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We present a project to implement a national common strategy for the mitigation of the steadily deteriorating Radio Frequency Interference (RFI) situation at the Italian radio telescopes. The project involves the Medicina, Noto, and Sardinia dish antennas and comprised the definition of a coordinated plan for site monitoring as well as the implementation of state-of-the-art hardware and software tools for RFI mitigation. Coordinated monitoring of frequency bands up to 40 GHz has been performed by means of continuous observations and dedicated measurement campaigns with fixed stations and mobile laboratories. Measurements were executed on the frequency bands allocated to the radio astronomy and space research service for shared or exclusive use and on the wider ones employed by the current and under-development receivers at the telescopes. Results of the monitoring campaigns provide a reference scenario useful to evaluate the evolution of the interference situation at the telescopes sites and a case series to test and improve the hardware and software tools we conceived to counteract radio frequency interference. We developed a multi-purpose digital backend for high spectral and time resolution observations over large bandwidths. Observational results demonstrate that the spectrometer robustness and sensitivity enable the efficient detection and analysis of interfering signals in radio astronomical data. A prototype off-line software tool for interference detection and flagging has been also implemented. This package is capable to handle the huge amount of data delivered by the most modern instrumentation on board of the Italian radio telecsopes, like dense focal plane arrays, and its modularity easen the integration of new algorithms and the re-usability in different contexts or telescopes., 39 pages, 10 Figures and 7 Tables. INAF Technical Report n. 149 (2022). http://hdl.handle.net/20.500.12386/32081

We present a project to implement a national common strategy for the mitigation of the steadily deteriorating Radio Frequency Interference (RFI) situation at the Italian radio telescopes. The project involves the Medicina, Noto, and Sardinia dish antennas and comprised the definition of a coordinated plan for site monitoring as well as the implementation of state-of-the-art hardware and software tools for RFI mitigation. Coordinated monitoring of frequency bands up to 40 GHz has been performed by means of continuous observations and dedicated measurement campaigns with fixed stations and mobile laboratories. Measurements were executed on the frequency bands allocated to the radio astronomy and space research service for shared or exclusive use and on the wider ones employed by the current and under-development receivers at the telescopes. Results of the monitoring campaigns provide a reference scenario useful to evaluate the evolution of the interference situation at the telescopes sites and a case series to test and improve the hardware and software tools we conceived to counteract radio frequency interference. We developed a multi-purpose digital backend for high spectral and time resolution observations over large bandwidths. Observational results demonstrate that the spectrometer robustness and sensitivity enable the efficient detection and analysis of interfering signals in radio astronomical data. A prototype off-line software tool for interference detection and flagging has been also implemented. This package is capable to handle the huge amount of data delivered by the most modern instrumentation on board of the Italian radio telescopes, like dense focal plane arrays, and its modularity easen the integration of new algorithms and the re-usability in different contexts or telescopes.

Lo scopo di questo rapporto interno è quello di descrivere la progettazione e la realizzazione di due prototipi di unità radar volti al rilevamento degli APR (Aeromobili a Pilotaggio Remoto), realizzati nell’ambito del progetto cluster top-down RADARDRONE e la successiva attività sperimentale condotta. RADARDRONE è la denominazione di un progetto cluster top-down che mette a sistema le competenze ed esperienze nel campo della ricerca tecnologica possedute dall’OAC (Osservatorio Astronomico di Cagliari), dal DIEE (Dipartimento di Ingegneria Elettrica ed Elettronica) dell’Università degli Studi di Cagliari e dalla compagine di aziende ed organizzazioni altamente innovative facenti parte del cluster. L’obiettivo principale del progetto è lo sviluppo di piccoli RADAR modulari, facilmente installabili, per il monitoraggio e la sicurezza delle aree critiche (per esempio aeroporti, porti, stadi di calcio, zone dove si svolgono grandi assembramenti di persone) o obiettivi sensibili al fine di fronteggiare eventuali intrusioni non autorizzate.

