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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]

The recently developed new generation, low-frequency Giant Ukrainian Radio Telescope (GURT) is built nearby the well-known Ukrainian T-shaped Radio Telescope. The new facility employs a phased antenna array composed of many subarrays of $5 \times 5$ active antenna elements. In this paper, the parameters of the active antenna used as array element are studied, with special attention paid to sensitivity. The electrical and noise parameters are calculated using computer simulation and wave techniques for noise modeling of two-port networks. The results of numerical calculations of the sensitivity are given in terms of the sky noise dominance (SND) and system equivalent flux density of the GURT element within 10–80 MHz. The calculated results are compared with in situ measurements. [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 new Giant Ukrainian Radio Telescope (GURT) intended for operation in 8–80 MHz range is now under construction. It employs an active phased array antenna composed of many dipole subarrays, several of which have been implemented and now are used for radio astronomy observations. In this two-part paper, the electrical and noise parameters of the subarray are studied by numerical and experimental ways. In this part, a theoretical model of the subarray based on the wave theory of noisy multiport networks that takes into account the mutual coupling in the dipole array placed over imperfect ground and the correlation between all existing noise sources is proposed. It is assumed that the initial parameters for this model should be obtained using the correct electromagnetic and circuit simulation. A technique for using of this model to calculate the effective area, radiation efficiency, internal and external noise temperatures, as well as sensitivity of the subarray in terms of system equivalent flux density (SEFD) for all possible beam directions in the frequency band of the GURT radio telescope is described. [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]

We describe the design, construction, and performance of a compact orthomode transducer (OMT) for the L-band receiver (1.3–1.8 GHz) of the Sardinia Radio Telescope (SRT). The complete OMT consists of a cylindrical orthomode junction (OMJ), which is presented in this paper, and two identical 180^\circ hybrid power combiners in a double-ridged waveguide, which have been proposed in a previous work. The OMT operates at the cryogenic temperature of 20 K to reduce its thermal noise contribution to the noise of the receiving chain. Therefore, particular care has been taken in the design of the OMJ to minimize its dimension and insure a good thermalization. The proposed OMT has been designed and optimized by using CST Microwave Studio, and then manufactured, tested at room temperature, and installed on the L-band receiver of the SRT. The measured results fully comply with the design specifications. In particular, the isolation between the OMT output ports is more than 40 dB, and the cross polarization is less than -\35 dB for both polarization channels. [ABSTRACT FROM PUBLISHER]

Front-end amplifiers with high input impedance are exploited to build active array elements for modern low-frequency radio telescopes. The combination of such loading and mutual coupling between adjacent elements is responsible for the deep nulls that are present in some embedded element patterns (EEPs) of the Low-Frequency Array. This paper quantifies this phenomenon with both models and experimental data. The full-wave array simulations and the measured amplifier scattering parameters are combined to obtain the EEP models. These models are in good agreement with the in situ measurements that have been performed with a micro unmanned aerial vehicle carrying a field source. [ABSTRACT FROM PUBLISHER]

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]

The new generation radio telescopes, such as the Square Kilometre Array (SKA) currently under construction, will use aperture array, technology for the low frequency regime. For SKA2, the second phase scheduled after the realization of SKA1, aperture array technology is proposed up to 1.4 GHz. The antenna element count, as well as the signal processing cost, of such a system will be high. In this paper we analyze an option to reduce the number of antenna elements by making the array sparse. To reduce the signal processing cost Fast Fourier Transform Beamforming is proposed and it performance is compared to traditional beamforming. To guide the system design a Figure of Merit for the performance cost ratio is proposed and evaluated for various levels of sparsity of the antenna array. It is concluded that, for equal front-end and back-end costs, a sparse system is only marginally better than a dense system. Only when signal processing cost is significantly lower than the front-end hardware, a sparse system can be competitive. [ABSTRACT FROM AUTHOR]

