TAVLBA tells SCHED to write a VLBA antenna-temperature measuring sequence in the VLBA control file for this scan. NOTAVLBA tells SCHED not to write such a sequence. Parameters PTSLEW and PTDUR are used as they are for PTVLBA. If antenna temperature measurements are desired as part of a VLBI project, a separate scan with TAVLBA set should be requested before or after the main VLBI scan. Do not rely on a long PTSLEW to get the VLBI data since during the setup part of the scan, the requested pointing position is at a half power point.
Use of TAVLBA is not the recommended calibration method for the VLBA. The apriori gains should be used instead. The VLBA antennas are not set up for accurate single dish measurements. The a priori values were obtained during good weather when this is not so much of a problem. If the weather is good for the VLBI project, the a priori values will be good to a few percent, probably better than any Ta measurement. If the weather is poor, the Ta measurements will probably be nearly useless.
This has no effect on VEX files.