[daip] [!17215]: AIPS - Regarding OBIT and AIPS: BDFLIST and BDF2AIPS

[Juhi Tiwari]

              Status: Open (was: Response Overdue)

Regarding OBIT and AIPS: BDFLIST and BDF2AIPS
---------------------------------------------

           Ticket ID: 17215
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/17215
                Name: Juhi Tiwari
       Email address: j_aquarian_t at yahoo.co.in
             Creator: User
          Department: AIPS Data Reduction
       Staff (Owner): Eric Greisen
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: NRAO E2E
      Template group: Default
             Created: 26 October 2020 03:42 PM
             Updated: 18 November 2020 09:47 AM
           Reply due: 20 November 2020 09:48 AM (2d 0h 0m)
      Resolution due: 13 August 2023 12:00 AM (997d 14h 12m)

 Hi Eric,
Could you help?
   ----- Forwarded message ----- From: Juhi Tiwari To: Eric Greisen Sent: Thursday, 5 November, 2020, 09:01:39 pm ISTSubject: Re: [#17215]: Regarding OBIT and AIPS: BDFLIST and BDF2AIPS
  Thanks Eric.
The archival data is AO104_1 observed on 29-JAN-1991. This is VLA L-band data taken in configuration B. I wish to create an image of the source 1233+169 listed as one of the target sources within the project. There are five calibration sources that show up in the output window of the task LISTR.I figured that the source 1328+307 (B1950) (alias 3C286) should be the standard flux density calibrator. The others can be used as secondary phase calibrators but I guess that the best choice would be 1219+285 (it has the best positional accuracy and its calibrator quality code is P) as mentioned here: https://science.nrao.edu/facilities/vla/observing/callist.
1. What are the other sources (just out of curiosity)? Did the old VLA observe multiple sources as part of a single project? 
2. I followed the bad data flagging steps (for old VLA) described in appendix O of the AIPS cookbook. These only involve identifying bad antennas using LISTR optype 'MATX' and 'LIST'.. looking for very low amplitudes and high rms values. Are we only looking for systematic errors here or do we flag individual points as well? Is it possible that only a particular baseline is bad as opposed to an antenna being bad at all times? eg. baseline 2-3 shows an anomalous amplitude/rms value but 2-4 and 3-4 do not? What about checking system temperature etc. (I saw this somewhere else.. not the cookbook procedure for old VLA). Any other bad data that I should be looking out for? For eg., the EVLA data flagging procedure is much more elaborate. Also, I guess UVPLT is just a visual-friendly way to look at the info that LISTR already provides. (I have tried using LISTR and UVPLT)
3. Every VLA data reduction example I have come across checks only the calibration sources for bad data and does the flagging. I have not seen the target source  (the one we are trying to do the science with) being screened for bad data in any of the examples. In principle, shouldn't the target source also be checked for bad data? 
4.The image header shows STOKES 4 which I guess corresponds to RR, LL, LR and RL. Where do these come into play while making an image? Does the data have to be screened for each polarization type?
Juhi    
    On Wednesday, 4 November, 2020, 11:03:52 pm IST, Eric Greisen  wrote:  
 
 
It might also help me to answer your questions if I knew why you are reducing these data, what do you hoe to accomplish?

Eric





Ticket Details
Ticket ID: 17215
Department: AIPS Data Reduction
Type: Issue
Status: Open
Priority: Default

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