TECHNOLOGICAL RESEARCH

Involved IRA Scientists and Collaborators: E. Carretti, G. Maccaferri, K.-H. Mack, F. Mantovani, M. Nanni, A. Orfei, A. Orlati, I. Prandoni, F. Tinarelli, A. Zanichelli, S. Righini, R. Verma.

UPGRADE OF THE MEDICINA RADIOTELESCOPE FOR HIGH-FREQUENCY CONTINUUM OBSERVATIONS

The advent of the new 20 GHz multi-beam receiver to be mounted on the 32-m Medicina antenna requires the adjustment of the entire hardware and software observing system to prepare the antenna for wide-area radio continuum measurements at high-frequency.  The upgrade which involves different aspects such as noise calibration for gain stability, on-the-fly mapping procedures, data output format and archiving, is expected to improve the continuum sensitivity by about two orders of magnitude. Following RadioNet recommendations we are working on a new User Support System including telescope manuals, Exposure Time Calculators and an electronic proposal submission tool based on the Northstar software developed by Synergy (a working group on RadioNet facility integration) and ASTRON (the Netherlands Foundation for Research in Astronomy). The upgrade will make the Medicina antenna (and subsequently the Noto antenna) one of the prime instruments for high-frequency continuum observations, as it combines both the necessary sensitivity and resolution for an efficient survey of large regions of the sky. The scientific goals of this work are manifold and range from Galactic studies to searches for specific extragalactic sources (e.g. young radio galaxies) up to cosmological applications. The system will also be an important instrument for any kind of high-frequency follow-up. To find out more about the Enhanced Single-Dish Control System see the online document by Righini et al. 2007 at the ESCS Medicina page.

SOFTWARE DEVELOPMENT FOR SKY SURVEYS WITH A 20 GHz 7-HORN MULTIBEAM

The recent development of multi-beam receivers will enable single-dish telescopes, like the future Sardinia Radio Telescope (SRT), to survey large areas of sky at high radio frequencies (>=20 GHz). High-frequency extragalactic sky surveys are expected to have a major impact on astrophysics. In particular, they can provide samples of rare, but very interesting, classes of sources with flat spectrum up to high frequencies. At low frequencies such sources are swamped by more numerous populations which fade away as the frequency increases. They can then help in opening a window on new classes of sources, such as those with strong synchrotron or free-free self-absorption corresponding to both very early phases of nuclear radio-activity (extreme GHz Peaked Spectrum or High Frequency Peakers) and late phases of the evolution of Active Galactic Nuclei, characterized by low accretion/radiative efficiency (ADAF/ADIOS sources). They will also play a vital role in the interpretation of temperature and polarization maps of the Cosmic Microwave Background, by allowing us to characterize and remove the contamination by astrophysical foregrounds.

The IRA has developed a cryogenic feed array receiver to be used with the new radiotelescope which is being built in Sardinia (SRT). The 7-beam receiver spans a frequency band from 18 to 26 GHz providing fourteen output channels with up to 2 GHz bandwidth each. The multi-feed is a state-of-the-art receiver exploiting the new Indium Phosphide technology for cryogenic Low Noise Amplifiers (LNAs). Monolithic design of the LNAs will provide robust and repeatable performance among the several amplifiers needed in the fourteen channels.  Beside the receiving parts, the Institute has started the development of a prototype of a digital multi-purpose back-end able to acquire, digitize and process raw data for both continuum and spectroscopic observations.  In the near future (beginning 2008) the multifeed receiver will be mounted on the Medicina single dish in order to test its performances and start the first astronomical observations.

In order to make fruitful survey observations, a lot of software algorithms must be developed. In particular it is important to:
1) implement convenient raster-scan/on-the-fly mapping observation algorithms;
2) produce dedicated data acquisition and processing algorithms.

CMB POLARIZATION EXPERIMENTS: STUDY OF NEW INSTRUMENT ARCHITECTURES FOR OBSERVATIONS OF THE B-MODE OF THE COSMIC MICROWAVE BACKGROUND POLARIZED EMISSION.

The study consists of a Work Package (WP) of a major Italian project funded by the Italian Space Agency (ASI) for Cosmology and Fundamental Physics studies. The WP activity is related to the study of new correlation receiver architectures oriented to array configurations. The aim is to obtain high sensitivity and high polarization purity (low instrumental polarization) instruments which is mandatory because of the weakness (of order of tens nK or less) and small polarization fraction (<< 1%) of the CMB B-mode signal.

