VLBI Observations
The VLA can now participate in VLBI observations with the VLBA. Currently, this is only allowed in phased array mode (i.e. single dish is not allowed) with highly restricted WIDAR correlator configurations. For more details see the VLBI at the VLA documentation. In phased array mode the program TelCal derives the antenna-based delay and/or phase corrections needed for antenna phasing in real time. This delay correction is then applied to the antenna signals in the correlator and the visibilities are then summed. The resulting phased array sum is recorded in VDIF format on the Mark5C recorder at the VLA site. The disk(s) are then transported to Socorro, NM and correlated on the DiFX correlator with other VLBI stations which participated in the observation. The standard WIDAR data are also archived in the NRAO science data archive.
