Large Radio Telescope Research Articles

Multimodality-based Wind Speed Forecasting Method for the Wind Resistance Control of Large Radio Telescope

A large, fully steerable radio telescope is susceptible to the wind load, leading to structure deformation and pointing deviation of the telescope. To effectively suppress the influence of dynamic wind load, the wind resistance control of the telescope is carried out based on wind speed forecasting. This study developed a wind speed forecasting model to efficiently forecast the wind speed at the telescope position. The proposed model successfully eliminates the random noise of the original wind speed, effectively extracts the wind speed features and solves the automatic optimization of the hyperparameters of the forecasting network. This model significantly improves the accuracy and reliability of wind speed forecasting. To verify the forecasting performance of the proposed model, the wind data from the Qitai Radio Telescope site is examined as a case study. The wind speed forecasting model’s MAE, RMSE and MAPE are 0.0361, 0.0703 and 3.87%, respectively. The performance of the proposed model meets the requirements of wind resistance control and can provide data support for the radio telescope.

Spectral Analysis of Ionospheric Density Variations Measured With the Large Radio Telescope in the Low‐Latitude Region

AbstractThe low‐latitude ionosphere is a dynamic region with a wide range of disturbances in temporal and spatial scales. The Giant Metrewave Radio Telescope (GMRT) situated in the low‐latitude region has demonstrated its ability to detect various ionospheric phenomena. It can detect total electron content (TEC) variation with precision of 10−3 TECU and also can measure TEC gradient with an accuracy of about 7 × 10−4 TECU km−1. This paper describes the spectral analysis of previously calculated TEC gradient measurements and validates them by comparing their properties using two bands. The analysis tracked individual waves associated with medium‐scale traveling ionospheric disturbances (MSTIDs) and smaller waves down to wavelengths of ∼10 km. The ionosphere is found to have unanticipated changes during sunrise hours, with waves changed propagation direction as the sun approached the zenith. Equatorial spread F disturbances during sunrise hours is observed, along with smaller structures moving in the same direction.

Phased Array Feed Experiments and Galactic H i Observations

The Phased Array Feed (PAF) is considered as one of the next generation receivers for radio telescopes, which can significantly enlarge the instantaneous Field-of-View of large aperture single dish radio telescopes and enable more flexible observing configurations. Study efforts on PAF development for radio telescopes have been made for more than two decades and have become more and more applicable. We report the development of an ambient-temperature 19 element L-band PAF system and the experimental results including its far field beam pattern and system temperature measurement, which achieve the expectations. Implementing the aperture array beam-forming method, we demonstrate a wide-field Galactic H i observations in the radio camera mode. The results indicate that this system might be applicable for strong Galactic transient detections. This system could be directly equipped to large telescopes like the Five-hundred-meter Aperture Spherical radio Telescope (FAST) and FAST array in the future.

INVESTIGATION OF THE MAGNETIC FIELD FROM OBSERVATIONS OF THE OH MASER IN THE G10.624–0.385 STAR FORMATION REGION

The results of a study of the variability of maser emission in OH lines in the 18 cm range in the G10.624–0.385 star formation region from monitoring data performed at the Large Radio Telescope in Nançay (France) in 2008–2023 are presented. It is obtained that for a Zeeman pair in line 1667 MHz splitting (about 1.96 km/s) and, consequently, the magnitude of the longitudinal magnetic field have been stable for more than 25 years. In the satellite lines of 1612 and 1720 MHz, broadband absorption and emission are observed, respectively. Mirrored The profiles of the OH 1612 and 1720 MHz satellite lines indicate that the levels of the corresponding transitions are pumped by IR radiation from a source immersed in a magnetized molecular cloud around the OH maser. Spatial identification of details in both main lines is carried out. It is found that the transverse magnetic field is directed mainly along some organized structure in the form of an arc.

