• General overview of FITS on Wikipedia
• Library of Congress description of FITS on the Digital Formats website
• FITS Overview: A brief history of the origins and evolution of FITS
• FITS Format Primer: An introduction to the basic structure of a FITS file
• FITS User's Guide (PDF): An out of date (April 1997) introduction to the history and usage of FITS. This document describes version 100-1.2 of the FITS Standard. Although much of the technical information in this guide is no longer valid, it still remains of historical interest. The User's Guide is also available in the following formats:
  • Postscript Format Historical User Guide
  • Historical User Guide Latex Source Text File
  • Historical User Guide Style File

The FITS community has developed many conventions for using certain keywords or FITS file structures. See the following links for more information.

• Registry of FITS Conventions submitted to the IAU (International Astronomical Union) FITS Working Group
• Unregistered conventions developed by various projects
• Extension names registered with the IAU FITS Working Group (IAUFWG)

FITS Keyword Dictionaries

The following data dictionaries contain compilations of the FITS header keywords that have been defined and used within various contexts.

• Keywords defined in the FITS Standard
• Other commonly used keywords
• UCO (University of California Observatories)/Lick keyword dictionary
• Space Telescope Science Institute (STScI) keyword dictionary
• NOAO (National Optical Astronomy Observatory) keyword dictionary (no longer publicly available because the IRAF (Image Reduction and Analysis Facility) project is no longer supported)
• ESO (European Southern Observatory) keyword dictionary

Documents and software dealing with World Coordinate System (WCS) conventions. Four WCS papers have been approved by the IAUFWG and are now officially recognized as part of the FITS Standard.

• FITSBITS newsgroup: The official discussion forum for issues related to FITS
  • FITS Community Demographics: An analysis of the demographics of the FITS community in March 1992 by Don Wells.
• FITS extensions: A list of extension names registered with the IAU FITS Working Group
• FITS MIME types (RFC 4047): The Internet Engineering Task Force issued the RFC 4047 Internet standards document that defines and registers the "image/fits" and "application/fits" Multipurpose Internet Mail Extensions (MIME) types in April 2005 after a long review process. The fitsmime email exploder (now closed) has an archive of the discussions on this topic. The MIME types are typically used to describe the type of content (or media type) of documents or data files that are passed between applications over the Internet. The MIME type indicates to the receiving application (e.g., a web browser) how to handle the information.
• Floating-point Agreement (Postscript file): 1989 agreement on how to store floating-point numbers in FITS using the IEEE-754 (Institute of Electrical and Electronics Engineers 754) 32-bit and 64-bit representation. Read the Floating-Point Agreement as a text version.
• 64-bit integers in the FITS Standard: This standard (i.e, images with BITPIX = 64 and binary table columns with TFORMn = 'K' and 'Q') was approved by the IAU FITS Working Group on 8 December 2005.
• Blocking of Fixed-block Sequential Media (1994) - Agreement on how to represent FITS files on physical media (magnetic tape) which can only access data in blocks of fixed length.
• Year 2000 Agreement on representing Dates (1997) - Redefined the format of the DATE-OBS keyword (and other date-related keywords) for representing dates in years 2000 and beyond. See also A Summary of the International Standard Date and Time Notation by Markus Kuhn.
• FITS Birthday Announcement - Historical note from Don Wells on the events leading up to the "birth" of the FITS format in 1979.
• One of the first published papers on FITS, "The need for a standard tape format for the transport of astronomical data" presented in 1979 by R. H. Harten. It describes the basics of the FITS format and recommends that it be adopted as the standard tape data format by major astronomical observatories.
• Historical Perspectives on FITS (PDF) by Eric Greisen, one of the original developers of FITS. This paper was published in Information Handling in Astronomy - Historical Vistas, edited by Andre Heck (Kluwer, Astrophysics and Space Science Library, 285 (2002). Read Historical Perspectives on FITS in Postscript format.
• Old descriptions of the FITS format from the NASA FITS Office:
  • 1992 FITS Format Overview
  • 1995 FITS Basics Part One
  • 1995 FITS Basics Part Two
• Some FITS Committee Status Reports are available to view on the FITS Archives page.
• FITS Comparison: A draft document written in 1992 by Barry Schlesinger (then the FITS support person at Goddard Space Flight Center-NOST) as part of a comparison of various data formats that was produced by NOST (NASA/Science Office of Standards and Technology).
• Formats Evolution Process in 1998 established several discussion forums for contrasting and comparing different data formats, including FITS, HDF (Hierarchical Data Format), and CDF (Common Data Format). Several researchers and archive sites present their experiences in using the FITS format.

