Level 3 FITS file : Extension 1 (Data)

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

Extension 1 - Data

Data cube

This extension contains the original header from the level 2 file. But it does not contain the data cube itself. When reading the level 3 file using FITS2ANA, the data cube is read from the level 2 file and rearranged so that it can be used in XCFIT_BLOCK. The WAVE dimension must be the first dimension for XCFIT_BLOCK to work.

If the level 2 file cannot be found, then a warning is printed and a dummy data cube is created.

Keywords

There are some adaptions and additions to the header of the original level 2 file:

 NAXIS    = Number of data axes                            

This is set to zero, since no data is saved in the extension. The keywords NAXISn are deleted. The original keywords are added to the header with the following keywords:

XDIMNA   = Number of data axes in the original data cube in level 2                            
XDIMNA1  = Size of 1st dimension in the original data cube in level 2  
XDIMNA2  = Size of 2nd dimension in the original data cube in level 2  
XDIMNA3  = Size of 3rd dimension in the original data cube in level 2  
XDIMNA4  = Size of 4th dimension in the original data cube in level 2  

The keywords pointing to the other extensions of this data window are also added to the header:

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