[daip] New Staff Reply - [!PHW-838284]: CLCOR versions

[Eric Greisen]

New Staff Reply: CLCOR versions

The version of AIPS are compatible within themselves but not
backwards compatible.  If you access your data set with 31DEC09
or 31DEC10 then you MUST NOT USE 31DEC08 on it period.  CLCOR in
the modern versions should be more accurate on VLBA.  CLCOR with
a right-hand VLBA antenna file in 31DEC08 will be completely
wrong.

31DEC09 and 31DEC10 are perfectly good for VLBA data - they are
just different and probably slightly better.  The CL tables should
look different in the 2 versions.  Remember, what a CL table contains
is an antenna phase.  The baseline phase - which is all that matters -
is the difference of the antenna phases of the two antennas.  If you
add a phase of 10^5 degrees to all antennas and have that change fast
then the baseline phase will not be changed except that the data storage
will limit the accuracy of the result rather badly.

If you load a dat set with version old and NEVER touch it in any way with
31DEC09 and 31DEC10, then a CLCOR on it will produce a different
**looking** CL table.  However, if you then run UVPRT applying the CL
table to the data and look at the values, you should see that they are
the same or nearly so.  If you run CLCOR on data with an AN file saying
XYZHAND in 31DEC08 you will not get this happy result.

Eric Greisen

Ticket Details
===================
Ticket ID: PHW-838284
Department: AIPS Data Processing
Priority: Default
Status: Closed
Link:  https://help.nrao.edu/staff/index.php?_m=tickets&_a=viewticket&ticketid=165