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A Brief Introduction to FITS

FITS is the standard computer data format widely used by astronomers to transport, analyze, and archive scientific data files.

History of FITS

The following paragraphs are reproduced from the 'Introduction' to the FITS Standard document.

In December 2002, after more than a decade of complex negotiations, the IAUFWG approved 2 papers that deal with the issue of representing World Coordinate Systems (WCS) in FITS. Two more papers in this WCS series are currently under development.

Brief highlights of the history of FITS:

How FITS Evolves

The IAU-FWG was given authority over FITS matters by the 1988 IAU General Assembly. When the developer of a data set finds that it does not fit well into the primary HDU or a standard extension format, a new design may be developed. No change can be made that would cause existing FITS files to be out of conformance -- the "once FITS, always FITS" rule. Because software to read FITS files uses the type name of an extension to determine whether or not the software can read the extension, extension type names must be unique. The IAUFWG maintains a list of extension type names that have been registered; the list is at the FITS Support Office. A unique name for any new extension type, even a developmental extension or one that will be used only locally, must be registered with the IAU-FWG. After astronomical community discussion, a formal proposal is distributed. This proposal is discussed by the community and may be further modified. Tests are run using the new format to confirm that it can be practically used for data transport. If the astronomical community reaches a consensus that the proposal should be adopted as standard FITS, and if successful data transfer using the proposed extension can be demonstrated, it is submitted for ratification to the regional committees -- the European FITS Committee, the Japanese FITS Committee, and the American Astronomical Society Working Group on Astronomical Software (WGAS) FITS Committee. Following approval by the regional committees, it is submitted to the IAU-FWG Approval by the IAU-FWG establishes it as a standard extension.

In addition to the formal rules, a number of conventions are widely observed. Some conventions are used throughout the community others only within a particular discipline such as high energy astrophysics or single dish radio astronomy. Usually, the originator(s) of a convention will circulate an initial proposal for comments among a small group in the same discipline or installation. After this proposal has been refined based upon these comments, it is put out for public comment, usually by announcement to the sci.astro.fits newsgroup of a URL from which it can be retrieved. Comments at this time may lead to additional changes. If the affected community accepts the convention, installations will start using it in their FITS files. Since failure to use a convention is not a violation of the FITS rules, FITS readers unaware of it must not terminate with an error or give incorrect results when encountering it.

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Last revised: Tuesday, 28-Oct-2014 11:50:29 EDT
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