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XMM-Newton Science Analysis System


dal (dal-1.182.1) [xmmsas_20080701_1801-8.0.0]

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Supported File Formats

The DAL supports three file formats:

• FITS, the preferred format, which conforms to the platform-independent FITS standard.
• DAL, a special internal format (which should be considered platform-specific) that will only be used for temporary intermediate files, probably for (high memory mode) tasks within meta-tasks.
• DECEIT, a special format used by the dataset creation tool deceit. To be used only by specialized tasks only.

When reading an existing file, the DAL will attempt to detect the file format; in the event that a file was opened with the modify mode, the same format will be used when it is rewritten.

When creating a new file, the default output format is FITS. This behaviour may be altered by defining the environment variable SAS_FORMAT. It can have the following values (the corresponding format for each each value is also shown):

• 1, FITS
• 2, DAL
• 3, DECEIT

The output format of a task can be overridden with a command line option.

The data model is abstract in that it is not dependant on an underlying representation (e.g.FITS). The following table shows the mapping to FITS, DAL and deceit files.

There are restrictions imposed by FITS ... e.g. Keyword Length is limited to 8 characters.