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In 2019, the Event Horizon Telescope (EHT) released the first-ever image of a black hole event horizon. Astronomers are now aiming for higher angular resolutions of distant targets, like black holes, to understand more about the fundamental laws of gravity that govern our universe. To achieve this higher resolution and increased sensitivity, larger radio telescopes are needed to operate at higher frequencies and in larger quantities. Projects like the next-generation Very Large Array (ngVLA) and the Square-Kilometer Array (SKA) require building hundreds of telescopes with diameters greater than 10 ms over the next decade. This has a twofold effect. Radio telescope surfaces need to be more accurate to operate at higher frequencies, and the logistics involved in maintaining a radio telescope need to be simplified to support them properly in large quantities. Both of these problems can be solved with improved methods for surface metrology that are faster and more accurate with a higher resolution. This leads to faster and more accurate panel alignment and, therefore, a more productive observatory. In this paper, we present the use of binocular fringe projection profilometry as a solution to this problem and demonstrate it by aligning two panels on a 3-m radio telescope dish. The measurement takes only 10 min and directly delivers feedback on the tip, tilt, and piston of each panel to create the ideal reflector shape. Highlights: Current methods for measuring and aligning radio telescope dishes are insufficient for future astronomy requirements. We've developed a 3D scanning method for measuring full aperture dishes outdoors that is faster, easier, and more reliable than current methods. We demonstrated the method by aligning two panels on a 3-m dish to a high accuracy. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

After years of preparation, the Indonesia National Observatory, located in Mount Timau, Kupang Regency, is currently in the completion stage of research in astronomy and astrophysics and related subjects. An optic telescope with a 3.8 m diameter is expected to receive its first light in mid-2024. A feasibility study for Indonesia's radio telescopes and networks is in progress. A single-dish parabolic radio antenna with a diameter of 20 m is proposed to work in a frequency range of 1–50 GHz. An array dipole antenna with an area of 100 m × 100 m will also be installed at a 70–350 MHz frequency. A feasibility study about system design is in progress, and a radio frequency interference (RFI) survey has been underway since 2014. In this paper, we described the design of radio telescopes such as parabolic reflectors, horn antenna, and the radio frequency interference (RFI) in the surrounding area of the National Observatory, covering the frequency band from 45 MHz to 18 GHz. The frequencies in 45–85 MHz and 120–360 MHz intervals are still relatively quiet and suitable for developing radio telescopes. The selected higher frequency of 1.4 GHz for a neutral hydrogen (HI) spectral line, 6.6 GHz for a methanol (CH3OH) spectral line, and 8.6 GHz for a helium (3 He+) spectral line is still relatively quiet and suitable for the development of radio telescopes. [ABSTRACT FROM AUTHOR]

This paper presents a report on the activities and the proposed action plan of the Education and Public Outreach Working Group (EPO WG) of Square Kilometre Array–India Consortium (SKAIC). Details of a set of flagship programs as well as supporting activities are presented, in consonance with the scale of India's involvement in Square Kilometre Array Observatory (SKAO), as well as the educational and science literacy contexts in the country. Ongoing independent EPO activities by some of the member institutions are also included. [ABSTRACT FROM AUTHOR]

We have developed, manufactured, and tested a new feed design for interferometric radio telescopes with "large-N, small-D" designs. Such arrays require low-cost and low-complexity feeds for mass production on reasonable timescales and budgets, and also require those feeds to be compact to minimize obstruction of the dishes, along with having ultra-wide frequency bands of operation for most current and future science goals. The feed presented in this paper modifies the exponentially tapered slot antenna (Vivaldi) and quad-ridged flared horn antenna designs by having an oversized backshort, a novel method of maintaining a small size that is well-suited for deeper dishes (f ∕ D ≤ 0. 2 5). It is made of laser cut aluminum and printed circuit boards, such that it is inexpensive (≲ 7 5 USD per feed in large-scale production) and quick to build; it has a 5:1 frequency ratio, and its size is approximately a third of its longest operating wavelength. We present the science and engineering constraints that went into design decisions, the development and optimization process, and the simulated performance. A version of this feed design was optimized and fabricated for the Canadian Hydrogen Observatory and Radio-transient Detector (CHORD) prototypes. When simulated on CHORD's very deep dishes (f ∕ D = 0. 2 1) and with CHORD's custom first-stage amplifiers, the on-sky system temperature T sys of the complete receiving system from dish to digitizer remains below 30 K over most of the 0.3–1.5 GHz band, and maintains an aperture efficiency η A between 0.4 and 0.6. The entire receiving chain operates at ambient temperature. The feed is designed to slightly under-illuminate the CHORD dishes, in order to minimize coupling between array elements and spillover. [ABSTRACT FROM AUTHOR]

Mulemba Astronomical Observatory, later known as the Mulemba Space Centre was founded in 1958 on Luanda's outskirts in Angola, then an African Portuguese colony, by the polymath Carlos Mar Bettencourt Faria. Being, from all accounts, a charming and knowledgeable individual who was mainly self taught, he managed to build several radio telescopes, a solar observing station, a state-of-the-art electronics laboratory and a satellite tracking facility. Financial support was obtained from a variety of individuals, commercial companies, public institutions and from 1971 onwards Angola's national government. Faria's ambitious plans were nevertheless always thwarted or delayed by lack of funds. In 1973 data started to be collected at the solar station but the whirlwind of 1970s politics had a decisive impact in Angola. Faria's beautiful dream effectively ended when he was assassinated at the Observatory in 1976. In this paper we recall Carlos Bettencourt Faria's life and his battle against all odds to establish a professional-level astronomical observatory in Angola. [ABSTRACT FROM AUTHOR]

