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Calibration table         CLdssvv
 
 

A. Overview
 
   This extension table for a uv data set contains  calibration
information and the total observed geometric observables.  This will
include both calibration information passed to AIPS from external sources
and that derived from AIPS calibration software.  This information will
not have been applied to the data.  This table will need to be updated
using the contents of the Gain table (GA) when satisfactory gain solutions
have been derived.  The information in this table will be used to
calibrate data.
  The records also contain the geometric observables: total group and
phase delay and their time derivatives divided into several parts.
These values should be updated whenever this table is updated using a
Gain table.

     The total model group and phase delays are divided into three
contributions: 1) the geometric delay which will include terms which
can be described by a single 24 hour sinusoid, 2) a atmospheric term, and
3) a "clock" (meaning everything else) term.  Interpolation of the
geometric term to times other than the reference time is  done using the
phase of the sinusoid at the reference time (GEOPHASE) and the earth
rotation rate at the reference time (GEORATE).  The other terms are
interpolated by using the first order time derivatives.  The total model
values are given by the sum of these three terms.  These values are the
total observed values and are not to be applied to the data; the residual
values are the corrections which need to be applied to the data.
 
Names: The file name is CLdsssvv where d is update 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.
     MGMOD    E     The mean gain modulus for the entire table.

   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
    GEODELAY        Seconds  1D   The total geometric delay at the reference
                                  time; should include only sinusiodal terms.
    GEOPHASE        Turns    1D   Fractional (0-1) phase of the reference
                                  time, used to interpolate GEODELAY.
    GEORATE         Hz       1D   The time derivative of GEOPHASE = earth
                                  rotation rate at the reference time.
    DOPPOFF         Hz       *E   Doppler frequency offset. (see note 1)
    CLKGD 1         Seconds  *E   Clock group delay for IF 1.
    DCLKGD 1        Sec/sec  *E   Time derivative of CLKGD 1.
    CLKPD 1         Seconds  *E   Clock phase delay for IF 1.
    DCLKPD 1        Sec/sec  *E   Time derivative of CLKPD 1.
    ATMGD 1         Seconds  *E   Atmospheric group delay for IF 1.
    DATMGD 1        Sec/sec  *E   Time derivative of ATMGD 1.
    ATMPD 1         Seconds  *E   Atmospheric phase delay for IF 1.
    DATPGD 1        Sec/sec  *E   Time derivative of ATMPD 1.
    REAL 1                   *E   Real part of the gain calibration factor;
                                  calibrated = raw * CALi * CALj for IFs i,j,
                                  for 1st IF of pair.
    IMAG 1                   *E   Imaginary part of the gain calibration.
    DELAY 1         Seconds  *E   Residual delay of IF 1
    RATE 1          Sec/sec  *E   Residual rate of IF 1
                                  Note: DELAY n and RATE n are the residual
                                  values by which the data are to be
                                  corrected during calibration.
    TSYS 1          Kelvins  *E   System temperature of 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
  ----------------- -------- ----  ---------------------------------------
    CLKGD 2         Seconds  *E   Clock group delay for IF 2.
    DCLKGD 2        Sec/sec  *E   Time derivative of CLKGD 2.
    CLKPD 2         Seconds  *E   Clock phase delay for IF 2.
    DCLKPD 2        Sec/sec  *E   Time derivative of CLKPD 2.
    ATMGD 2         Seconds  *E   Atmospheric group delay for IF 2.
    DATMGD 2        Sec/sec  *E   Time derivative of ATMGD 2.
    ATMPD 2         Seconds  *E   Atmospheric phase delay for IF 2.
    DATPGD 2        Sec/sec  *E   Time derivative of ATMPD 2.
    REAL 2                   *E   Real part of the gain calibration factor;
                                  calibrated = raw * CALi * CALj for IFs i,j,
                                  for 2nd IF of pair.
    IMAG 2                   *E   Imaginary part of the gain calibration.
    DELAY 2         Seconds  *E   Residual delay of IF 2
    RATE 2          Sec/sec  *E   Residual rate of IF 2
    TSYS 2          Kelvins  *E   System temperature of 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.  DOPPOFF, REAL n, IMAG n, DELAY n, RATE n, TSYS n,
WEIGHT n and REFANT n are arrays whose dimensions are given by the
header keyword NO_IF.

     The geometric observables should be updated everytime the file is
updated from a Gain table.
 
 
D.  AIPS routines to write CL files:
     CALINI and TABCAL
Also chapter 13 of "Going AIPS" given a detailed description of routines to
access tables files.
 
E.  AIPS routines to access CL files:
     CALINI and TABCAL
Also chapter 13 of "Going AIPS" given a detailed description of routines to
access tables files.
