Re-Weighting Visibility

After solving for antenna-based gain solutions (based on QSOs), one might realize that the gain corrections in amplitude are lower for some antennas due to some reasons (such as larger pointing errors, larger coherence loss and etc.). One might want to include those factors in the visibility weighting in the imaging process in addition to the visibility variance calculated based on the systemp temperature, bandwidth, and integration time. The Miriad smarewt provides a software tool to calculate the mean values of antenna gains in amplitude and multiply the visibility variances by the mean antenna gains. The re-scaled visibility variances can be used as the weights in the imaging process. Here is an example of usage:

smarewt% inp
  Task:   smarewt
  vis      = uvdata_rx0.lsb        %the input uvdata
  gain     = uvdata_rx0.lsb        %the uvdata that contains the 
                                    antenna-gain table.
  options  = report                %to report the mean gains.
  out      = uvdata_rx0.lsb.rw     %the output uvdata in which the 
                                    systemp (or variance) has been 
                                    mupltiplied by the re-weighting
                                    factors that are calculted based
                                    on the antenna gains.

Note that one must turn on the options=systemp in invert in the imaging process in order to make this re-weighting effective.