The paper is devoted to the analysis of the observation results with the single-mirror radio telescope RT-22 (PRAO, LPI) in the water vapor maser line at 22 GHz in the direction of dust clumps from the ATLASGAL and Bolocam large-scale blind surveys in the millimeter continuum. The aim of this paper is to search for masers in the water vapor line in previously unexplored sources and to study the variability of known masers. Observations of 140 sources resulted in the detection of maser emission at 22 GHz in six sources, and in four sources (ATLASGAL 016.987+00.981, 017.216+00.821, 018.701–00.229, and Bolocam 081.174–00.100) masers were detected for the first time. In two sources (ATLASGAL 034.195–0.592 and Bolocam 081.174–0.1), the water vapor line masers showed significant variability during the 8-month observation and follow-up program. Comparison of RT-22 observational data with archival data from the GBT‑100 telescope (US National Radio Astronomy Observatory) showed that 9 out of 140 sources show a significant change in the radiation flux density of masers: two sources changed from the category of masers with low brightness ( Jy) to the category bright (more than 10 Jy), and in seven relatively bright earlier (more than 3 Jy) masers, no radiation was detected. Significant changes in the characteristics of the maser emission may indicate changes in the environmental conditions in which the maser emission was produced, which is of interest for further study of maser-related processes. [ABSTRACT FROM AUTHOR]

Low-frequency aperture arrays represent sensitive instruments to detect signals from radio astronomic sources situated in the universe. In Italy, the Sardinia Aperture Array Demonstrator (SAAD) consists of an ongoing project of the Italian National Institute for Astrophysics (INAF) aimed to install an aperture array constituted of 128 dual-polarized Vivaldi antennas at the Sardinia Radio Telescope (SRT) site. The originally envisaged 128 elements of SAAD were re-scoped to the 16 elements of its precursor named SADino, with the aim to quickly test the system with a digital beam-former based on the Italian Tile Processing Module (iTPM) digital back-end. A preliminary measurements campaign of radio frequency interference (RFI) was performed to survey the less contaminated spectral region. The results of these measurements permitted the establishment of the technical requirements for receiving a chain for the SADino telescope. In this paper, the design, implementation, and characterization of this signal acquisition chain are proposed. The operative frequency window of SAAD and its precursor, SADino, sweeps from 260 MHz to 420 MHz, which appears very attractive for radio astronomy applications and radar observation in space and surveillance awareness (SSA) activities. [ABSTRACT FROM AUTHOR]

Radio astronomy uses radio telescopes to detect very faint emissions from celestial objects. However, human-made radio frequency interference (RFI) is currently a common problem faced by most terrestrial radio telescopes, and it is getting worse with the development of the economy and technology. Therefore, it is essential to monitor and evaluate interference during the planning, construction, and operation stages of the radio telescope and protect the quiet radio environment around the radio astronomical site. In this paper, we present a software for an RFI analysis of the radio environment around the telescope. In this software, information has been collected, including the location of the site; the technical specifications, such as aperture and the frequency range of the radio telescopes; and the terrain around the site. The software and its modules are composed of telescope, geographic, and meteorological databases, and analysis modules of terrestrial and space-based RFI. Combined with the propagation characteristics of radio waves, we can analyze and evaluate RFI on the ground and in space around the radio telescope. The feasibility of the software has been proved by the experimental implementation of the propagation properties and RFI source estimation. With this software, efficient technical support can be expected for protecting the radio environment around the telescope, as well as improving site selection for planned radio astronomical facilities. [ABSTRACT FROM AUTHOR]

One of the key factors of space weather is solar flare activity, the monitoring and prediction of which is an important task of specialized dedicated groups of space experts and solar astronomers. Solar flare forecasts are based on identifying and detecting the so-called precursors, specific processes in solar activity events that occur before flares. Collecting data for space weather analysis and prediction comes down to several types of measurements performed by more than a dozen spacecraft. Ground-based observations and monitoring nowadays are becoming more or less complimentary. One of the reasons for this is the limitation of observation time with ground-based telescopes due to adverse Earth weather conditions. However, solar radio astronomy is immune to almost any weather activity, and the main question here is what new quality it can bring. Observational data accumulated in the 20th century show that solar radio bursts can be associated with flare activity. In addition, the existing network of solar radio telescopes is already well established. As an example, in this paper, we describe the possibilities of a fully steerable 32-meter radio telescope of Ventspils International Radio Astronomy Centre (VIRAC), Latvia, which can be useful for searching for new precursors of solar flares. [ABSTRACT FROM AUTHOR]

Mobile communication base stations have become ubiquitous with the popularization and development of mobile communication services. Although the Chinese government has designated a radio quiet zone (RQZ) specifically for Five-hundred-meter Aperture Spherical radio Telescope (FAST), the 4G International Mobile Telecommunications (4G-IMT) system is still heavily used to meet the communication needs around the RQZ. To assess the Electromagnetic Interference (EMI) caused by 4G-IMT base stations on the performance of FAST, this paper employs the International Telecommunication Union (ITU) deterministic radio wave propagation prediction model. The interference of 4G-IMT base stations on FAST is evaluated based on relevant parameters, such as the frequency used by both FAST and the base station, in conjunction with the FAST threshold protection requirements. The results indicate that 47.73 % of the data exceed the radio astronomy protection threshold of FAST. In addition, a field experiment was conducted to verify the accuracy of the radio wave propagation prediction method used. The root-mean-square error between the predicted value and the measured value was found to be 6.94 dB, supporting the accuracy of the predicted results. The findings of this study can help suppress interference from mobile communication services around the RQZ of FAST and optimize the electromagnetic environment around FAST. [ABSTRACT FROM AUTHOR]