1. FITS: A Flexible Image Transport System, Wells, D. C., Greisen, E. W., and Harten, R. H., Astronomy & Astrophysics Supplement Series, 44, 363-370, 1981. (HTML, PDF)
2. An Extension of FITS for Groups of Small Arrays of Data, Greisen, E. W. and Harten, R. H., Astronomy & Astrophysics Supplement Series, 44, 371-374, 1981. (NOTE: The random groups format described in this paper has been used almost exclusively to transport radio interferometry and has now largely been replaced by binary tables. Writing data other than radio interferometry data using this format is not recommended.) (HTML, PDF)
3. Generalized Extensions and Blocking Factors for FITS, Grosbøl, P., Harten, R. H., Greisen, E. W., and Wells, D. C., Astronomy & Astrophysics Supplement Series, 73, 359-364, 1988. (HTML, PDF)
4. The FITS Tables Extension, Harten, R. H., Grosbøl. P., Greisen, E. W., and Wells, D. C., Astronomy & Astrophysics Supplement Series, 73, 365-372, 1988. (HTML, PDF)
5. The FITS Image Extension, Ponz, J. D., Thompson, R. W., and Munoz, J. R., Astronomy & Astrophysics Supplement Series, 105, 53-55, 1994. (HTML, PDF). The original Image extension proposal document is also available: (Postscript, Latex Source)
6. Binary Table Extension to FITS, Cotton, W. D., Tody, D. B., and Pence, W. D., Astronomy & Astrophysics Supplement Series, 113, 159-166, 1995. (HTML, PDF, Latex Source (draft)). The original Binary Table extension proposal document is also available: (Postscript, Latex Source)
7. Definition of the Flexible Image Transport System (FITS), Hanisch, R. J., Farris, A., Greisen, E. W., Pence, W. D., Schlesinger, B. M., Teuben, P. J., Thompson, R. W., and Warnock, A., Astronomy & Astrophysics, 376, 359-380, 2001. (HTML, PDF). The PDF version includes only the main body of the paper and not the appendixes. This document has been replaced by a newer version.
8. Representations of World Coordinates in FITS, Greisen, E. W., and Calabretta, M. R., Astronomy & Astrophysics, 395, 1061-1075, 2002. (PDF, HTML). Reprints are also available from the author's website in PDF format.
9. Representations of Celestial Coordinates in FITS, Calabretta, M. R., and Greisen, E. W., Astronomy & Astrophysics, 395, 1077-1122, 2002. (PDF, HTML). Reprints are also available from the author's web site in PDF format.
10. Representations of spectral coordinates in FITS, Greisen, E. W., Calabretta, M. R., Valdes, F. G., and Allen, S. L., Astronomy & Astrophysics, 446, 747-771, 2006. (PDF, HTML). Reprints are available from the author's website.
11. Representations of time coordinates in FITS. Time and relative dimension in space, Rots, A. H., Bunclark, P. S., Calabretta, M. R., Allen, S. L., Manchester, R. N. & Thompson, W. T. 2015, Astronomy & Astrophysics, 574, A36, 2015 (PDF format)

This list only contains the papers that are primarily focused on FITS issues presented at the first 13 Astronomical Data Analysis Software and Systems (ADASS) meetings.

