Last revised 1995 August 9 1700 GMT Preface This Flexible Image Transport System (FITS) information is updated periodically by the FITS Support Office, operated under the guidance of the Astrophysics Data Facility at the NASA Goddard Space Flight Center. It provides a brief description of FITS and information on software and documentation, discusses some topics that have appeared on the Usenet newsgroup sci.astro.fits, and answers some questions on FITS frequently received by the FITS Support Office. Substantive changes this revision: o Information on Blocking Agreement o Information on List of Registered extensions o Note that the instructions for the FPCT discuss its capabilities and limitations o Note that FITS Support Office software to list headers is in ANSI C Revisions made 1995 June 16: o Information on IDL Astronomy User's Library o FITS Support now part of xv3.10a (replaces unsupported xv 3.0 modifications) o ViewFITS for (OS/2) no longer listed - access and support unavailable (not to be confused with FITSview for Windows, which is very much available) o New URL information for GraphicConverter for Macintosh Table of Contents Preface Recent Revisions Table of Contents 1 Introduction 1.1 What FITS Is 1.2 How FITS Evolves 1.3 What FITS Is Not 2 FITS Documents 2.1 Published Papers 2.2 Binary Tables 2.3 User's Guide 2.4 NOST Definition of FITS 2.4.1 Version 1.0 2.4.2 Proposed Revision on Units Specification 2.5 Floating Point Agreement 2.6 Blocking Agreement 2.7 List of Registered Extensions 2.8 World Coordinates 2.9 Proposed Conventions 3 Software and Sample Data 3.1 FITS Support Office 3.1.1 FITS Product Conformance Tester with Instructions 3.1.2 Header Lister 3.1.3 Error Test Files 3.2 HEASARC 3.2.1 FITSIO 3.2.2 FTOOLS 3.2.3 VERIFITS 3.3 ADC FITS Table Browser 3.4 FITS I/O software in IDL 3.5 Display of FITS Image Files 3.5.1 Major Astronomical Image Analysis Packages 3.5.2 pbm+ 3.5.3 IMDISP (IBM/PC) 3.5.4 SAOimage 3.5.5 Applications with XV 3.5.6 FITS and the Macintosh 3.5.7 FITSview (Windows) 3.6 World Coordinates 4 On-line Information Sources 4.1 FITS Support Office 4.2 HEASARC 4.3 NRAO 4.4 HEAFITS exploder 5. Contributors (non-exhaustive list) 6. FITS Support Services from GSFC 1 Introduction 1.1 What FITS Is FITS (Flexible Image Transport System) is a data format designed to provide a means for convenient exchange of astronomical data between installations whose standard internal formats and hardware differ. A FITS file is composed of a sequence of Header Data Units (HDUs). The header consists of keyword=value statements, which describe the format and organization of the data in the HDU and may also provide additional information, for example, about instrument status or the history of the data. The data follow, structured as the header specifies. The data section of the HDU may contain a digital image, but, except for the first, *it doesn't have to*. Other possible formats include tables and multidimensional matrices that are not images. The first HDU must contain a multidimensional matrix or no data at all; the data in subsequent HDUs, called extensions, may be of any type, consistent with certain rules. The "Image" in the name FITS comes from the original use of the format to transport digital images, but it's not just for images any more. FITS supports 5 data types in primary or IMAGE data arrays: 8-bit unsigned binary integers, 16-bit twos-complement signed binary integers, 32-bit twos-complement signed binary integers, 32-bit IEEE-754 standard floating point numbers, and 64-bit IEEE-754 floating point numbers. For signed integers, the byte that includes the sign bit is first and the byte that has the 1-bit as its least significant bit is last. FITS does not support the 16-bit unsigned integer data type generated by many analog/digital converters. Conforming FITS files can be produced from such data by subtracting 32768 (decimal) from the converter output before writing to the file, while setting the BZERO keyword in the FITS header equal to 32768 and the BSCALE keyword equal to 1. A FITS reader will then add 32768 to the value in the file, restoring the original value, before interpreting it. Whether a 16-bit unsigned data type should be added, and if so, how, is controversial and under discussion, especially in sci.astro.fits. 1.2 How FITS Evolves The International Astronomical Union (IAU) FITS Working Group (IAUFWG) was given authority over FITS matters by the 1988 IAU General Assembly. This Group is associated with the Working Group on Astronomical Data. The current chair is D. Wells (NRAO) and the vice-chair is E. Raimond (NFRA). When the developer of a data structure finds that it does not fit well into an existing standard FITS 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. A unique name for any new extension type must be registered with the IAU FITS Working Group, optionally through the FITS Support Office. After astronomical community discussion, most of which will be electronic, 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 FITS Working Group. Approval by the Working Group establishes it as a standard extension. 