GAUSS_SMOOTH

        GAUSS_SMOOTH

    This  task performs a 2-D smoothing by an elliptical gaussian.   The al-
    gorithm  works  in  the  Fourier  plane and the first 2  dimensions  (in
    pixels) should therefore be powers of two (but need not be  equal).   It
    is  much  faster than the equivalent sky plane algorithm, but you should
    beware of aliasing effects when the  size  of  the  convolving  gaussian
    becomes a sizeable fraction of the map (say 30%).