RESTORE

     RESTORE

     The most frequently-used method for making single-beam maps from dual-
     beam data is implemented in RESTORE. It uses the Emerson-Klein-Haslam
     algorithm, a two-step process, in which the two-dimensional dual-beam
     map of the source is treated as a set of separate one-dimensional
     strips, so-called subscans.  The following is executed:

        - the dual-beam maps obtained via MAKPLAN are convolved with a
          function which filters out spatial frequencies of wavelength
          equal to multiples of the double-beam spacing, and
        - the double-beam maps are convolved using a discrete up-and-down
          comb-like restoring function to deconvolve the maps of the
          dual-beam response due to the wobbling.

     The first step is executed if the relative gain of the ON to OFF beams
     is either equal to plus or to minus one (UNBAL), the second one is exe-
     cuted if RESTORE_FILTER is true.  Finally, if variable RESTORE_MASK is
     true, RESTORE restricts both steps to a region within a polygonal sup-
     port defined via the SUPPORT command. Flagged channels are not reduced.
! Task RGBTOPS !