THE 32m-DISH PARABOLIC ANTENNA SYSTEM AT MEDICINA OBSERVATORY

Involved IRA Scientists,Technicians and Collaborators: A. Orfei, G. Zacchiroli, J. Roda, M. Morsiani, M. Nanni, F. Fiocchi, G. Maccaferri, A. Orlati, A. Maccaferri, A. Cattani, J. Monari, M. Poloni, A. Scalambra, S. Mariotti, A. Cremonini, E. Natale, R. Nesti, F. Cresci, D. Panella, S. Righini, P. Bolli.

The IRA operates a 32m dish parabolic antenna in Medicina (Bologna) since 1983. The observatory is part of the EVN-VLBI (Europena VLBI Network) consortium and of the worldwide geodetic VLBI network. The antenna is also used by Italian and foreign scientists in many single-dish projects which perform continuum, polarimetric and spectroscopic observations.  In over twenty years the R&D team has refurbished practically all the antenna and observing system components allowing the original design to be upgraded in the field of mechanics, electronics, microwave receivers, control system and control software. Some remarkable results can be summarized in the following:

- capability to switch among all receivers very fast (less than 4 minutes in the worst case) and automatically (frequency agility) (Figure 26a and Figure 26b)

Fig 26a - Primary focus agility system at the 32m dish parabolic antenna in Medicina (Bologna)

Fig 26b - Secondary focus agility system at the 32m dish parabolic antenna in Medicina (Bologna).

- new concept for the antenna track and rail system

- development of new generation microwave receivers with wide bandwidth using mono- and multi-feed schemes with coherent and heterodyne architecture (Figure 27)

Fig 27 - New generation micro-wave receiver: MMIC-LNA, 3.2x2.25mm.

- new generation Low Noise Amplifiers using monolithic technology up to a frequency of 100 GHz (3mm band) (Figure 28)

Fig 28 - New generation Low Noise Amplifier using monolithic technology: 18 - 26 GHz cryogenic multifeed system.

- new concept for down conversion boards for heterodyne microwave receivers

- implementation of an active surface system (patented in Europe,USA and Japan) to overcome the effects of gravitational deformations on the antenna gain. This allows us to use an antenna originally designed for centimetric wavelengths up to the millimetric range avoiding additional expensive structural changes necessary in high frequency antennas (Figure 29)

Fig 29 - Actuators for the Active Surface system to overcome the effects of gravitational deformations on the antenna gain.

- implementation of six generations of VLBI data acquisition systems, from the original 2 MHz bandwidth MK2 system over MK3 and MK4 up to the MK5 1 Gb/s system. Today the station is also routinely used to send the data directly to the JIVE correlator through a fiber optical link (e-VLBI) (Figure 30a and Figure 30b)

Fig 30a -VLBI data acquisition system MK5 at 1 Gbit/s.

Fig 30b - First fringes with of e-VLBI used to send data directly to the JIVE correlator through optical fiber link.

- development of back-ends with integrated control and acquisition system for single-dish observations in total power, polarimetry and   spectroscopy.

Together with the R&D activity the staff of the parabolic antennas has routinely maintained all the observing systems allowing the station to serve its duties in many international and national contexts. The reliability and continuity of the work of the station has been acknowledged in many occasions. Here it is worth to mention a NASA Achievement Award to Medicina VLBI Station (1993) and a Certificate of Appreciation to the IRA, Medicina, from the JAXA (Japan Aerospace Exploration Agency, 2006) in the framework of the VSOP-1 (VLBI Space Observatory Project).

In these last years the Medicina staff has been heavily involved in the design, construction and implementation of primary and secondary mirrors panels, active surface, tertiary mirrors, receivers, back-ends, servosystems and antenna control software, antenna equipments for the Sardina Radio Telescope.

SKA DESIGN STUDIES

Involved IRA Scientists, Technicians and Collaborators: S. Montebugnoli, M. Nanni, F. Perini, G. Bianchi, E. Carretti, M. Schiaffino,  J. Monari.

