Giuseppe Valente

Agenzia Spaziale Italiana

Context. One of the most important objectives of solar physics is to gain a physical understanding of the solar atmosphere, whose structure can also be described in terms of the density ( N ) and temperature ( T ) distributions of the atmospheric matter. Several multi-frequency analyses have shown that the characteristics of these distributions are...

We present deep total intensity and polarization observations of the Coma cluster at 1.4 and 6.6 GHz performed with the Sardinia Radio Telescope. By combining the single-dish 1.4 GHz data with archival Very Large Array observations, we obtain new images of the central radio halo and of the peripheral radio relic where we properly recover the bright...

Context. The Sun is an extraordinary workbench, on which several fundamental astronomical parameters can be measured with high precision. Among these parameters, the solar radius R ⊙ plays an important role in several aspects, for instance, in evolutionary models. Moreover, it conveys information about the structure of the different layers that com...

In this work, we present the preliminary results of radar observations of Near-Earth Objects (NEOs) carried out by European radio telescopes in the framework of the European Space Agency (ESA) project “NEO observation concepts for radar systems”, aimed at deriving the functional requirements of a planetary radar system, evaluating the available Eur...

In this work, we present preliminary results of radar observations of near-Earth Objects (NEOs) carried out by European radio telescopes in the framework of the European Space Agency (ESA) project “NEO observation concepts for radar systems”, which was aimed to derive the functional requirements of a radar system, evaluate the available European as...

PKS 1830−211 is a γ-ray emitting, high-redshift (z =2.507 ± 0.002), lensed flat-spectrum radio quasar. During the period mid-February to mid-April 2019, this source underwent a series of strong γ-ray flares that were detected by both AGILE-GRID and Fermi-LAT, reaching a maximum γ-ray flux of FE > 100 MeV ≈ 2.3 × 10−5 photons cm−2 s−1. Here we repor...

The biasing of low noise amplifiers (LNA) is of paramount importance for the receivers of large radio telescopes. High stability, optimal trade-off between gain and noise figure, remote control, and mitigation of the radio frequency interferences (RFIs) are all desirable features in the choice of the electronic board devoted to power supply the LNA...

We present a new solar radio imaging system implemented through the upgrade of the large single-dish telescopes of the Italian National Institute for Astrophysics (INAF), not originally conceived for solar observations. During the development and early science phase of the project (2018 – 2020), we obtained about 170 maps of the entire solar disk i...

The Sardinia deep space antenna (SDSA), managed by the Italian Space Agency (ASI) has started its operations in 2017 aiming to provide tracking and communication services for deep space, near earth, and lunar missions, and to support new and challenging radio science experiments. The SDSA shares with the Sardinia Radio Telescope (SRT) a part of the...

We present a new solar radio imaging system implemented through the upgrade of the large single-dish telescopes of the Italian National Institute for Astrophysics (INAF), not originally conceived for solar observations. During the development and early science phase of the project (2018-2020), we obtained about 170 maps of the entire solar disk in...

The design and characterization of the coaxial dual-band L-P radio astronomical receiver for the prime focus of the Sardinia radio telescope are presented. The main feature of this receiver is to allow simultaneous radio astronomical observations in the P (305 – 410 MHz) and L (1.3 – 1.8 GHz) frequency bands. This functionality, which has been requ...

Space debris monitoring is nowadays a priority for worldwide space agencies, due to the serious threat that these objects present. More and more efforts have been made to extend the network of available radar systems devoted to the control of space. A meticulous review has been done in this paper, in order to find and classify the considerable amou...

Il modulo Q-CONV è parte di un ricevitore in sviluppo, destinato a SRT (Sardinia Radio Telescope), costituito da un multifeed a 19 beam, doppia polarizzazione circolare operante nella banda 33-50GHz. I Q-CONV, in quantità di 38 moduli, verranno localizzati dentro al criostato in parte calda a 300K, e ognuno sarà collegato, via guida d’onda e gap te...

