Radio Astronomy Telescopes Research Articles

Cryogenic Systems for Astronomical Research in the Special Astrophysical Observatory of the Russian Academy of Sciences

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.

Wind-Induced Vibrations and Gust Response Factors of the Cabin–Cable–Tower System

A large-scale radio astronomical telescope is a typical complex coupled system, consisting of a feed cabin, cables, and supporting structures. The system is extremely sensitive to wind loads, especially the feed cabin, which has high requirements for vibration displacement during operation, and excessive vibration may affect normal operation. To investigate the wind-induced vibration characteristics of such coupled systems, this study takes the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) as an example to conduct research. First, a refined finite element model of FAST is established, and a dynamic analysis using simulated random wind loads is conducted. The influence of the cable boundary on the time–frequency domain responses of the feed cabin is particularly considered. Then, the gust response factor (GRF) for different structural components within the coupled system is calculated. Finally, the evolution law of the GRF under various wind speeds and directions is revealed by parametric analysis. The parameter analysis only considers the wind directions ranging from 0° to 60°, because FAST is a symmetric structure. The results indicate that obvious differences are observed in both the rotational and translational displacements of the feed cabin under northward wind, especially the results along the east–west axis. When the supporting towers are considered, there is no change in the power spectral density (PSD) of the feed cabin in the low-frequency range. However, in the high-frequency range, taking the supporting towers into account leads to an increase in PSD and a resonance near the first-order natural frequency of the supporting tower. The GRF based on the dynamic response exhibits substantial deviations compared to those obtained from design codes, highlighting the need for an independent analysis when determining GRF for such coupled systems.

Control system performance of a 7.3-meter radio telescope converted from telecommunication antenna to radio astronomy purposes in Malaysia

We present a crucial step in converting a commercial telecommunication antenna system into a radio astronomy telescope. This step involved the development of a newly installed and simple control system to manage the telescope movement with relatively good pointing accuracy. The control system was designed using a programmable logic controller (PLC) that is robust and affordable. Based on the performance testing, this control system achieved average accuracies of 0.95 and 1.083 arcmin in azimuth and elevation positioning respectively, and an RMS of 9 arcmin across the open sky. In addition, it reached average rotation speeds of about 5.4, 2.4, and 4.8 arcmin/s for azimuth, elevation, and tracking rate, respectively. The results also showed that the converted radio telescope has an acceptable tracking accuracy of errors below 10% of the antenna half-power bandwidth at a frequency of 1.4 GHz while generating movement speed suitable for basic radio astronomy observations. These results show that this converted small radio telescope has the basic requirements for tracking and imaging celestial radio objects, primarily via interferometry with larger radio telescopes at low observation frequencies.

Low-Noise Amplifier for Next-Generation Radio Astronomy Telescopes: Review of the State-of-the-Art Cryogenic LNAs in the Most Challenging Applications

Radio astronomy is a subfield of astronomy that explores the universe via radio signals up to a few terahertz. Since the first detection of radio signals from the Milky Way by Karl G. Jansky in 1932, various types of radio sources have been identified from our solar system, the local universe, extragalactic space, and all of the way back to the beginning of the universe.

Pre-Correction of Water Vapour Emission for Radio Astronomy Observations at Al-Uyayna Observatory

Al-Uyayna radio astronomy telescope near Riyadh, Saudi Arabia has been built as a prototype to study the nearby sky objects at ∼10 GHz. Good observations were obtained during the operation period of the telescope. The measurements indicated that the contribution of water vapour has a significant contribution to the observations of the weak astronomical signals. This contribution has to be taken into account and flagged to achieve correct and more accurate results depending on the strength of the astronomical signal observed at 10.3 GHz. Our study showed that the astronomical data must be corrected by 0.205 ± 0.003 for the noise from water vapour radio emission. A model was made for this purpose, and more studies will be shown in future work.

On Detecting the Fourth Gyrofrequency Harmonic in Microwave Emission Spectra above Sunspots

Spectral polarization observations of radio sources above sunspots are regularly carried out with the RATAN-600 radio telescope (RATAN is a Russian acronym for the Radio Astronomical Telescope of the Academy of Sciences). The in-depth studies of the spectra reveal new effects. In this paper, we analyze the manifestation of radio emission of the fourth gyrofrequency harmonic in microwave spectra obtained with 1-percent frequency resolution in a range of 3–18 GHz. Registration of the extraordinary mode in the short-wavelength range of the spectrum is compared to the model calculations of the second-to-fifth gyrofrequency harmonics against a background of the thermal bremsstrahlung emission of flocculi, surrounding the spot structure of an active region. The brightening of the extraordinary mode in the short-wavelength spectral range and the kinks in the intensity spectra of emission are analyzed. The interpretation of the RATAN-600 observational data with probable diagnostics of the emission of the fourth gyrofrequency harmonic is considered as examples.

