Difference between revisions of "Gencal"

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Help on gencal task:
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==Help on gencal task:==
 
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<pre>
 
Specify Calibration Values of Various Types
 
Specify Calibration Values of Various Types
  
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               of the sign convention adopted when applying antpos  
 
               of the sign convention adopted when applying antpos  
 
               corrections.
 
               corrections.
 +
</pre>

Revision as of 14:17, 21 May 2010

Help on gencal task:

Specify Calibration Values of Various Types

     The gencal task provides a means of specifying antenna-based
     calibration values manually.  The values are put in designated
     tables and applied to the data using applycal.

     Current antenna-based gencal options (caltype) are:
        'amp'= amplitude correction
        'ph' = phase correction
        'sbd'= single-band delay (phase-frequency slope for each spw)
        'mbd'= multi-band delay (phase-frequency slope over all spw)
        'antpos' = ITRF antenna position corrections
        'antposvla' = VLA-centric antenna position corrections 

     The calibration specifications are not time-variable in the
     present implementation.  Calibration values can be assigned to
     each spw, antenna and pol selection, where applicable.  The 
     same caltable can be specified for multipl runs of gencal, 
     in which case the specified parameters will be incorporated 
     cumulatively.  E.g., amplitude parameters (caltype='amp')
     multiply and phase-like parameters ('ph', 'sbd','mbd','antpos') 
     add.  'amp' and 'ph' parameters can be incorporated into the 
     same caltable (in separate runs), but each of the other types
     require their own unique caltable.   A mechanism for
     specifying manual corrections via a text file will be provided in
     the future.

     The caltables are applied to the data by using applycal.  Other
     calibration tables must also be present, if applicable.

     For antenna position corrections (caltype='antpos'), the antenna 
     position offsets are specified in the ITRF frame.  For VLA position
     corrections in the VLA-centric frame, use caltype='antposvla', and gencal
     will rotate them to ITRF before storing them in the output caltable.

     Keyword arguments:

     vis -- Name of input visibility file
             default: none.  example: vis='ngc5921.ms'
     caltable -- Name of input/output caltable.  If it does not
                  exist, it will be created.  Specifying an
                  existing table will result in the parameters
                  being applied cumulatively. Only a single
                  time-stamp for all calibrations are supported,
                  currently.  Do not use a caltable
                  created by gaincal, bandpass, etc.  
                  default: none.  example: caltable='test.G'
     caltype -- The calibration parameter type being specified.
                 Options include:
                 'amp' = gain (G) amplitude (1 real parameter per
                         pol, antenna, spw)
                 'ph'  = gain (G) phase (deg) (1 real parameter per
                         pol, antenna, spw)
                 'sbd' = single-band delays (nsec) (1 real parameter 
                         per pol, antenna, spw)
                 'mbd' = multi-band delay (nsec) (1 real parameter 
                         per pol, antenna, spw)
                 'antpos' = antenna position corrections (m) (3 real
                            ITRF offset parameters per antenna; spw, pol
                            selection will be ignored)
                 'antposvla' = antenna position corrections (m) specified
                               in the old VLA-centric coordinate system
                 default: none.
                 example: caltype='ph'
     spw -- Spectral window selection for specified parameters. 
             default: spw='' (specified parameters apply to all spws)
             example: spw = '2,3,4'
     antenna -- Antenna selection for specified parameters. 
                 default: antenna='' (specified parameters apply to all antennas)
                 example: antenna='EA02, EA03' (specified parameter(s) to
                           apply to EA02 and EA03 only)
     pol -- Polarization selection for specified parameters.
             default: pol='' (specified parameters apply to all polarizations)
             example: pol='R' (specified parameters to apply to
                                 R only)
     parameter -- The calibration parameters, specified as a list, to 
                   store in the caltable for the spw, antenna, and pol 
                   selection.  The required length of the list is 
                   determined by the caltype and the spw, antenna, pol
                   selection.  One "set" of parameters (e.g., one value
                   for 'amp', 'ph', etc., three values for 'antpos')
                   specified the same value for all indicated spw, antenna,
                   and pol.
                   OR, 
                   When specifying a long list of calibration parameter values,
                   these should be ordered first (fastest) by pol (if pol!=''),
                   then by antenna (if antenna!=''), and finally (sloweset) by 
                   spw (if spw!='').  Unspecified selection axes must not be
                   enumerated in the parameter list
      