One of the main technologies to open up a wider field of view for today's radio telescopes are phased arrays. This is especially the case for radio astronomy instruments operating below 2 GHz. Nowadays, the existing dish-type instruments are being upgraded with phased array feeds (PAF) in the focal plane. This increases the field of view at the expense of needing more analog electronics and digital signal processing. One of the digital signal processing functionalities used to combine the digitized signals from the PAF is a beam-former which creates multiple high sensitivity beams within the field of view of the dish. Before beams can be formed, the signals from the PAF need to be calibrated using a correlator. In this paper, we present a solution where these two operations are combined by using the beam-former also as a correlator. The statistics unit used as part of the beam-former implementation, can be used as well for calculating correlation products. With the proper settings of the beam-former weight of each beamlet, a frequency sub-band with a direction, can be used as a single cross correlation product. By implementing the correlator on the beam-former, the digital resources and development time can be reduced. To validate the idea, two versions of the algorithm are implemented in the Apertif PAF system on the Westerbork Synthesis Radio Telescope (WSRT). Results show that two full-bandwidth correlation matrices per beam, needed to determine the static beam weights for the calibration, and a single column of the correlation matrix, used to compensate for any drift between the receiver chains, can be performed. [ABSTRACT FROM AUTHOR]

The very demanding requirements of the SKA-low instrument call for a challenging antenna design capable of delivering excellent performance in radiation patterns, impedance matching, polarization purity, cost, longevity, etc. This paper is devoted to the development (design and test of the first prototypes) of an active ultra-wideband antenna element for the low-frequency instrument of the SKA radio telescope. The antenna element and differential low noise amplifier described here were originally designed to cover the former SKA-low band (70-450 MHz) but it is now aimed to cover the re-defined SKA-low band (50-350 MHz) and furthermore the antenna is capable of performing up to 650 MHz with the current design. The design is focused on maximum sensitivity in a wide field of view (+/− 45° from zenith) and low cross-polarization ratios. Furthermore, the size and cost of the element has to be kept to a minimum as millions of these antennas will need to be deployed for the full SKA in very compact configurations. The primary focus of this paper is therefore to discuss various design implications for the SKA-low telescope. [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]

The Ultralong‐Wavelength (ULW) regime of longer than 10 m (corresponding to frequencies below 30 MHz) remains as the last virtually unexplored window in radio astronomy and is presently attracting considerable attention as an area of potentially rewarding studies. However, the opaqueness of the Earth's ionosphere makes the ULW celestial radio emission very difficult to detect with ground‐based instrumentation. The impact of the ionosphere on ULW radio emission depends on the solar cycle activities and varies with time. In addition, the ULW spectrum region is densely populated by intensive artificial radio frequency interference. An obvious solution of these problems is to place an ULW radio telescope in space. However, this solution is expensive and poses nonnegligible technological challenges. An alternative approach is triggered by recent studies showing that the period of post 2020 will be most suitable for exploratory ground‐based ULW radio observations due to the expected "calm" state of the ionosphere; the ionospheric cutoff frequency could be well below 10 MHz, even in the day time. In anticipation of this upcoming opportunity, we propose and present in this paper a concept of an experimental ULW radio array, with the intention of setting it up in Inner Mongolia, China. This ULW facility will use the infrastructure of the currently operational Mingantu spectral radio heliograph. The proposed ULW array covers the frequency range from 1 to 72 MHz. This experimental array will be used for exploratory studies of celestial radio emission in the ULW range of the spectrum. Key Points: We propose an experimental Ultralong‐Wavelength (ULW) radio array operating in the frequency range of 1–72 MHzThe proposed ULW radio array is of low cost with easy implementability and will be useful post 2020 during the solar cycle minimum [ABSTRACT FROM AUTHOR]

