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RFI Environment at the Shanghai Sheshan Site

RFI Environment at the Shanghai Sheshan Site. Zhi-Qiang Shen, Bin Li, and Tao An (Shanghai Astronomical Observatory). “RFI2010 - RFI Mitigation Workshop” 29 - 31 March, 2010, Groningen (NL). Major Facilities for RA in China. 21CMA. Delingha 13.7m. Location of the Shanghai Sheshan Site.

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RFI Environment at the Shanghai Sheshan Site

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  1. RFI Environment at the Shanghai Sheshan Site Zhi-Qiang Shen, Bin Li, and Tao An (Shanghai Astronomical Observatory) “RFI2010 - RFI Mitigation Workshop” 29 - 31 March, 2010, Groningen (NL)

  2. Major Facilities for RA in China 21CMA Delingha 13.7m

  3. Location of the Shanghai Sheshan Site Telescope site （30-40 km away） Headquarter of ShAO

  4. Shanghai Sheshan 25m RT (1987) Diameter: 25m Band: L, S/X, C, K VLBI Recording system: MK4, MK5A, MK5B

  5. Location 25m RT 65m RT 6.1 KM 4 KM 2.4 KM 多波束射电接收时代的天体物理 南京 2009年9月 5

  6. Shanghai 65m Radio Telescope • 65-m in diameter fully steerable radio telescope • Active surface • Cover 1.4 – 46 GHz with 8 bands： • L(1.6GHz) • S/X(2.3/8.4GHz) • C(5GHz) • Ku(15GHz) • K(22GHz) • Ka(30GHz) • Q(43GHz) • General-purpose (radio astronomy, geodynamics, single-dish, VLBI ) 6

  7. Frequency coverage: 1.4~46 GHz Aperture Efficiency： L/S/C >60%, X >55%, Ku >40%, K >20% Ka >50%, Q >45% (with active surface) Surface accuracy： 0.6mm RMS (without active surface) 0.3mm RMS (with active surface) Pointing accuracy： 3 arcsec (wind < 4m/s) 10 arcsec (wind < 10m/s) 30 arcsec (wind < 20m/s) First secondary lobes: <20 dB under main Elevation limits: 5~90 degree Slew rates: 0.5 degree/s (azimuth), 0.3 degree/s (elevation) Telescope Specifications 7

  8. Receiver Specifications Note: S/X and X/Ka are dual-frequency bands 8

  9. 2008：funded, contract to CETC54 for the antenna construction 2009: complete design, start manufacturing 2010: foundation completed 2011: antenna completed 2012: L/S/C/X band test observations, ready for participation in the Chinese Lunar Mission 2013-14: active surface tested, Ku/K/Ka/Q band test observations 2015: project finished Project Timeline 9

  10. 多波束射电接收时代的天体物理 南京 2009年9月 10

  11. East South West North • L: 1.25～1.80GHz 1.25—1.52 GHz L波段的详细测试图 LNA =40dB. 1200MHz~1520MHz，测试天线水平极化，以下四附图依次为天线指向东南西北四个方向测到的频谱图

  12. L: 1.25～1.80GHz 1.52—1.80 GHz

  13. S: 2.15～2.45GHz C:4.5～7.0 GHz

  14. C:4.5～7.0 GHz X:8.0～9.0 GHz

  15. 9.2 ~ 17.8 GHz

  16. Active surface control • Compensate (repeatable) gravitational deformations, to maintain the nominal shape of the primary reflector (to improve the efficiency at high frequencies) • Used on the USA GBT100-m and ItalyNoto32-m 16

  17. EMC testing with 300kg load 17

  18. Results from EMC testing Power-on & in motion Power-on & hold still 18

  19. solutions • Administrative level: Shanghai Radio Administration Bureau • Was done in 1990’s • Good contact • Hardware: • Superconductor filter • Shielding etc • Software: • learned from this workshop 19

  20. Superconductor Filter • Mitigate strong RFI which saturates the first cryogenic LNA. • Working at 10~20K, low loss, low phase degeneration. • Example • Frequency: 2.2~2.3GHz (3G mobile RFI@ 2.14GHz) • Style: hairpin, 12 sections • Material: thin film TL-2212 • Insertion loss: 0.05dB at 20K 20

  21. Superconductor Filter Provided by CETC-16 institute 21

  22. Conclusions and Future Work • RFI has become an important issue to the sites of radio telescopes in China • Observatory will pay close attention to both the technical and regulatory issues related to RFI • Superconductor filter (considered for 65m) • Shielding (under consideration) • Softwares • … • Spectrum management at different levels • Origins of RFI (Shanghai Radio Administration Bureau) • More frequent RFI monitoring is necessary to ensure a reliable assessment at Shanghai Sheshan site 22

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