US Government security requirements no longer permit CDDIS to offer data via traditional unencrypted anonymous ftp; this service was discontinued on October 31, 2020. All data are still available, however access must be via HTTPS or ftp-ssl.

Instructions with examples and our FAQ can be found at:

If you still have difficulty after reading and attempting the examples on that page, please contact us at

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VLBI data holdings

The VLBI data are archived in experiment files, organized by experimental session and frequency band. These experiment files are available in two formats, designed for use by different processing packages: binary databases (Goddard database format) and an ASCII format (NGS card). Multiple versions of the binary databases are retained in the IVS archives; the NGS card version of the experiment data is created from the last updates made to the databases.

Spatial coverage

Temporal coverage

Data volume

  • Experiment files (binary Goddard database format): ~10 Kbytes-6Mbytes (compressed)
  • Experiment files (ASCII NGS card format): ~10–150 Kbytes (compressed)

Data formats

Auxiliary information

  • Schedules
  • Notes
  • Session logs

These are available under the directory

Auxiliary data useful to the analysis of the VLBI data can can be found in

More detailed information about the current and historic VLBI observing programs, including experiment schedules, observing stations, and temporal coverage, is available through the IVS website.

VLBI experiment data are available from the CDDIS in subdirectories by format type (Goddard database, NGS, SINEX) and year.

The starting directory for these files is:

Append the following directory and file names to the starting directory:



sinex (future)

as described in the table below.

Code Meaning
YYYY4-digit year
YY 2-digit year
MON 3-character month
DD 2-digit day
BB database code
### 3-digit version number
.gz gzipped file