Content-type: text/html Manpage of gmakes

gmakes

Section: User Commands (1)
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NAME

gmakes - Convert a visibility dataset into a gain visibility dataset  

PERSON RESPONSIBLE

pjt  

CATEGORIES

calibration  

DESCRIPTION

GMAKES creates a gain calibration dataset (which in actuality is a regular visibility dataset) from a single visibility dataset assuming a model for the observed source (point source or planet)

  ** In antenna based mode the visibilities are written as if 
     the data is an autocorrelation dataset

NOTE: this is the new GMAKES, with new keyword focus=  

PARAMETERS

vis
Name of input visibility dataset. Only one dataset can be given; to use multiple datasets, use UVCAT with the proper LINE= to speed up I/O in this program. No default.
select
Standard uv data selection criteria. Generally this should not include a "dra" and "ddec" selection, as GMAKES automatically matches data with the appropriate pointing center.
model
Name of the input models. Several models can be given, which can cover different channel ranges, different pointing centers, and different polarizations of the input visibility data. Generally the model should be derived (by mapping and deconvolution) from the input visibility file, so that the channels in the model correspond to channels in the visibility file. Though the maps can be made using any linetype, generally "channel" linetype will give best results (??). The units of the model MUST be Jy/pixel, rather than Jy/beam. If no models are given, a point source model is assumed. (see also the ``apriori'' option below)
clip
Clip level. Anything, in the input model, below the clip level is set to zero. Default is 0.
interval
The length of time, in minutes, of a gain solution. Default is 5, but use a larger value in cases of poor signal to noise, or if the atmosphere and instrument is fairly stable. **bug** For multisource datasets and long intervals pathological situations could occur where the computed timestamps are wrong.
options
This gives several processing options. Possible values are:
    amplitude  Perform amplitude and phase self-cal.
    phase      Perform phase only self-cal.
    baseline   Baseline based gains!!  ** NOT IMPLEMENTED YET **
    polarized  The source is polarised. By default the source is
               assumed to be unpolarised. For a polarized source,
               SELFCAL cannot perform polarization conversion. That
               is, if the model is of a particular polarization, then
               the visibility file should contain that sort of
               polarization. For example, if the model is Stokes-Q,
               then the visibility file should contain Stokes-Q.
    mfs        This is used if there is a single plane in the input
               model, which is assumed to represent the image at all
               frequencies. This should also be used if the model has
               been derived from MFCLEAN.
    relax      Relax the convergence criteria. This is useful when
               GMAKES'ing with a very poor model.
    apriori    This is used if there is no input model, and the
               source in the visibility data is either a planet,
               or a standard calibrator. This causes the model data
               to be scaled by the known flux of the source. For a
               planet, this flux will be a function of baseline. If
               the source is a point source, the ``apriori'' option
               is only useful if the ``amplitude'' and ``noscale''
               option are being used. For a planet, this option
               should also be used for a phase GMAKES, to get the
               correct weighting of the different baselines in the
               solution.
    noscale    Do not scale the model. Normally the model is scaled
               so that the flux in the model visibilities and the
               observed visibilities are the same. Generally this
               option should be used with at least the apriori option.
               It must be used if GMAKES is being used to determine
               Jy/K, and should also be used if the model is believed
               to have the correct scale.

  Note that "amplitude", "phase" and "baseline" are mutually exclusive.

The default is options=apriori,amp,noscale. Note that this is different from the defaults for SELFCAL.

minants
Data at a given solution interval is deleted if there are fewer than MinAnts antennae operative during the solution interval. The default is 3 for options=phase and 4 for options=amplitude.
refant
This sets the reference antenna, which is given a phase angle of zero. The default, for a given solution interval, is the antennae with the greatest weight.
offset
This gives the offset in arcseconds of a point source model (the offset is positive to the north and to the east). This parameter is used if the MODEL parameter is blank. The default is 0,0. The amplitude of the point source is chosen so that flux in the model is the same as the visibility flux.
line
The visibility linetype to use, in the standard form, viz:
    TYPE,NCHAN,START,WIDTH,STEP
Generally if there is an input model, this parameter defaults to the linetype parameters used to construct the map. If you wish to override this, or if the info is not in the header, or if you are using a point source model, this parameter can be useful. Default: wide,2,1,1,1; i.e. the first two (digital) wide band channels.
fluxes
List of sources and associated fluxes in Jy to be used for calibration. The format is name of the source, followed by its flux, and optionally more sources, e.g.
      fluxes=3c273,10.3,3c84,12.3,bllac,2.2
Currently no frequency dependency can be specified.
fluxtab
Name of the calibrators flux table file. The user can also supply fluxes by hand (see keyword FLUXES=) in which case the flux table derived values are ignored. * ? Note that reported frequencies of 0.0 means the flux was
  ? determined from interpolation accross different frequencies.
Default: $MIRCAT/cals.fluxes
error
The percentage error in amplitude, and the phase error above which antennae are reported when the gain solution deviates from the observed values. Default: 20,20 (20% in amplitude, 20 degrees phase error).
 Note: not implemented yet.
focus
Maximum (sum of) focus change allowed (in volts) to force a break point and hence start of a new averaging interval. Note: a new uv variable, sfocus, is copied to the output gain visibility dataset. NOTE: CARMA has no focus values (yet) Default: 0.1 (volts)
out
Output gain visibility dataset. No default.


 

Index

NAME
PERSON RESPONSIBLE
CATEGORIES
DESCRIPTION
PARAMETERS

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Time: 18:35:38 GMT, July 05, 2011