1.3 What FITS Is Not FITS is not principally a graphics format designed for the transfer of pictures; it does not incorporate "FITS viewers," packages for decoding the data into an image. Users must develop or obtain separate software to read and display the data from the FITS file. There is no standard package for all applications; section 3.5 discusses some possibilities. 2 FITS Documents 2.1 Published Papers The fundamental references on FITS are the following five papers. The first four have often been referred to collectively as the "Four FITS Papers". These five papers, along with the Floating Point Agreement (section 2.5) and the binary tables definition (section 2.2), are the formal standard for FITS, endorsed by the IAU. Wells, D. C., Greisen, E. W., and Harten, R. H., "FITS: A Flexible Image Transport System," Astronomy and Astrophysics Supplement Series, 44, 363-370, 1981. Greisen, E. W. and Harten, R. H., "An Extension of FITS for Small Arrays of Data," Astronomy and Astrophysics Supplement Series, 44, 371-374, 1981. (NOTE: The format described in this paper has been used almost exclusively to transport radio interferometry and is likely to be replaced by other formats in the future. Writing data other than radio interferometry data using this format is not recommended.) Grosbol, P., Harten, R. H., Greisen, E. W., and Wells, D. C., "Generalized Extensions and Blocking Factors for FITS," Astronomy and Astrophysics Supplement Series, 73, 359-364, 1988. Harten, R. H., Grosbol. P., Greisen, E. W., and Wells, D. C., "The FITS Tables Extension, Astronomy and Astrophysics Supplement Series, 73, 365-372, 1988. Ponz, J. D., Thompson, R. W., and Munoz, J. R., "The FITS Image Extension," Astronomy and Astrophysics Supplement Series, 105, 53-55, 1994. 2.2 Binary Tables On June 15, 1994, the IAU FITS Working Group announced the acceptance of BINTABLE, the binary table extension, as a standard extension. The description of the extension, to be published in the Astronomy and Astrophysics Supplement Series, is available at the National Radio Astronomy Observatory (NRAO) site (see section 4.3). 2.3 User's Guide A User's Guide for FITS, commissioned by NASA Headquarters, is maintained by the FITS Support Office. This Guide is intended to be a tutorial for new FITS users. In addition to presenting the rules of FITS, it provides some of the history and reasoning behind the choice of the rules, adds recommendations on good practices, and discusses current developments in FITS. The current version, 3.1, was issued in May 1994. 2.4 NOST Definition of FITS 2.4.1 Version 1.0 The NASA/Science Office of Standards and Technology (NOST) has codified FITS as endorsed by the IAU into a formal standard, eliminating some contradictions and ambiguities in the original FITS papers. This Definition of FITS, version 1.0, was developed by a Technical Panel chaired by R. J. Hanisch (STScI), with review by the astronomical community. On June 18, 1993, it was approved as a NOST Standard by an Accreditation Panel consisting of the NOST Executive Board and an astronomical community representative; this review was to confirm that the community had been given a satisfactory opportunity to review the standard and that the Technical Panel had properly considered and responded to all comments. The NOST standard has been submitted to the IAUFWG for endorsement as the international FITS standard. Version 1.1 will replace the original endorsed standard -- the four FITS papers, with the addition of the Floating Point Agreement. While oversights in non-controversial areas may be rectified as a result of the review by the IAUFWG, significant changes are unlikely because members of this committee were active in the process of reviewing the standard and their comments were given significant weight in the deliberations of the Technical Panel. The IAUFWG has since endorsed the IMAGE and BINTABLE extensions, and the agreement on physical blocking. A new Technical Panel has been formed, primarily to draft a revised NOST Standard incorporating these additions, but also to rectify any oversights or omissions that may be brought to its attention by the community. Dr. Hanisch, the chair of the panel that developed version 1.0 of the Definition of FITS, is chairing this new panel. 2.4.2 Proposed Revision on Units Specification In response to community comments on the version 1.0 treatment, the new panel developed and released text covering requirements and recommendations on units to be used in FITS files. The Technical Panel has now approved the submission of this text for NOST accreditation as a revision to the NOST Standard. The proposed text is available in flat ASCII text form, with an approximate length of two printed pages. The NSSDC Coordinated Request and User Support Office (see section 6) can provide printed copies and electronic copies for those without ftp access. Upon approval by the Accreditation Panel, this text will be incorporated in the NOST Definition of FITS, producing version 1.1. 