PDS_VERSION_ID               = PDS3                                           
                                                                              
/* FILE CHARACTERISTICS DATA ELEMENTS */                                      
                                                                              
RECORD_TYPE                  = FIXED_LENGTH                                   
RECORD_BYTES                 = 2880 /* FITS standard record length */         
FILE_RECORDS                 = 3                                              
FILE_NAME                    = "RA_WAVE_003.LBL"                              
DATA_FORMAT                  = FITS                                           
                                                                              
/* INSTRUMENT AND MISSION DESCRIPTIVE DATA ELEMENTS */                        
                                                                              
INSTRUMENT_ID                = "ALICE"                                        
INSTRUMENT_NAME              = "ALICE"                                        
INSTRUMENT_TYPE              = "ULTRAVIOLET SPECTROMETER"                     
INSTRUMENT_HOST_ID           = "RO"                                           
INSTRUMENT_HOST_NAME         = "ROSETTA-ORBITER"                              
MISSION_ID                   = "ROSETTA"                                      
MISSION_NAME                 = "INTERNATIONAL ROSETTA MISSION"                
                                                                              
/* DATA OBJECT POINTERS IDENTIFICATION DATA ELEMENTS */                       
^HEADER                      = ("RA_WAVE_003.FIT",1)                          
^WAVELENGTH_OFFSET_IMAGE     = ("RA_WAVE_003.FIT",3)                          
                                                                              
/* PRODUCT, DATA SET, AND VOLUME DATA ELEMENTS */                             
                                                                              
PRODUCT_ID                   = "RA_WAVE_003"                                  
PRODUCT_CREATION_TIME        = 2007-04-04                                     
DATA_SET_ID                  = "RO-CAL/E-ALICE-3-EAR2-V1.0"                   
PRODUCER_ID                  = "ROSETTA_ALICE"                                
PRODUCER_FULL_NAME           = "ANDREW J. STEFFL"                             
PRODUCER_INSTITUTION_NAME    = "SOUTHWEST RESEARCH INSTITUTE"                 
                                                                              
                                                                              
/* DATA OBJECT DEFINITIONS */                                                 
                                                                              
OBJECT                       = HEADER                                         
  BYTES                      = 5760 /* RECORD_BYTES x RECORDS */              
  HEADER_TYPE                = FITS                                           
  INTERCHANGE_FORMAT         = BINARY                                         
  RECORDS                    = 2                                              
  DESCRIPTION                = "                                              
    FITS header for Rosetta-Alice Wavelength calibration file. This           
    header contains keywords that describe the variation of the               
    wavelength scale with the detector electronics temperature."              
END_OBJECT                   = HEADER                                         
                                                                              
                                                                              
OBJECT                       = WAVELENGTH_OFFSET_IMAGE                        
  LINE_SAMPLES               = 32 /* FITS NAXIS1 keyword */                   
  LINES                      = 1 /* FITS NAXIS2 keyword */                    
  SAMPLE_BITS                = 32                                             
  SAMPLE_TYPE                = IEEE_REAL                                      
  AXIS_ORDER_TYPE            = "FIRST_INDEX_FASTEST"                          
  LINE_DISPLAY_DIRECTION     = "UP"                                           
  SAMPLE_DISPLAY_DIRECTION   = "RIGHT"                                        
  DESCRIPTION                = "                                              
    FITS (Flexible Image Transport System) format is defined in 'Astronomy    
    and Astrophysics', volume 376, page 359; bibcode 2001A&A...376..359H      
                                                                              
    This FITS file contains constants used by the IDL routine                 
    'ralice_wavecal.pro' to determine the wavelength solution for the         
    Rosetta Alice UV spectrometer. Since Alice uses a delay-line              
    detector, the pixel location of a photon event assigned by the            
    electronics will vary as a function of temperature (due to the            
    changing resistance).                                                     
                                                                              
    To monitor this shift, the electronics produce artificial events          
    (stim pulses) at two locations (near [17, 22] and [1023,12]).             
    Unfortunately, the second stim pulse is recorded by the detector          
    electronics as lying outside of the standard 1024x32 region, and          
    as a result, most of the counts produced by this stim are assigned        
    to a single pixel [1023,12]. Consequently, only the first stim pulse      
    can be used to determine the wavelength shift.                            
                                                                              
    The average location of the stim pulse (weighted by counts) was           
    calculated. Gaussians were then fit to the emission lines: Lyman gamma,   
    Lyman beta, Lyman alpha, O I 1304, C I 1561,and C I 1657 present in       
    the spectra of comet C/2002 LINEAR T7 observed in April and May           
    2004 and the Lyman alpha in sky observations obtained in 2004 and 2005.   
                                                                              
    The wavelength scale for row 15 of the Alice data is given, by the        
    following equation:                                                       
                                                                              
    lambda = m_s*X + alpha_S + beta_s*S + gamma_s*S**2 + delta_s*S**3         
                                                                              
    where X is the column number on the detector and S is the centroid        
    position of the stim pulse. m_s is the instrument dispersion and is       
    derived from comparison of the Mars dayglow observed by Rosetta Alice     
    with that observed by HUT (Feldman et al. 1995)                           
                                                                              
    Although the stim pulses are usually on for Alice observations,           
    there are some observations made without stim pulses. For these, the      
    stim position S is derived from the detector electronics temperature      
    via the following equation:                                               
                                                                              
    S = alpha_T + beta_T*T + gamma_T*T**2 + delta_T*T**3                      
                                                                              
    In addition to the temperature dependence of the wavelength scale,        
    some distortion is introduced by the Alice optics. This distortion        
    is most pronounced in rows 5-12 of the detector, where lower              
    wavelengths are shifted to lower column numbers, relative to the          
    central row (row 15, zero-indexed). The 32-element vector contains        
    offsets (relative to row 15 and in units of pixels) for each row of       
    the Alice detector, as derived from Mars dayglow observations."           
                                                                              
END_OBJECT                   = WAVELENGTH_OFFSET_IMAGE                        
                                                                              
END