[daip] UVCOP error copying IM tables.

[Craig Walker]

When UVCOP is used to copy a VLBA UV data set, the IM table is not 
copied correctly.  The column PRATE_2 is a duplicate of the preceding 
column GDELAY_2 rather than having values similar, or identical, to 
PRATE_1 as it should.

I found this while doing DiFX/Hardware correlator comparisons.  For the 
hardware correlator, I was using the pipeline processed data from the 
archive.  The data (MT831) is from a multi-band observation so the 
preprocessing involves generating separate files for each frequency 
using UVCOP.  I downloaded the archive file for the input job for the 
time range I'm looking at (fortuitously the only one available).  That 
file, which had not been through UVCOP, had reasonable looking values 
for PRATE_2.  They are the same as PRATE_1, as expected since there were 
no parallactic angle corrections and no dispersive medium corrections to 
my knowledge.  Looking at the history of the processed file, the only 
task that had been run that looked like it touched the IM table was 
UVCOP.  So I ran that and, indeed, the output IM table has the problem.
I have test data on my linux box in the AOC (user 400 on noatak) if that 
is needed, but this sounds like it should be simple to find.

The question now is whether PRATE_2 is actually used anywhere.  The main 
possibility is on the path to total delays for geodetic use.  I included 
Ed on the mail so he can think about that one.  The other possibility is 
if any task is interested in the raw fringe rate, it might use it.  But 
I would guess that is unlikely.

Cheers,

Craig

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     R. Craig Walker            Array Operations Center
     cwalker at nrao.edu           National Radio Astronomy Observatory
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