We present a new waveguide thermal isolator, based on a simple gap in a standard rectangular waveguide, developed for the Q-band cryogenic receiver of the Sardinia Radio Telescope. The proposed component is very compact and consists of a single module, including both the horizontal and vertical polarization channels and the noise injection channel....

Space debris (SD) is an important problem for space operations and a hot topic for space surveillance research. A structured network of radar sensors is available worldwide, offering vital information about debris status. Recently, the Sardinia Radio Telescope (SRT), a 64-m dish located in Sardinia, Italy, was introduced in the European plan for SD...

The main characteristics in the radio continuum spectra of Supernova Remnants (SNRs) result from simple synchrotron emission. In addition, electron acceleration mechanisms can shape the spectra in specific ways, especially at high radio frequencies. These features are connected to the age and the peculiar conditions of the local interstellar medium...

Since 1998, Italian astrophysics institutes (now part of the Italian National Institute for Astrophysics, INAF) have been collaborating with the SETI group at the University of California, Berkeley. Thanks to this collaboration, the SERENDIP IV setup was installed at the 32-m Medicina radio telescope near Bologna, Italy. This setup was used for SET...

We report the detection of diffuse radio emission which might be connected to a large-scale filament of the cosmic web covering a 8° × 8° area in the sky, likely associated with a z ≈ 0.1 overdensity traced by nine massive galaxy clusters. In this work, we present radio observations of this region taken with the Sardinia Radio Telescope. Two of the...

Radio loud Active Galactic Nuclei are episodic in nature, cycling through periods of activity and quiescence. In this work we investigate the duty cycle of the radio galaxy B2~0258+35, which was previously suggested to be a restarted radio galaxy based on its morphology. The radio source consists of a pair of kpc-scale jets embedded in two large-sc...

A novel printed antenna is designed for wearable and RFID applications in the UHF band. The antenna design is performed following energy-based design guidelines available in the recent literature. High robustness with respect to the human body coupling is achieved by confining the electric energy density in a region far from the antenna borders. Th...

The main characteristics in the radio continuum spectra of Supernova Remnants (SNRs) result from simple synchrotron emission. In addition, electron acceleration mechanisms can shape the spectra in specific ways, especially at high radio frequencies. These features are connected to the age and the peculiar conditions of the local interstellar medium...

Space debris represent a major risk for every spacecraft and satellite. In fact, other than cause serious damages to these structures, new collisions could exponentially increase the amount of debris and so the level of threat represented by the objects. To avoid new impacts, the monitoring of the space environment with space-based and ground-based...

We report the detection of diffuse radio emission which might be connected to a large-scale filament of the cosmic web covering a 8deg x 8deg area in the sky, likely associated with a z~0.1 over-density traced by nine massive galaxy clusters. In this work, we present radio observations of this region taken with the Sardinia Radio Telescope. Two of...

The Sardinia Radio Telescope (SRT) is a 64-m, fully-steerable single-dish radio telescope that was recently commissioned both technically and scientifically with regard to the basic observing modes. In order to improve the scientific capability and cover all the requirements for an advanced single-dish radio telescope, we developed the SArdinia Roa...

A microstrip-to-waveguide transition has been realized for radio astronomy applications, designed to operate in the Q-band (33–50 GHz). As part of an array radio frequency (RF) receiver, the main requirement of such a transition is the reduction of transverse space occupation for the integration in the entire receiver chain, so an in-line configura...

Space debris represent an increasing problem for the ongoing space operations and they are the primary reason of the space environment pollution. The study and monitoring of the known objects, as well as the detection of new ones, is essential to prevent the risk of collision between debris and spacecraft but also between debris themselves. Radar m...

In order to prevent the harmful impacts for spacecrafts deriving from the presence of space debris, many surveillance and monitoring programs of the space environment have been started in recent years. The Sardinia Radio Telescope is a new comer in such a scenario, but it has already showed its potential. However, since the actual receiving chain i...

We observed the galaxy cluster CIZA J2242.8+5301 with the Sardinia Radio Telescope to provide new constraints on its spectral properties at high frequency. We conducted observations in three frequency bands centred at 1.4 GHz, 6.6 GHz and 19 GHz, resulting in beam resolutions of 14$^{\prime}$, 2.9$^{\prime}$ and 1$^{\prime}$ respectively. These sin...