INVESTIGATION OF OH 18 CM MASER EMISSION AND MAGNETIC FIELD IN THE S128 STAR FORMATION REGION

The results of a study of the variability of OH maser emission in the lines of 18 cm in the S128 star formation region from monitoring data in 2007–2022 at the Large Radio Telescope in Nançay (France) are presented. Maser emission was observed in the main line of 1665 MHz during the entire monitoring, and only short-term emission was observed in the satellite lines of 1612 and 1720 MHz. For the four strongest features in the 1665 MHz line, the variability of the positional angle of linearly polarized emission was found. The dependence of the angle on the radial velocity to some extent resembles a limited sinusoid, which may be due to the existence of an organized spatial structure of maser spots and the associated transverse magnetic field. For two Zeeman pairs in the 1612 MHz line having similar radial velocities (–75.344/–75.236 and –74.980/–74.903 km/s), the detected splits have opposite signs and, therefore, opposite directions of the longitudinal magnetic field. The directions of the transverse magnetic field vectors are also determined for these features. Apparently, the magnetic field is swirling and is associated with a swirling molecular outflows of matter.

Research on Wind Flow Control by Windbreak Fence for a Large Radio Telescope Site Based on Numerical Simulations

The higher the pointing accuracy of the radio telescope, the more obvious the influence of wind disturbance on antenna performance. Taking the site of the 110 m aperture QiTai radio Telescope (QTT) as an example, the terrain and air flow characteristics of the site are studied. It is found that the wind direction with high incoming wind frequency and relatively high speed is mostly located in the mountain gap on the periphery of the antenna. If the wind resistance facilities are precisely arranged in the upstream tuyere, the wind speed in the antenna area can be effectively reduced. This study proposes a method to control the wind flow at a telescope site based on the precise arrangement of the windbreak fence. The windbreak fence simulation model is constructed using the theory of porous jump. The mean error of the simulation results is less than 14% compared to the wind tunnel measured data, indicating that the constructed windbreak fence model has high reliability. The computational domain model of the working conditions for the site is constructed. The extreme condition of the windbreak fence arrangement is considered, and the simulation results show that the wind speed in the antenna area can be reduced by more than 30% through the control of the windbreak fence. It verifies the feasibility of the method of controlling the wind flow by the windbreak fence for the site which provides a reference for the subsequent research on the precise arrangement of the windbreak fence.

Exploring diffuse radio emission in galaxy clusters and groups with uGMRT and SKA

Diffuse radio emission has been detected in a considerable number of galaxy clusters and groups, revealing the presence of pervasive cosmic magnetic fields, and of relativistic particles in the large scale structure of the Universe. Since the radio emission in galaxy systems is faint and its spectrum is steep, its observations are largely limited by the instrument sensitivity and frequency of observation, leading to a dearth of information, more so for lower-mass systems. The recent commissioning or upgrade of several large radio telescope arrays, particularly at the low frequency bands (<GHz) is, therefore, a significant step forward. The unprecedented sensitivity of these new instruments, aided by the development of advanced calibration and imaging techniques, have helped in achieving unparalleled image quality and revolutionised the study of cluster-scale radio emission. At the same time, the development of state-of-the-art numerical simulations and the availability of supercomputing facilities have paved the way for high-resolution numerical modelling of radio emission, and the structure of the cosmic magnetic fields, associated with large-scale structures in the Universe, leading to predictions matching the capabilities of observational facilities. In view of these rapidly-evolving developments in modeling and observations, in this review, we summarise the role of new telescope arrays and the development of advanced imaging techniques and discuss the range of detections of various kinds of cluster radio sources, both in dedicated surveys as well as in numerous individual studies. We pay specific attention to the kinds of diffuse radio structures that have been able to reveal the underlying physics in recent observations. In particular, we discuss observations of large-scale sections of the cosmic web in the form of supercluster filaments, and studies of emission in low-mass systems, such as poor clusters and groups of galaxies, and of ultra-steep spectrum sources, the last two being notably aided by low-frequency observations and high sensitivity of the instruments being developed. We also discuss and review the current theoretical understanding of various diffuse radio sources in clusters and the associated magnetic field and polarisation in view of the current observations and simulations. As the statistics of detections improve along with our theoretical understanding, we update the source classification schemes based on the intrinsic properties of these sources. We conclude by summarising the role of the upgraded GMRT (uGMRT) and our expectations from the upcoming Square Kilometre Array (SKA) observatories.