     Examples:

       gencal(vis='test.ms',caltable='test.G',caltype='amp',
              spw='',antenna='',pol='',
              parameter=[3])

         --> Antenna-based gain amplitude corrections for all spws, antennas, 
              and polarizations will be multiplied by 3.  When applied
              to visibility data, this correction will produce a
              corrected visibility than is (1/3*1/3) less than the 
              uncorrected visibility.

       gencal(vis='test.ms',caltable='test.G',caltype='ph',
              spw='',antenna='EA03,EA04',pol='',
              parameter=[45,120])

         --> Gain phase corrections for antennas EA03 and EA04
              will be adjusted (additive) by 45 and 120 
              degrees (respectively), for all spws and polarizations.
              When these phases are applied to visibility data, the
              visibility phases will decrease or increase by the
              specified amount where the selected antennas occur
              first or second (respectively) in each baseline.  E.g., 
              the phase of baseline EA03-EA04 will change by (-45+120)
              = + 75 degrees.  Baseline EA01-EA03's phase will change
              by +45 degrees; baseline EA04-EA05's phase will change
              by -120 degrees.  The same phase sign convention is
              used for delay and antenna position corrections.

       gencal(vis='test.ms',caltable='test.G',caltype='ph',
              spw='',antenna='EA05,EA06',pol='R',
              parameter=[63,-34])

         --> Gain phase corrections for antennas EA05 and EA06
              will be adjusted (additive) by 63 and -34 
              degrees (respectively), in R only, for all spws

       gencal(vis='test.ms',caltable='test.G',caltype='ph',
              spw='',antenna='EA09,EA10',pol='R,L',
              parameter=[14,-23,-130,145])

         --> Gain phase corrections in all spws will be adjusted for 
              antenna EA09 by 14 deg in R and -23 deg in L, and for
              antenna EA10 by -130 deg in R and 145 deg in L.

       gencal(vis='test.ms',caltable='test.G',caltype='ph',
              spw='2,3',antenna='EA09,EA10',pol='',
              parameter=[14,-23,-130,145])

         --> Gain phases corrections in both polarizations will be adjusted for 
              antenna EA09 by 14 deg in spw 2 and -23 deg in spw 3, and for
              antenna EA10 by -130 deg in spw 2 and 145 deg in spw 3.

       gencal(vis='test.ms',caltable='test.G',caltype='sbd',
              spw='2,3',antenna='EA09,EA10',pol='',
              parameter=[14,-23,-130,145])

         --> Delay corrections in both polarizations will be adjusted for 
              antenna EA09 by 14 nsec in spw 2 and -23 nsec in spw 3, and for
              antenna EA10 by -130 nsec in spw 2 and 145 nsec in spw
              3.  See the above example for caltype='ph' for details
              of the sign convention adopted when applying delay corrections.

       gencal(vis='test.ms',caltable='test.G',caltype='antpos',
              antenna='EA09,EA10',
              parameter=[0.01,0.02,0.03, -0.03,-0.01,-0.02])

         --> Antenna position corrections in meters (in ITRF) for
              antenna EA09 (dBx=0.01, dBy=0.02, dBz=0.03) and for
              antenna EA10 (dBx=-0.03, dBy=-0.01, dBz=-0.02)
              See the above example for caltype='ph' for details
              of the sign convention adopted when applying antpos 
              corrections.

       gencal(vis='test.ms',caltable='test.G',caltype='antposvla',
              antenna='EA09,EA10',
              parameter=[0.01,0.02,0.03, -0.03,-0.01,-0.02])

         --> Antenna position corrections (in the traditional VLA-centric
              frame) will be introduced in meters for
              antenna EA09 (dBx=0.01, dBy=0.02, dBz=0.03) and for
              antenna EA10 (dBx=-0.03, dBy=-0.01, dBz=-0.02)
              These offsets will be rotated to the ITRF frame before
              storing them in the caltable.
              See the above example for caltype='ph' for details
              of the sign convention adopted when applying antpos 
              corrections.