Space debris are orbiting objects that represent a major threat for space operations. In this work a bistatic radar configuration named BIstatic RAdar for LEo Tracking (BIRALET) is used to detect a set of space debris. Signal-to-Noise Ratios, Doppler shift measures as well as the frequency specters for each debris are presented.

Space debris are orbiting objects that represent a major threat for space operations. The most used countermeasure to face this threat is, by far, collision avoidance, namely the set of maneuvers that allow to avoid a collision with the space debris. Since collision avoidance is tightly related to the knowledge of the debris state (position and spe...

A 180° hybrid and a directional coupler to be employed in the P-band cryogenic receiver of the Sardinia Radio Telescope are proposed in this work. An in-depth study of the issues related to the use of microwave components for cryogenic radio astronomy receivers is carried out to select the best suited technology and configuration. As a result, a pl...

Observations of supernova remnants (SNRs) are a powerful tool for investigating the later stages of stellar evolution, the properties of the ambient interstellar medium, and the physics of particle acceleration and shocks. For a fraction of SNRs, multi-wavelength coverage from radio to ultra high-energies has been provided, constraining their contr...

[Abridged] The Sardinia Radio Telescope (SRT) is the new 64-m dish operated by INAF (Italy). Its active surface will allow us to observe at frequencies of up to 116 GHz. At the moment, three receivers, one per focal position, have been installed and tested. The SRT was officially opened in October 2013, upon completion of its technical commissionin...

We study the intra-cluster magnetic field in the poor galaxy cluster Abell 194 by complementing radio data, at different frequencies, with data in the optical and X-ray bands. We analyze new total intensity and polarization observations of Abell 194 obtained with the Sardinia Radio Telescope (SRT). We use the SRT data in combination with archival V...

The Space Debris monitoring is part of the INAF-OAC research activity in the framework convention ASI/INAF n. 2015-028-R.O, named “Detriti Spaziali – Supporto alle attività IADC e validazione pre-operativa SST”. In this framework, the INAF participation concerns about the testing of the SRT operative capacities in the detection of signals scattered...

The robustness of wearable UHF-band ungrounded antennas with respect to body-coupling effects is addressed. Two different configurations of single-layer antennas, with different energy density distributions, are presented, and a design criterion to improve their performance with respect to the antenna-body separation is derived. Through an analysis...

In this article, we present the design and performances of the radio receiver system installed at the Sardinia Radio Telescope (SRT). The three radio receivers planned for the first light of the Sardinian Telescope have been installed in three of the four possible focus positions. A dual linear polarization coaxial receiver that covers two frequenc...

SETI, the Search for ExtraTerrestrial Intelligence, is the search for radio signals emitted by alien civilizations living in the Galaxy. Narrow-band FFT-based approaches have been preferred in SETI, since their computation time only grows like N*lnN, where N is the number of time samples. On the contrary, a wide-band approach based on the Kahrunen-...

We present new observations of the galaxy cluster 3C 129 obtained with the Sardinia Radio Telescope in the frequency range 6000−7200 MHz, with the aim to image the large-angular-scale emission at high-frequency of the radio sources located in this cluster of galaxies. The data were acquired using the recently-commissioned ROACH2-based backend to pr...

A feed horn for the multifeed S-band receiver of the Sardinia Radio Telescope (SRT) has been designed. The antenna consists of a truncated circular waveguide with four ridges of variable height inside. The horn antenna has been designed and tested using Ansys HFSS and, then, the multifeed system has been coupled with the SRT using GRASP by TICRA. T...

A dual-band printed log-periodic dipole array (LPDA) antenna for wireless communications, designed on a low-cost PET substrate and implemented by inkjet-printing conductive ink, is presented. The proposed antenna can be used for wireless communications both within the UHF (2.4-2.484 GHz) and SHF (5.2-5.8 GHz) wireless frequency bands, and presents...