Modern studies of solar radio emission are complicated by continuous power amplification and multifrequency external interference, which often completely overlap important frequency ranges. Many topical problems in solar radio astronomy require large effective areas of radio telescopes, high frequency and time resolutions, accurate spatial measurements, and a large dynamic range. It becomes relevant to change the concept of receiving recording equipment. This paper deals with topical problems of the physics of the solar corona in combination with optimal methods of observation with large instruments. The features and difficulties of combining high parameters—dynamic, spatial, temporal, and frequency resolutions—are considered. The proposed solutions of the new-generation observation complex implement the possibilities of intelligent selection of registration conditions in a multioctave mode with multichannel over 8000 channels/GHz with temporary permission up to 8 ms/spectrum. A multiobject observation mode becomes available from powerful flaring objects to faint structures of various nature. High-speed data processing makes it possible to implement an online mode of interference elimination, which is based on a fast statistical analysis of the spectrum with the selection of non-Gaussian (interference) structures. Methods for high-speed analysis of large-volume data (the principal component analysis method) and their presentation to the user are proposed. Examples of the operation of the complex in the range of 1–3 GHz are given. The prospects of a new approach for multiobject radio astronomy observations in the implementation of the RATAN-600 tracking mode are considered: from recombination lines to wide-range spectra, from low-contrast fluctuations to fast changes in flares, etc. [ABSTRACT FROM AUTHOR]

National Astronomical Research Institute of Thailand (Public Organization) initiated a national flagship project in 2017 for development of radio astronomy and geodesy in Thailand. In this project, a 40-m Thai National Radio Telescope (TNRT) and a 13-m VLBI Global Observing System (VGOS) radio telescope as its co-location are constructed in Chiang Mai. The 40-m TNRT is the largest telescope for radio astronomy in South-East Asia. Its flexible operation with a wide-coverage of observable frequencies 0.3-115 GHz will allow us to uniquely contribute to the time-domain astronomy as well as carry out unbiased surveys for a wide variety of science research fields, which were published in a white paper. Within the framework of collaboration with VLBI arrays in the world, TNRT will drastically improve the imaging quality and performances based on its unique geographical location, for both radio astronomy and geodetic VLBI studies in South-East Asia for the first time. On-going commissioning of TNRT particularly in the L-band system (1.0–1.8 GHz) is introduced as well as vision for establishment of forthcoming regional VLBI networks based on TNRT: Thai National VLBI Array and South-East Asian VLBI Network in collaboration with Indonesia, Malaysia, and Vietnam. [ABSTRACT FROM AUTHOR]

The development of methods for the radio frequency interference mitigation becomes a fundamental challenge for any radio astronomy research. In this paper, we report on the development and creation of a new spectrometer designed for solar observations at the RATAN-600 radio telescope, capable of excising radio interference using a statistical algorithm based on the spectral kurtosis estimation. The implementation of the external analog interface and the operation of the digital signal processing system based on the FPGA are described. The maximum spectral resolution reached is 122 kHz in the frequency band of 1.0–3.0 GHz. The output spectrum has from 64 to 8192 frequency bins, depending on the requirements of the observer, the output rate is 120 spectra per second. The test results and the first observations of the Sun show that the research method can successfully detect and suppress interference from most of the local radio interference sources. [ABSTRACT FROM AUTHOR]

Radio astronomy is a discipline of dynamics and wonders. The vast universe has many secrets to unravel. As one of the important facilities in this discipline, radio telescopes play a key role in collecting astronomical data and unraveling mysteries. With the demand of radio astronomy for a higher frequency, wider bandwidth, higher gain, and higher pointing accuracy, the aperture of the radio telescope is gradually increasing, and its electrical performance and structure have become tightly coupled. Therefore, how to ensure the stable and efficient operation of the telescope for the long-term operation has become the urgent demand for large aperture high-performance radio telescopes. Therefore, this paper firstly makes a comparison of the overall condition of large radio telescopes in nearly a decade that are both constructed and operated, including the progress of radio telescopes that are being constructed and the planning for construction. Then, systematically summarized the latest research progress of electromechanical coupling technology from 3 aspects of connotation and application of electromechanical coupling, and performance guarantee under slowly varying load and performance guarantee under rapidly varying load from the perspectives of design, manufacturing, and observation operating. Lastly, the future research direction of electromechanical coupling technology is pointed out according to the development trend of radio astronomy. [ABSTRACT FROM AUTHOR]

Nowadays there is increasing interest in narrowing coronal areas with reduced brightness temperatures (LTR – Low Temperature Regions) associated with local open magnetic fields (S-web, "coronal partings", "dark coronal corridors") as one of the eventual sources of slow solar wind. Ventspils International Radio Astronomy Centre (VIRAC) performs routine spectral polarimetric observations of the Sun with RT-32 radio telescope equipped with the multi-channel (16 frequency channels) spectral polarimeter for the wave length range of 3.2–4.7 cm (6.3–9.3 GHz) and both circular polarizations simultaneously. The analysis of relevant tasks of clear and reliable observations and detections of LTR shows the necessity to improve noise parameters, dynamic range and stability of the actual solar spectral polarimeter and to expand its wavelength range. Taking into account these requirements, the low noise and thermally stabilized solar spectral polarimeter was developed. The new multi-channel spectral polarimeter is expected to observe right and left circular polarization of the solar emission in the wavelength range of 2.1–7.5 cm (4.1–14.3 GHz) divided into 12 frequency bands. The dynamic range was expanded to >36 db and the signal/noise ratio (referred to as quiet Sun brightness temperatures) was enhanced to > 22–24 db. The paper deals with some test observations of the newly developed solar spectral polar-imeter and its feature analysis. Some eventual problems of solar physics which could be solved with the spectral polarimeter are also discussed. [ABSTRACT FROM AUTHOR]

Given the rise of satellite television, radio telescopes in the Ku‐band (12–18 GHz) constitute a potential alternative to introduce low‐scale astronomical observatories and amateur astronomers to radio astronomy. In this paper, we show a methodology for the calibration of Ku‐band radio telescopes and the evaluation of the techniques used for the observation of celestial bodies in this frequency range. To reduce the pointing error, we present a method of observation through matrix windows around the Sun. By observing the solar transits, our methodology allows to determine the system temperature, the beamwidth, the gain, the effective area, and the efficiency of the radio telescope. In addition, we developed the Compact Radio Telescope (CRT) software, designed to perform the calibration, and carry out observations. We tested our methodology with the Ku‐band radio telescope of the Observatorio Astronómico of the Universidad Tecnológica de Pereira (OAUTP), Colombia. After observing the Sun and the Moon, we obtained a brightness temperature of 8,600 ± 800 K and 240 ± 50 K, and radiation fluxes of 2,970,000 ± 690,000 Jy and 55,000 ± 10,000 Jy, respectively. These observations demonstrated the usefulness of our methodology and CRT software in the calibration of compact Ku‐band radio telescopes for the observation of celestial bodies in radio waves. [ABSTRACT FROM AUTHOR]

