This CDDIS collection is composed of geodetic, Very Long Baseline Array (VLBI) level 2 observational and supporting data (including observations, standard deviations, station coordinates, and more) and derived products which are stored and exchanged in a format named vgosDB, which is the International VLBI Service for Geodesy and Astrometry (IVS) standard format for storing, transmitting, and archiving VLBI data. vgosDB datasets are comprised of NetCDF and ASCII files which contain almost all the information that is required to process a single VLBI session (typically 24-hours of data per single session).

Very Long Baseline Interferometry (VLBI) binary files provided by the International VLBI Service for Geodesy and Astrometry (IVS) in vgosDB format.

SWIN files contain the VLBI fringe visibilities of an observing session (24 hours long or 1 hour long). The files are created by the International VLBI Service for Geodesy and Astrometry (IVS) correlation centers and constitute the raw output of the Distributed FX-style (DiFX) software correlator running on a Swinburne supercomputer. These data form the basis for the fringe fitting process and can also be used to make source maps of the observed quasars.

Very Long Baseline Interferometry (VLBI) ASCII files in the NGS card format. Very Long Baseline Interferometry (VLBI) auxiliary ASCII files provided by the International VLBI Service for Geodesy and Astrometry (IVS) include schedules, notes, and session log files.

The Terrestrial Reference Frame product consists of a set of station positions, velocities, and correlations. A minimum of three years of data is used in each solution. The TRF operational product is available on the IVS Data Centers approximately quarterly.

Celestial Reference Frame (CRF) product derived from analysis of Very Long Baseline Interferometry (VLBI) data. These products are the generated by analysis centers in support of the International VLBI Service for Geodesy and Astrometry (IVS) and combined by the IVS analysis coordinator to form the official IVS CRF product.

Terrestrial Reference Frame (TRF) product derived from the analysis of Very Long Baseline Interferometry (VLBI) data. The Terrestrial Reference Frame product includes station positions, velocities, and correlations. A minimum of three years of data are used in each solution. The TRF operational product is available quarterly at International VLBI Service for Geodesy and Astrometry (IVS) Data Centers.

Troposphere Zenith Path Delay (ZPD) values derived from analysis of Very Long Baseline Interferometry (VLBI) data. These products are the generated by analysis centers in support of the International VLBI Service for Geodesy and Astrometry (IVS).

Very Long Baseline Interferometry (VLBI) auxiliary ASCII files provided by the International VLBI Service for Geodesy and Astrometry (IVS) include schedules, notes, and session log files.

Very Long Baseline Interferometry (VLBI) is a geometric technique: it measures the time difference between the arrival at two Earth-based antennas of a radio wavefront emitted by a distant quasar. VLBI precisely locates points on Earth by comparing radio signals from a quasar radio source located in deep space received at different times at different Earth ground stations. This method gives relative positions of the Earth stations. VLBI data can be used to calculate information on Earth rotation, length of day, polar motion, baseline and velocities of stations. Products generated by VLBI contribute to research in many areas, including solid Earth, tides, studies of the vertical, fundamental astronomy, and VLBI technique improvement. More information about these data and products are available on the CDDIS website at https://cddis.nasa.gov/Data_and_Derived_Products/VLBI/VLBI_data_and_product_archive.html.