[daip] New Staff Reply - [!LJF-732007]: ACCOR vs. DiFX-correlated data

[Eric Greisen]

New Staff Reply: ACCOR vs. DiFX-correlated data

I have made myself more familiar with this task and think I can give you
a more definitive response.

The Deller paper read the DiFX data in RPFITS from an AT version of DiFX.
That version applied the normalization correction of ACCOR on the fly so
that the data were already corrected before being read into AIPS.  Those data
did not go through FITLD and so DIGICOR was also not in question.  The EVN
correlator also applies the ACCOR correction on the fly prior to AIPS.  The
VLBA correlators do not apply this correction - so data from the older hardware 
correlator AND the new software DiFX correlator should be run through ACCOR.

Note that EVN and RPFITS data should have the autocorrelations rescaled as
well and so should average 1.0.  Thus, ACCOR applied to such data should make
an SN table very close to (1.0, 0.0).  You could check this by running ACCOR
and plotting the output SN table with SNPLT.  Note that ACCOR does not change
your data unless you choose to apply the SN table to your working CL table
version.

FITLD applies digital corrections needed for VLBA data from either correlator
and avoids one of them that should not be applied to DiFX output.  No intervention
from the use is needed there.

Sorry for the previous replies which mixed up the 2 tasks.

Eric Greisen  

Ticket Details
===================
Ticket ID: LJF-732007
Department: Data Processing (AIPS)
Priority: Default
Status: Closed
Link:  https://help.nrao.edu/staff/index.php?_m=tickets&_a=viewticket&ticketid=107