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V.1 Real-time calibration tables: TLCAL

The VLA on-line system determines antenna-based complex gain and delay values for the average of every calibrator scan. These are written into a text file which is stored at the VLA site on a computer named mchammer. The actual file name is

/home/mchammer/evladata/telcal/year/month/asdmfile.GN

where year is the four-digit year, month is the two-digit month, and asdmfile is the long complicated name assigned to the particular scheduling block. It is possible to read such files directly from computers in Socorro and task TLCAL supports such access. The text file may also be copied by, for example, the analysts and made available to users in Socorro and elsewhere. The gains in the telcal file all assume that every source is 1.0 Jy in all spectral windows. If you have run SETJY on your data set before using TLCAL, then you can adjust the gains of the known flux calibrators using the fluxes stored in the source (SU) table. In this case, the SN table produced will be ready for use with GETJY.

To run TLCAL on a file in your data area, enter

> TASK ’TLCAL’  C R

> INDI n ; GETN m  C R

to specify the data set.

> DOAPPLY 1  C R

to use the fluxes in the source table.

> ASDMFILE(1) = ’MYAREA:  C R

two parts are concatenated.

> ASDMFILE(2) = ’TSUB0001.sb23643640.eb23666175.56454.14034020834  C R

> INP  C R

to check that you remembered to leave off the close quotes above.

> GO  C R

to run the task.

Substitute your file name parameters for those used above and leave off the .GN part of the name and the close quotes (to preserve your desired case). It would be wise to check the SN table produced with, e.g., SNPLT . Bad RFI may render some telcal values bogus.

The Telcal file is text file with very long lines beginning with 3 header lines. Then there are columns for MJD (to high accuracy), UTC (sexagesimal), LST (days), LST (sexagesimal), IFID (5-character string), Sky frequency (MHz), Antenna ID (e.g., ea03), gain amplitude, phase(degrees), residual, delay (ns), flagged (true/false), zeroed (true/false). hour angle (radians), azimuth (radians), elevation (radians), source name, and flag reason. TLCAL uses the MJD, antenna, amplitude, phase, delay, flagged, and source columns. A combination of the IFID (peculiar to the EVLA) and the sky frequency is used to identify the IFs to which these apply.

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