[daip] RE: CALIB issues

[Carl Gross]

Thanks for looking into it Eric.  I will check our version of AIPS and make
sure that it is the latest version.

Thanks,

Carl

-----Original Message-----
From: Eric Greisen [mailto:egreisen at nrao.edu] 
Sent: Friday, May 05, 2006 7:45 PM
To: Carl Gross
Cc: daip at aoc.nrao.edu; Clarke, Tracy
Subject: Re: CALIB issues


Carl Gross writes:

 > 1.  During the initial calibration of each single polarization data set,
> CALIB reported the correct number of good and failed solutions.  But when
I  > calibrated a dual polarization data set in which I had flagged data in
one  > polarization but not the other, then CALIB would sometimes
incorrectly  > report those flagged data as failed solutions.  This
definitely occurred in  > only SOME such instances, and not ALL such
instances.  In both cases (single  > and dual polarization), CALIB would
report the correct number of good  > solutions.

       I have tried a number of tests and do not confirm your observations.
For 2 polarization, 2 IF data the number of good solutions was reported as
1620 (no failures).  If I flagged 1 polarization of 1 IF, the number of good
solutions bacme 1215 (3/4 of the total as expected).  No failures were
reported in 31DEC05 or 31DEC06 although 31DEC04 reported 405 failures.

 > 
 > 2.  After I combined all six data sets and began self cal, CALIB would  >
report odd numbers as well.  If I combined one or two data sets into a  >
single DBCON UV file, the solutions that CALIB reported were dictated by the
> parameters I detailed in #1.  If I combined three to six data sets (I did
> not combine any more than 6 data sets, so I can't comment on anything
else)  > into a single DBCON UV file however, the story changed.  For the
single  > polarization data (i.e. the subarrays that were from the single
polarization  > data sets), CALIB reported the correct number of good
solutions.  But the  > number of failed solutions it reported obeyed this
equation:  # of failed  > solutions reported = # of actual good solutions +
2*(# of actual failed  > solutions).  For the dual polarization data (i.e.
the subarrays that were  > from the dual polarization data sets), CALIB
again reports the correct  > number of good solutions.  But the number of
failed solutions again suffers  > from the problem described in #1.

     In the DBCON data set the single-polarization data are actually
recorded as dual polarization with 1 polarization completely flagged. The
#failed = #actual good + 2 * actual failed makes sense in the old version
where every possible solution in one polarization "failed" plus some
solutions in the good polarization also actually failed.


 > This calculations are not based on speculation; I arrived at them by  >
thoroughly plotting SN and FG tables and making sure that failed solutions
> were indeed occurring where data were flagged.  
 > 
 > With initial calibration, I'd like to ensure as few failed solutions as
> possible.  The fact that CALIB reports the incorrect number of failed  >
solutions for dual polarizations requires me to track down every failed  >
solution to make sure that it is indeed a failed solution and not just  >
flagged data.  When self cal'ing, I would like the know the percentage of  >
good solutions to ensure that it is increasing during every step of self  >
cal.  The issues I descbribed in #2 require me to again track down every  >
failed solution to see whether it is indeed an actual failed solution.  I  >
was wondering if you had ever heard of this before, and if so, is there a  >
work around?  If not, I will just continue to be thorough and make sure that
> all the CALIB failed solutions are definitely failed solutions.  I know
that  > one of my colleagues here, Tracy Clarke, has experienced similar
problems  > when calibrating data with multiple IFs.  I have included her on
this  > e-mail, as she would be interested to know any thoughts you might
have on  > the issue.  Thanks for any help you can provide.  > 
 > Carl Gross
 > Naval Research Lab
 > 
 > PS -- These issues are observed in AIPS versions 31DEC03 and 31DEC05.  > 
 
I conclude that you are running older versions of the AIPS code - the fact
that some dates in your 31DEC05 came after the fix worries me.  I suspect
that something went wrong with your MNJ and you do not actually have a
complete version to the dates you found.

Note - I did try another test flagging 10 antennas in one polarization.  In
that case failed solutions were reported in all versions (= 10 * number of
solution times).

I suggest that you get a current version of 31DEC06 - we have added all
sorts of goodies to aips recently.

Eric Greisen