in the exploitation of distinct input data, including the observed EOP values from various operational data centers and modeled effective angular momentum functions. Considering these developments and recently emerged new methodologies, the Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC) was pursued in 2021–2022. The campaign was led by Centrum Badań Kosmicznych Polskiej Akademii Nauk in cooperation with Deutsches GeoForschungsZentrum and under the auspices of the International Earth Rotation and Reference Systems Service. This paper provides the analysis and evaluation of the polar motion predictions submitted during the 2nd EOP PCC with the prediction horizons between 10 and 30 days. Our analysis shows that predictions are highly reliable with only a few occasional discrepancies identified in the submitted files. We demonstrate the accuracy of EOP predictions by (a) calculating the mean absolute error relative to polar motion observations from September 2021 through December 2022 and (b) assessing the stability of the predictions in time. The analysis shows unequal results for the x and y components of polar motion (PMx and PMy, respectively). Predictions of PMy are usually more accurate and have a smaller spread across all submitted files when compared to PMx. We present an analysis of similarity between the participants to indicate what methods and input data give comparable output. We also prepared the ranking of prediction methods for polar motion summarizing the achievements of the campaign. Plain Language Summary Polar motion consists of two time‐variable angles that characterize the orientation of the Earth's rotational axis with respect to a terrestrial reference frame attached to the surface of the solid Earth. It can be measured by space geodetic techniques, like Global Navigation Satellite Systems or Very Long Baseline Interferometry (VLBI). However, the final VLBI solutions used by geodetic processing centers to provide the values of polar motion have a latency of around 1 month. Therefore, predicted values are necessary for operational applications such as spacecraft navigation. To assess current methods of predicting polar motion time series, the Second EOP Prediction Comparison Campaign was pursued under the auspices of the International Earth Rotation and Reference Systems Service. The campaign aimed to test current achievements in polar motion predictions obtained with a variety of computational methods (including least squares, machine learning, and a Kalman filter) under realistic conditions. By evaluating the results of the campaign, we show that some of the prediction methods utilized do indeed reduce prediction errors and enhance prediction accuracy by using geophysical information from the fluid Earth's layers: Atmosphere, oceans, and terrestrial hydrosphere. Key Points Polar motion predictions for the y component are more accurate than for the x component Least squares and auto regression with effective angular momentum data provides the best results for polar motion prediction Some of the submitted predictions show higher accuracy than the IERS solution

We present the first report on an innovative new project named \"RAD@home\", a citizen-science research collaboratory built on free web-services like Facebook, Google, Skype, NASA Skyview, NED, TGSS etc.. This is the first of its kind in India, a zero-funded, zero-infrastructure, human-resource network to educate and directly involve in research, hundreds of science-educated under-graduate population of India, irrespective of their official employment and home-location with in the country. Professional international collaborators are involved in follow up observation and publication of the objects discovered by the collaboratory. We present here ten newly found candidate episodic radio galaxies, already proposed to GMRT, and ten more interesting cases which includes, bent-lobe radio galaxies located in new Mpc-scale filaments, likely tracing cosmological cluster accretion from the cosmic web. Two new Speca-like rare spiral-host large radio galaxies have also been been reported here. Early analyses from our follow up observations with the Subaru and XMM-Newton telescopes have revealed that Speca is likely a new entry to the cluster and is a fast rotating, extremely massive, star forming disk galaxy. Speca-like massive galaxies with giant radio lobes, are possibly remnants of luminous quasars in the early Universe or of first supermassive black holes with in first masssve galaxies. As discoveries of Speca-like galaxies did not require new data from big telescopes, but free archival radio-optical data, these early results demonstrate the discovery potential of RAD@home and how it can help resource-rich professionals, as well as demonstrate a model of academic-growth for resource-poor people in the underdeveloped regions via Internet.

Precision engineering applications need for compliant micro positioning stages with a wide travel range, high accuracy, and a small footprint. These advantages are provided by monolithic compliant insertion stages, which have been the focus of the majority of earlier research, but they also have the significant drawback that damaged components cannot easily be replaced, necessitating a time-consuming machining process such wire electric discharge machining. A stage with a parallelogram flexure module and a modular design idea is suggested to solve these restrictions. The modular architecture makes it simple to repair damaged components. Large range voice coil actuators (VCA) power the stage. Stiffness matrix-based static and dynamic analytical models are used to assess the stage's performance, and the results of finite element analysis (FEA) are used to check the accuracy of these models. Experimental setup is built to verify the stage performance. The stage offers restricted cross-axis coupling of 15 μm in other directions to accommodate for nonlinear behaviour, and a translational motion of ± 7 mm along the working direction. The suggested stage displays a 18 Hz resonance frequency. The results reveal that the modular micro-positioning stage exhibits comparable static and dynamic performances, as well as capability for trajectory tracking, as the monolithic stage.

A growing trend in the utilization of compliant micro-motion stages, which offer exceptional precision and repeatability in positioning. These stages enable the creation of dual-range positioning systems, allowing for precise positioning at the nanoscale within a centimeter-scale working area when combined with conventional stages. However, such systems often come with a high price tag and require substantial physical space. This research presents an alternative solution in the form of a compact, cost-effective XY micro-motion stage with dual-range manipulation to address these limitations. The primary objective is to maintain workspace efficiency while improving positioning accuracy. This is achieved by integrating a long-range, low-resolution linear encoder with short-range, high-resolution capacitive sensors. The linear encoder determines the stage's position and provides coarse positioning data, while the capacitive sensors step in to correct any positional errors, enabling precise fine positioning. By adopting this approach, an impressive positioning precision of approximately 1.5 μm is attained within a 3 mm × 3 mm workspace. The compliant stage is constructed using aluminum, and wire electric discharge machining is employed. This material is well-suited for this application due to its high reversible strain and compatibility with compliant systems.