The paper presents results of calculating the RATAN-600 beam pattern (BP) and BP drift scans of point radio sources in the West Sector radio telescope operation mode at a frequency of 4.7 GHz. When calculating the BP, the properties of the radio telescope antenna system in this operation mode were taken into account: the use of a large secondary mirror, asymmetric radiation of the primary mirror, and the location of the primary feeds (feed horns) along the focal line of the secondary mirror. The shape of the calculated drift scans of sources through the BP is compared with that of the experimental drift scans of sources obtained from observations in the West Sector. The main characteristics of the drift scans are calculated and compared when the radio telescope operates with the West and North Sectors. A new method for determination of flux densities of sources passing through the BP outside its central cross-section is proposed, and its accuracy is estimated. [ABSTRACT FROM AUTHOR]

The Mexican Array Radio Telescope (MEXART) is a transit instrument mainly dedicated to performing interplanetary scintillation (IPS) observations with a central operating frequency of 139.65 MHz. The main scientific objective is to perform studies of solar wind properties and space weather effects. MEXART initially operated with an analog beam former (16 × 16 Butler matrix), which produced 16 fixed latitudinal beams. MEXART began operations and reported the first measurements of IPS sources. MEXART's beam forming system had several problems, however. The North‐South beams had poor directivity, with large side lobes, and the instrument did not achieve the expected performance. Therefore, we commissioned the design and construction of a digital back‐end. The digital system solved the problems with the beam forming, increases the bandwidth, and significantly improves the instrument's sensitivity. In this paper, we present the first light of MEXART's digital system. We describe the new technical capabilities of the instrument, and we show some preliminary results: an estimation of the radio telescope's sensitivity (ΔSmin = 2.28 ± 0.23 Jy), the transit of the Galaxy at 140 MHz with the simultaneous tracking of 62 latitudinal beams, and an example of an IPS observation and the single‐station methodology for calculating the solar wind speed. The new technical capabilities of the radio telescope will provide the potential for participating in several scientific studies. These include solar wind properties, space weather forecasting, ionospheric perturbations, and astrophysical aims such as the monitoring of repeating fast radio bursts and pulsars' observations. Key Points: Radio telescope dedicated to the study of solar wind properties and space weather effects using the interplanetary scintillation techniqueThe new digital backend has several beamforming configurations, increases the bandwidth, and improves the instrument's sensitivityWith the new technical capabilities, the instrument can participate in space weather forecasting and other astrophysical studies [ABSTRACT FROM AUTHOR]

Featured Application: The results described in this paper will be used to develop low-noise receiving systems for ground-based radio telescopes and future space missions. We report on research in the field of low-noise receiving systems in the sub-terahertz (THz) range, carried out in recent years, aimed at developing receivers with quantum sensitivity for implementation in space and ground-based radio telescopes. Superconductor-Insulator-Superconductor (SIS) mixers based on high-quality tunnel junctions are the key elements of the most sensitive sub-THz heterodyne receivers. Motivations and physical background for technology improvement and optimization, as well as fabrication details, are described. This article presents the results of the SIS receiver developments for the 211–275 GHz and 790–950 GHz frequency ranges with a noise temperature in the double sideband (DSB) mode of approximTELY 20 K and 200 K, respectively. These designs and achievements are implemented in the development of the receiving systems for the Russian Space Agency mission "Millimetron", and for the ground-based APEX (Atacama Pathfinder EXperiment) telescope. [ABSTRACT FROM AUTHOR]

Delingha 13.7 m telescope is one of the most important radio telescopes in China. Since installing the superconducting spectroscopic array receiver (SSAR) and adopting the On The Fly (OTF) observation mode, the telescope has operated for nearly 10 years. During this period, a large number of astronomical observation projects have been carried out and completed, a large amount of astronomical data have been accumulated, and a series of important scientific results have been achieved. This paper introduces the operating status of SSAR in astronomical observations, the problems in operations, as well as the fault phenomena and solutions. The performance test and performance analysis of SSAR are described in detail, including the receiver noise temperature and telescope system noise temperature, image rejection ratio (IRR), receiver stability, beam performance and so on. The updating and development of SSAR are listed, including the automatic adjustment of LO (Local Oscillator) power, the updating of pre-amplification circuits of the sideband separation superconducting mixer, and the optimization of control program, etc. This paper summarizes the experiences and rules, and connects the past with the future, for applying the experiences of the maintenance and operation of SSAR to the next-generation large-scale receiver system. [ABSTRACT FROM AUTHOR]

Baghdad University Radio Telescope (BURT) is a 3 meter radio telescope that was installed in the main campus of the University of Baghdad in Jadiriyah. Radio telescopes, in general, offer a wide range of applications in radio astronomy, which are usually used to detect the neutral hydrogen emission line at a wavelength of 21 cm. One of the key applications of BURT is to observe the Milky Way galaxy and to determine its rotation curve. However, performing such observations requires accurate determination of the appropriate observing time as well as the coordinates. This paper focuses on how the observing time and coordinates are calculated correctly and accurately. The horizontal coordinate that corresponds to the galactic coordinates (b=0° and 0° ≤ l ≤ 90°) in every single day of 2023 at 10 am have been calculated using a c++ code that has been written for the purpose of this work. The results showed that the appropriate time for observing the Milky Way using BURT in 2023 is during January, February, March, November and December of 2023. The medians of altitude during those months are 50.9798°, 62.7919°, 50.6198°, 9.6562° and 30.5041°, respectively. During those months, the altitude is found, in general, larger than zero which means that the galactic position is above the horizon. [ABSTRACT FROM AUTHOR]