2.5 Floating Point Agreement Originally, FITS permitted only integers in the data array following the first, or primary header. The IAU has since endorsed the Floating Point Agreement, which specifies the use of IEEE-754 floating point and describes its use in FITS. The basic agreement appears verbatim in the User's Guide, and the substance is incorporated in the NOST standard. 2.6 Blocking Agreement The IAU FITS Working Group has endorsed a set of rules for physical blocking of FITS files, designed to address the requirement that many controllers and devices for high density storage media can access data only in blocks of fixed length. These rules prescribe the number of 2880-byte FITS logical records in a physical block and how to proceed when the block size is not an integral multiple of 2880 bytes. They have been formulated for fixed-block sequential media, variable block sequential media, and bitstream devices. They are available in this directory in the file blocking94.txt. 2.7 List of Registered Extensions The rules for generalized extensions in FITS require a unique name for every extension type, to permit software readers to identify whether or not an extension is of a type that the software can handle. In order to ensure uniqueness, all extension type names, even for local extensions used only at one installation, must be registered with the IAU FITS Working Group. The FITS Support Office maintains the List of Registered Extensions, in this directory, in the file xtension.lis. This list includes a brief description of the extension each type name identifies, the developer or responsible organization, and the status of the extension (e. g., standard, under discussion, local). Also described is the procedure for registration of extension type names. This list is updated as new extension type names are proposed and extensions with reserved names progress through the process required for IAU FITS Working Group approval. Consequently, it should be used as the primary reference on registered extensions rather than the appendix in the Definition of FITS or the corresponding section in the User's Guide. 2.8 World Coordinates A draft text of conventions for World Coordinates is currently under community review. It proposes rules for describing the physical coordinate values attached to each member of a FITS data array, with detailed discussion of projections from the celestial sphere to the array plane. It is available electronically from the NRAO site (4.3). 2.9 Proposed Conventions R. Seaman and W. Pence have proposed a scheme for embedding a checksum within a FITS header. This checksum could be used to verify that the data in a file were transported without errors. A copy is available from ftp://iraf.noao.edu/misc/checksum/. IAU FITS Working Group Chair D. Wells has recommended that this proposal be considered by the regional FITS committees. D. Jennings, W. Pence, M. Folk, and B. Schlesinger have proposed a convention for logically grouping together FITS HDUs that are physically separated in a given file or are located in different files. This convention would facilitate HDU-FITS conversion. Versions in LaTeX/PostScript are available at ftp://ssvs.gsfc.nasa.gov/pub/convert/; an html version may be viewed at http://acadia.gsfc.nasa.gov/convert/group.html. 3 Software and Sample Data 3.1 FITS Support Office All FITS Support Office software is available from this ftp site. 3.1.1 FITS Product Conformance Tester with Instructions The FITS Product Conformance Tester (FPCT), under development by the FITS Support Office, is a software package designed to validate FITS files. The programs are coded in C. The available prototype validates required keywords in the primary header and, at the user's option, prints selected values from the primary data array. Even after finding an error in a required keyword, it will continue to evaluate the file, looking for additional errors in required keywords. If the user specifies, and if major header syntax errors do not prevent retrieval of the array dimensions, the FPCT will try to read the primary data array. The separate instructions should be read before running the software. In addition to providing directions for use, they also discuss the capabilities and limitations of the prototype. 3.1.2 Header Lister This program prints out all the headers in a FITS file, including the primary header and all extension headers. It does not evaluate them for errors. It is a useful tool for obtaining a quick summary of the contents of a FITS file. It is written in ANSI C; users with Sun and other systems that normally use earlier C dialects will need to devolve the function prototyping syntax or use an ANSI C compiler. 