[daip] [!5094]: aips - WTMOD sometimes writes out u,v,w == 0

[Michael Bietenholz]

Michael Bietenholz updated #5094
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WTMOD sometimes writes out u,v,w == 0
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           Ticket ID: 5094
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/5094
           Full Name: Michael Bietenholz
               Email: mbieten at yorku.ca
             Creator: User
          Department: AIPS Data Processing
       Staff (Owner): -- Unassigned --
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: NRAO E2E
      Template Group: Default
             Created: 30 June 2014 05:26 PM
             Updated: 30 June 2014 05:26 PM
                 Due: 02 July 2014 05:26 PM (2d 0h 0m)
      Resolution Due: 09 July 2014 05:26 PM (9d 0h 0m)



For VLBI data files, WTMOD seems to produce output files with u,v,w being identically 0.  I tried it on a VLA data set and it worked okay, but it produced u,v,w=0 output on both an LBA and a global VLBI visibility file.  The failure seems to be independent of settings of APARM or NOISE.

(31DEC2014 AIPS; updated a few days ago)

A nicety would be to add an explanation to the UVMOD explain file that the adverb NOISE does *not* represent any form of noise, but is just a numerical scaling factor, since most people would probably expect the weights to scale with 1/noise^2 if it were some form of noise.  In reality, WTMOD scales the weights on baseline i,j, as advertised, just by NOISE(i) * NOISE(j)

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