A new archival infrastructure for highly-structured astronomical data

With the advent of the 2020 Radio Astronomy Telescopes era, the amount and format of the radioastronomical data is becoming a massive and performance-critical challenge. Such an evolution of data models and data formats require new data archiving techniques that allow massive and fast storage of data that are at the same time also efficiently processed. A useful expertise for efficient archiviation has been obtained through data archiving of Medicina and Noto Radio Telescopes. The presented archival infrastructure named the Radio Archive stores and handles various formats, such as FITS, MBFITS, and VLBI’s XML, which includes description and ancillary files. The modeling and architecture of the archive fulfill all the requirements of both data persistence and easy data discovery and exploitation. The presented archive already complies with the Virtual Observatory directives, therefore future service implementations will also be VO compliant. This article presents the Radio Archive services and tools, from the data acquisition to the end-user data utilization.

Modeling of Solar Atmosphere Parameters Above Sunspots Using RATAN-600 Microwave Observations

Models of the upper transition region of sunspots have been derived based on the observed radio spectrum between 3 and 18 GHz from Radio Astronomical Telescope of the Academy of Sciences 600 (RATAN-600) observations. Our objective is to match the spectrum to show that, within the limits of the one-dimensional observations and modeling, we have obtained a reasonable description of the upper transition-region structure of sunspots. We have developed a diagnostic method, based on iterative correction of the temperature–height profile in the transition region and lower corona, and applied it to three selected active regions with unipolar gyroresonance sources. Good agreement is achieved between observed and modeled microwave spectra using one-dimensional, time-independent models in hydrostatic equilibrium characterized by a given temperature as a function of height. We found that above sunspots the upper height of a transition region is located at 2 – 2.3 Mm, and the temperature of the low corona is about 1.5 – 2.5 MK.

5-bit 5-GS/s Noninterleaved Time-Based ADC in 65-nm CMOS for Radio-Astronomy Applications

This paper presents a 5-bit noninterleaved time-based analog-to-digital converter (ADC), which operates at a 5-GS/s rate. The ADC is designed for the use in radio-astronomy telescopes, for which time interleaving is not acceptable. The ADC employs a dynamic, differential voltage-to-time converter, a folded-flash time-to-digital converter (TDC), and calibration circuitry. To generate reference delays, the calibration circuitry utilizes a delay-time reference network, which is designed to map the input voltage range into 16 equal time intervals that are used for the calibration of the TDC. The 65-nm CMOS ADC achieves the Signal-to-noise plus distortion ratio/spurious-free dynamic range of 27/32 dB at Nyquist, an effective number of bits (ENOB) of 4.7 bit at low frequencies and 4.1 bit at high frequencies with a power consumption of 21.5 mW at Nyquist.

High Efficiency Wideband Refractive Optics for ALMA Band-1 (35-52 GHz)

We present the design, implementation, and characterization of the optics of ALMA Band 1, the lowest frequency band in the most advanced radio astronomical telescope. Band 1 covers the broad frequency range from 35 to 50 GHz, with the goal of minor degradation up to 52 GHz. This is, up to now, the largest fractional bandwidth of all ALMA bands. Since the optics is the first subsystem of any receiver, low noise figure and maximum aperture efficiency are fundamental for best sensitivity. However, a conjunction of several factors (small cryostat apertures, mechanical constraints, and cost limitations) makes extremely challenging to achieve these goals. To overcome these problems, the optics presented here includes two innovative solutions, a compact optimized-profile corrugated horn and a modified Fresnel lens. The horn profile was optimized for optimum performance and easy fabrication by a single-piece manufacturing process in a lathe. In this way, manufacturability is eased when compared with traditional fabrication methods. To minimize the noise contribution of the optics, a one-step zoned lens was designed. Its parameters were carefully optimized to maximize the frequency coverage and reduce losses. The optical assembly reported here fully complies with ALMA specifications.

Ethernet Node Controller for Main Reflector of Radio Telescope

An Ethernet node controller for main reflector of radio astronomical telescope is provided. The controller completes the communication with the main control PC, as well as control and monitoring of actuators through Ethernet and embedded technology. The system is made up of embedded processor and peripheral circuit, Ethernet communication module, power management module, motor control feedback module, data storage and time module, display module, motor control module and interface circuit. The controller uses LPC2368 as the core, DM9161 as the network communication physical layer chip, FM3130 to realize of data storage and real-time clock function. Motor controller can store the control algorithm and control data. And through the Ethernet receive and process control command and control data from the control PC to implement the control of actuators. At the same time, the controller also has regular state detection and alarm function, through the manual control module to achieve positive or reversal control operation of the corresponding channel actuators motor.

Streaming Big Data Processing in Datacenter Clouds

Today, we live in a digital universe in which information and technology are not only around us but also play important roles in dictating the quality of our lives. As we delve deeper into this digital universe, we're witnessing explosive growth in the variety, velocity, and volume of data1,2 being transmitted over the Internet. A zetabyte of data passed through the Internet in the past year; IDC predicts that this digital universe will explode to an unimaginable eight Zbytes by 2015. These data are and will be generated mainly from Internet search, social media, mobile devices, the Internet of Things, business transactions, next-generation radio astronomy telescopes, high-energy physics synchrotron, and content distribution. Government and business organizations are now overflowing with data, easily aggregating to terabytes or even petabytes of information.