Lo scopo di questo rapporto interno è di illustrare lo studio preliminare effettuato nel biennio 2019-2020 per la progettazione di un sistema RADAR per la rilevazione degli APR (Aeromobili a Pilotaggio Remoto) nell’ambito del progetto RADARDRONE. RADARDRONE è la denominazione di un progetto cluster top down che intende mettere a sistema le competenze, conoscenze ed esperienze nel campo della Ricerca Tecnologica possedute dall’OAC (Osservatorio Astronomico di Cagliari), dal DIEE (Dipartimento di Ingegneria Elettrica ed Elettronica) dell’Università degli Studi di Cagliari e dalla compagine di aziende ed organizzazioni altamente innovative facenti parte del cluster.

GAIA,Progettazione, realizzazione e caratterizzazione della GAIA Board. In questo report viene illustrata la GAIA board implementata per fornire e monitorare il BIAS degli LNA (Low Noise Amplifier) installati nei ricevitore radioastronomici.

PHAROS2 (PHased Arrays for Reflector Observing Systems2) è un dimostratore di Phased Array Feed in banda C (4-8 GHz) per applicazioni radio astronomiche che è stato progettato nell’ambito dell’Advanced Instrumentation Program dei PAF per lo Square Kilometer Array da una collaborazione internazionale che coinvolge l’Istituto Nazionale di Astrofisica. PHAROS2 è basato su un array di 10×11 antenne di tipo Vivaldi a doppia polarizzazione raffreddato a 20 K all’interno di un criostato (vedi Figura 1) insieme a degli amplificatori a bassissimo rumore di tipo LNA (low-noise amplifier). L’array è popolato con 24 LNA su uno dei due canali di polarizzazione, mentre i restanti elementi sono terminati su un carico adattato a 50 Ω. I 24 segnali RF in uscita dal criostato di PHAROS2 vengono inviati tramite cavi coassiali ad una Warm Section, ovvero un ricevitore multicanale a 32 ingressi (di cui sono utilizzati solo 24) che permette il filtraggio, l’amplificazione e la downconversione di ciascun canale ad una banda di frequenza intermedia IF compresa tra 375 e 650 MHz. Tale banda IF è adatta al successivo processamento da parte del backend digitale iTPM (Italian Tile Processing Module) che è stato sviluppato nell’ambito del progetto SKA Low Frequency Aperture Array (LFAA). Tale backend, basato su Field Programmable Gate Array (FPGA) consente di campionare fino a 32 segnale RF su una larghezza di banda istantanea di ≈500 MHz. I 24 segnali IF in uscita dalla Warm Section vengono inviati al backend tramite 12 link analogici in fibra ottica di tipo WDM (Wavelength Division Multiplexing). Tali link consentono di trasmettere due segnali IF all’interno di un’unica fibra mediante due trasmettitori laser operanti alle lunghezze d’onda ottiche (infrarosse) λ=1270 nm e λ=1330 nm. Uno schematico della catena di ricezione PHAROS2 è indicata in Figura 2.

Radio Frequency Interference is one of the most pressing problems in cm-wavelength world-wide radio astronomy, in particular for single-dish telescope observations. Due to both the increasing abundance of man-made interfering signals and the improved performance of the telescope instrumentation, the impact of RFI at the Italian radio telescope sites is now a major concern, thus strategies for its mitigation are to be applied. Dish Washer is a new software tool for the detection and flagging of RFI in signals collected by single-dish radio telescopes. It implements both interactive flagging and some level of automatic detection of RFI through dedicated algorithms. Its first public release is foreseen as free software under the GNU General Public License.

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 reflector of the antenna. The instrument status and performance proved to be in good agreement with the expectations in terms of surface panels alignment (at present 300μmrms to be improved with microwave holography), gain (̃0.6K/Jy in the given frequency range), pointing accuracy (5 arcsec at 22GHz) and overall single-dish operational capabilities. Unresolved issues include the commissioning of the receiver centered at 350MHz, which was compromised by several radio frequency interferences, and a lower-than-expected aperture efficiency for the 22-GHz receiver when pointing at low elevations. Nevertheless, the SRT, at present completing its Astronomical Validation phase, is positively approaching its opening to the scientific community.