[daip] [!16434]: AIPS - Why the solution changes after add more flags

[Aiyuan Yang]

              Status: Open (was: On Hold)

Why the solution changes after add more flags
---------------------------------------------

           Ticket ID: 16434
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/16434
                Name: Aiyuan Yang
       Email address: ayyang at mpifr-bonn.mpg.de
             Creator: User
          Department: AIPS Data Reduction
       Staff (Owner): Eric Greisen
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: NRAO E2E
      Template group: Default
             Created: 26 June 2020 11:02 AM
             Updated: 23 September 2020 11:44 AM
           Reply due: 25 September 2020 11:44 AM (2d 0h 0m)
      Resolution due: 10 April 2023 12:00 AM (928d 12h 16m)

Hi Eric, 

Many thanks for your suggestions and this problem has been solved. 

Cheers,
Aiyuan

> On 08 Jul 2020, at 23:13, Aiyuan Yang  wrote:
> 
> Hi Eric, 
> 
> Many thanks for the details!
> 
> Cheers,
> Aiyuan
> 
>> On 08 Jul 2020, at 19:13, Eric Greisen > wrote:
>> 
>> The sudden shift from reasonable delays to 100 ns is odd.   That is a very very large delay error for the VLA.  You should look at the data for antenna 28 at these times with POSSM using a CL table before your FRING and not using the flags you genertaed.  See if there is a large slope in the phases or if FRING got confused.  Normally for the VLA one does not run FRING with a smallish SOLINT over all times as you seem to have done.  Chapter 4 of The CookBook describes what is usually done.  Delays on the VLA tend to be very stable.  Try doing one single scan on the delay calibrator and applying that one solution to all data.  Then look at selected data with POSSM to see if the phase slopes with frequency have been mostly removed.  The odd solution in the polarization and at a time not affected by your flags is strange.  If it persists you will want to flag it.  But back up first to deal with the delay issue.
>> 
>> Eric Greisen
>> 
>> 
>> 
>> 
>> Ticket Details
>> Ticket ID: 16434
>> Department: AIPS Data Reduction
>> Type: Issue
>> Status: Response Overdue
>> Priority: Default
>> 
>> Helpdesk: https://help.nrao.edu/index.php? 
> 




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