We report the discovery of three millisecond pulsars (MSPs): PSRs J1120âˆ'3618, J1646âˆ'2142, and J1828+0625 with the Giant Metrewave Radio Telescope (GMRT) at a frequency of 322 MHz using a 32 MHz observing bandwidth. These sources were discovered serendipitously while conducting the deep observations to search for millisecond radio pulsations in the directions of unidentified Fermi Large Area Telescope (LAT) Îł -ray sources. We also present phase coherent timing models for these MSPs using ∼5 yr of observations with the GMRT. PSR J1120âˆ'3618 has a 5.5 ms spin period and is in a binary system with an orbital period of 5.6 days and minimum companion mass of 0.18 M ⊙, PSR J1646âˆ'2142 is an isolated object with a spin period of 5.8 ms, and PSR J1828+0625 has a spin period of 3.6 ms and is in a binary system with an orbital period of 77.9 days and minimum companion mass of 0.27 M ⊙. The two binaries have very low orbital eccentricities, in agreement with expectations for MSP-helium white dwarf systems. Using the GMRT 607 MHz receivers having a 32 MHz bandwidth, we have also detected PSR J1646âˆ'2142 and PSR J1828+0625, but not PSR J1120âˆ'3618. PSR J1646âˆ'2142 has a wide profile, with significant evolution between 322 and 607 MHz, whereas PSR J1120âˆ'3618 exhibits a single peaked profile at 322 MHz and PSR J1828+0625 exhibits a single peaked profile at both the observing frequencies. These MSPs do not have Îł -ray counterparts, indicating that these are not associated with the target Fermi LAT pointing emphasizing the significance of deep blind searches for MSPs. [ABSTRACT FROM AUTHOR]

Radio astronomy file formats are now required to store wide frequency bandwidths and multiple simultaneous receiver beams and must be able to account for versatile observing modes and numerous calibration strategies. The need to capture and archive high-time and high frequency-resolution data, along with the comprehensive metadata that fully describe the data, implies that a new data format and new processing software are required. This requirement is suited to a well-defined, hierarchically-structured and flexible file format. In this paper we present the Spectral-Domain Hierarchical Data Format ('SDHDF') — a new file format for radio astronomy data, in particular for single dish or beam-formed data streams. Since 2018, SDHDF has been the primary format for data products from the spectral-line and continuum observing modes at Murriyang, the CSIRO Parkes 64-metre radio telescope, and we demonstrate that this data format can also be used to store observations of pulsars and fast radio bursts. [ABSTRACT FROM AUTHOR]

The computational requirements of future large scale radio telescopes are expected to scale well beyond the capabilities of conventional digital resources. Current and planned telescopes are generally limited in their scientific potential by their ability to efficiently process the vast volumes of generated data. To mitigate this problem, we investigate the viability of emerging quantum computers for radio astronomy applications. In this a paper we demonstrate the potential use of variational quantum linear solvers in Noisy Intermediate Scale Quantum (NISQ) computers and combinatorial solvers in quantum annealers for a radio astronomy calibration pipeline. While we demonstrate that these approaches can lead to satisfying results when integrated in calibration pipelines, we show that current restrictions of quantum hardware limit their applicability and performance. [ABSTRACT FROM AUTHOR]

The LOw Frequency ARray (LOFAR) is a European radio telescope operating since 2010 in the frequency bands 10 - 80 MHz and 110 - 250 MHz. This article provides an analysis of the energy consumption and the carbon footprint of LOFAR. The approach used is a Life Cycle Analysis (LCA). We find that one year of LOFAR operations requires 3,627 MWh of electricity, 48,714 m3 gas and 135,497 liters of fuel. The associated carbon emission is 1,867 tCO2e/year. Results include the footprint stemming from operations of all LOFAR stations and central processing, but exclude scientific post-processing and activities. The electrical energy required for scientific processing is assessed separately. It ranges from 1% (standard imaging and time-domain), to 40% (wide field long baseline imaging) of the energy consumption for the observation. The outcome provides a transparent baseline in making LOFAR more sustainable and can serve as a blueprint for the analysis of other research infrastructures. [ABSTRACT FROM AUTHOR]

This article presents the main results and new plans for the development of receivers which are cooled cryogenically to deep cryogenic temperatures and used in optical and radio astronomy research at the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) on both the Big Telescope Alt-Azimuthal optical telescope (BTA) and the Radio Astronomical Telescope Academy of Sciences (RATAN-600) radio telescope, 600 m in diameter. These two instruments almost completely cover the frequency range from long radio waves to the IR and optical bands (0.25–8 mm on RATAN and 10–0.3 μm, on BTA) with a certain gap in the terahertz part (8–0.01 mm) of the spectrum. Today, this range is of the greatest interest for astronomers. In particular, the ALMA (Atacama Large Millimeter Array) observatory and the worldwide network of modern telescopes called the EVH (Event Horizon Telescope) operate in this range. New developments at SAO RAS are aimed at mastering this part of the spectrum. Cryogenic systems of receivers in these ranges are a key element of the system and differ markedly from the cooling systems of optical and radio receivers that ensure cooling of the receivers to sub-Kelvin temperatures. [ABSTRACT FROM AUTHOR]

Radio astronomical observations at millimeter and submillimeter wavelengths are a very important tool for astrophysical research. However, there is a huge area in northeastern Eurasia, including the whole Russian territory, which lacks sufficiently large radio telescopes effectively operating at these wavelengths. In this review, we describe our long-term efforts to find suitable sites for such radio telescopes in this area, that is, sites with good atmospheric transparency at millimeter and submillimeter waves. We describe methods and instruments used for measurements and evaluations of the atmospheric opacity. They include special radiometric systems, which are used for estimations of the atmospheric opacity in the transparency windows from the sky brightness measurements. Evaluation of the precipitable water vapor from such measurements by the artificial neural network is discussed. Other approaches use water vapor radiometers, global atmospheric models and signals of the Global Navigation Satellite Systems. To date, long-term radiometric monitoring has been performed at several candidate sites, and atmospheric conditions for many sites have been evaluated using global atmospheric models. Several sites with the best atmospheric transparency at millimeter and submillimeter wavelengths have been selected. They can be effectively used for astronomical observations, at least in the major atmospheric transparency windows at 1.3 mm and 0.85 mm. In general, the results show that northeastern Eurasia is a promising area for submillimeter astronomy. These results can also be used for space communications and radar systems. [ABSTRACT FROM AUTHOR]

