Very Long Baseline Interferometry

Very Long Baseline Interferometry (VLBI) is a variant of the radio interferometry technique currently used in astronomy, but combining the signals of extremely distant telescopes. VLBI provides observations of an object with an exquisite angular resolution, equivalent to that of a telescope whose size is the separation between the distant telescopes. This distance can reach thousands of km (transcontinental VLBI), thus allowing measurement of details as small as 10 milli-arcsec (mas), i.e., one hundred times finer than with a conventional telescope in visible light. To achieve VLBI observations, the radio signal is locally recorded together with time stamps of an atomic clock and later the different data from all antennas are correlated using digital electronics and computers to produce the resulting image.