Irbene RT-32 radio telescope is one of the main instruments operated by Ventspils International Radio Astronomy Center (VIRAC), which is used for participation in VLBI and single-dish mode observations, including European VLBI Network (EVN) and other astronomy projects such as recently started research on small bodies of solar system, which involves weak spectral line detection at L-band. Since start of the operation as a radio telescope, single C-X band receiver has been available at RT-32, but regular demand for L-band frequencies has been received due to its importance in spectral line science. In case of RT-32 geometry, optimum dimensions of L-band feed antenna system are inconveniently large and its installation without significant feed cone rebuilding is complicated. While work is currently ongoing to redesign the feed cone for multiple receiver support and to develop high performance L-band feed system, temporal, compact and low-cost receiver has been built and installed laterally to secondary focus, which in sense of performance and functionality has been proven to be appropriate for most of the current needs. Receiver is based on small parabolic reflector allowing one to use a compact dual circular polarized horn antenna, which together with a Cassegrain antenna forms a three-mirror system. Front-end is uncooled that allows reducing operational and maintenance costs, while still providing acceptable noise performance. Practical tests show average overall sensitivity of 750 Jy at 1650 MHz in terms of system effective flux density (SEFD). The paper describes the development of the receiver and presents the main results of performance characterization obtained at Irbene RT-32. [ABSTRACT FROM AUTHOR]

Complementary to the conventional dish radio telescopes, aperture arrays provide a technically attractive approach to achieve a large field of view and flexibility in observational parameters e.g. Sky area vs. bandwidth. Designs of both aperture array elements and overall geometry for the SKA Mid Frequency Aperture Array are presented here, together with resulting trade-offs. The paper reports the latest developments of global efforts on the front-end design of Mid-Frequency Aperture Array, not attempting to make technology selections, as the priority of sciences and the time for implementing Mid-Frequency Aperture Array is yet to be fully confirmed. Different on-going front-end solutions are introduced, particularly crossed ring antenna array with a planar structure is explored in more detail as it is less known in the community. Key performances of the candidate front-end technologies are addressed by examining the prototypes. The objective of the collaborative study is to increase technology readiness for implementation of Mid-Frequency Aperture Array in the future. [ABSTRACT FROM AUTHOR]

This paper reports a design study for a space-based decametric wavelength telescope. While not a new concept, this design study focused on many of the operational aspects that would be required for an actual mission. This design optimized the number of spacecraft to insure good visibility of approx. 80% of the radio galaxies- the primary science target for the mission. A 5,000 km lunar orbit was selected to guarantee minimal gravitational perturbations from Earth and lower radio interference. Optimal schemes for data downlink, spacecraft ranging, and power consumption were identified. An optimal mission duration of 1 year was chosen based on science goals, payload complexity, and other factors. Finally, preliminary simulations showing image reconstruction were conducted to confirm viability of the mission. This work is intended to show the viability and science benefits of conducting multi-spacecraft networked radio astronomy missions in the next few years. [ABSTRACT FROM AUTHOR]

This paper reports two Low Noise Amplifiers (LNA) for Aperture Array system of the international Square Kilometre Array (SKA) project. LNA design for SKA is a step change in traditional LNA design approach for radio astronomy applications as the defining aspects of performance are low noise along with low power consumption and adequate gain. The LNAs are designed, fabricated and characterised for frequency range of 20 −1000 MHz. One LNA has single ended input to single ended output configuration (LNA1) while the other LNA has balanced input to single ended output (LNA2). The S-parameter, noise figure (NF) and large signal response of the LNAs are measured at room temperature. Both LNAs show flat gain of higher than 30 dB over specified frequency range. Average NF values of LNA1 and LNA2 are 0.55 dB and 0.75 dB respectively. Mixed mode S-parameter response based on theoretical analysis of differential configuration is presented. The LNAs have exceptionally low power consumption of less than 25 mW; 20 times lower than the other reported LNAs available for the SKA and also covering complete frequency band with less than 1 dB NF. Therefore implication of these LNAs is a significant step forward as the projected number of LNAs required for the lower frequency band of SKA Aperture Array system is 5,600,000 (Dewdney et al., Proc. IEEE 97(8), 1482-1496, ; Faulkner et al. ). [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]