3.1.3 Error Test Files These files consist of several versions of the same FITS file, one in conformance with the FITS standard and recommended practices, several with different kinds of header errors, and two that are in technical conformance but have features that might cause problems for some readers. The are useful for testing the ability of FITS reading software to cope with erroneous or unusual files and to identify correctly the errors encountered. Users who download the files from direct anonymous ftp should remember to use binary transfer. 3.2 HEASARC The NASA/Goddard High Energy Astrophysics Science Archive Research Center (HEASARC) has developed and maintains FITS software and utilities, including the FITSIO package and the FTOOLS utilities. See 4.2 for information on electronic access to FITSIO and supporting documentation. 3.2.1 FITSIO The FITSIO package, maintained by W. D. Pence, is a machine-independent subroutine interface for reading or writing data files in FITS format. FITSIO is written in portable Fortran-77 and runs on most commonly used computers. In addition to the Fortran subroutine interface, a set of C macros, one for each FITSIO subroutine is provided to make it easier to call FITSIO from C programs. FITSIO supports all the standard FITS extensions and contains world coordinates subroutines for conversion between pixel and celestial coordinates. In addition, software support for the checksum proposal is available. 3.2.2 FTOOLS J. K. Blackburn and W. D. Pence document the FTOOLS collection of over 100 utility programs to create, examine, or modify FITS data files. These programs are useful for examining the contents of FITS files and modifying them for input to more involved analysis tasks; they cannot generally be used for detailed data analysis or model fitting. New versions are released about every 3 months. Users have the option of installing the entire FTOOLS package, which includes many routines specific to high energy astrophysics, or a core set that contains only the routines that perform general operations on FITS files. FTOOLS can be built as a package within IRAF or as a set of stand-alone executable tasks. FTOOLS is supported on the following platforms: Unix: ALPHA/OSF, DEC/ULTRIX, SUN/SunOS, SUN/Solaris, MODCOMP/REALIX VMS: ALPHA/VMS, VAX/VMS. Questions or comments should be sent to ftoolshelp@athena.gsfc.nasa.gov 3.2.3 VERIFITS W. D. Pence (GSFC/HEASARC) has announced the VERIFITS program to verify the conformance of any FITS format data file on magnetic disk to the standard, checking keywords and data. At user option it will list the total number of pixels, the number of null pixels and the maximum and minimum data values. If an error is found while evaluating the header, validation ceases, the error is reported and the first 72 keywords of the header are listed. The VERIFITS program is a stand-alone version of the fverify task that is included in the IRAF or Host FTOOLS package. Both VERIFITS and fverify perform the same verification checks, but fverify has a nicer user interface, as provided by the IRAF or Host environments. Several different binary executable versions of VERIFITS are available, for running on Sun workstations, DECstations, DEC Alphas running OSF/1 or VAX/VMS machines. The VERIFITS source code is also provided and may be easily linked with the FITSIO library to run on the other types of machine on which FITSIO is supported. While VERIFITS has been extensively tested, under some unusual circumstances not covered by the tests it may still fail to detect a FITS format error, or it may issue an error message that does not accurately describe the problem. VERIFITS has broader applicability than the FITS Product Conformance Tester (FPCT), being able to handle all standard extensions, while the currently available FPCT can handle only primary HDUs. The FPCT however is more forgiving and more thorough; VERIFITS will usually reject a file after finding one error, while the FPCT will attempt to retrieve the information needed to read the data if doing so is possible even with errors in the file, and will continue to check the header even after an error has been found. The VERIFITS program is available at ftp://heasarc.gsfc.nasa.gov/software/fitsio/verifits/. 