[daip] [!6302]: aips - TYALP

[Eric Greisen]

Eric Greisen updated #6302
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              Status: Closed (was: Open)
                 Due: - Cleared - (was: 10 March 2015 02:10 AM)

TYALP
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           Ticket ID: 6302
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/6302
           Full Name: Trisha L Ashley
               Email: trisha.ashley at gmail.com
             Creator: User
          Department: AIPS Data Processing
       Staff (Owner): Eric Greisen
                Type: Issue
              Status: Closed
            Priority: Default
      Template Group: Default
             Created: 05 March 2015 10:44 PM
             Updated: 06 March 2015 04:42 PM



The purpose of TYAPL is to provide an initial calibration of
amplitude based on the Tsys measurements.  If all were 
perfect, CALIB would subsequently find gains of nearly 1.0
at all times.  Unfortunately, the Tsys measures are badly
affected by RFI even when the visibilities are not and the SY
table is prone to such issues in several IFs at L band and seems
also to do other strange things unrelated to obvious RFI.
You can calibrate your data without TYAPL and, if the SY table
has such oddities as you describe, that might be your best
bet in this case.  I suspect that the messages from TYAPL are
caused by applying flags to the SY table in TYSMO, but not
applying the same flags to the visibility data in TYAPL.  But note
that application of suspect SY values to data will degrade the
data - so looking at visibilities versus time will inform you
whether the data look fine and if so, TYAPL might well be skipped.

Eric Greisen
 



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