The Analyses of Globular Cluster Pulsars and Their Detection Efficiency

Up to 2022 November, 267 pulsars had been discovered in 36 globular clusters (GCs). In this paper, we present our studies on the distribution of GC pulsar parameters and the detection efficiency. The power law relation between average dispersion measure () and dispersion measure difference (ΔDM) of known pulsars in GCs is . The sensitivity could be the key to finding more pulsars. As a result, several years after the construction of a large radio telescope facility, the number of known GC pulsars will likely be increased accordingly. We suggest that currently GCs in the southern hemisphere could have higher possibilities for finding new pulsars.

Effect of the reflector system thermal behavior on the pointing accuracy of large radio telescopes

The thermal behavior of the reflector system under solar radiation has great effects on the pointing accuracy of large radio telescopes. To estimate the dynamic pointing error of large radio telescopes caused by the thermal behavior of the reflector system under solar radiation, the nonuniform temperature field and the thermal deformation of the Wuqing 70 m radio telescope (WRT70) on three specific sunny days are first simulated by finite-element (FE) software. Then the pose variations of the reflector system are calculated equivalently based on the FE thermal-structural coupling analysis of the reflector system. Finally, the dynamic pointing errors of the WRT70 on three specific sunny days, caused by the thermal behavior of the reflector system, are estimated according to the beam deviation factor. The research results show that the rotations of the main reflector and the offsets of the subreflector on sunny days have great influences on the pointing error of large radio telescopes. In addition, the pointing error caused by the rotations of the main reflector and the pointing error caused by the offsets of the subreflector cancel each other out, but the pointing error caused by the rotations of the main reflector plays a dominant role. Furthermore, the effect of the thermal behavior of the reflector system on the pointing accuracy of large radio telescopes is less than the influence of the thermal behavior of the alidade. These findings could provide valuable references for the compensation of dynamic pointing errors of large radio telescopes.

Towards optimal phased-array tile configurations for large new-generation radio telescopes and their application to NenuFAR

Context. Recent instrumental developments have aimed to build large digital radio telescopes made of ~100k antennas. The massive data rate required to digitise all elements drives the instrumental design towards the hierarchical distribution of elements by groups of 𝒪(10) that form small analogue phased arrays that lower the computational burden by one to two orders of magnitude. Aims. We study possible optimal layouts for a tile composed of five to 22 identical elements. We examine the impact of the tile layout on the overall response of an instrument. Methods. We used two optimisation algorithms to find optimal arrangements of elements in the tile using: (i) a deterministic method (Kogan) based on beam pattern derivative properties; and (ii) a stochastic method (modified simulated annealing) to find global optima minimising the side-lobe level while increasing the field of view (FOV) of the tile, a required condition for all-sky surveys. Results. We find that optimal tile arrangements are compact circular arrays that present some degree of circular symmetry while not being superimposable to any rotated version of themselves. The ‘optimal’ element number is found to be 16 or 17 antennas per tile. These could provide a maximum side-lobe level (SLL) of −33 dB (−24 dB) used with dipole (isotropic) elements. Due to constraints related to the analogue phasing implementation, we propose an approaching solution but with a regular arrangement on an equilateral lattice with 19 elements. By introducing random relative rotations between tiles, we compared and found that the 19-element equilateral tile results in better grating lobe mitigation and a larger FOV than that of rectangular tiles of 16 antennas. Conclusions. Optimal tile arrangements and their regular versions are useful to maximise the sensitivity of new-generation hierarchical radio telescopes. The proposed solution was implemented in NenuFAR, a pathfinder of SKA-LOW at the Nançay Radio Observatory.

