Documentation on xyphase

Task: xyphase
Purpose: Determine XY phase corrections from on-line measurements.
Categories: uv analysis

        XYPHASE is a MIRIAD task, which determines XY phase corrections
        from the on-line XY phase measurements. This can calculate
        an antenna gain and/or a bandpass function.

        This cannot cope with multi-IF data-sets. Bad solutions will result
        if you attempt to use it for this data.

        The input data should contain either the "xyphase" uv variable
        (the on-line XY phase measurement), and/or autocorrelation data. The
        autocorrelation data is required if the bandpass is being solved for.
        Note that the "xyphase" variable is lost if the data enters Miriad
        via FITS (unless ATMERGE is used). The autocorrelation data is
        currently not written when using the standard correlator
        configurations.

Key: vis
        The input visibility data-set. No default. This should contain
        raw ATCA polarisation data (i.e. XX,YY,XY,YX correlations).

Key: select
        Normal uv selection criteria. The default is to select all data.
        Polarisation selection should not be used.

Key: refant
        The reference antenna. By default XYPHASE computes the gains and
        bandpasses for all antennae. By specifying a reference antenna,
        XYPHASE finds solutions for only the reference antenna, and sets the
        other phases to zero. This is as other programs (such as GPCAL and
        MFCAL) can determine all but the reference antennas XY phases.

Key: interval
        This gives one or two numbers, both given in minutes, both being used
        to determine the interval over which the antenna XY phase is assumed
        to remain constant. The first number gives the maximum length of
        a solution interval. The second number gives the maximum gap size in
        a solution interval. A new solution is started when either the
        maximum time length is exceeded, or a gap larger than the max gap is
        encountered. The default is a maximum length of 5 minutes, and a
        gap size which is the same as the maximum length.

Key: break
        The times, in the normal Miriad format, where to insert the
        break point. A ``break point'' gives a time where some form of
        instrumental glitch took place, and the xyphases jumped. By
        giving a break point, you prevent a solution interval from spanning
        this time, and you inhibit gain interpolation across the time.

Key: options
        Extra processing options. Several options can be given, separated
        by commas. Minimum match is used.
          noxy    Do not determine the antenna XY phases. By default
                  XYPHASE will solve for this when the "xyphase" variable
                  is present in the data.
          nopass  Do not determine the XY bandpass function. By default
                  XYPHASE will solve for this when autocorrelations are
                  present in the data.