PDS_VERSION_ID        = PDS3                                                  
RECORD_TYPE           = STREAM                                                
DATA_SET_ID           = "RO-C/CAL-ALICE-2-ESC1-V2.0"                          
PRODUCT_CREATION_TIME = 2010-03-26T19:10:00                                   
PRODUCT_ID            = "ALICE_DATA_TO_RAYLEIGHS"                             
OBJECT                = TEXT                                                  
  INTERCHANGE_FORMAT    = ASCII                                               
  PUBLICATION_DATE      = 2010-04-01                                          
  NOTE                  = "Description of the how to convert calibrated Alice 
     data (CODMAC level 3 or 4) data from the default flux units to units of  
     Rayleighs per Angstrom."                                                 
END_OBJECT            = TEXT                                                  
                                                                              
END                                                                           
                                                                              
The primary data extension of CODMAC level 3 Rosetta Alice data (SCI) is in   
flux units (photons cm^-2 s^-1). To convert to differential flux units, it is 
neccesary to first divide the image by the dispersion for each pixel. This is 
approximately 1.73 Angstroms/pixel, however it varies across the detector. The
following IDL code illustrates how this could be done:                        
                                                                              
IDL> rdfits_struct, SCI_filename, data                                        
IDL> dlambda = data.im2 - shift(data.im2, -1)                                 
IDL> dlambda[1023,*] = dlambda[1022, *]                                       
IDL> data.im0 /= dlambda                                                      
                                                                              
In the above example, data.im0 will now be in units of photons cm^-2 s^-1     
Angstrom^-1. Linearized Alice data (LIN) are already in these units.          
                                                                              
To convert from photons cm^-2 s^-1 Angstrom^-1 to Rayleighs per Angstrom      
(10^6 / (4 Pi) photons cm^-2 s^-1 sr^-1 A^-1) it is necessary to multiply each
pixel by 4 Pi/10^6. Finally the pixels in each row of the detector must be    
divided by the solid angle subtended by the source. In the case of a uniformly
illuminated slit, this solid angle is that subtended by that detector         
row. Rows subtend approximately 0.30 degrees in the spatial direction and     
between 0.05 and 0.10 degrees in the spectra dimension. The following list    
gives the solid angle (in units of steradians) subtended by each row as a     
function of row number (zero-indexed):                                        
                                                                              
Row Number Solid Angle                                                        
       0          NaN                                                         
       1          NaN                                                         
       2          NaN                                                         
       3          NaN                                                         
       4          NaN                                                         
       5  9.38222e-06                                                         
       6  9.38222e-06                                                         
       7  9.38222e-06                                                         
       8  9.38222e-06                                                         
       9  9.38222e-06                                                         
      10  9.38222e-06                                                         
      11  9.38222e-06                                                         
      12  7.03666e-06                                                         
      13  4.69111e-06                                                         
      14  4.69111e-06                                                         
      15  4.69111e-06                                                         
      16  4.69111e-06                                                         
      17  4.69111e-06                                                         
      18  4.69111e-06                                                         
      19  9.38222e-06                                                         
      20  9.38222e-06                                                         
      21  9.38222e-06                                                         
      22  9.38222e-06                                                         
      23  9.38222e-06                                                         
      24          NaN                                                         
      25          NaN                                                         
      26          NaN                                                         
      27          NaN                                                         
      28          NaN                                                         
      29          NaN                                                         
      30          NaN                                                         
      31          NaN