1 UV_REF_POINT Phase and/or amplitude reference a UV table on a nearby point source

        UV_REF_POINT  does  a Phase and/or Amplitude Referencing of a UV ta‐
    ble, using another one representing a point source observed quasi‐simul‐
    taneously.  In details:

       ‐ UV_REF_POINT self‐calibrates first  the observed visibilities of the
         Gaussian  source used  as reference,  based  on the  knowledge of  the
         geometry and  flux of this  source.  The self‐calibration  is baseline
         based (i.e. it does not take into account closure relationships).
       ‐ UV_REF_POINT   then   applies   the   gains  derived   in   previous
         self‐calibration to the visibilities of the source to be calibrated.

    It  is  STRONGLY ADVISED to self‐calibrate the phase first, then the am‐
    plitude using a longer smoothing time.  Moreover UV_REF_POINT enables to
    subtract (part of) the input reference source, typically to provide con‐
    tinuum‐free spectral line maps.

    See also UV_REF_GAUSS or UV_REF_MODEL, which does the  same  thing,  but
    using a Gaussian or modeled source as input.

2 UV_TABLE$
        TASK\CHARACTER "UV table to be calibrated by reference" UV_TABLE$

    UV table to be calibrated by reference.

2 SELF$
        TASK\CHARACTER "UV table used as reference" SELF$

    UV table of the observed visibilities of the point source used as refer‐
    ence. In general, this is a continuum table.

2 DTIME$
        TASK\REAL"The smoothing time constant in seconds" DTIME$

    Visibilities of the reference table will be averaged on DTIME$ time  in‐
    tervals  to  improve signal to noise ratio before self‐calibration.  In‐
    deed, signal to noise MUST BE SUFFICIENT TO IMPROVE the phase or  ampli‐
    tude determinations.  If DTIME$ is too short, noise will be added to the
    data, rather than the expected improvement.  Required values are

            S/N    =  11  for 5 degree phase noise
            S/N    =  20  for 5 % amplitude correction

2 WCOL$
        TASK\INTEGER "The reference channel" WCOL$

    If the reference UV table (SELF$) is a spectral line UV table, WCOL$  is
    the spectral channel to be used.

2 TYPE$
        TASK\CHARACTER "Type of self‐cal, Ampli, Phase, Both or None" TYPE$

    It  is recommended to  self‐calibrate  the  phase  first,  then  the am‐
    plitude  using  a  longer  smoothing  time, rather than  both  together.
    Type NONE can be used just to subtract a time‐smoothed  continuum  value
    from a spectral line table (see also UV_SUBTRACT task).

2 SUB$
        TASK\REAL "Fraction of the continuum source to subtract" SUB$

    Typically 1 or 0, to remove or not the continuum model.

1 ENDOFHELP