RATAN-600 Observations of Small-Scale Structures with High Spectral Resolution

We present observations of quiet-sun small-scale structures (SSS) in the microwave range with the {\it Radio Astronomical Telescope of the Academy of Sciences 600} (RATAN-600) spectral-polarization facility in a wide range of frequencies. SSS are regularly recorded in routine observations of the large reflector-type radio telescope and represent manifestations in the radio range of various structures of the quiet-sun: supergranulation network, bright points, plage patches and so on. A comparison with with images from the {\it Solar Dynamics Observatory} (SDO) showed that the microwave emission comes from a region extending from the chromosphere to the low transition region. We measured the properties of the SSS as well as the degree of circular polarization averaged over the beam of the radio telescope and from this we estimated the magnetic field at the formation level of the radiation.

A massive eye on the universe

A massive eye on the universe

RFI profiles of prime candidate sites for the first radio astronomical telescope in Malaysia

Radio astronomy is a very young research field in South East Asia. There has not been a research-grade radio telescope built in this part of the world yet. A plan has been proposed by the University of Malaya’s Radio Cosmology Research Laboratory to build a medium-sized radio telescope in order to eventually join the global projects of the Very Long Baseline Interferometry (VLBI) Network and Square Kilometer Array (SKA). Main parameters taken into consideration in finding the main prime candidate sites involves features that produce Radio Frequency Interference (RFI). These features are mainly telecommunication and satellite navigation signals and population density. Other important features considered are rainfall level, land contour and availability for future collaboration with institutions at the chosen sites. In this paper we described the experimental procedure and the RFI measurement on our five prime candidate’s sites in Malaysia, covering frequency band from 1 MHz to 2000 MHz. The levels and sources of RFI on these sites were monitored and analyzed. The RFI level in Langkawi showed the lowest average of - 100.33 dB m ( 4.4 × 10 6 Jy ) . These RFI have been found to fluctuate relatively lowly (between 1 dB m and 2 dB m). This site is also ideally located close to the Langkawi National Observatory and we recommend that this site as the best site to build the first research-grade radio telescope in this region.

A Wideband Superconducting Filter Using Strong Coupling Resonators for Radio Astronomy Observatory

A 12-pole wideband superconducting microstrip bandpass filter, which has a fractional bandwidth of 38% and a center frequency of 1455 MHz, is presented for the Miyun 50-m radio astronomy telescope, Beijing, China. A novel resonator, which can not only generate very large coupling, but also push its first spurious resonant peak away from the passband, is introduced. A new style interleaved coupling structure is proposed and successfully used in this study to realize the remarkably required strong coupling. To achieve high edge slope on the high side of the passband, as required, a single transmission zero was introduced. The filter was fabricated on a 36 mm times 30 mm times 0.5 mm double-sided YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> film deposited on an MgO substrate. The measured results showed that the filter had 0.05-dB minimum insertion loss, 0.08-dB passband ripple, and 23-dB return loss at a temperature of 40 K. The first spurious peak did not appear until 2632 MHz. The overall measured performance showed good agreement with the simulation.

RFI excision using a higher order statistics analysis of the power spectrum

A method of radio frequency interference (RFI) suppression in radio astronomy spectral observations based on the analysis of the probability distribution of an instantaneous spectrum is described. This method allows the separation of the Gaussian component due to the natural radio source and the non-Gaussian RFI signal. Examples are presented in the form of computer simulations of this method of RFI suppression and of WSRT observations with this method applied. The application of real time digital signal processing for RFI suppression is found to be effective for radio astronomy telescopes operating in a worsening spectral environment.

Funding woes spell doom for US radio dish

WASHINGTON The only millimetre-wavelength radioastronomy telescope that serves the entire US research community will be shut down in July, the victim of continuing tight budgets.

A high‐speed parallel FFT‐processor for a radio astronomy telescope

AbstractA radio astronomy telescope with a wide field of view is an efficient tool for locating such transient radio sources in space as supernova explosions. A promising method of designing this type of telescope is to apply Fourier transformation to the output signals from a phased array antenna. the implementation of a high‐speed parallel FFT processor to an eight‐element linear phased array antenna output is reported in this paper. Small size and low‐power con sumption are achieved by utilizing conventional digital video signal processing LSIs. In the present pilot system, arithmetic operation up to a speed of 2.7 COPS (giga operations per second) has been attained. the basic operation has been confirmed by solar observation.

Conducting Radio Astronomy in the EMC Environment

Radio signals from pulsars and distant galaxies are difficult enough to detect on their own, but the problems encountered in making accurate astronomical observations at microwave frequencies are greatly compounded by terrestrial sources of electromagnetic interference (EMI). This paper discusses a wide variety of EMI sources as they affect the operation of radio-astronomy telescopes. These sources can be as simple as a pulsing automotive spark plug or as complex as an aircraft-to-aircraft radio transmission. Various protective countermeasures can be taken; however, compatibility between sensitive microwave receivers and the rest of the radio-frequency (RF) world has yet to be achieved.