1 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.

     It is possible to use the restoring comb-like function on a smaller 
     support to reduce noise resulting from the restoring process.   
     This is controled by variable COMB_TEETH.