A Study of Variability of the Stokes Parameters and the Magnetic Field of G43.8–0.1 in the OH Line 1665 MHz

We present results of the study of maser emission variability in the 1665 MHz OH line in the G43.8–0.1 star formation region based on observations (monitoring) in 2008–2022 at the Large Radio Telescope in Nancy (France). Variability of all polarization parameters of the majority of spectral features, which has a monotonic regular character, has been found. Spatial identification of the main spectral features of the OH 1665 MHz line with maser spots (condensations) on the VLA map has been carried out. For the Zeeman pair VLSR=44.15 km/s, a monotonic change of the splitting with time during 2008–2022 was found and, consequently, a change of the magnitude of the longitudinal magnetic field. According to our calculations, at the end of 2012, the direction of the magnetic field changed to the opposite. Сorrelated with H∥, there were changes in the angle χ and, as a consequence, changes in the direction of the vector of the transverse magnetic field H⊥0. For the maser feature at 44.5 km/s, a change of H⊥ by 180° was found. In 2016–2022, some reorientation of the global magnetic field (H⊥) in G43.8–0.1 occurred. The field became less chaotic: in the eastern part, the field in maser condensations is perpendicular to the arc, and in the western part, it is parallel to the arc. It is assumed that the global magnetic field in the entire U H II region of the G43.8–0.1 source has the same direction: along the axis (northeast)—(southwest).

Observations of Hydroxyl in the Onsala 1 Source at 18 cm

We present results of polarization observations of the ON 1 source in the 1665, 1667, and 1612 MHz hydroxyl lines at the Large Radio Telescope in Nançay (France). Spatial identification of the spectral features of OH in the 1665 and 1667 MHz lines with maser spots (condensations) on the VLBI map according to the data of Fish et al. (2005) was carried out. Emission from hitherto unknown spectral features in the 1665 MHz main line at radial velocities of –2.98, 9.35, and 11.8 km/s has been detected. Five Zeeman pairs were found: four in the 1665 MHz line and one in the 1667 MHz line. The vectors of the transverse magnetic field H⊥ are oriented mainly along the arc (in the upper and lower parts of the UC H II region), while the vectors of the longitudinal magnetic field H|| in the northern and central parts of the UC H II region are oriented away from the observer, while in the southern part toward the observer.

Pulsar search acceleration using FPGAs and OpenCL templates

The Square Kilometre Array (SKA) is the world’s largest radio telescope currently under construction, and will employ elaborate signal processing to detect new pulsars, i.e. highly magnetised rotating neutron stars. This paper addresses the acceleration of demanding computations for this pulsar search on Field-Programmable Gate Arrays (FPGAs) using a new high-level design process based on OpenCL templates that is transferable to other scientific problems. The successful FPGA acceleration of large-scale scientific workloads requires custom architectures that fully exploit the parallel computing capabilities of modern reconfigurable hardware and are amenable to substantial design space exploration. OpenCL-based high-level synthesis toolchains, with their ability to express interconnected multi-kernel pipelines in a single source language, excel in this domain. However, the achievable performance strongly depends on how well the compiler can infer desirable hardware structures from the code. One key aspect to excellent performance is commonly the uninterrupted, high-bandwidth streaming of data into and through the design. This is difficult to achieve in complex designs when data order needs to be re-arranged, e.g. transposed. It is equally hard to pre-fetch and burst-load from DDR memory when reading occurs in non-trivial patterns. In this paper, we propose new approaches to these two problems that use OpenCL-based code templates.We demonstrate the practical benefits of these approaches with the acceleration of a key component in the SKA’s pulsar search pipeline: the Fourier Domain Acceleration Search (FDAS) module. Using our proposed methodology, we are able to develop a more scalable FDAS accelerator architecture than previously possible. We explore its design space to eventually achieve a 10x throughput improvement over a prior, thoroughly optimised implementation in plain OpenCL.

