[daip] [Minor] AIPS problems

[Eric Greisen]

>  I'm running AIPS (version 31-Dec-2001) on the VLBI data set from the

    It would appear that you are running a very early version of
31DEC01, not the final or even a late version.

>  VSOP experiment W418a correlated in Socorro. The observation included
>  all VLBA antennas, VLA (phased array), WSRT and HALCA. In the course of
>  data reduction I've encountered several AIPS hiccups. None of them is
>  fatal, and, in fact, some of them are known to me and other people
>  around here in Dwingeloo from previous experiences for quite a while.
>  However, this time I decided to report them and ask you to try to fix
>  the problems. Several of them albeit belonging to the category
>  "we-can-live-with" are a bit annoying. All the cases described below
>  correspond to the same multi-source file loaded in the standard manner
>  using FITLD:
>  
>  1). According to the EXPLAIN text of APCAL:
>  
>      ...An error will be reported by APCAL if source flux densities are
>      required but cannot be found in the source table.
>  
>  Mistakenly, I've attempted to run APCAL before using SETJY for VLA.
>  Quietly, without any error message, APCAL creates an SN table throwing
>  out VLA.
>  
>  2). Apparently, there is no way to use POSSM for plotting a
>  cross-spectrum of just one IF if this IF is not #1. Another words, in
>  the case of, say, total of two IFs in the data set, parameters BIF=2
>  and EIF=2 do not result in a plot of cross-spectrum of the second IF.
>  It still plots both IF1 and IF2.

       This was fixed June 12, 2001

>  
>  Also, the numbering convention for channels (continuing numbering in
>  case of multiple IFs) is very confusing especially if one uses ECHAN
>  and/or BCHAN non-equal zero and dealing with the situation described in
>  the previous paragraph.
>  
>  Finally, it would be very helpful to describe somewhere what is the
>  vertical scaling convention for amplitudes in POSSM. Using the same
>  data with the same CL table, POSSM and VPLOT give quite different
>  values of amplitudes.

      The vertical scaling is Jy.  POSSM and VPLOT do very different
things.  VPLOT averages all spectral channels at individual times abd
antenna pairs.  POSSM, depending on how you drive it, averages all
times and/or all antenna pairs but does not average spectral channels.
I suspect that your channels are individually noisy and would not be
the least suprised to see rather different decorrelation effects inthe
two averages.  You do not say how they differ so I can only make these
general remarks.

>  
>  3). In some cases, VPLOT produces plots with a bizarre horizontal
>  axis. The plot attached (PostScript) was created by VPLOT with the
>  parameters

       This was fixed May 25, 2001

I will look at APCAL - or have Amy check it...


Eric Greisen