Understanding dark matter is one of the most urgent questions in modern physics. A very interesting candidate is primordial black holes (PBHs). For the mass ranges <10−16 M ⊙ and >100 M ⊙, PBHs have been ruled out. However, they are still poorly constrained in the mass range 10−16–100 M ⊙. Fast radio bursts (FRBs) are millisecond flashes of radio light of unknown origin, mostly from outside the Milky Way. Due to their short timescales, gravitationally lensed FRBs, which are yet to be detected, have been proposed as a useful probe for constraining the presence of PBHs in the mass window of <100 M ⊙. Up to now, the most successful project in finding FRBs has been CHIME. Due to its large field of view, CHIME has detected at least 600 FRBs since 2018. However, none of them is confirmed to be gravitationally lensed. Taiwan plans to build a new telescope, the Bustling Universe Radio Survey Telescope in Taiwan (BURSTT), dedicated to detecting FRBs. Its survey area will be 25 times greater than CHIME. BURSTT can localize all of these FRBs through very long baseline interferometry. We estimate the probability to find gravitationally lensed FRBs, based on the scaled redshift distribution from the latest CHIME catalog and the lensing probability function from Munõz et al. BURSTT-2048 can detect ∼24 lensed FRBs out of ∼1700 FRBs per annum. With BURSTT's ability to detect nanosecond FRBs, we can constrain PBHs to form a part of dark matter down to 10−4 M ⊙. [ABSTRACT FROM AUTHOR]

We have demonstrated spectrum sharing and coexistence between a 5G network and a radio telescope without causing interference to the radio astronomer. This was realized by using optical heterodyning between two distributed feedback (DFB) semiconductor lasers as a flex-spectrum photonic RF transmitter. The 5G network was designed to identify and avoid any radio frequency interference (RFI). The generated 5G RF carrier signal is used as the primary RF data carrier for the 5G network. A second RF signal, acting as noise signal, is introduced to the 5G network using an electrical mixer. When the frequencies at the mixer ports are the same, an error signal is generated which triggers the control circuit of the 5G network to correct for the RFI by shifting the primary RF data carrier of the 5G network to a new RF carrier frequency. An impressive RFI correction time of about 3 milliseconds was recorded. [ABSTRACT FROM AUTHOR]

Faraday tomography is a new method of the study of cosmic magnetic fields enabled by broad-band low-frequency radio observations. Using Faraday tomography it is possible to obtain the Faraday dispersion function, which contains information on the line-of-sight distributions of magnetic fields, thermal electron density, and cosmic ray electron density by measuring the polarization spectrum from a source of synchrotron radiation over a wide band. Furthermore, by combining it with two-dimensional imaging, Faraday tomography allows us to explore the three-dimensional structure of polarization sources. Faraday tomography has been active over the last 20 years, since the broad-band observation has become technically feasible, and polarization sources such as interstellar space, supernova remnants, and galaxies have been investigated. However, the Faraday dispersion function is mathematically the Fourier transform of the polarization spectrum. And since the observable band is finite, it is impossible to obtain a complete Faraday dispersion function by performing a Fourier transform. For this purpose, various methods have been developed to accurately estimate the Faraday dispersion function from the observed polarization spectrum. In addition, the Faraday dispersion function does not directly reflect the distribution of magnetic field, thermal electron density, and cosmic ray electron density in the physical space, and its physical interpretation is not straightforward. Despite these two difficult problems, Faraday tomography is attracting much attention because it has great potential as a new method for studying cosmic magnetic fields and magnetized plasmas. In particular, the next-generation radio telescope SKA (Square Kilometre Array) is capable of polarization observation with unprecedented sensitivity and broad bands, and the application of Faraday tomography is expected to make dramatic progress in the field of cosmic magnetic fields. In this review, we explain the basics of Faraday tomography with simple and instructive examples. Representative algorithms to realize Faraday tomography are introduced, and some applications are shown. [ABSTRACT FROM AUTHOR]

The Haystack Telescope is an antenna with a diameter of 37 m and an elevation-dependent surface accuracy of ≤ 100 μ m that is capable of millimeter-wave observations. The radome-enclosed instrument serves as a radar sensor for space situational awareness, with about one-third of the time available for research by MIT Haystack Observatory. Ongoing testing with the K-band (18–26 GHz) and W-band receivers (currently 85–93 GHz) is preparing the inclusion of the telescope into the Event Horizon Telescope (EHT) array and the use as a single-dish research telescope. Given its geographic location, the addition of the Haystack Telescope to current and future versions of the EHT array would substantially improve the image quality. [ABSTRACT FROM AUTHOR]