Copyright of Latvian Journal of Physics & Technical Sciences is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In radioastronomy the interferometric measurement between radiotelescopes located relatively close to each other helps removing ionospheric effects. Unfortunately, in case of networks such as LOw Frequency ARray (LOFAR), due to long baselines (currently up to 1500 km), interferometric methods fail to provide sufficiently accurate ionosphere delay corrections. Practically it means that systems such as LOFAR need external ionosphere information, coming from Global or Regional Ionospheric Maps (GIMs or RIMs, respectively). Thanks to the technology based on Global Navigation Satellite Systems (GNSS), the scientific community is provided with ionosphere sounding virtually worldwide. In this paper we compare several interpolation methods for RIMs computation based on scattered Vertical Total Electron Content measurements located on one thin ionospheric layer (Ionospheric Pierce Points-IPPs). The results of this work show that methods that take into account the topology of the data distribution (e.g., natural neighbour interpolation) perform better than those based on geometric computation only (e.g., distance-weighted methods). [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]

Copyright of Latvian Journal of Physics & Technical Sciences is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, I will give a brief overview of the largest radio telescope in the world, the Square Kilometre Array (SKA). The history of this instrument, its development as a huge international project, as well as its main scientific goals, will be summarised. I will then focus on a particular science case by presenting how the first phase of the SKA (SKA1), whose observations are expected to start in the early 2020's, will change our radio view of the largest gravitationally bound structures of the Universe: galaxy clusters. [ABSTRACT FROM AUTHOR]

This paper presents an improved input-buffer architecture for the X part of a very large FX correlator that optimizes memory use to both increase performance and reduce the overall power consumption. The architecture uses an array of two-accumulator CMACs that are reused for different pairs of correlated signals. Using two accumulators in every CMAC allows the processing array to alternately correlate two sets of signal pairs selected in such a way so that they share some or all of the processed data samples. This leads to increased processing bandwidth and a significant reduction of the memory read rate due to not having to update some or all of the processing buffers in every second processing cycle. The overall memory access rate is at most 75 % of that of the single-accumulator CMAC array. This architecture is intended for correlators of very large multi-element radio telescopes such as the Square Kilometre Array (SKA), and is suitable for an ASIC implementation. [ABSTRACT FROM AUTHOR]

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) has started the Commensal Radio Astronomy FasT Survey (CRAFTS). In this paper, we use the technical parameters of FAST derived from commissioning observations to simulate the completeness function for extragalactic H  i survey of CRAFTS, H  i galaxies from two kinds of mock catalogues are selected. One is generated by Monte Carlo simulation based on the interpolated mass–velocity width function of the ALFALFA |$100{{\ \rm per\ cent}}$| (a.k.a. α.100) catalogue. The other is constructed by semi-analytical N -body simulation based on the ΛCDM model. Our results suggest that a two-pass CRAFTS extragalactic H  i survey will be able to detect nearly 4.8 × 105 galaxies, from which the 'faint end' slope of the H  i mass function (HIMF) can be recovered to |$\mathrm{10^{7}\, M_{\odot }}$| and the 'knee mass' of the HIMF can be measured to a redshift of 0.1. Considering the radio frequency interference status and sensitivity limitation, CRAFTS will be efficient in detecting H  i galaxies at redshifts below 0.1, which implies a tremendous potential in exploring the galaxy interactions in different environments and the spatial distribution of H  i galaxies in the local universe. [ABSTRACT FROM AUTHOR]

