Very Long Baseline Interferometry (VLBI) is a technique used by radio
astronomers and geodesists to determine the celestial and terrestrial reference frames
and to predict the variable orientation of the Earth in
Available products include positions of extragalactic radio sources that define an astrometric
quasi-inertial Celestial Reference Frame (CRF), positions and
velocities of radio antennas that define a VLBI-based Terrestrial
Reference Frame (TRF) and the Earth Orientation Parameters (EOP) that link the CRF and the TRF.
Available products include PostScript format contour plots of Radio
Reference Frame source images at frequencies of 2 GHz, 8
GHz, 15 GHz, 24 GHz and 43 GHz. Plots of visibility data in PostScript
format are also available. These products are the results of an ongoing program to image International Celestial
Reference Frame (ICRF) sources on a regular basis.
Information regarding USNO VLBI-based products including astrometry, reference frames, earth orientation, and imaging data.