Stelio Montebugnoli

Low frequency aperture array developments for phase 1 SKA

Aperture Arrays (AA) mark a new era in radio astronomy combining high sensitivity with a large field-of-view, enabling very high survey and imaging speeds. This paper describes the development of low frequency aperture arrays leading up to SKA phase 1 within the Aperture Array Verification Program (AAVP) as part of the SKA program.

Water masers in the Kronian system

The presence of water has been considered for a long time as a key condition for life in planetary environments. The Cassini mission discovered water vapour in the Kronian system by detecting absorption of UV emission from a background star (Hansen et al. 2006). Prompted by this discovery, we started an observational campaign for search of another manifestation of the water vapour in the Kronian system, its maser emission at the frequency of 22 GHz (1.35 cm wavelength). Observations with the 32 m Medicina radio telescope (INAF-IRA, Italy) started in 2006 using Mk5A data recording and the JIVE-Huygens software correlator. Later on, an on-line spectrometer was used at Medicina. The 14 m Metsahovi radio telescope (TKK-MRO, Finland) joined the observational campaign in 2008 using a locally developed data capture unit and software spectrometer. More than 300 hours of observations were collected in 2006-2008 campaign with the two radio telescopes. The data were analysed at JIVE using the Doppler tracking technique to compensate the observed spectra for the radial Doppler shift for various bodies in the Kronian system (Pogrebenko et al. 2009). Here we report the observational results for Hyperion, Titan, Enceladus and Atlas, and their physical interpretation. Encouraged by these results we started a campaign of follow up observations including other radio telescopes.

Water masers in the Saturnian system

Context. The presence of water has long been seen as a key condition for life in planetary environments. The Cassini spacecraft discovered water vapour in the Saturnian system by detecting absorption of UV emission from a background star. Investigating other possible manifestations of water is essential, one of which, provided physical conditions are suitable, is maser emission. Aims. We report detection of water maser emission at 22 GHz associated with several Kronian satellites using Earth-based radio telescopes. Methods. We searched for water maser emission in the Saturnian system in an observing campaign using the Metsahovi and Medicina radio telescopes. Spectral data were Doppler-corrected over orbital phase for the Saturnian satellites, yielding detections of water maser emission associated with the moons Hyperion, Titan, Enceladus, and Atlas. Results. The detection of Saturnian water molecules by remote astronomical observation can be combined with in situ spacecraft measurements to harmonise the physical model of the Saturnian system.

Reliability Tests and Experimental Analysis on Radioreceiver Chains

In this work two solutions (coaxial cable and optical fiber) of receiver chains for the new SKA radiotelescope are evaluated by their reliability performance in their operating environment. In the case of the most reliable solution (optical fiber), other reliability test have been performed and their results are here reported

Italian bistatic radar system for surveillance of space debris in Low Earth Orbit

Space debris are man made objects distributed at different altitudes around Earth. The space debris environment represents a serious hazard for both past and future space activities and a collision avoidance system is desirable to protect operative spacecraft and human activities. In this paper we investigate on the performance of an Italian bistatic C band radar system configuration for surveillance of space debris at the orbital altitude range of the COSMO-SkyMed radar satellites, approximately 620 km. In the nearly future this system should be realized and constituted by the Medicina (Emilia-Romagna) radiotelescope receiver and a continuous wave (CW) transmitter located in Noto (Sicily). The bistatic radar sensitivity, as a function of object size and altitude, is evaluated for both catalogued and uncatalogued objects near COSMO-SkyMed orbit. Finally some simulation results will be presented to show the expected performances of the system.

Northern Cross Radiotelescope: Test and Measurements of Reliability Performance on Radioreceiver Chains

In this paper, the results of reliability measurements and tests are presented. The systems taken into account concern two different architectures of a receiver chain for implementation in the Northern Cross Radiotelescope. A reliability analysis of the circuit and reliability tests implemented on critical parts of a fiber receiver chain were performed. The target was to chose the receiver chain with the highest value of mean time between failures and minimize faults in the structure. Moreover, since the reliability prediction indicated the front end, which was installed on the focal line of the antenna, as the more stressed block of the entire radioreceiver chain by environmental and climatic factors, we proposed specific development tests. The whole test plan has been characterized, and some results after a combination of temperature and humidity cycles, as well as random vibrations tests, are reported in this paper. The measurement and tests implemented in this paper for the solution of the receiver chain in the Northern Cross Radiotelescope can represent a useful aid for the new design of the international SKA project.

A real-time KLT implementation for radio-SETI applications

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-Lo`eve Transform (KLT) algorithm would be preferable, but it would scale like N*N. In this paper, we describe a hardware-software infrastructure based on FPGA boards and GPU-based PCs that circumvents this computation-time problem allowing for a real-time KLT.

Electromagnetic Design of Broadband Antenna Feed Systems for the Northern Cross Radio Telescope

This contribution deals with the design and implementation of broadband antenna feed systems for the cylindrical offset parabolic reflector of the Northern Cross radio telescope, in the framework of the Square Kilometer Array Design Study (SKADS-FP6) project. Such feed systems have to maintain a proper radiation pattern as well as a good matching condition in the operative frequency band (120-430 MHz) in order to efficiently feed the main reflector. This task is not trivial since more than octave bandwidths are required. Several feed system designs have been carried out on the basis of different architectures such as log periodic antenna arrays, linear arrays of fat dipoles and branched Vivaldi (tapered slot) radiators inside a wired subreflector. Each configuration provides a different trade-off between electrical performance and manufacturing complexity. The most significant computed and experimental results are discussed. Some of the proposed configurations have already been mounted on the Northern Cross Radio Telescope. The adopted mechanical and electronic solutions such as wiring, canalization, amplifier housing and protection are reported. A preliminary study on the application of Focal Plane Arrays on the E/W Arm is also discussed.

Test and measurements of reliability performance on radioreceiver chains for the Northern Cross Radio Telescope

Reliability analysis of two radioreceiver chains architecture were performed in order to choose the solution with the highest value of Mean Time Between Failures and minimize faults in the system, with the consequent lower maintenance costs. Located the most stressed devices from a climatic-environmental point of view, we decided to monitor their real thermal solicitation in order to evaluate the proper reliability performances varying temperature and the possible degradation of the critical subsystem and consequently of the entire chain. The design for reliability approach proposed in this research for the reinstrumentation of the Northern Cross Radiotelescope could be an useful aid for the design of the international SKA Telescope. Since it will be extremely large (1 square kilometre) the maintenance costs, related to the reliability, become an important parameter to evaluate. This research activity was developed in partnership with the Istituto di Radioastronomia, Istituto Nazionale di Astrofisica, in the context of the Square Kilometer Array Design Study supported by UE FP6.

Implementing the KLT

SETI-Italia is an observing program led by the INAF-IRA (Istituto Nazionale di Astrofisica - Istituto di Radioastronomia). At present, Italy is the only European country conducting a SETI (Search for Extraterrestrial Intelligence) program. Occasional SETI searches may be conducted at the Nanacy French Kraus type radiotelescope and some artificial signals are sometime transmitted with the 70-m dish in the Ukraine. Outside Europe, continuous SETI programs are conducted in the USA, Australia and Argentina.