! $Id$
!
! ---

!======================================================================
! Apply the reflectance coefficients to produce a reflectance
!======================================================================
subroutine REF_CAL(Num_Scans_Read)

 integer, intent(in):: Num_Scans_Read
 integer:: iline

 !--- channel 1
  where (Chan_Counts_Avhrr(1,:,:) <= Ch1_Switch_Count_Cal)
    Ref_Ch1 = Ch1_Gain_low*(Chan_Counts_Avhrr(1,:,:) - Ch1_Dark_Count_Cal) 
  elsewhere
    Ref_Ch1 = Ref_Ch1_Switch + Ch1_Gain_High*(Chan_Counts_Avhrr(1,:,:) - Ch1_Switch_Count_Cal) 
  end where

!--- channel 2
 where (Chan_Counts_Avhrr(2,:,:) <= Ch2_Switch_Count_Cal)
    Ref_Ch2 = Ch2_Gain_low*(Chan_Counts_Avhrr(2,:,:) - Ch2_Dark_Count_Cal) 
 elsewhere
    Ref_Ch2 = Ref_Ch2_Switch + Ch2_Gain_High*(Chan_Counts_Avhrr(2,:,:) - Ch2_Switch_Count_Cal) 
 end where

!--- channel 3a
 where (Chan_Counts_Avhrr(3,:,:) <= Ch3a_Switch_Count_Cal)
    Ref_Ch6 = Ch3a_Gain_low*(Chan_Counts_Avhrr(3,:,:) - Ch3a_Dark_Count_Cal) 
 elsewhere
    Ref_Ch6 = Ref_Ch6_Switch + Ch3a_Gain_High*(Chan_Counts_Avhrr(3,:,:) - Ch3a_Switch_Count_Cal) 
 end where

 do iline = Line_Idx_Min_Segment,Line_Idx_Min_Segment + Num_Scans_Read - 1
  !--- check for a bad scan, if so then skip
  if (Bad_Scan_Flag(iline) == sym%YES) then
    Ref_Ch1(:,iline) = Missing_Value_Real4 
    Ref_Ch2(:,iline) = Missing_Value_Real4 
    Ref_Ch6(:,iline) = Missing_Value_Real4 
  endif

  !--- set Ref_Ch6 to missing for Ch3a = off
  if (Ch3a_On(iline) == sym%NO) then
    Ref_Ch6(:,iline) = Missing_Value_Real4 
  endif

 enddo
  
 end subroutine REF_CAL