[daip] New Ticket - [!EZG-265803]: Weird data from AT345, 2007Dec12, mix of EVLA and VLA antennas

[Jean Turner]

New Ticket: Weird data from AT345, 2007Dec12, mix of EVLA and VLA antennas

> Dear analysts:
>
> I am struggling to reduce data from program AT345, 2007Dec12, a run at K band with the VLA. I have done a calibration on the data, and the calibration seems to work fine. However when I map the sources and calibrators, for two of the three sets, the calibrator maps cannot be "cleaned" and still look dirty after 100 iterations and the source maps look like the calibrators. A phase offset? For the third source, the only northern source, the calibrator looks ok but there are big stripes. They go away with clipping, and I can map the source but then given the other problems I don't know whether to trust this map or the calibration even if the map and calibrator look OK. I have done the calibration for both EVLA+VLA antennas and VLA antennas only and the calibrations differ by 60-70% (i.e., the GETJY fluxes)
>
> I have also noticed that when I download this dataset from the current archive, and I do an edita, the EVLA antennas, which constituted about half the array then, all look bad, that is, the Tsys look abnormally low and constant and don't change with source like the VLA ants do. However, when I go back to the data we have on disk here, which we originally downloaded and reduced two years ago, the EVLA antennas look OK in edita!  This is very weird.
>
> The log file alludes to the EVLA antennas and the fact that the flagger was not working for them but it is hard to see how to "flag" the data if CALIB doesn't complain.
>
> If you want to see what I"m talking about, my calibrated dataset can be found at
>
> ftp anonymous at wise-gate.tau.ac.il
> (password=email address)
>
> then cd pub/sara
>
> and the file is called
> 20071210.kband.jtcal3.fits
>
> Or, perhaps you can just tell me what the problem is without looking. Since I have not seen these problems before in my many years of mapping, I'm guessing these weird problems have something to do with the mix of EVLA and VLA antennas. I would just ditch the EVLA antennas except this is K band and fast switching and the calibration is not all that easy as it is, even with minimum antennas set to 4. But if I have to, I have to.
>
> Thank you,
>
> Jean Turner
>   

Ticket Details
===================
Ticket ID: EZG-265803
Department: AIPS Data Processing
Priority: Default
Status: Open
Link:  https://help.nrao.edu/staff/index.php?_m=tickets&_a=viewticket&ticketid=1071