The proposed next generation Event Horizon Telescope (ngEHT) concept envisions the imaging of various astronomical sources on scales of microarcseconds in unprecedented detail with at least two orders of magnitude improvement in the image dynamic ranges by extending the Event Horizon Telescope (EHT). A key technical component of ngEHT is the utilization of large aperture telescopes to anchor the entire array, allowing the connection of less sensitive stations through highly sensitive fringe detections to form a dense network across the planet. Here, we introduce two projects for planned next generation large radio telescopes in the 2030s on the Chajnantor Plateau in the Atacama desert in northern Chile, the Large Submillimeter Telescope (LST) and the Atacama Large Aperture Submillimeter Telescope (AtLAST). Both are designed to have a 50-meter diameter and operate at the planned ngEHT frequency bands of 86, 230 and 345 GHz. A large aperture of 50 m that is co-located with two existing EHT stations, the Atacama Large Millimeter/Submillimeter Array (ALMA) and the Atacama Pathfinder Experiment (APEX) Telescope in the excellent observing site of the Chajnantor Plateau, will offer excellent capabilities for highly sensitive, multi-frequency, and time-agile millimeter very long baseline interferometry (VLBI) observations with accurate data calibration relevant to key science cases of ngEHT. In addition to ngEHT, its unique location in Chile will substantially improve angular resolutions of the planned Next Generation Very Large Array in North America or any future global millimeter VLBI arrays if combined. LST and AtLAST will be a key element enabling transformative science cases with next-generation millimeter/submillimeter VLBI arrays. [ABSTRACT FROM AUTHOR]

The Pulsar Science Collaboratory (PSC) is a research project engaging high school students, teachers, and undergraduates in searching for pulsars in data collected using radio telescopes. The goals are to stimulate student interest in science, technology, engineering, and mathematics careers; prepare teachers to implement authentic research with students by training them within a professional scientific community; promote student use of information technologies; and assist the research community through pulsar discoveries. The learning is facilitated through online training, in-person workshops and camps, discussion forums, participation in capstone events, conferences, and so on. The PSC is powered by HUBzero, a platform for building science gateways, and combines analytical tools, community management, course components, and collaborations in one ecosystem. The participants gain access to radio astronomy data after successful completion of training workshops and passing a certification test. PSC students make authentic research contributions to the scientific community, pulsar astrophysics, and radio astronomy. [ABSTRACT FROM AUTHOR]

We have designed a low-cost radio telescope system named the Bose Horn Antenna Radio Telescope (BHARAT) to detect the 21 cm hydrogen line emission from our Galaxy. The system is being used at the Radio Physics Laboratory (RPL) (Radio Physics Lab, IUCAA NCRA-TIFR, , ), Inter-University Centre for Astronomy and Astrophysics (IUCAA), India, for laboratory sessions and training students and teachers. It is also a part of the laboratory curriculum at several universities and colleges. Here, we present the design of a highly efficient, easy to build, and cost-effective dual-mode conical horn used as a radio telescope and describe the calibration procedure. We also present some model observation data acquired using the telescope for facilitating easy incorporation of this experiment in the laboratory curriculum of undergraduate or post-graduate programs. We have named the antenna after Acharya (teacher or an influential mentor) Jagadish Chandra Bose, honoring a pioneer in radio-wave science and an outstanding teacher, who inspired several world renowned scientists. [ABSTRACT FROM AUTHOR]

Results of a study of powerful H2O maser flares in the W51 region from observations (monitoring) in 2009–2022 with the 22-m radio telescope in the Pushchino Radio Astronomy Observatory are presented. Three powerful maser flares were detected at radial velocities of 69.7, 61.6, and 59.0 km/s with flux densities at peaks of 23.1, 29.4, and 66.1 kJy, respectively. The first and third of them are identified with the main source (W51 Main). A probable reason for their occurrence may be the superposition of two maser condensations with close radial velocities on the line of sight. A large number of flares with flux densities above 10 kJy were also detected, most of which were identified with W51 North. The mechanism for the appearance of the asymmetry of the line for the most powerful flare at a radial velocity of 59 km/s is discussed. [ABSTRACT FROM AUTHOR]

• Calibration algorithm of a radio telescope in the presence of man-made radio waves. • Array signal processing model that considers the presence of interferences. • Maximum likelihood estimation of the model parameters. • Development of a Space Alternating Generalized Expectation-Maximization algorithm. Radio interferometers are phased arrays producing high-resolution images from the covariance matrix of measurements. Calibration of such instruments is necessary and is a critical task. This is how the estimation of instrumental errors is usually done thanks to the knowledge of referenced celestial sources. However, the use of high sensitive antennas in modern radio interferometers (LOFAR, SKA) brings a new challenge in radio astronomy because they are more sensitive to Radio Frequency Interferences (RFI). The presence of RFI during the calibration process generally induces biases in state-of-the-art solutions. The purpose of this paper is to propose an alternative to alleviate the effects of RFI. For that, we first propose a model to take into account the presence of RFI in the data across multiple frequency channels thanks to a low-rank structured noise. We then achieve maximum likelihood estimation of the calibration parameters with a Space Alternating Generalized Expectation-Maximization (SAGE) algorithm for which we derive originally two sets of complete data allowing closed-form expressions for the updates. Numerical simulations show a significant gain in performance for RFI corrupted data in comparison with some more classical methods. [ABSTRACT FROM AUTHOR]

On the African continent, South Africa has world-class astronomical facilities for advanced radio astronomy research. With the advent of the Square Kilometre Array project in South Africa (SA SKA), six countries in Africa (SA SKA partner countries) have joined South Africa to contribute towards the African Very Long Baseline Interferometry (VLBI) Network (AVN). Each of the AVN countries aims to construct a single-dish radio telescope that will be part of the AVN, the European VLBI Network, and the global VLBI network. The SKA and the AVN will enable very high sensitivity VLBI in the southern hemisphere. In the current AVN, there is a gap in the coverage in the central African region. This work analyses the increased scientific impact of having additional antennas in each of the six countries in central Africa, i.e., Cameroon, Gabon, Congo, Equatorial Guinea, Chad, and the Central African Republic. A number of economic human capital impacts of having a radio interferometer in central Africa are also discussed. This work also discusses the recent progress on the AVN project and shares a few lessons from some past successes in ground stations retrofitting. [ABSTRACT FROM AUTHOR]

