[daip] Ringing from BPASS

[Eric Greisen]

lincoln greenhill wrote:
> Hi Eric,
> 
> Ingyin is certainly not yet broadly experienced, and a conceptual
> error would not be plausible to anticipate.
> 
> I had never seen anyone break bp calibration as she
> appeared to have done.  Did she send to you her BPASS
> input parameters? I scanned them before she contacted you, and
> thought that they looked OK.
> 
> She has not gone on to use CPASS, but I will
> ask her to return to BPASS as some point so that learning
> continues.
>
I do not understand the origins of the data - I had thought that the one 
source was just a UVCOP extract from the multi-source - but in fact the 
two had different BP tables.  The history file of the one-source seemed 
to contain several runs of BPASS - but according to local VLB folks, 
using BPASS at all is the first conceptual problem.  For astrometry 
anyway, it is not needed.  I do not know why the 2 bandpasses are 
different - they are very similar except at the edges but I noticed a 
column in the bP table that is not used for much contains the apparent 
shifts by antenna and time and they were different which I do not 
understand at all.  If I thoiught that bPASS were broken I would spend 
time on this but I have already spent 2 days or more with time from Amy 
and Vivek and I conclude that the issues are not with AIPS (at least 
this time).

CPASS should not be used for the gross BP shape although it has use 
according to some for slight shape changes with time in e.g. the VLA.

ERic Greisen