[daip] aips_gripe

[Ketan Desai]

> {27-MAY-2000 10:55:39}
> {rgalp8       UN-REGISTERED!!!!!!!}
> {   24  31DEC99  DEC}
> {lincoln}
> {cfa, ms42}
> {617 495 7194}
> {For multi-src files, CALIB does not appear to make consistent choices
>  of the times tagging entries in the solution table.  My tests involve a
>  phase referenced VLA observation.  Scan lengths are 27 sec, with 3 sec
>  deadtime between scans. (This is what is shown in the NX table.) The time
>  entries for a scan that starts at 13:21:13 are 13:21:43.3 (length 0 sec)
>  and 13:21:58.3 (length 23.3 seconds) and 13:22:43.3 (length 0 sec) and
>  13:22:58.3 (length 23.3 sec) etc.
>   
>  In the past I have found that for a different multi-source file, one that
>  features longer scans, I obtain better self-cal results with CALIB is I
>  delete the NX table before running CALIB (this is a multi source file with
>  only one source in it).  At that time Ketan mentioned that CALIB does not
>  divide up time into SOLINTS properly.  I believe that I obtained better
>  results w/o the NX table because it prevented the introduction of irregularly
>  spaced time tags.

I stand by that assertion.

>   
>  In the case detailed in paragraph 1, the phase solutions for the 0 length
>  records are substantially different than their closest neighbors, which is
>  a worry.  My remedy in this case will be to use TABED to delete them.
>   
>  Perhaps FRING also suffers this problem.  I have not checked but expect
>  the same machinery to be used as in CALIB.

FRING also suffers from this problem.
There is some relief because people do not tend to run FRING 
with only one data point per solution interval.

In KRING, this problem is treated better [says me!].

>   
>  Final note:  There are occasional instances in the files discussed in para. 1
>  where the 0 length records are absent. For example:  present at 13:20:4x,
>  13:21:4x, 13:22:4x, missed at 13:23:4x, present 13:24:4x, etc
>   
>   }
> {CALIB does not compute time tags correctly in multi-source files w/ NX tbls.}
> {greenhill at cfa.harvard.edu}
> { }


-- ketan
M.O.T.U.