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Solution table         SNdssvv
 
 
A. Overview
 
   This extension table for a uv data set contains gain solutions
derived  from calibration software in AIPS.  This information may or
may not have been applied to the data or calibration "CL" table
depending on the uv data file type. For multisource files the SN table
is to be applied to the CL table; for single source data files, the SN
table is applied directly to the data.  The table keyword APPLIED
indicates if the appropriate application has been made.
 
Names: The file name is SNdsssvv where d = release code, sss=catalog
number and vv = version number.
 
B.  File structure.

     Logical records consist of the information for all IFs
for a single antenna.  An IF (channel) is considered to be the output from
a single recorded channel which needs to be calibrated independently,
multiple frequency channels derived from a single recorded channel,
(e.g. spectral line data) are not considered separate IFs.

     A pair of IFs consists of the IFs which are cross correlated, for
example right and left circular polarized IFs at the same frequency.  In
practice a pair will consist of a single IF or a pair of orthogonally
polarized IFs.  All IF pairs must be identical, i.e. have the same number
and types of IF.
 
 
    The file header record contains the following KEYWORDs:
 
     Keyword  Code   Description
     -------- ----  ---------------------------------------------------
     NO_ANT   I     The number of antennas for which there is
                    information
     NO_POL   I     The number of IFs per IF pair.
     NO_IF    I     The number of IF pairs.
     NO_NODES I     The number of interpolation nodes.
     MGMOD    E     The mean gain modulus for the entire table.
     APPLIED  L     If true then the table has already been applied.
     TYPE     I     "Solution" type: 1=>"Clock", 2=>"atmosphere"
                    This is to be used to determine which total model
                    parameters are to be updated.
     RA_OFF1  E     The right ascension offset of the first interpolation
                    node. (degrees)
     DEC_OFF1 E     The declination offset of the first
      ...
     RA_OFFn  E     The right ascension offset of the n th
                    interpolation node n = NO_NODES.
     DEC_OFn  E     The declination offset of the n th
                    interpolation node n = NO_NODES.
   Table entries:

       Title          Units  code      Description
  ----------------- -------- ----  -------------------------------------------
    TIME              Days   1D   Time of center of interval since 0h on
                                  reference day.
    TIME INTERVAL     Days   1E   Interval over which solution was obtained.
    SOURCE ID                1I   Identification number of the source used.
    ANTENNA NO.              1I   Antenna number.
    SUBARRAY                 1I   Subarray number
    FREQ ID                  1I   Freq Id number
    I.FAR.ROT       Rad/m**2 1R   Ionospheric Faraday Rotation
    NODE NO.                 1I   Node number
    REAL 1                   *E   Real part of the gain calibration factor;
                                  calibrated = raw * CALi *
                                  conjg(CALj) for antennas i,j,
                                  for 1st IF of pair. (see note 1)
    IMAG 1                   *E   Imaginary part of the gain calibration.
    DELAY 1         Seconds  *E   Residual pair delay for IF 1.
    RATE 1          Sec/sec  *E   Residual phase delay rate for IF 1.
    WEIGHT 1                 *E   Weight of 1st IF of pair.
    REFANT 1                 *I   Reference antenna used for solution.

The following are present only if NO_POL = 2

       Title          Units  code      Description
  ----------------- -------- ----  -------------------------------------------
    REAL 2                   *E   Real part of the gain calibration factor;
                                  calibrated = raw * CALi *
                                  conjg(CALj) for antennas i,j,
                                  for 2nd IF of pair.
    IMAG 2                   *E   Imaginary part of the gain calibration.
    DELAY 2         Seconds  *E   Residual pair delay for IF 2.
    RATE 2          Sec/sec  *E   Residual phase delay rate for IF 2.
    WEIGHT 2                 *E   Weight of 2nd IF of pair.
    REFANT 2                 *I   Reference antenna used for solution.

C. User notes.

  The "code" column is element_count + basic type code.
basic type codes: D=Double precision, E=single precision,
   A=character, J=long integer, L=logical, I=short integer, X=bit.


      Note 1.  REAL n, IMAG n, DELAY n, RATE n, WEIGHT n and REFANT n
are arrays whose dimensions are given by the header keyword NO_IF.

 
D.  Routines to write SN files:
     Routine SNINI will create/initilize/open/read-keywords-from/
write-keywords-to a solution table and TABSN will do I/O.
Also chapter 13 of "Going AIPS" given a detailed description of routines to
access tables files.
 
E.  Routines to access SN files:
     See D.
