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Disk files for observations

Observations saved by the system computer are stored on disk in NDF structures, which can be read by Figaro, by DIPSO and by Starlink's ADAM-based software.

The NDF structure is a specific organization of objects in the disk format HDS and is described in the Starlink document SGP/38. NDFs are stored in HDS files with an extension `.SDF' to the file name.

Naming conventions are used to identify observations: RUN_FILES:R80200.SDF is an NDF containing run 80200; SCRATCH_FILES:S3.SDF is an NDF containing scratch exposure number 3.

The NDFs produced at the WHT contain images with an 16-bit unsigned-integer datum for each pixel. This is HDS type `_UWORD' which corresponds to Figaro's type `USHORT'. The headers are stored in a standard NDF-extension `FITS' (component name <file>.MORE.FITS) which is an array of 80-byte character strings, each string containing one FITS record.

Observations saved by the Observer's SPARCstation are stored on disk in IRAF's file format.

Mon Oct 3 21:59:29 WET 1994