Level 3 FITS file : Extension 3 (Weights)

• Level 3 FITS file
• Extension 0 - Results (Fit components and parameters)
• Extension 1 - Data
• Extension 2 - Lambda
• Extension 3 - Weights
  • Data cube
  • General Keywords
  • World Coordinate System (WCS) keywords
• Extension 4 - Includes
• Extension 5 - Constants
• Extension X - Residuals

Extension 3 - Weights

This extension is only saved if there are any non-default values in the cube. I.E. if at least one value is different from 1.0.

Data cube

This extension contains the weights of each pixel. The dimensions are as follows:

• Lambda, X, Y, Time

General Keywords

EXTNAME  = Extension name              
RESEXT   = Extension name of results extension
DATAEXT  = Extension name of data extension (this is a link to an external extension)
XDIMXT1  = Extension name of 1st dimension absorbed by analysis
WGTSEXT  = Extension name of weights extension
INCLEXT  = Extension name of include extension
CONSTEXT = Extension name of constant extension

World Coordinate System (WCS) keywords

WCSNAME = Name of coordinate system                                            
LONPOLE = Native longitude of the celestial pole                                             
SPECSYS = Spectral coord. not corrected for S/C velocity                                               
VELOSYS = [m/s] Default for SPECSYS='TOPOCENT'                                               

CTYPE1   = Type of 1st coordinate (fit parameter)                        
CNAME1   = Name of 1st coordinate                        
CUNIT1   = Units for 1st coordinate (for CRVAL1, CDELT1)  
CRVAL1   = [nm] 1st coordinate of reference point          
CDELT1   = [nm] Increment of 1st coord at ref point        
CRPIX1   = [pixel] 1st pixel index of reference point    
PC1_1    = Contribution of dim 1 to coord 1                    
                                                                            
CTYPE2   = Type of 2nd coordinate                        
CNAME2   = Name of 2nd coordinate  
CUNIT2   = Units for 2nd coordinate (for CRVAL2, CDELT2)  
CRVAL2   = [arcsec] 2nd coordinate of reference point    
CDELT2   = [arcsec] Increment of 2nd coord at ref point  
CRPIX2   = [pixel] 2nd pixel index of reference point    
PC2_2    = Contribution of dim 2 to coord 2   
PC2_3    = Contribution of dim 3 to coord 2  
                                                                            
CTYPE3   = Type of 3rd coordinate                        
CNAME3   = Name of 3rd coordinate  
CUNIT3   = Units for 3rd coordinate (for CRVAL3, CDELT3)  
CRVAL3   = [arcsec] 3rd coordinate of reference point    
CDELT3   = [arcsec] Increment of 3rd coord at ref point  
CRPIX3   = [pixel] 3rd pixel index of reference point    
PC3_2    = Contribution of dim 2 to coord 3 due to roll  
PC3_3    = Contribution of dim 3 to coord 3  
                                                                            
CTYPE4   = Type of 4th coordinate                         
CNAME4   = Description of 4th coordinate                  
CUNIT4   = Units for 4th coordinate (for CRVAL4, CDELT4)  
CRVAL4   = [s] 4th coord of ref point, relative to DATEREF  
CDELT4   = [s] Increment of 4th coord at ref point        
CRPIX4   = [pixel] 4th pixel index of reference point     
PC4_2    = Contribution of dim 2 to coord 4 due to roll  ; _optional, only for rasters_  
PC4_4    = Contribution of dim 4 to coord 4                    

BTYPE    = Type of data                                   
UCD      = Unified Content Descriptors v1.23           
BUNIT    = Physical units of calibrated data