1 MOSAIC
        MOSAIC

    Combines individual fields of a mosaic in a single image  for  cleaning.
    This task makes assumptions about file extensions for the images and the
    dirty beams, and computes the primary beams.

    Noting x the direct product, and * a convolution, the combined image is
        Sum (Bj x Ij)
    where Bj is the primary beam of field j, and Ij its dirty  image.   This
    task also compute a weight image, W = 1/Sum(Bj^2).

    If the dirty beams Dj were Diracs, the sky distribution would just be
        S = W . B
    because Ii = Di * (Bi x S)


2 FIELDS$
        TASK\INTEGER "Number of fields" FIELDS$

    Number of fields in the mosaic.
2 NAME$
        TASK\CHARACTER "Generic file name (without extension)" NAME$

    The generic file name for all files. Actual file names  are  derived  as
    follow
    Input
        'NAME'-'I'.LMV   for dirty image of field I (Ij)
        'NAME'-'I'.BEAM  for dirty beam of field I (Dj)
    Output
        'NAME'.BEAM      a cube of dirty beams for all fields (Dj)
        'NAME'.LOBE      a cube of primary beams (Bj)
        'NAME'.LMV       the linear combination of fields (Sum(Bi.Ii))
        'NAME'.WEIGHT    the inverse of the sum of square of the primary beams
                         1/Sum(Bj^2)
    Before using MOSAIC_CLEAN, the 'NAME'.LOBE file must be transposed  into
    'NAME'.PRIMARY with order 312.

2 BEAM$
        TASK\REAL "Half-Power Primary Beam (in radians)" BEAM$

    The half power beam of the interferometer dishes.
1 END