Pulse Tube Cooler with &gt; 100 m Flexible Lines for Operation of Cryogenic Detector Arrays at Large Radiotelescopes

Pulse Tube Cooler with &gt; 100 m Flexible Lines for Operation of Cryogenic Detector Arrays at Large Radiotelescopes

Simulation-driven Wind Load Analysis and Prediction for Large Steerable Radio Telescopes

Large steerable radio telescopes can rotate in azimuth and elevation, with various upwind postures and complex wind load characteristics. In order to 5 Corresponding authors obtain the wind load distribution on the reflector and the wind force coefficients in different upwind postures, this work took the reflector of the QiTai Telescope in Xinjiang as the object. The wind pressure distribution, drag coefficient, side force coefficient, lift coefficient, and total force coefficient of 361 groups of reflectors with different upwind postures were calculated and analyzed by a numerical simulation method. The results show that the force on the reflector when the concave surface faces the wind is significantly greater than when the convex surface faces the wind. The surrogate models for calculating wind force coefficients were established based on the polynomial response surface model (PRSM) and regularized minimum-energy tensor-product spline (RMTS). The adjusted R-squared of RMTS is 0.98, and the root mean square error is below 0.1, which proves RMTS is significantly better than PRSM. Compared with the numerical simulation values, the absolute errors of the drag coefficient, side force coefficient, lift coefficient, and total force coefficient of the reflector with azimuth and elevation of 45° predicted by RMTS are 0.02, 0.027, 0.032, and 0.046, respectively. The relative errors are 2.42%, 2.76%, 2.23%, and 2.43% , respectively. It is proved that the RMTS surrogate model is reliable and that the predicted data can fast provide sufficient information for the wind-resistant design of the large steerable radio telescopes.

中国SKA区域中心跨洲际高速数据传输进展及展望

The Square Kilometre Array (SKA) is the largest radio telescope, and the data generated from its observations are first transmitted from Australia and South Africa to the scientific data processing center 100 km away, and then distributed to various SKA Regional Centres (SRC) with a distance of tens of thousands of kilometers through a high-speed network.In the SKA Phase 1 (SKA1) stage, 710 PB of data needs to be distributed to each SRC through a network of at least 100 Gbps each year. Such high network bandwidth and data scale bring great challenges to data transmission and distribution. This study analyzes a variety of network protocols, such as TCP/UDP/HTTP, and uses different software in the field of radio astronomy for testing and research. Then, the optimal transmission scheme parameters under the current infrastructure of a 10 Gbps network are obtained. In this study, the factors affecting high-speed transmission are discussed, and the corresponding performance optimization strategies are given.This study provides the technical foundation for China's network construction and layout before the official observation of the first stage of SKA and the technology accumulation of global network operations of the SRC in the future.The technical details and methods described in this study are essential for scientific applications that rely on large data cross-international nodes.

