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RFI2010 - RFI Mitigation Workshop 29 - 31 March, 2010, Groningen (NL)

RFI2010 - RFI Mitigation Workshop 29 - 31 March, 2010, Groningen (NL) The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope R. Ambrosini (IRA), P. Bolli (OAC), C. Bortolotti (IRA), F. Gaudiomonte (OAC), F. Messina (OAC), M. Roma (IRA).

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RFI2010 - RFI Mitigation Workshop 29 - 31 March, 2010, Groningen (NL)

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  1. RFI2010 - RFI Mitigation Workshop 29 - 31 March, 2010, Groningen (NL) The RFI monitoring systems for the Medicina and the Sardinia Radio Telescope R. Ambrosini (IRA), P. Bolli (OAC), C. Bortolotti (IRA), F. Gaudiomonte (OAC), F. Messina (OAC), M. Roma (IRA)

  2. Agenda • The Italian radio telescopes; • Update of the SRT’s construction; • The RFI monitoring systems of Medicina and SRT: • Fixed station; • Mobile station; • Recent activity of the RFI group: (i) faraday room, (ii) wind farm, and (iii) routine measurements.

  3. Italian network Matera operato da ASI

  4. SRT TechnicalSpecifications • Fully steerable radio telescope for: Radio astronomy , Geodynamical studies, Deep Space Network, Single dish and VLBI • 0.3-100 GHz continuous frequency coverage • 64 m diameter primary mirror; 7.9 m diameter secondary mirror • Gregorian configuration with Shaped Surfaces • Active Surface: Primary mirror with 1116 actuators • a) Compensate gravitational and thermal deformations • b) Convert Shaped surface of the primary to a Parabolic • surface for primary focus operation • Six focal positions (up to 20 receivers): • Primary, Gregorian, Four Beam Wave Guide • Primary surface accuracy:  150 um RMS • Pointing accuracy (RMS): 2 ÷ 5arcsec

  5. RA receiversfor the first light

  6. RFI campaigns in Sardinia

  7. Featuresof SRT site The SRT site is located 35 Km North of Cagliari (700 m asl). Latitude: 39d 29m 50s N Longitude: 9d 14m 40s E The site is well shielded by mountains sorrounding the radio telescope. The area is far away from populated centers.

  8. SRT update High level meeting between INAF and Communication Department of the Government are underway. Full support from National Administration.

  9. RFI monitoring system: goals • …. monitoring the frequency bands allocated by ITU to RAS. If man-made signals interfere with the radio astronomical observations, an official claim must be reported to the National Administration asking for protection. • …. monitoring also the out-of-RAS bands used by astronomers to observe the sky. The RFI information can improve the design of microwave receivers, the strategies of scientific observation, and the mitigation techniques.

  10. RFI monitoring system: scheme A fixed station with antennas placed on a tower close to the radio telescope A mobile laboratory to move closer to the RFI transmitter (i) receive the interference, (ii) collect as many data as possible of the RFI, (iii)identify the content of the signal, (iv) and detect the exact position of the transmitter (triangulation). (i) good sensitivity, (ii) high compression point, (iii) wide frequency bands, (iv) automatically (24 h / day) and remotely controlled.

  11. Fixed RFI station: scheme

  12. Microwavefront-end

  13. Fixed RFI station: comparison >25 m 18 GHz Opticalfiber link PSA 4446E

  14. RFI towers SRT MEDICINA

  15. RFI laboratories SRT MEDICINA

  16. Fixed RFI station: performance MEDICINA SRT

  17. Mobile RFI stations SRT MEDICINA

  18. SRT Mobile RFI station

  19. Mobile RFI station: comparison

  20. Mobile RFI station: performance MEDICINA SRT

  21. Faraday room at SRT site RFI measurements were conducted to evaluate the emission of a super-computing facility (80 nodes with dual CPU dual core each) to be placed at SRT. Goal of the measurement was to evaluate if the auto-interference are compatible with Rec. 769. If not, to identify the shielding level of a Faraday room to be installed at SRT station.

  22. Faraday room at SRT site The figures we got (especially at frequencies lower than 1 GHz) exceed by about 60 dB, the detrimental values suggested by ITU-R RA.769-2 as the ones representative for continuum and spectral line radio astronomy observations.

  23. RFI campaign at a wind farm

  24. RFI campaign at a wind farm -85 dBW (0 dBi) Very strong wide band impulsive signal mainly in P (350 MHz) and L (1.5 GHz) bands associated electrical discharges in the power station of the wind farm.

  25. Routine RFI measurements Routine RFI measurements are conducted every week to monitor the band of interest for the first light of SRT. The P frequency band of the dual frequency receiver was reduced from 305-425 MHz to 305-410 MHz. Power [dBm] withrespectto 0 dBi (RBW=100 KHz) External CW at 426 MHz Two identical HTS microwave band-pass filters are underway in collaboration with Prof. Lancaster and Dr. Huang (Univ. of Birmingham) Frequency [MHz]

  26. Conclusions • SRT is very close to its inauguration; • A team of local technicians has been trained to take care of the RFI problems; • SRT is in progress to be equipped with state-of-the-art RF instrumentation for monitoring the RFI, following the thirty-year experience gathered at Medicina; • The RFI activity consists both: (i) in routine measurements at the site, and (ii) in ad hoc campaign addressed to specific questions.

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