- Primary Header
contains information about the mission, the instrument, the observation and the initial processing. As with all FITS headers, this information is in the form of keywords with assigned values.
- Primary Image Array
is blank.
- First Extension Header
contains keywords which provide a complete and detailed description of the contents of the first extension. For convenience, it also contains some of the same information as the primary header.
- First Extension
contains the scientific data. In the case of of science array files, the first extension is called XTE_SA. In the case of science event files, it is called XTE_SE.
- Second Extension Header
contains keywords which provide a complete and detailed description of the contents of the second extension. For convenience, it also contains some of the same information as the primary header.
- Second Extension
lists the standard good time intervals, i.e. the start and stop times of all the potentially useable data in the file. It is called GTI.
- Third Extension Header
contains keywords which provide a complete and detailed description of the contents of the third extension. For convenience, it also contains some of the same information as the primary header.
- Third Extension
lists the good time intervals, i.e. the start and stop times of all the data in the file, regardless of whether the data are actually useable. Like the second extension, it is called GTI.
A general guide to FITS format can be obtained via anonymous FTP at
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