НАЗЕМНА ПІДТРИМКА КОСМІЧНОЇ МІСІЇ PARKER УКРАЇНСЬКИМИ НИЗЬКОЧАСТОТНИМИ РАДІОТЕЛЕСКОПАМИ

Subject and Purpose. The sporadic radio emissions coming from the Sun in a broad frequency range contain a lot of important information concerning the solar corona, parameters of the radio frequency sources therein, and the parameter variations resulting from active processes on and about the Sun. These have been the reasons for recent launches of the space missions intended for stud- ying the Sun and its corona, such as the Parker Solar Probe (PSP) and the Solar Orbiter. The present work is aimed at demonstrating effectiveness of the ground-based support for the space missions, the PSP before all, which is provided by the large Ukrainian radio telescopes of the decameter wavelength range. Another purpose has been cross-calibration of the space-borne radiometer against calibrated data from a ground-based instrument. Methods and Methodology. One of the remote diagnosis techniques widely used with respect to the solar corona is to analyze parameters of the radio frequency emissions from sources lying at a variety of altitudes within the corona. The methodology of such joint, space-borne/terrestrial investigations suggests simultaneous observations of certain individual events during closest approach of the space probe PSP to the Sun, with analysis over a widest possible frequency range. The data obtainable within overlapping fre- quency bands are proposed for calibrating the on-board radio receivers of the space probe. Results. The methodology proposed for joint, space-based / terrestrial observations has been substantiated. Data from the UTR-2 and URAN-2 radio telescopes and the space probe PSP have been used to plot the dynamic and the polarization spectra of the June 9, 2020 solar bursts, with identification and comparison of the relevant individual events. A joint dynamic spectrum of these bursts has been obtained for the frequency band of 0.5 to 32 MHz. The calibrated data from the ground-based radio telescopes have allowed performing cross-calibration of the HF receiver in the FIELDS-PSP data taking module within the frequency band of 10 to 18 MHz. Conclusions. The paper has provided evidence of an effective ground-based support for the space mission PSP on the part of large Ukrainian radio telescopes. Examples of joint observations have been given, and a methodology described which is employed for cross-calibrating the HF receivers of the FIELD-PSP module. Prospects are outlined of further ground-based support for solar space research missions.

Web Performance Evaluation of High Volume Streaming Data Visualization

Many applications such as, software, and hardware generate an increasing volume of data and logs in real-time. Visual analytics is essential to support system monitoring and analysis of such data. For example, the world’s largest radio telescope, the Square Kilometer Array (SKA), is expected to generate an estimated 160 TB a second of raw data captured from different sources. Transporting large amounts of data from distributed sources to a web browser for visualization is time-consuming due to data transport latencies. In addition, visualizing real-time data in the browser is challenging and limited by the data rates which a web browser can handle. We propose a novel low latency data streaming architecture, which uses a messaging system for real-time data transport to the web browser. Based on this architecture, we propose techniques and provide a tool for analyzing the performance of serialization protocols and the web-visualization rendering pipeline. We empirically evaluate the performance of our architecture using three visualizations use cases relevant to the SKA. Our system proved extremely useful in streaming high-volume data in real-time with low latency and greatly enhanced the web-visualization performance by enabling streaming an optimal number of data points for different visualizations.

Arduino-based high-frequency radio telescope and observations

This is a pilot project undertaken by the UG and PG students of the Department of Physics, St. Xavier's College (Autonomous), Kolkata under the supervision of Dr. Suparna Roychowd hury and Dr. Shibaji Banerjee and with the assistance of Mr. Bappaditya Manna, Technical Officerof Father Eugene Lafont Observatory (FELO) on building a low-cost high-frequency radiotelescope using Arduino. This paper presents the design of the smallArduino-based radio telescope recently developed by the group to observe radio emission at high frequencies (12-18GHz)and the initialobservations including detection of geostationary andnon-geostationary satellites. Preliminary results demonstrate the effectiveness of this Arduino-based radio telescope in the eraof large radio telescopes that are inaccessible to students. As the radio telescope operates in ahigh-frequency range, it is easier to observe in city areas where Radio Frequency Interference(RFI) is a significant issue. The system can be pointed either manually or using a computerized mount to any radio source and data can be collected from a satellite finder as well asfrom Arduino micro-controller. This system can be used for a basic understanding of radioastronomy and for training purposes for University and College students at a very lowcost. Further, we would also like to extend this to a two-element radio interferometer andundertake interferometric observations of astronomical radio sources in future.

A New Monitor and Control Power Supply PCB for Biasing LNAs of Large Radio Telescopes Receivers

A New Monitor and Control Power Supply PCB for Biasing LNAs of Large Radio Telescopes Receivers