System Temperature Correction

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4.3.1 System Temperature Correction

Some telescopes, including the JVLA and the VLBA, record the visibilities in the form of raw correlation coefficient with weights proportional to the number of bits correlated. The correlation coefficient is the fraction of the total signal that is correlated, and thus multiplication by the system temperature and the antenna gain (in Jy/K) will produce visibilities with units of correlated flux density. Note that the old VLA system did this initial calibration on-line, and ALMA will also provide some level of on-line calibration (TBD).

ALERT: There is as yet no mechanism available in importvla or in the calibration tasks to use the system temperature information provided by the VLA/JVLA on-line system to calibrate JVLA or VLBA data in raw form. This includes VLA data taken after the Modcomp turn-over in late June 2007. You may pass the data through AIPS first. You can also just forge ahead with standard calibration. The drawback to this is that short-term changes in T_sys which are not tracked by calibrator observations or self-calibration will remain in the data.

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