9.8 Summary of VLBI calibration tables
Several different tables are supplied with a VLBI data set created by the Socorro and other correlator; various other
tables (e.g., SN tables) are created by the calibration process. A list of these tables is given below for your edification.
Not all tables will be present with all files.
- Antenna table. Contains a list of the antenna names and station coordinates. Also contains instrumental
- Antenna characteristics table. Contains additional information about antenna properties, including
some time variable quantities.
- Baseline offset table. Contains non-closing baseline-dependent phase and amplitude errors as
determined by BLCAL.
- Baseline solution table. Contains baseline delay, rate and phase solutions as determined by BLING.
- Calibration table. Version 1 contains, amongst other things, the default calibration parameters for the
amplitude (usually unity), phase, and single-band delay (usually zero) for each source for each IF as
a function of time. It also contains polynomial coefficients allowing the correlator delay and phase
models to be recomputed. As calibration proceeds, higher versions of this table are created which
incorporate more and more calibration effects into the phase, delay, and amplitude entries.
- Correlator parameter frequency table. Contains VLBA correlation parameters for each IF, and
activates VLBA delay decorrelation corrections. Type EXPLAIN FXVLB for further information.
- CALC table. Contains the input parameters passed to CALC to generate the polynomials recorded in the
- Flag table. Contains information used to delete selected portions of the data.
- Frequency table. Contains information about the IF frequencies, channel spacings, bandwidths, etc.
- Gain Calibration table. Contains the expected zenith gain and gain-elevation curve for each antenna.
It is used for amplitude calibration.
- Haystack FRNGE table. Contains information generated from the tables that can be exported to
the CALC and SOLVE package.
- Interferometer model table. Contains the actual polynomial coefficients which the VLBA correlator
used to calculate the geometrical model. Unlike the coefficients in the CL table, these have not been
re-interpolated onto the CL time grid, but have time stamps corresponding to the times at which the
correlator computed the geometrical model.
- Model Components table. Contains the various components of the geometric model used in the VLBA
correlator to generate the IM table.
- Index File. Contains information about the time, source, sub-array and location within the data file
of each observation or “scan.” It is used by some tasks in accessing the main data file and
- Spacecraft Orbit table. Contains information about the positions and velocities used by the correlator
for an orbiting antenna.
- Phase-calibration table. Contains phases within each IF computed from the injected phase calibration
signals. It is used to determine the phase offsets and single-band delays for each IF channel.
- Solution table. Contains antenna delay, rate, phase, and amplitude corrections solved for by CALIB and
FRING and other tasks.
- Source table. Contains a list of the sources found within the multi-source file, including information on
source positions and flux density.
- System temperature table. Contains the system temperature as a function of time for each antenna and
IF channel. It is used for amplitude calibration.
- VLBA Tape table. Contains tape playback statistics for use mainly by the VLBA correlator group.
- Weather table. Contains weather-related information for each station.