A multiband printed microstrip antenna for wireless communications is presented. The antenna is fed by a proximity-coupled microstrip line, and it is printed on a flexible substrate. The antenna has been designed using a general-purpose 3D computer-aided design software (CAD), CST Microwave Studio, and then realized. The comparison between simulate...

In the period 2012 June–2013 October, the Sardinia Radio Telescope (SRT) went through the technical commissioning phase. The characterization involved three first-light receivers, ranging in frequency between 300MHz and 26GHz, connected to a Total Power back-end. It also tested and employed the telescope active surface installed in the main reflect...

In this paper we describe the installation and first light of a coaxial dual-feed X-Ka band receiver on the primary focus of Sardinia Radio Telescope (SRT) to perform an experimental verification of our antenna potential capabilities in Space Science. The SRT is a 64-m dish antenna operated by INAF (National Institute for Astrophysics-Italy) in Sar...

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 hybrid power combiners in a double-ridged waveguide, w...

In this paper we present a low cost 7-pole elliptic microwave filter. The operating band of the filter is between 2 and 5 GHz. The proposed filter has been designed and optimized both on a FR-4 substrate and on a paper substrate, using a commercial electromagnetic software, and finally fabricated on the FR-4 substrate.

The noise temperature of existing radio telescope receivers has actually achieved very low values. In any case, there are other practical ways to increase the observational speed of a single dish antennas without using longer integration time: observe with multi-beam and large bandwidth receiver. In this paper we present the front end and the cryog...

We present the optical and mechanical design of a 3mm band SIS receiver for the Gregorian focus of the Sardinia Radio Telescope (SRT). The receiver, was designed and built at IRAM and deployed on the IRAM for the Plateau de Bure Interferometer antennas until 2006. Following its decommissioning the receiver was purchased by the INAFAstronomical Obse...

Radio astronomical observations are ordinarily aimed at reaching a specific scientific goal. Radio telescopes are equipped with a certain number of receivers and back-ends, and the choice of the most suitable receiver/back-end combination in order to best match the scientific application of interest is up to the astronomer. However, the opportunity...

Radio Frequency Interferences (RFI) represents one of the major issues especially in single-dish low frequency radioastronomic observations. Several solutions have been investigated to face the problem. Among them a wide-band digital spectrometer is used together to a RFI monitoring station placed close to the radio-telescope and eventually support...

A microstrip directional coupler with high directivity is proposed for microwave applications requiring a weak coupling factor. This component has been used in the L-band radio-astronomical receiver of the Sardinia radio telescope. To improve the performance of the receiver, the operating temperature is lowered to 20 K. An in-house cryostat has bee...

The Sardinia Radio Telescope is approaching to its official inauguration. Nowadays, the technical staff is accomplishing the last remaining activities to set up and integrate the microwave receivers, the digital processing systems and all the equipment necessary to reach a top level in the international scenario of large radio telescopes. Even if t...

We describe the design, construction and perfor- mance of a 180 hybrid power divider with integrated band pass filter for L-band (1.3-1.8 GHz). The hybrid is based on a cavity and two novel broadband coaxial-to-double ridged waveguide transitions. The design was optimized using a commercial 3-D electromagnetic simulator. The device was tested at ro...

We describe the design construction and performance of a L-band (1300-1800 MHz) Ortho Mode Junction for the L-P dual-band receiver to be installed on the 64 m Sardinia Radio Telescope (SRT), a new radio telescope which is being built in Sardinia, Italy. The Ortho Mode Junction (OMJ) separates two orthogonal linearly polarized signals propagating in...

We present the design of the passive feed system of the dual-band receiver for the prime focus of the Sardinia Radio Telescope (SRT), a new 64 m diameter radio telescope which is being built in Sardinia, Italy. The feed system operates simultaneously in P-band (305-410 MHz) and L-band (1300-1800 MHz). The room temperature illuminators are arranged...

We describe the design, construction and performance of a novel 180° hybrid power divider for L-band (1.3-1.8 GHz). The hybrid is based on a double ridged waveguide cavity that also integrates a band pass filter. The device will operate at 77 K inside a cryogenically cooled receiver to be installed at the primary focus of the Sardinia Radio Telesco...