The design of a radio telescope with 1.000.000 m^(2) of collecting area to observe the redshifted hydrogen emission to the earliest cosmological epochs has long been a dream of radio astronomers. The EU has funded (10 MEuro) the European SKA Design Studies, SKADS, a 3-year program aimed at producing technological demonstrators. One of these is obtained by the re-commissioning of a part of the Italian Northern Cross radiotelescope, a T-shaped array equipped with more than 5000 dipoles. This programme, the Basic Element for SKA Training (BEST ), consists of three demonstrators of increasing sizes (the third one will have 7000 m^(2)) formed by N/S and E/W cylindrical concentrators equipped with a certain number of low cost, high dynamic range and low noise receivers. The main aim of these test beds is to check the validity of some concepts that are at the heart of the SKA philosophy. First, there is the multi-beaming concept, the construction of different beams in the field-of-view of a single parabolic receiver. Then we will study adaptive beam forming, the technique that allows one to reconstruct a beam by putting together signals from separate receivers with the proper phase delay. Finally, we want to test the effectiveness of algorithms for mitigating and (preferably) cancelling radio frequency interference. So far BEST-1 was successfully finished.  BEST-2 is now mechanically ready, since the antennas have been modified and the radio signals can now be transmitted via optical fiber to the receiver room. In 2008 the final BEST-3 demonstrator will be constructed. Due to its huge amount of collecting area it will be able to produce the first science for a SKA demonstrator. These demonstrators will play a fundamental role in the design of new technologies applicable to many industrial fields. By having the required funds, the overall Northern Cross could be re-instrumented obtaining in this way a more powerful and flexible low frequency array until the starting operation of SKA in 2020.

LOFAR (LOw Frequency ARray)

Involved IRA Scientists, Technicians and Collaborators: G. Brunetti, E. Carretti,  K.-H. Mack, J. Monari, S. Montebugnoli, G. Naldi, F. Perini, T. Venturi, D. Dallacasa, G. Giovannini, G. Setti.

LOFAR is one of the most innovative and ambitious projects in radioastronomy. Currently under development at ASTRON (the Netherlands Foundation for Research in Astronomy), LOFAR will be the first large radio telescope for low frequency observations. In particular, it will work in two frequency ranges that are still largely unexplored: the first one goes from 30 to 80 MHz, and the second one from 120 to 240 MHz. Thanks to the innovative approach of LOFAR it will be possible to observe the Universe even in these spectral bandwidths usually full of terrestrial interferences.  Astronomers will be able to study the past history of the Universe till the re-ionization epoch, as well as the synchrotron emission of radio sources in a substantially unexplored frequency range.  In addition transient phenomena due to high energy emission, like Gamma Ray Bursts (GRB) or Ultra High Energy Cosmic Rays (UHECR), will also be observed.

From the technological and structural point of view LOFAR will be the first new generation radio telescope that will be composed of an array of many simple and low-cost omni-directional antennas instead of a large dish antenna. This represents a break-through with respect to traditional architectures of radio telescopes. The electronic signals from the antennas will be digitized, transported via optical fibers to a central digital processor, and combined to emulate a conventional antenna.

The Medicina observatory is directly involved in this project. A program to recommission the Northern Cross radio telescope has already started. At the end of this process, the resulting telescope will allow us to perform LOFAR test observations. This kind of test would demonstrate that it is possible to connect in real time the Medicina Northern Cross telescope with LOFAR stations in the Netherlands. In addition the Medicina observatory will extend geographically the network of LOFAR remote stations by increasing the LOFAR telescope baseline. In fact, Medicina is an ideal site for the installation of a standard LOFAR station since it is already equipped with fast optical fiber links and thus provides the desirable environment to host this kind of equipment.

DEVELOPMENT OF NEW MULTI-TASKING SPECTROMETERS

Involved IRA Scientistsi, Technicians and Collaborators: S. Montebugnoli, L. Zoni, M. Bartolini, M. Cecchi.

The new hardware system SPECTRA-1 (SPECTRum Analizer 1) is a modular programmable, general-purpose back-end for radio telescopes, able to meet the requirements of different kinds of applications (spectrometry, polarimetry, radar detection, etc.). The implementation of such a device obviates the need to install separate back-ends dedicated to single acquisition tasks.  This approach reduces expenses and makes available more compact and flexible (reconfigurable) back-ends. This has become possible due to the use of an innovative electronic device - the Field Programmable Gate Array (FPGA) - which can provide large amounts of digital hardware resouces on the same chip. SPECTRA-1 (Figure 31) has a compact design and runs at very high speeds.

