! $Header$
function get_planck_radiance_39um ( tmp , sensor ) result ( rad )
   implicit none
   real, intent ( in) :: tmp
   character (len =  * ) :: sensor
   !real, intent ( out), optional :: db_dt
   real :: rad
	  
   real :: db_dt_tmp
   integer, parameter:: nplanck = 161
   real, dimension(nplanck) :: B20
   real, parameter :: T_planck_min = 180.0  
   real, parameter :: delta_T_planck = 1.0
   real, dimension(nplanck) :: T_planck
   integer :: l , i
      
   real :: nu_20 , a1_20 , a2_20
   real , parameter :: c1 = 1.191062e-5
   real , parameter :: c2 = 1.4387863
	
   select case ( sensor )
   case ( 'GOES-11')
      nu_20 = 2562.0840
	  a1_20 = -0.64474519
	  a2_20 = 1.0007721
	case ( 'GOES-12')
      nu_20 = 2651.7708
	  a1_20 = -1.9052739
	  a2_20 = 1.003010 
   case ( 'GOES-13')
      nu_20 = 2563.5837
	  a1_20 = -1.4757495
	  a2_20 = 1.0021472
   case ( 'GOES-15')
      nu_20 = 2562.1383
	  a1_20 = -1.661627
	  a2_20 = 1.0023207
   case ( 'MODIS-AQUA')
      nu_20 = 2642.3820
	  a1_20 = -0.48854008
	  a2_20 = 1.0005735
   case ( 'MODIS-TERRA')
      nu_20 = 2642.2448
	  a1_20 = -0.48752945
	  a2_20 = 1.0005738
   case ( 'VIIRS')
      nu_20 = 2708.3865
	  a1_20 = -0.59392036
	  a2_20 = 1.0006466	
   case ( 'NOAA-07')
      nu_20 = 2684.5233
	  a1_20 = -1.9488269
	  a2_20 = 1.0029260	      
   case ( 'NOAA-08')
      nu_20 = 2651.3776
	  a1_20 = -1.7764105
	  a2_20 = 1.0024260	  
   case ( 'NOAA-09')
      nu_20 = 2690.0451
	  a1_20 = -1.8832662
	  a2_20 = 1.0028978	      
   case ( 'NOAA-10')
      nu_20 = 2672.6164
	  a1_20 = -1.7986926
	  a2_20 = 1.0026426	      
   case ( 'NOAA-11')
      nu_20 = 2680.05
	  a1_20 = -1.738973
	  a2_20 = 1.003354 	  
   case ( 'NOAA-12')
      nu_20 = 2651.7708
	  a1_20 = -1.9052739
	  a2_20 = 1.003010	        
   case ( 'NOAA-14')
      nu_20 = 2654.25
	  a1_20 = -1.885330
	  a2_20 = 1.003839	
   case ( 'NOAA-15')
      nu_20 = 2695.9743
	  a1_20 = -1.624481
	  a2_20 = 1.001989		 
   case ( 'NOAA-16')
      nu_20 = 2681.2540
	  a1_20 = -1.6774586
	  a2_20 = 1.0017316 	 
   case ( 'NOAA-17')
      nu_20 = 2669.1414
	  a1_20 = -1.7002941
	  a2_20 = 1.0026724 	   
   case ( 'NOAA-18')
      nu_20 = 2660.6468
	  a1_20 = -1.7222650
	  a2_20 = 1.0028633	 
   case ( 'NOAA-19')
      nu_20 = 2670.2425
	  a1_20 = -1.6863857
	  a2_20 = 1.0025955		     
	case ('MTSAT-1R')
	  nu_20 = 2647.9998
	  a1_20 = -2.455206
	  a2_20 = 1.0042972 
   case ('MTSAT-2')
	  nu_20 = 2680.1828
	  a1_20 = -2.3876343
	  a2_20 = 1.0042061   
   case ('METOP-A')
	  nu_20 = 2687.0392
	  a1_20 = -2.0653147
	  a2_20 = 1.0034418   
   case ('METOP-B')
	  nu_20 = 2664.3384
	  a1_20 = -1.7711318
	  a2_20 = 1.0029931   
   case ('Meteosat-8')
	  nu_20 = 2561.4547
	  a1_20 = -3.2692076
	  a2_20 = 1.0056489   
   case ('Meteosat-9')
	  nu_20 = 2562.2502
	  a1_20 = -3.2790754
	  a2_20 = 1.0059926   
   case ('Meteosat-10')
	  nu_20 = 2560.1576
	  a1_20 = -3.2146560
	  a2_20 = 1.0058230  
	  
	  
   case default
      print*,'missing sensor calibration for sensor ', sensor
	  print*, 'add to get_planck_radiance_39um'
      stop
   end select 	
	  
   
   do i = 1 , nplanck 
      t_planck(i) = T_planck_min + ( i - 1 ) * delta_T_planck
      B20(i) = c1*( nu_20 ** 3) / ( exp ( ( c2 * nu_20 ) / &
              (( T_planck(i) - a1_20 ) / a2_20 ) ) - 1.0) 
   end do		  
     
   l = ( tmp - T_planck_min ) / delta_T_planck
   l = max (1, min ( nplanck - 1 , l ) )
	  
   dB_dT_tmp = (B20(l+1)-B20(l))/(T_planck(l+1)-T_planck(l))
	  
   rad = B20(l) + (tmp - T_planck(l)) * (dB_dT_tmp)
	  
  ! if ( present (db_dt) ) then
  !    db_dt = db_dt_tmp
  ! end if
end function get_planck_radiance_39um