• ADASS I - 1991, ASP Conference Series, Vol. 25.
  • FITS Kernel Interface in IRAF, Zarate, N. R.
  • FITSIO and FITS File Utility Software, Pence, W. D.
  • Definition of a Distribution Format for X-ray Data, Conroy, M. A., et al.
  • Wavelet-Based Compression Software for FITS Images, Press, W. H.
• ADASS II - 1992, ASP Conference Series, Vol. 52.
  • The ROSAT Implementation of a Proposed Multi-Mission X-ray Data Format, Corcoran, M. F., et al.
  • FITS Data Conversion Efforts at the Compton Observatory Science Support Center, Jennings, D. G., et al.
  • FTOOLS---A FITS Utility Package for Multiple Environments, Pence, W. et al.
  • The IRAF/NOAO Spectral World Coordinate Systems, Valdes, F.
• ADASS III - 1993, ASP Conference Series, Vol. 61.
  • The Design of an Intelligent FITS File Database, A. H. Rots
  • Compression Software for Astronomical Images, J. P. Veran, J. R. Wright
  • FITS Image Compression Using Variable Length Binary Tables, W. D. Pence
• ADASS IV - 1994, ASP Conference Series, Vol. 77.
  • Proposed FITS Keywords and Column Headers for ALEXIS Mission Data Files, J. Bloch and J. Theiler
  • The OGIP FITS Working Group, M. F. Corcoran, et al.
  • A Generic Data Exchange Scheme Between FITS Format and C Structures, W. Peng and T. Nicinski
  • Reformatting the Ginga Database to FITS and the Creation of a Data Products Archive, R. H. D. Corbet, et al.
  • Representations of Celestial Coordinates in FITS, E. W. Greisen, M. Calabretta
  • A Proposed Convention for Writing FITS Data Tapes: DRAFT 0, ROSAT/ASCA/XTE Development Team
  • FITSIO Subroutine Library Update, W. D. Pence
  • FITS Checksum Verification in the NOAO Archive, R. Seaman
  • FTOOLS: A FITS Data Processing and Analysis Software Package, J. K. Blackburn
• ADASS V - 1995, ASP Conference Series, Vol. 101.
  • STSDAS Tables Package Uses FITSIO, P. Hodge
  • IDA---A FITS Table Browser and Editor, C. G. Page
  • A FITS Image Extension Kernel for IRAF, N Zarate, P Greenfield
  • Availability of Copernicus UV Data in FITS Format, Daniel A. Klinglesmith III, et al.
  • The XTE FITS Database (XFDB), A. H. Rots,
• ADASS VI - 1996, ASP Conference Series, Vol. 125.
  • Practical Applications of a Relational Database of FITS Keywords, De Clarke and S. L. Allen
  • Multiple World Coordinate Systems for DEIMOS Mosaic Images, S. L. Allen, De Clarke
  • WCSTools: Image World Coordinate System Utilities, D. J. Mink
  • The SAOtng Programming Interface, E. Mandel
  • Speculations on the Future of FITS, Donald C. Wells
  • FV: A New FITS File Visualization Tool, W. Pence, J. Xu, L. Brown
  • FITS++: An Object-Oriented Set of C++ Classes to Support FITS, A. Farris
  • The FITS List Calculator and Bulk Data Processor, E. B. Stobie and D. M. Lytle
  • FITS BoF Session, P Teuben, D Wells
• ADASS VII - 1997, ASP Conference Series, Vol. 145.
  • New Developments in the FITSIO and Fv Software Packages, W. Pence
  • IRAF Multiple Extensions FITS (MEF) Files Interface, N. Zarate
  • HST Keyword Dictionary, D. A. Swade, et al.
• ADASS VIII - 1998, ASP Conference Series, Vol. 172.
  • A Scheme for Compressing Floating-Point Images, R. L. White and P. Greenfield
  • PyFITS, a FITS Module for Python, P. E. Barrett and W. T. Bridgman
  • CFITSIO, v2.0: A New Full-Featured Data Interface, W. D. Pence
• ADASS IX - 1999, ASP Conference Series, Vol. 216.
  • PyFITS, a Python FITS Module, P. E. Barrett and W. T. Bridgman
  • SDFITS: A Standard for Storage and Interchange of Single Dish Data, R. W. Garwood
  • A FITS Image Compression Proposal, W. Pence, R. L. White, P. Greenfield, and D. Tody
  • Representations of World Coordinates in FITS, M. Calabretta and E. W. Greisen
• ADASS X - 2000, ASP Conference Series, Vol. 238.
  • The FITS Embedded Function Format, A. H. Rots, J. C. McDowell, M. Wise, X. H. He, and P. E. Freeman
  • Converting FITS into XML: Methods and Advantages, B. Thomas, E. Shaya, and C. Cheung
• ADASS XI - 2001, ASP Conference Series, Vol. 281. (not currently available)
• ADASS XII - 2002, ASP Conference Series, Vol. 295.
  • Representations of DEIMOS Data Structures in FITS, Steven L. Allen, De A. Clarke, Robert I. Kibrick
  • Representations of Spectral Coordinates in FITS, E. G. Greisen, F. G. Valdes, M. R. Calabretta, and S. L. Allen
  • New Features of SAOImage DS9, W. A. Joye and E. Mandel
• ADASS XIII - 2003, ASP Conference Series, Vol. 314.
  • Chandra FITS Dictionary, S. L. Winkelman, A. H. Rots, K. Michaud, and S. E. Blecksmith
  • Developments in the Starlink AST Library - an Intelligent WCS Management System, D. S. Berry
  • Making FITS available on Dot Net and its applications, V. Haridas, T. Budavári, W. O'Mullane, A. S. Szalay, A. Thakar, A. Conti, A. Volpicelli, and B. Pence
  • Representations of distortions in FITS world coordinate systems, M. R. Calabretta, F. Valdes, E. W. Greisen, and S. L. Allen
  • Demo of numarray, PyFITS, and related software, J.-C. Hsu and P. E. Hodge