Algorithm

   subroutine backcorr

      Arfgen computes the effective area curves for both the source
      (arf_in_src.arf) and background (arf_in_bkg.arf) regions. The
      extraction region is read directly in the input spectra through
      the data sub space.

      Calls the subroutine make_backcorr which :

         Reads in the two temporary arf files: arf_in_src.arf & arf_in_bkg.arf

         Reads in the input background spectrum (==> bkg_input_spectrum)

         Makes the appropriate correction :
            bkg_corrected_spectrum=(arf_src/arf_bkg)*bkg_input_spectrum

         Writes out bkg_corrected_spectrum into a FITS file with the
         same header of the input file + an updated history

      End of make_backcorr

      Delete temporary arf files
     
   end subroutine  backcorr