VLBI


Also found in: Dictionary, Acronyms, Wikipedia.
Related to VLBI: eVLBI

VLBI

Abbrev. for very long baseline interferometry. A method of using widely separated radio telescopes as parts of an interferometer without connecting them directly. The very long baselines achieved give the interferometer a high angular resolution and allow the study of fine structure in very distant radio sources such as quasars.

Broad-bandwidth signals from each telescope are recorded on magnetic tape, together with timing information from high-precision clocks – usually based on hydrogen masers. The tapes are then transported to a central site where they are replayed to a VLBI correlator which processes them to produce an image (see aperture synthesis).

Telescopes at many observatories are routinely diverted from their normal programmes to make VLBI observations, and standard broad-bandwidth recording systems such as the ‘Mark III’ are used. Dedicated networks also exist (see VLBA) whose sole purpose is VLBI. Sometimes telescopes from around the world are combined to give intercontinental VLBI with baselines of more than 10 000 km. Baselines greater than the diameter of the Earth can be achieved by using a telescope mounted on an orbiting satellite, as is suggested for VSOP and RadioAstron.

VLBI can also be used to measure certain geodynamical phenomena, such as the movements of tectonic plates, polar wobble, and the rise and fall of Earth tides.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

VLBI

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The scale difference is estimated at the level of 0.1 mm/yr for DORIS, SLR, and VLBI and the orientation differences reach 0.4 mm/yr in the case of SLR.
which carries out a wide range of research and development activities in VLBI-related fields, including radio astronomy data processing and applications of VLBI and radio astronomy technologies.
Sample topics include: new orbit and new possibilities of the Radioastron Project, VLBI observations of sources of maser radiation by a ground-space interferometer, the use of lens antennae in radio astronomy, multichannel spectrum analyzer for observation of pulsars, and synthesis of VLBI images using the regularization methods.
Since 1972 the new space geodesy techniques (Doppler, VLBI) started and their results were combined in BIH with those by optical astrometry to determine Earth rotation paprameters.
Because it uses a technique called VLBI, the satellite was originally going to be called VSO-VLBI Space Observatory.
One of the most demanding applications for data recording is radio astronomy, especially very-long-baseline interferometry (VLBI).
An approach adopted by the radio astronomy community for a data-capture technique known as Very Long Baseline Interferometry (VLBI) recognizes these physical limitations but nevertheless reduces the track width to 1.5 mil at the head-to-tape interface.
DE421 included additional ranging and Very Long Baseline Interferometry (VLBI) measurements of Mars spacecraft and Venus Express spacecraft, the updated estimates of planetary masses, additional lunar laser ranging, and so on, and the Mars position accuracy predicted to 2008 was expected to be better than 300 m [7]; moreover, because of the perturbations by asteroids, the accuracy was expected to be lower.
The strategy of combining several telescopes to create a simulated larger dish area, known as Very Long Baseline Interferometry (VLBI), is not new.