Fig 31 - The compact design of SPECTRA-1

The observations performed by using SPECTRA-1 also include spectroscopy with the possibility to compensate a large range of Doppler shifts. The back-end, together with new low-noise 22 GHz receiver mounted on the 32-m antenna of Medicina, allows astronomers more efficient observations than was possible with previous equipment.

The system is modular: up to 4 data-acquisition boards can be added if required: the parallel use of more boards allows the increase of both the input bandwidth and the number of channels. One particular feature of this system is the parallel real-time FFT (bandwidth < 400 MHz) and the use of KL transforms. This characteristic could play a fundamental role, either for basic line observations or for future applications, when an even higher processing speed and computing power is required to enable an enhancement in quality of real-time complex algorithms.

BEE-2

Involved IRA Scientists, Technicians and Collaborators: S. Montebugnoli, L. Zoni, M. Bartolini.

The BEE2 system is designed to be a modular, scalable Field Programmable Gate Array (FPGA)-based computing platform with a software design methodology that targets a wide range of high-performance applications, such as:

1. - Real-time radio telescope signal processing

2. - Cognitive radio systems

3. - Hyperspectral image processing

4. - E&M antenna simulation

5. - Bioinformatics sequence matching

6. - Simulation of large-scale, ad-hoc and traditional networks

7. - ECAD tool acceleration

8. - Scientific computing

9. - Computer architecture emulation

The modular system architecture can not only provide a reduction in overall cost and design time by orders of magnitude, but also closely tracks the early adoption of state-of-the-art IC fabrication by FPGA vendors. Users of the BEE2 have the freedom to choose the appropriate number of computational modules needed to tackle the application at hand, and to rapidly reconfigure to a different application.
The BEE2 is a general-purpose processing module based on five high-performance Xilinx FPGAs (Virtex II Pro 70). In addition to the large amount of processing fabric provided by the FPGAs, the BEE2 also provides up to 20 Gb/s of high-speed, DDR2 DRAM memory. Each of the five FPGAs has four independent channels to DDR2 DIMMs which provides very high memory bandwidth. Finally, the FPGAs on the BEE2 are highly connected with both high-speed, serial and parallel links.

The FPGAs are laid out in a star topology with four user FPGAs in a ring and one control FPGA connected to each user. The user FPGAs each have four independent high-speed serial channels (4 bonded MGTs) which are capable of transfering data at 10 Gb/s through CX4 connectors (both copper and fiber). The user FPGA ring consists of parallel connections of 138 high-speed LVCMOS traces between the FPGAs which can run at a maximum of 400 Mb/s. The control FPGA has two high-speed serial channels, 64 LVCMOS traces to each user FPGA, and connections to common peripherals such as 10/100 ethernet, USB 1.1, RS232 serial, DVI, and GPIOs.

RADIO SPECTRUM MANAGEMENT

Involved IRA Scientists, Technicians and Collaborators: R. Ambrosini, P. Bolli, C. Bortolotti, F. Messina, G. Nicotra, M. Roma.

No observations can be afforded at the level of sensitivity required by modern radio astronomy (RA) experiments, without a continuous surveillance of the radio frequencies bands assigned to the RA service and of the evolution of the Regulatory frame, under which they are protected by international and national laws.

This activity requires:

- technical skills and day by day work (experimental band monitoring) (http://www.med.ira.cnr.it/Interferenze_page_EN.htm);

- continuous hard/software upgrades to the most recent developments of the telecommunication devices and modulation schemes, used by present and new potential interferers;

- systematic reports to the Italian Communication Administration of the detected interferences in the form of official procedures;

- extremely careful track of all activities at National, European and International levels concerning the development of Spectrum Management. At present this implies to follow and propose specific contributions to the work of Institutions like CEPT (Conference of European Post and Telecommunications), ITU (International Telecommunication Union) and also, since now on, of the European Commission, for example trough RSPG (Radio Spectrum Policy Group). Italy is one of the most active members of CRAF (Committee for Radio Astronomical Frequencies), the Expert Committee of the European Science Foundation, that represents the interests of all the European Radio Astronomy Observatories. CRAF is a Sector Member of ITU, has an official status in CEPT and is affiliated to IUCAF (Scientific Committee on Frequency Allocations for Radio Astronomy and space Science) for the worldwide matters. For more details see Committee on Radio Astronomy Frequencies (http://www.craf.eu/).