_-_BEIC_6348759.jpg) Photo byPaolo Monti, 1974 | |
| Organization | |
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| Location | Bologna,Metropolitan City of Bologna,Emilia-Romagna, Italy |
| Coordinates | 44°31′15″N11°38′49″E / 44.5208°N 11.6469°E /44.5208; 11.6469 |
| Website | www |
| Telescopes |
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  Location of Medicina Radio Observatory | |
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 Related media on Commons | |
TheMedicina Radio Observatory is an astronomical observatory located 30 km fromBologna, Italy. It is operated by the Institute for Radio Astronomy of theNational Institute for Astrophysics (INAF) of the government of Italy.
The site includes:
TheNorthern Cross Radio Telescope (also known as the Medicina Northern Cross (MNC))[3] (andCroce del Nord in Italian) is one of the largest transit radio telescopes in the world. Observations are focused around 408 MHz (UHF band), corresponding to 73.5 cm wavelength. The older receivers of the telescope function with a 2.5 MHz wide frequency band, while the upgraded parts have a 16 MHzbandwidth.[4] The telescope is steerable only in declination, meaning that it can solely observe objects that are culminating on the localcelestial meridian.[2] The telescope is T-shaped and consists of:
The telescope can provide 22880 possible theoretical independent beams and has afield of view of 55.47 degrees (east–west) by 1.8 degrees (north–south).[4] The resolution is around 4–5arcminutes in the north–south direction, and 4 arcminutes in the east–west direction. While less than the resolution of largeoptical telescopes, the amount of radiation that can be gathered with the Northern Cross is much greater, proportional to the mirror surface of approximately 27400 square meters. Northern Cross represents the largest UHF-band antenna in theNorthern Hemisphere, with anaperture efficiency of 60%, making it second in the world, after theArecibo radio telescope.[4] This allows the Northern Cross to identify and measure extremely faint sources, making the telescope is particularly suitable toextragalactic research.[2]
There are plans upgrade of the east–west arm telescope to aLOFAR SuperStation, due to the good performances of a cylindrical-parabolic antenna in the 100–700 MHz frequency range. Since LOFAR operates in the 120–240 MHz range, some of the sensors on the Northern Cross Radio Telescope, optimized for 408 MHz, will have to be replaced with broadband antennas. This installation will have an effective area much larger than any other remote LOFAR station. If extended to the whole 22000 square meters area of the east–west arm, this single element effective area of 20 standard remote LOFAR stations. The resulting system will provide significant improvement in observation sensitivity.[5][6]
The Cross is currently used as a pathfinder for theSquare Kilometre Array.[7] The work is focused on studying the amplification and filtering of signals between the LNA (Low Noise Amplifier) output and theanalog-to-digital converter input for the SKA. The Medicina Radio Observatory is studying all problems related to "antenna array implementation" through a prototype installation called MAD (Medicina Array Demonstrator).[8]
The observatory staff have also built new receiver demonstrators for the SKA calledBEST (Basic Element for SKA Training), part of theEU-funded SKADS (SKA Design Studies) programme.[9] The project started in 2005 and finished in 2009. It involved the installation of the new receivers on some reflectors of the north–south section (and later east–west section) of the Northern Cross telescope, along with new analogfiber-optic andcoaxial digital finks from the front-end receiver boxes to the back-ends.[10][11] The BEST project was divided in three parts:[9]
There is an ongoing effort to use the 32-meter dish as a receiver for radar-based tracking ofartificial satellites andspace debris inEarth orbit. The system functions as abistatic radar, where an emitter located in a different location sends a signal, which bounces off objects in orbit and the echo is picked up by a receiver. The 32-meter dish acts as a receiver, while usually theYevpatoria 70 meter located inCrimea, functions as a transmitter. The systems can either actively track debris to determine their orbit more precisely or utilize a technique calledbeam park, where the transmitting and receiving antennas are kept fixed at a given position and the debris pass in and out of the observed area. The measurements obtain through such a system can be used to determine objectradar cross-section, time of peak occurrence,polarization ratio, bistaticdoppler shift and target rotation. In one of the carried-out tests, Yevpatoria-Medicina system was able to detect an object with an estimated radar cross-section of 0.0002 square meters, which was created by theIridium 33 and Kosmos-2251 satellite collision. The system can also function as amultistatic radar using the 32-meter receivers at Medicina, theNoto Radio Observatory in Italy and theVentspils Starptautiskais Radioastronomijas Centrs inLatvia.[15]
The Northern Cross radio telescope has also been part of space debris tracking studies, utilized as a multiple-beam receiver for a bistatic radar system. The first tested configuration is a quasi-monostatic radar system with a 3 m dish as the transmitter, located inBagnara – 20 km from the receiver. The second configuration was a simulation of a true bistatic radar system with 7 m dish as the transmitter located at the site of theSardinia Radio Telescope (SRT). The system has a maximum field-of-view of about 100 square degrees and a collecting area of approximately 27400 square meters and is capable of providing up to 22880 beams, each 4 by 4 arcminutes wide. Tracking the sequence of beams that are illuminated, makes it possible for the system to track with a higher level of detail, with respect to the single-beam systems, theground track of a transiting object.[4] The Northern Cross radio telescope in a bistatic radar configuration is also part of the Space Surveillance and Tracking (SST) segment of theESASpace Situational Awareness Programme (SSA).[16]
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