VLBI for Geodesy: Fundamentals, Operation, Products & Applications

The RAEGE network (Portuguese-Spanish acronym for Atlantic Network of Geodynamic and Space Stations) is a project resulting from the cooperation between the National Geographic Institute of Spain (IGN) and the Government of Azores. It is a unique project at a geodetic and geodynamic level, in which it is committed to the combination of space geodetic techniques in four stations (two in Spain (Yebes and Gran Canaria) and two in Azores (Flores and Santa Maria). One of the techniques is the geodetic VLBI (Very Long Baseline Interferometry), which consists in measuring the time delay that radio signals emitted by extragalactic sources (quasars: quasi-stellar radio sources) take to be captured by pairs of radio telescopes in different positions on Earth’s surface. Then, the data signals collected by each station are compared (cross-correlated) to determine the time delay between stations. By multiplying the time delay with the speed of light, the distance between the two antennas can be determined with an accuracy of few millimetres. The VLBI radio telescopes form geometrical networks used to determine the relative positions of the antennas to a few millimetres and the quasar positions to fractions of a milliarcsecond. In this workshop, the fundamentals of the VLBI technique and an outline on the network infrastructure and operations, as well as a general overview on the VLBI data analysis and products will be presented.