Catalogue formats

Local catalogues may be stored in several formats. The ``native'' version is called a ``tab separated table'' (TST). This is a simple text file in which the values of the various fields are separated by a single <TAB> character and the catalogue headers are separated from these by a dashed line:

#  comment
keyword1: value1
keyword2: value2

...
ID   <TAB>   RA     <TAB>   DEC   <TAB>  MAG     ...
--           --             ---          ---
OBJ1 <TAB>   210.00 <TAB>   54.00 <TAB>  16.1
OBJ2 <TAB>   210.01 <TAB>   54.01 <TAB>  15.1
....

The usual format of a catalogue is as above, i.e. an object identifier followed by an RA and DEC (in J2000 decimal degrees). Note the <TAB> strings shouldn't be typed in, they are shown explicitly just to make clear where they should be placed. The TST format is also recognised by the TOPCAT and CURSA packages (SUN/190). CURSA also contains a description of this format.

Additional formats that can be also read and written by GAIA (with a performance penalty) are those supported by the CURSA package (i.e. FITS-tables and STL format) and the ``ASCII_HEAD'' format of the SExtractor/EXTRACTOR package (SUN/226), as well as the XML VOTable format.

The format that is used to open or write a catalogue, is determined by the file extension:

• FITS tables, accepted file types: .FIT .fit .FITS .fits .GSC .gsc
• STL, accepted file types: .TXT .txt
• ASCII_HEAD, accepted file types: .asc .ASC .lis .LIS
• VOTable, accepted file types: .xml .XML .vot .VOT

All other file extensions are assumed to indicate a TST (the preferred extensions for these are .tab or .TAB).