After introducing Leonardo da Vinci's (LdV) predecessors in the field of light propagation research, his drawings on the topic of reflecting light by a spherical mirror are analysed. The discovery of LdV is presented, according to which, at an infinitely distant source of rays, a small fragment of the canopy is enough to generate a focus, while the rest of the mirror forms a caustic for which LdV did not indicate an application. An analytical description of the energy concentration in the focus and on the caustic is given, together with its reference to the geometric representation of the acoustic field in rooms. Based on the general principles of wave motion, symmetry is shown in the description of energy relations in acoustics and electromagnetism. It is explained why in the sound field in existing halls, instead of a whole caustic only its cusp is observed, which is perceived as a point-like sound focus. The size of the mirror aperture, shown graphically by LdV, is determined. How the development of receiving techniques increased the mirror aperture compared to the LdV estimate is also shown. The implementation of these improvements is presented via the example of the Arecibo and FAST radio telescopes. [ABSTRACT FROM AUTHOR]

The new generation radio telescopes, such as the Square Kilometre Array (SKA), are expected to reach sufficient sensitivity and resolution to provide large number densities of resolved faint sources, and therefore to open weak gravitational lensing observations to the radio band. In this paper we present RadioLensfit , an open-source tool for an efficient and fast galaxy shape measurement for radio weak lensing shear. It performs a single source model fitting in the Fourier domain, after isolating the source visibilities with a sky model and a faceting technique. This approach makes real sized radio datasets accessible to an analysis in this domain, where data is not yet affected by the systematics introduced by the non-linear imaging process. We detail the implementation of the code and discuss limitations of the source extraction algorithm. We describe the hybrid parallelization MPI+OpenMP of the code, implemented to exploit multi-node HPC infrastructures for accelerating the computation and dealing with very large datasets that possibly cannot entirely be stored in the memory of a single processor. Finally, we present performance results both in terms of measurement accuracy and code scalability on SKA-MID simulated datasets. In particular, we compare shape measurements of 1000 sources at the expected source density in SKA Phase 1 with the ones obtained from the same dataset in a previous work by a joint fitting of the raw visibility data, and show that results are comparable while the computational time is highly reduced. [ABSTRACT FROM AUTHOR]

The front-end circuit used in the pulsar acquisition of the radio telescope determines the availability of the entire pulsar-based timing framework. However, it would be expensive and resource consuming to use a real radio telescope in the circuit design process. To address this issue, in this article, the hardware-in-the-loop simulation solution is proposed to generate, sample, and extract pulse signals in real time. The artificial pulse generation method is first proposed to generate the pulses that are close to real pulsar signals. Then, three analog front-end circuit architectures (AFCAs) are proposed to generate the analog pulses, including the superposition, attenuator, and attenuator-based superposition structures. The generated pulses are close to the real pulsar signal in shape, amplitude, and noise level. Next, a pulsar-based timing synchronization framework that can be used to improve the timing accuracy of the wide-area monitoring systems is developed to process the sampled data. Multiple experiments are conducted to verify the effectiveness of the analog front-end and the pulsar-based timing synchronization framework using the simulated pulse and real pulsar signals. The results demonstrated that the designed AFCAs can generate effective analog pulses, and is convenient and flexible. [ABSTRACT FROM AUTHOR]

This article presents the design of a new dual-polarized Vivaldi feed for the Hydrogen Epoch of Reionization Array (HERA) radio telescope. This wideband feed has been developed to replace the Phase I dipole feed and is used to illuminate a 14 m diameter dish. It aims to improve the science capabilities of HERA, by allowing it to characterize the redshifted 21 cm hydrogen signal from the Cosmic Dawn as well as from the Epoch of Reionization. This is achieved by increasing the bandwidth from 100–200 to 50–250 MHz, optimizing the time response of the antenna–receiver system and improving its sensitivity. This new Vivaldi feed is directly fed by a differential front-end module placed inside the circular cavity and connected to the back end via cables that pass in the middle of the tapered slot. We show that this particular configuration has minimal effects on the radiation pattern and the system response. [ABSTRACT FROM AUTHOR]

We consider some properties and possible observational manifestations of the very heavy primordial black holes (PBHs), with masses ∼ (1 0 9 − 1 0 1 0) M ⊙ . These black holes should be surrounded by the dense dark matter and baryonic halos even at early cosmological epochs. There are mechanisms as for radiation emission in the centers due to accretion and for deep absorption of relic radiation at the periphery of the halos. We calculate the absorption profile in the 21 cm line of atomic hydrogen by solving the equations of radiation transfer through the baryonic halo around a PBH. The calculations show that a spherical absorbing layer appears around the object, which can be observed with radio telescopes. Also, at some epochs, shock waves may form at the periphery of the objects. The accelerated charged particles can radiate in radio frequency band, so it is possible that these objects can explain the recently discovered radio circles. [ABSTRACT FROM AUTHOR]

The common phenomenon of lightning still harbors many secrets such as what are the conditions for lightning initiation and what is driving the discharge to propagate over several tens of kilometers through the atmosphere forming conducting ionized channels called leaders. Since lightning is an electric discharge phenomenon, there are positively and negatively charged leaders. In this work we report on measurements made with the LOFAR radio telescope, an instrument primarily build for radio-astronomy observations. It is observed that a negative leader rather suddenly changes, for a few milliseconds, into a mode where it radiates 100 times more VHF power than typical negative leaders after which it spawns a large number of more typical negative leaders. This mode occurs during the initial stage, soon after initiation, of all lightning flashes we have mapped (about 25). For some flashes this mode occurs also well after initiation and we show one case where it is triggered twice, some 100 ms apart. We postulate that this is indicative of a small (order of 5 km 2 ) high charge pocket. Lightning thus appears to be initiated exclusively in the vicinity of such a small but dense charge pocket. [ABSTRACT FROM AUTHOR]

Returned to Cambridge in 1974 as a research associate in the Cavendish Laboratory, a transition that put him on the threshold of a dazzling career in millimetre wave astronomy. Graph B Richard Hills (1945-2022) b Simon Mitton remembers a world-class pioneer and innovator of submillimetre astronomy. Emeritus Professor Richard Edwin Hills FRS, a world leading innovator of millimetre and submillimetre radio astronomy died on 5 June 2022. [Extracted from the article]