[daip] Tsys calibration time variability

[Eric Greisen]

Mpati wrote:

> I am hoping you might be able to assist me. I have a question regading 
> system temperature calibrations in AIPS.
> 
> 
> So when applying the Tsys calibration how does account for the 
> variability with time without averaging over ther whole thing?
> 
> I have been using clcal with intepol '2PT'.

CLCAL is used to interpolate the solutions in one or more SN tables to a 
CL table, where the former has samples at the times of calibration and 
the latter has samples at the beginning and end of each scan and at 
regular intervals in between.

In the VLB world, system temperature tables are interpreted by APCAL to 
make an SN table for interpolation by CLCAL.  The SN table contains 
samples at the times occurring in the TY table and the TY table is 
either supplied with the binary data or created through ANTAB.

For the EVLA, the calibration is different since the system does not 
measure a normalized correlation coefficient.  AIPS task TYAPL is used 
to apply a suitable correction directly to the data interpolating as 
needed in an SY table - but that SY table may be recorded on an even 
finer grid in time than the visibility data themselves.  Note that both 
the TY and SU tables are functions of time, so a time-variable 
correction is applied.

Without further information about what you are trying to dom it is hard 
for me to understand your question.

ERic Greisen