Very Long Baseline Interferometry – VLBI

Definitions:

Radio Interferometer: In radio astronomy, an instrument that combines the amplitudes and phases of signals received from different antennas. Such an instrument will greatly improve the angular resolution of the distribution of brightness in the sky as seen from the ground. This implies the ability to study extremely fine details of the apparent structure of radio sources.
The process of combining or correlating the signals from the different interferometer elements requires, in addition to two or more separate antennas each receiving radiation from the same source, a central computing correlator to reconstruct the map of a radio source from data recorded over many hours. One of the advantages of interferometers is that they can reject background noise collected at individual antennas (if this noise is uncorrelated over the full array); the disadvantage is that their field of view is quite limited. This means that a sky survey over a finite solid angle of the sky requires much more observing time than when using a single dish instrument.

Very Long Baseline Interferometry – VLBI: when the mutual distances of the interferometer elements are several hundred or even several thousand kilometres, special recording techniques are needed at each element or station in order to preserve the phase of the radio astronomical signal, an atomic frequency standard is used as the local oscillator; many terabytes of data are recorded per day. These data are later sent to a correlator centre for the final processing.

European VLBI Network:

Full members of the European VLBI Network, EVN:

  • China: Shanghai Radio Observatory and Urumqi Radio Observatory
  • Germany: Effelsberg Radio Observatory
  • Italy: Medicina Radio Observatory and Noto Radio Observatory
  • the Netherlands: Westerbork Radio Observatory
  • Sweden: Onsala Radio Observatory
  • United Kingdom: Jodrell Bank Radio Observatory Associate members of the European VLBI Network, EVN:
  • Germany: Wettzell Radio Observatory (geodetic VLBI)
  • Finland: Metsähovi Radio Research Station
  • Poland: Torun Radio Observatory
  • Spain: Yebes Radio Observatory
  • Ukraine: Simeiz Radio Observatory
  • South Africa: Hartebeeshoek Radio Observatory

Other arrays:

  • Australia: Australia Telescope
  • United Kingdom: MERLIN
  • U.S.A.: Very Large Array, VLA, VLBA

Note:

VLBI can be distinguished as a terrestrial radio astronomical facility and space VLBI.

Technical capabilities of European VLBI Network

  • The EVN technical capabilities are reported here.

Frequency bands used by the Russian VLBI stations:

  • 0.315 – 0.335 GHz (Pushchino, Medveziy Ozera)
  • 1.385 – 1.435 GHz (Kalyazin)
  • 1.645 – 1.695 GHz (Pushchino, Medveziy Ozera)
  • 2.075 – 2.325 GHz (Kalyazin)
  • 4.805 – 4.855 GHz (Pushchino)
  • 5.000 – 5.020 GHz (Medveziy Ozera)
  • 7.80 – 8.7 GHz (Kalyazin)
  • 22.195 – 22.245 GHz (Pushchino)

Committee on Radio Astronomy Frequencies