3.3 ADC FITS Table Browser The Astronomical Data Center has developed a FITS Table Browser, which has been tailored specifically for use with the ADC CD-ROMs but may be used with other FITS ASCII Tables. It reads standard FITS ASCII tables and allows the user to browse through them interactively and selectively display any field or record in a table. File extraction facilities allow the writing of all or part of the input table to disk in FITS or text file format. Copies of the program for MS-DOS and Unix are available at ftp://nssdc.gsfc.nasa.gov/pub/ADC/software/ftb/. See the file README.FTB for instructions on downloading, installation, and use. 3.4 FITS I/O software in IDL W. Landsman (Hughes STX; landsman@stars.gsfc.nasa.gov) has announced that FITS I/O software written in IDL is available as part of the IDL Astronomy User's Library, a central repository for general purpose astronomy procedures written in IDL, including procedures to convert between spherical coordinates and plan map coordinates. The library is not meant to be an integrated package, but rather is a collection of procedures from which users can select. Submitted procedures are given a cursory testing but are basically stored in the library as submitted. The IDL Astronomy User's Library is supported under the NASA Astrophysics Software Aids program and is available at ftp://idlastro.gsfc.nasa.gov. Get the README file for details. 3.5 Display of FITS Image Files Disclaimer: The mention of particular software packages is not intended as an endorsement of those packages to the exclusion of others. Users should obtain proper licensing for any proprietary package or format mentioned. Information about publicly available nonproprietary packages is welcome and will be added to this posting if the package appears relevant and useful. Such information should include how to obtain the package and whom to contact with questions. It should also describe any limits on the FITS files that the package can handle (e. g., NAXIS must be 2; data array members must be integers). 3.5.1 Major Astronomical Image Analysis Packages The three major astronomical image analysis packages -- the Astronomical Image Processing System (AIPS), the European Southern Observatory Munich Image and Data Analysis System (ESO-MIDAS), and the Image Reduction and Analysis Facility (IRAF) -- provide facilities for displaying images stored in FITS files. These packages are large and probably best installed on major systems. AIPS was developed by the National Radio Astronomy Observatory (NRAO), and IRAF by the National Optical Astronomy Observatories (NOAO). 3.5.2 pbm+ The Extended Portable Bitmap Toolkit (pbm+) can be used to convert many FITS files to image format. However, support is not guaranteed for all FITS files where the data are in the form of an image. In particular, there may be problems when the data array members are in IEEE floating point format (BITPIX<0) or the array has more than two dimensions (NAXIS>2). 3.5.3 IMDISP (IBM/PC) A. Warnock and R. Baalke have announced release of version 7.9 of IMDISP, an interactive image processing program that runs on an IBM PC computer and supports FITS input. IMDISP 7.9 is available at ftp://explorer.arc.nasa.gov/pub/SPACE/SOFTWARE/ (128.102.32.10) in a file called imdisp79.zip and from ftp://nssdc.gsfc.nasa.gov/pub/ADC/software/imdisp/ . 3.5.4 SAOimage SAOimage is an X11 display tool which can be used stand-alone or in conjunction with IRAF to display FITS or IRAF images. It was developed at Smithsonian Astrophysical Observatory. SAOimage source code as well as compiled executables for SUN, HP, DEC, and VMS workstations are available at ftp://sao-ftp.harvard.edu/pub/saoimage/ (128.103.42.3). Questions about the use of SAOimage may be sent to hotseat@cfa.harvard.edu or iraf@noao.edu New bug fixes to SAOimage currently are being provided by NOAO in order to ensure that SAOimage will continue to work with IRAF. A new version of SAOimage, called "SAOimage: The Next Generation (SAOtng)" is being developed as a joint project between SAO and NOAO. An alpha release is planned for the spring of 1995. 3.5.5 Applications with XV The XV package, as of version 3.10a, now includes FITS support. It can handle more than 2 axes and IEEE single and double precision regular floating point values in the primary array. It can not handle IMAGE extensions or IEEE special values (NaN, Infinity, denormalized). The package is available from ftp://ftp.cis.upenn.edu/pub/xv/ as Z-compressed and GNU compressed .tar files. That site also lists electronic mail addresses for general XV questions, technical questions, and questions about licensing. 3.5.6 FITS and the Macintosh

FITS and the Macintosh

T. Lemke (100102.104@compuserve.com), at Peine in Germany has added FITS support to GraphicConverter for the Macintosh and provided the following information. GraphicConverter 1.7.7 or later can import FITS array files with all five permitted data types (8, 16, 32 bit integer and 32, 64 bit real). Every FITS file will be converted to 8 bit gray scale on opening because this is the maximum number of grays on a Macintosh. GraphicConverter can convert a FITS files to the PICT, TIFF, GIF, PCX, IFF, PPM, and other graphic file formats. GraphicConverter is available via the ftp info-mac archives at ftp://ftp.amug.org/pub/info-mac/gst/grf/ in the folder graphic-converter-212*. This site is often busy. If Web access through the URL does not succeed, use an ftp client to access ftp.amug.org for information on mirror sites.