To interpret radio interferometric observations sensitive to linear polarization it is necessary to take into account the effect of instrumental or 'parasitic' polarization. In the case of ground-space very-long-baseline interferometry, this procedure involves a session of polarization-sensitive mapping with the sufficient number of ground stations and sufficiently small projections of ground-space baselines. In the paper, the problem of estimating the value of the instrumental polarization of the Spectr-R space radio telescope of the RadioAstron project using the results of the early scientific program for observing active galactic nuclei is addressed. We use a statistical approach to estimate the value of the instrumental polarization associated with the analysis of already obtained to present time intermediate results of the review of brightness temperatures. Estimates obtained for the frequency bands C and L (95% probability intervals [0.0646, 0.1267] and [0.0945, 0.1736] for 6 and 18 cm, respectively) suggest that the instrumental polarization of the radio telescope does not exceed the values typical for the ground VLBI stations. [ABSTRACT FROM AUTHOR]

This paper outlines the methods used at the ASC LPI for generating instruction sequences that control operation modes of the onboard scientific equipment and describes the means for timely receipt of information about the current state of the onboard equipment, thus making it possible to quickly assess the adequacy of the selected modes for the solution of scientific problems and respond to emergency situations. The main points of interaction with other subsystems and their controls are briefly described. [ABSTRACT FROM AUTHOR]

We present the description of Fakerat software developed for scheduling Very Long Baseline Interferometry (VLBI) observations on ground-space bases exceeding the size of the Earth. The results of scheduled observations using the Fakerat package, carried out during the first two years after launching the space radio telescope (SRT) in the space-ground interferometer mode, are reported in the paper. [ABSTRACT FROM AUTHOR]

Context. The nuclear starburst in the nearby galaxy M82 provides an excellent laboratory for understanding the physics of star formation. This galaxy has been extensively observed in the past, revealing tens of radio-bright compact objects embedded in a diffuse free-free absorbing medium. Our understanding of the structure and physics of this medium in M82 can be greatly improved by high-resolution images at low frequencies where the effects of free-free absorption are most prominent. Aims. The aims of this study are, firstly, to demonstrate imaging using international baselines of the Low Frequency Array (LOFAR), and secondly, to constrain low-frequency spectra of compact and diffuse emission in the central starburst region of M82 via high-resolution radio imaging at low frequencies. Methods. The international LOFAR telescope was used to observe M82 at 110â'126â€MHz and 146â'162â€MHz. Images were obtained using standard techniques from very long baseline interferometry. images were obtained at each frequency range: one only using international baselines, and one only using the longest Dutch (remote) baselines. Results. The 154 MHz image obtained using international baselines is a new imaging record in terms of combined image resolution (0.3â€â€) and sensitivity (σ = 0.15 mJy/beam) at low frequencies (<327 MHz). We detected 16 objects at 154 MHz, six of these also at 118 MHz. Seven objects detected at 154 MHz have not been catalogued previously. For the nine objects previously detected, we obtained spectral indices and emission measures by fitting models to spectra (combining LOFAR with literature data). Four weaker but resolved features are also found: a linear (50 pc) filament and three other resolved objects, of which two show a clear shell structure. We do not detect any emission from either supernova 2008iz or from the radio transient source 43.78+59.3. The images obtained using remote baselines show diffuse emission, associated with the outflow in M82, with reduced brightness in the region of the edge-on star-forming disk. [ABSTRACT FROM AUTHOR]

The results of refining the parameters of the Spektr-R spacecraft (RadioAstron project) motion after it was launched into the orbit of the Earth's artificial satellite in July 2011 showed that, at the beginning of 2013, the condition of staying in the Earth's shadow was violated. The duration of shading of the spacecraft exceeds the acceptable value (about 2 h). At the end of 2013 to the beginning of 2014, the ballistic lifetime of the spacecraft completed. Therefore, the question arose of how to correct the trajectory of the motion of the Spektr-R satellite using its onboard propulsion system. In this paper, the ballistic parameters that define the operation of onboard propulsion system when implementing the correction, and the ballistic characteristics of the orbital spacecraft motion before and after correction are presented. [ABSTRACT FROM AUTHOR]