[daip] Tsys calibration time variability

[Amy Mioduszewski]

If you have VLBI data then you should use 'SELF' for the interpolation of Tsys 
(or as Eric correctly points out the SN table out of APCAL).  SELF will 
interpolate on individual sources.  Usually 2PT should not be used as you will 
interpolate between different sources, which is not a good idea with amplitude 
calibration.  If you have calibration for only one source and and want to 
interpolate to other sources then 2PT can be a good choice.

Amy

Eric Greisen wrote:
> 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
> 
> _______________________________________________
> Daip mailing list
> Daip at listmgr.cv.nrao.edu
> http://listmgr.cv.nrao.edu/mailman/listinfo/daip
>