;+ ; Project : SOHO - CDS ; ; Name : PIX2WAVE ; ; Purpose : Calculate CDS wavelength given a detector pixel location. ; ; Explanation : Uses dummy transformations to translate a pixel value to a ; wavelength for any of the CDS's six spectral regions. To be ; updated when the wavelength calibration is known. ; ; Use : IDL> lambda = pix2wave(spectrum [,pixel, slit=slit]) ; ; Inputs : spectrum - the spectrum identifier (string). Only the first ; and last characters are used to identify the ; spectrum so inputs such as NIS1 and N1 are ; equivalent. Valid entries are NIS1, NIS2, GIS1, ; GIS2, GIS3, GIS4 (and their abbreviations). ; ; Opt. Inputs : pixel - the pixel value to translate. If not supplied the ; wavelengths for the extreme pixels are returned. ; The input can be an array. ; ; Outputs : The function value returned is the corresponding wavelength. ; A value of -1 is returned for an error condition. ; ; Opt. Outputs: None ; ; Keywords : Limit - If input pixel is out of range, then return the ; appropriate wavelength limit. ; NoLimit - If input pixel is out of range, then return a value ; anyway. ; Slit - specifies the slit to cater for slit dependence ; Throwaway - do not retain input pixel numbers intact ; ; Calls : None ; ; Restrictions: Only dummy transformations at present ; ; Side effects: None ; ; Category : Calibration, GDS, VDS, Wavelength ; ; Prev. Hist. : None ; ; Written : C D Pike, RAL, 28-May-1993 ; ; Modified : Update VDS constants, CDP, 18-Nov-93 ; Include Limit keyword, CDP, 2-Feb-94 ; Updated wavelength ranges. CDP, 30-Jan-95 ; Version 5, William Thompson, GSFC, 1 March 1995 ; Added keyword NOLIMIT ; Version 6, Incorporate results of first calibration from ; s54r00 by BJIB. 27-Feb-96 ; Version 7, Rewrite to use common block communication with ; LOAD_WAVECAL. CDP, 11-mar-96 ; Version 8, Make NIS quadratic. CDP, 23-Jul-96 ; Version 9, Various updates suggested by SVVH. Float return ; and economise calculation. ; Version 10, 19-Jan-2000, William Thompson, GSFC ; Allow SPECTRUM to be an array ; ; Version : Version 10, 19-Jan-2000 ;- function pix2wave, spectrum, pixel_in, limit=limit, nolimit=nolimit,$ slit=slit, throwaway=throwaway ; ; communication common block ; common cds_wavecal, ncoff, gcoff ; ; check parameters ; if n_params() eq 0 then begin print,"Use: IDL> lam = pix2wave(spectrum_id [,pixel, /limit, /nolimit, $" print,' slit=slit]' print,"eg IDL> lam = pix2wave('NIS1',[300,301,302])" return,0 endif ; ; If spectrum was passed as an array, and matches the dimensions of pixel_in, ; then call pix2wave individually for each point. ; if n_elements(spectrum) gt 1 then begin if n_elements(spectrum) eq n_elements(pixel_in) then begin result = 0.*pixel_in for i=0,n_elements(result)-1 do result(i) = pix2wave(spectrum(i), $ pixel_in(i), limit=limit, nolimit=nolimit, slit=slit, $ throwaway=throwaway) return, result end else begin print, 'SPECTRUM_ID must be either a scalar' print, 'or have the same number of elements as PIXEL' return, 0 endelse endif ; ; copy input pixels in case they are changed within ; if keyword_set(throwaway) then pixel = temporary(pixel_in) $ else pixel = pixel_in ; ; parse the spectrum identifier ; s = strtrim(spectrum,2) sg = strupcase(strmid(s,0,1)) snum = fix(strmid(s,strlen(s)-1,1)) case sg of 'N': begin if datatype(ncoff,1) ne 'Structure' then begin if load_wavecal('n') then begin print,'Loaded default NIS coefficients.' endif else begin print,'Error loading default NIS coefficients.' return, -1 endelse endif c = float(ncoff.coeff) if n_elements(pixel) eq 0 then begin pixel = [0,1023] endif else begin small = where(pixel lt 0) big = where(pixel gt 1023) if big(0) ge 0 or small(0) ge 0 then begin if keyword_set(limit) then begin if small(0) ge 0 then pixel(small) = 0 if big(0) ge 0 then pixel(big) = 1023 endif else if not keyword_set(nolimit) then begin bell print,'Pixel specification out of range for this spectrum.' print,'Must be in the range 0 < pixel < 1023.' return,-1 endif endif endelse if snum eq 1 or snum eq 2 then begin temp = c(snum-1,1,0) + c(snum-1,2,0)*pixel lam = c(snum-1,0,0) + temporary(temp)*temporary(pixel) endif else begin bell print,'Normal incidence spectrum number not recognised.' print,'Value was ',snum return,0 endelse end 'G': begin if datatype(gcoff,1) ne 'Structure' then begin if load_wavecal('g',gset_id=!def_gset_id) then begin print,'Loaded default (gset_id='+trim(!def_gset_id)+$ ') GIS coefficients.' endif else begin print,'Error loading default GIS coefficients.' return,-1 endelse endif c = float(gcoff.coeff) if n_elements(pixel) eq 0 then begin pixel = [0,2047] endif else begin small = where(pixel lt 0) big = where(pixel gt 2047) if big(0) ge 0 or small(0) ge 0 then begin if keyword_set(limit) then begin if small(0) ge 0 then pixel(small) = 0 if big(0) ge 0 then pixel(big) = 2047 endif else if not keyword_set(nolimit) then begin bell print,'Pixel specification out of range for this spectrum.' print,'Must be in the range 0 < pixel < 2047.' return,-1 endif endif endelse if snum ge 1 and snum le 4 then begin temp = c(snum-1,1,0) + c(snum-1,2,0)*pixel lam = c(snum-1,0,0) + temporary(temp)*temporary(pixel) endif else begin bell print,'Grazing incidence spectrum number not recognised.' print,'Value was ',snum return,0 endelse end else: begin bell print,'Spectrum identifier not recognised. Must be N or G.' print,'Character was ',sg return,0 end endcase ; ; successful return ; return, float(lam) end