D. Norton of Otter Solution has written a Photoshop plug-in called "PhotoFITS" which reads 8-, 16-, or 32-bit integer and 32- or 64- bit floating point FITS images and converts them to 8-bit or RGB images. It allows conversion of three-image FITS files to RGB. It allows multiple image files to be read in as a mosaic. It can be found at ftp://zippy.nimh.nih.gov/pub/nih-image/plug-ins/ Questions and problem reports should be sent to ottersol@aol.com. 3.5.7 FITSview (Windows) W. Cotton at NRAO has announced an updated beta release, version 0.4.0, of FITSview, a FITS image viewer for Windows. Celestial positions are determined using world coordinate projections. All defined FITS data types are recognized, as are blanked pixels. Two and three dimensional simple FITS images can be viewed. FITSview runs on Windows 3.1 or later and uses any multicolor (or multiple gray level) display. Extensive on-line documentation is included. It is available by ftp from the NRAO site: ftp://fits.cv.nrao.edu/fits/os-support/ms-windows/fitsview/fitsv040.txt ftp://fits.cv.nrao.edu/fits/os-support/ms-windows/fitsview/fitsv040.zip Installation is described in fitsv040.txt. 3.6 World Coordinates Two ANSI C functions, worldpos() and xypix(), convert (RA, dec) <--> pixel location for 8 common types of projective geometries where "(RA,Dec)" are more generically (long,lat). These functions are based on the World Coordinates implementation of Classic AIPS. The software is in src/wcs/worldpos.tar.gz at the NRAO site (section 4.3) and supporting documentation can be found in documents/wcs/. M. Calabretta (ATNF) has announced the general release of WCSLIB 1.0 - a suite of routines which implements the spherical projections proposed for the "World Coordinate System" (WCS) convention in FITS discussed in 2.6. The WCSLIB distribution kit contains independent C and FORTRAN implementations of the library. It is available via anonymous ftp from ftp.atnf.csiro.au:/pub/software/wcslib/wcslib-1.0.tar.gz and also fits.cv.nrao.edu:/fits/src/wcs/wcslib-1.0.tar.gz 4 On-line Information Sources 4.1 FITS Support Office The FITS Support Office maintains this directory of FITS information at ftp://nssdc.gsfc.nasa.gov/pub/fits. The aareadme.doc file describes the contents of this directory. The software and errtest subdirectories contain separate aaareadme.doc files describing their content. 4.2 HEASARC The HEASARC FITS software, utilities, and accompanying documentation are available as follows: ftp://legacy.gsfc.nasa.gov/software/fitsio contains the FITSIO package, and supporting documentation. ftp://legacy.gsfc.nasa.gov/software/fitsio/verifits contains the VERIFITS validator and supporting documentation. ftp://legacy.gsfc.nasa.gov/software/ftools/release contains the FTOOLS collection, and supporting documentation. The FTOOLS software is being distributed as compressed tar files. All three directories contain informational README files. HEASARC also provides information on the activities of the OGIP/HEASARC FITS Working Group (OFWG), the internal legislative body on FITS-related matters within the Office of Guest Investigator Programs (OGIP) at NASA/GSFC. OFWG has developed a number of FITS conventions that are more specific than the requirements of the FITS standards. Proposed OGIP conventions are publicized to the FITS community as a whole, with the goal of collaborative development of a set of conventions that will be accepted throughout the community as well as within OGIP/HEASARC. 