;+; NAME:;	brightness_temp;; PURPOSE:;	calculate the brightness temperatures for a NOAA AVHRR image of an;	IR channel (3,4 or 5); 	Brightness temperatures can be calculated from Planck's radiation equation; 	using the slopes and intercept calibration values stored with each scan; 	(cf. Polar Orbiting Users Guide Section 3.3 or ask Dominik);	; CATEGORY:;	NOAA satellite image processing;; CALLING SEQUENCE:;	brightness_temp,image,channel,cal_coeff,satnr=satnr,temp=temp,eightbit=eightbit;; EXAMPLE:;; INPUTS:;	image	: the GAC or LAC image produced with gac_channel.pro or lac_channel.pro;		  Array(scansize,no_of_scans) of Pixel_Struct;	channel : the channel number (must be 3,4, or 5);	cal_coeff : LonArr(2,5,no_of_scans);; OPTIONAL INPUT PARAMETERS: ;	satnr:	(BYTE) the number of the NOAA-satellite (11,12, or 14);; KEYWORD INPUT PARAMETERS:;	eightbit:	set this keyword if image is an 8-Bit resolution image only;			(usually when it is a LAC image);; OUTPUTS:;	temp	: FltArr(scansize,no_of_scans): the brightness temperatures for each pixel;		  of the image;; COMMON BLOCKS:;; SIDE EFFECTS:;; RESTRICTIONS:;	; PROCEDURE:;	; MODIFICATION HISTORY:;	All information describing the format;	of GAC data can be found on WWW in;	<A HREF="http://www2.ncdc.noaa.gov/docs/podug/">Polar Orbiter Guide</A>;	First implementation Oct, 25, 1997 by Dominik Brunner, ETH Zurich;-pro brightness_temp,image,channel,cal_coeff,satnr=satnr,temp=temp,eightbit=eightbitprint,'Calculate brightness temperature for an IF channel'; check for input parametersIF (n_elements(image) EQ 0) OR (n_elements(channel) EQ 0) OR $   (n_elements(cal_coeff) EQ 0) THEN returnIF n_elements(image(0,*)) NE n_elements(cal_coeff(0,0,*)) THEN BEGIN   print,'parameter cal_coeff has wrong size!'   returnENDIFIF channel LT 3 THEN BEGIN   print,'no brightness temperature can be calculated for this channel'   returnENDIF; enter the satellite number (because individual calibration factors aply)IF n_elements(satnr) EQ 0 THEN BEGIN   print,''   read,'Enter Satellite number (11,12, or 14): ',satnr   IF NOT ((satnr EQ 11) OR (satnr EQ 12) OR (satnr EQ 14)) THEN BEGIN   	print,'no correction factors for this satellite number entered in the table yet'  	print,'therefore the corrections for satellite number 14 will be applied'   	satnr=14   ENDIFENDIFCASE satnr OF     11: satno=0     12: satno=1     14: satno=2ENDCASEprint,''; enter the temperature range which should be fit bestREPEAT BEGIN  print,'select the approx. temperature range to fit the best'  print,'range 1: 190-230 K (CB clouds up to tropopause)'  print,'range 2: 230-270 K (mid tropospheric clouds and cold earth)  print,'range 3: 270-310 K (sea surface temperatures)  print,'range 4: 290-330 K (warm land surface)  read,'Enter your selection (1-4): ',range  print,''END UNTIL ((range GT 0) AND (range LT 5))range=range-1; define the satellite specific central wavenumbers (in cm-1) for each channel; the central wavelengths are different for the four temperature ranges; range1=190-230K, range2=230-270K, range3=270-310K (sea surface), range4=290-330K      cwnr=FltArr(3*4,3)	; (3 channels x 4 temp. ranges per channel) x 3 satellitescwnr(*,0)=[2663.50,2668.15,2671.40,2670.96,$ 		; channel 3, satnr 11	   926.81,927.36,927.83,927.75,$		; channel 4, satnr 11	   841.40,841.81,842.20,842.14]			; channel 5, satnr 11cwnr(*,1)=[2632.713,2636.669,2639.61,2640.817,$ 	; channel 3, satnr 12	   920.0158,920.5504,921.0291,921.2741,$	; channel 4, satnr 12	   836.6847,837.0251,837.3641,837.5612]		; channel 5, satnr 12cwnr(*,2)=[2638.652,2642.807,2645.899,2647.169,$ 	; channel 3, satnr 14	   928.2603,928.8284,929.3323,929.5878,$	; channel 4, satnr 14	   834.4496,834.8066,835.1647,835.374]		; channel 5, satnr 14; define central wavenumber for current selectionscwnr=cwnr((channel-3)*4+range,satno)print,'central wavenumber for channel'+STRING(channel,format='(I2)')+$      ' on NOAA-'+STRING(satnr,format='(I2)')+' is'+strcompress(cwnr); define constants for planck's lawc1=1.1910659E-05	; in mW m-2 steradian cm-4c2=1.438833D		; cm K-1; define scaling factors for calibration coefficients; Channel counts must be multiplied by a factor of 4 in eightbit version; Therefore the scale factor is a factor of 4 lower than usualIF keyword_set(eightbit) THEN scale1=2D^28 ELSE scale1=2D^30			; for slopescale2=2D^22		; for intercepttemp=FltArr(n_elements(image(*,0)),n_elements(image(0,*)))FOR i=0,n_elements(image(0,*))-1 DO BEGIN    radiance=Double(image(*,i).value)*cal_coeff(0,channel-1,i)/scale1+$	     cal_coeff(1,channel-1,i)/scale2    temp(*,i)=c2*cwnr/alog(1+c1*cwnr^3/radiance)ENDFORindex=WHERE(temp EQ 0,count)IF count GT 0 THEN temp(index)=!values.f_nanend