VLBI-based Products

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 three-dimensional space.

• Reference Frames (CRF/TRF/EOP)
  

  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. 

• The Radio Reference Frame Image Database (RRFID)

  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.

• VLBI-based Product Information

  Information regarding USNO VLBI-based products including astrometry, reference frames, earth orientation, and imaging data.