4.3 NRAO A library of FITS material can be found at ftp://fits.cv.nrao.edu/fits, located at NRAO. This machine supports a WAIS server named nrao-fits which has an index of all of the FITS-related text files in the archive; the file nrao-fits.src is available at think.com and at ftp://fits.cv.nrao.edu/fits/wais-sources/nrao-fits.src. There is a World Wide Web server for the FITS Archive as well, at the URL http://fits.cv.nrao.edu. The documents subdirectory of the fits directory contains a number of subdirectories. The BINTABLE draft for Astronomy and Astrophysics is, in various formats, in files bintable_aa.*. A proposals subdirectory is reserved for detailed proposals currently being considered by the FITS committees. A drafts subdirectory contains drafts of designs not yet submitted. The wcs subdirectory contains a draft of the current proposal for world coordinate system conventions now under community review and earlier documents and presentations on world coordinates. Other subdirectories include sample FITS files -- both actual data files and files specially constructed to test the ability of software to read all kinds of FITS structures, some code for particular environments, pointers to other code, and an archive of Usenet postings related to FITS. 4.4 HEAFITS Exploder An electronic mail listserver called HEAFITS has been set up for discussion of High Energy Astrophysics-specific FITS issues that would not necessarily be of interest to the majority of subscribers to the sci.astro.fits newsgroup and fitsbits mailing list. To *subscribe* to the HEAFITS group, send the following one-line e-mail message to listserv@legacy.gsfc.nasa.gov: subscribe heafits Your Name where 'Your Name' is your actual First and Last names. Messages to the actual mailing list should be sent to heafits@legacy.gsfc.nasa.gov. There is an archive of messages at http://heasarc.gsfc.nasa.gov/listserv/heafits/maillist.html . 5. Some contributors (non-exhaustive list) A. Bernstein (JPL) D. Beauchamp (U. Laval) W. Cotton (NRAO) C. S. Grant (CfA) T. Lemke (U. of Brunswick) W. Pence (GSFC/HEASARC) D. Wells (NRAO) and the participants in sci.astro.fits and the fitsbits mailing list 6. FITS Support Services from GSFC The NSSDC Coordinated Request and User Support Office (CRUSO) can provide printed copies of the User's Guide and the NOST Standard. CRUSO can be reached as follows: (Postal) Coordinated Request and User Support Office Code 633 National Space Science Data Center NASA Goddard Space Flight Center Greenbelt MD 20771 USA (Electronic mail) request@nssdca.gsfc.nasa.gov (Telephone) +1-301-286-6695 8:00 A. M. - 4:30 P.M. U. S. Eastern Time (-0500 from the last Sunday in October through the first Saturday in April; -0400 the remainder of the year) When no one is available, messages can be left on voice mail. (FAX) +1-301-286-1635 Because of restrictions set by ESO, the copyright holder, copies of the four FITS papers may be sent only to non-profit organizations, . The IEEE floating point standard is copyrighted by IEEE, and must be purchased from them. Ordering and contact information is on-line at http://stdsbbs.ieee.org:70/0/pub/htmlfiles/stcord/html . Use the FITS Support Office electronic mail address below for questions about this FITS information. Other staff members monitor the FITS electronic mail address when I am away from the office, providing a greater certainty of rapid response. Please provide your name, affiliation, and location. Barry M. Schlesinger Coordinator, FITS Support Office +1-301-441-4205 fits@nssdca.gsfc.nasa.gov NCF::FITS NASA Contacts: ADF - David Leisawitz(leisawitz@stars.gsfc.nasa.gov) NOST - Donald M. Sawyer (sawyer@nssdca.gsfc.nasa.gov)