From bschlesinger at nssdca.gsfc.nasa.gov Mon May 18 14:26:38 1992 X-VM-VHeader: ("From:" "Sender:" "Resent-From" "To:" "Apparently-To:" "Cc:" "Subject:" "Date:" "Resent-Date:") nil X-VM-Bookmark: 4 Status: RO X-VM-v5-Data: ([nil nil nil nil nil nil nil nil nil] ["6138" "Mon" "18" "May" "1992" "17:46:00" "GMT" "Barry Schlesinger" "bschlesinger at nssdca.gsfc.nasa.gov " nil "126" "FITS Basics and Information (regular monthly posting)" "^From:" nil nil "5"]) Newsgroups: sci.astro.fits News-Software: VAX/VMS VNEWS 1.41 Keywords: FITS, images, references Nntp-Posting-Host: nssdca.gsfc.nasa.gov Organization: NASA - Goddard Space Flight Center From: bschlesinger at nssdca.gsfc.nasa.gov (Barry Schlesinger) Subject: FITS Basics and Information (regular monthly posting) Date: Mon, 18 May 1992 17:46:00 GMT This basic FITS information will be posted and updated periodically for the benefit of new readers and the reference of old readers. FITS (Flexible Image Transport System) is a data format designed to allow convenient exchange of astronomical data between installations whose standard internal formats and hardware may be different. A FITS file consists of a sequence of Header Data Units (HDUs). The header consists of keyword=value statements, which describine the format and organization of the data in the HDU, and may contain other information such as information about the instrument or the history of the data or data set. 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 comes from the original use of the format to transport digital images, but it's not just for images any more. FITS is not principally a graphics format designed for the transfer of pictures that includes support for many platforms as part of the package for decoding the image. Separate software must be developed or obtained for converting the data from the FITS file into a form that can be readily displayed. As has been discussed in this newsgroup, and in alt.sci.astro.fits before it, the Extended Portable Bitmap Toolkit (pbm+) can be used for converting many FITS files to such a format, but support for all FITS files where the data are in the form of an image, in particular those where the data matrix members are in IEEE floating point format (BITPIX<0) or the matrix has more than two dimensions (NAXIS>2), is not guaranteed. Discussion of FITS - image converters appears in this newsgroup from time to time. The fundamental references on FITS are the following four papers, often referred to collectively as the "Four FITS Papers". These papers are the formal standard for FITS, endorsed by the International Astronomical Union (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. A User's Guide for FITS, commissioned by NASA Headquarters, is maintained by the NASA/OSSA Office of Standards and Technology (NOST). 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. This document is available only in hard copy form. NASA is sponsoring development of a formal standard for FITS. The goal of this process is a document consistent with FITS as endorsed by the IAU, eliminating some contradictions and ambiguities in the original FITS papers, that can be endorsed by the IAU FITS Working Group as the FITS standard. The document is being developed by a Technical Panel chaired by Dr. Robert J. Hanisch (STSci), with review by the astronomical community. Only minor revisions are expected to the current draft, version 0.3b, but the form of the standard is not final, and it does not supersede the four papers and Floating Point Agreement endorsed by the IAU as the official standard for FITS. The IAU has endorsed the Floating Point Agreement, which defines how floating point numbers are to be stored in the data matrix defined in the first of the four papers. The basic agreement appears verbatim in the User's Guide, and the substance is incorporated in the Draft NASA Standard. The NOST maintains a file of FITS information available by anonymous ftp from nssdca.gsfc.nasa.gov or DECnet copy from NSSDCA, in the directory FITS. It includes copies of the current draft NASA Standard in flat ASCII, PostScript, and LaTeX, and a list of the current extension type (structure) names registered with the IAU FITS Working Group. It also contains, in LaTeX form, the text of the proposal for one of these new extension types, IMAGE. A README. file describes the contents of the directory. There is a further subdirectory, SOFTWARE, described by README.FIRST, containing a program in C to read and list the headers of a FITS file and another file with information on publicly available FITS software packages. Paper copies of many of the documents listed above can be obtained from the NOST Librarian. Paper copies of the User's Guide and either paper or electronic copies of the Draft Implementation Standard, for those without ftp access, are available. Because of restrictions set by the copyright holder, NOST can send copies of the four FITS papers only to non-profit organizations. The addresses of the NOST are as follows: (Postal) NASA/OSSA Office of Standards and Technology Code 933 Goddard Space Flight Center Greenbelt MD 20771 USA (Internet) nost at nssdca.gsfc.nasa.gov (DECnet) NCF::NOST Please mention this posting in your request. Barry M. Schlesinger Coordinator, NASA/NSSDC NOST FITS Support Office (301) 513-1634 fits at nssdca.gsfc.nasa.gov NCF::FITS From landsman at stars.gsfc.nasa.gov-286-3625) Mon May 18 19:24:29 1992 Status: RO X-VM-v5-Data: ([nil nil nil nil nil nil nil nil nil] ["687" "" "18" "May" "92" "21:36:00" "GMT" "301" "landsman at stars.gsfc.nasa.gov (Wayne Landsman -286-3625)" nil "17" "Allowed TFORMnnn values in Binary Tables" "^From:" nil nil "5"]) Newsgroups: sci.astro.fits Organization: NASA/GSFC-Laboratory for Astronomy and Solar Physics News-Software: VAX/VMS VNEWS 1.4-b1 Nntp-Posting-Host: stars.gsfc.nasa.gov From: landsman at stars.gsfc.nasa.gov (Wayne Landsman (301)-286-3625) Subject: Allowed TFORMnnn values in Binary Tables Date: 18 May 92 21:36:00 GMT What are the allowed characters in the TFORMnnn field of a binary table? The NOST manual gives L,X,I,J,A,E,D,B,C,M, or P corresponding to logical,bit,16-bit integer, 32 bit integer, character, single precision, double precision, unsigned bytes, single complex and double complex, and 64 bit array descriptor. However, the FITS test file f09.fits in fits.cx.nrao.edu includes the character 'F' in the TFORM5 field, presumably meaning single precision, and I have seen other binary tables use the 'F' format. Should I go ahead and modify my FITS reader to parse an 'F' format as an alias for 'E'? Thanks, Wayne Landsman landsman at stars.gsfc.nasa.gov (301)-286-3625 From pgrosbol at eso.org Tue May 19 08:24:58 1992 Status: RO X-VM-v5-Data: ([nil nil nil nil nil nil nil nil nil] ["532" "Tue" "19" "May" "1992" "10:54:17" "GMT" "pgrosbol at eso.org" "pgrosbol at eso.org" nil "11" "Re: Allowed TFORMnnn values in Binary Tables " "^From:" nil nil "5"]) Newsgroups: sci.astro.fits Organization: National Radio Astronomy Observatory From: pgrosbol at eso.org Subject: Re: Allowed TFORMnnn values in Binary Tables Date: Tue, 19 May 1992 10:54:17 GMT The test files available on anonymous ftp were made in the summer of 1991 before the final definition of allowed formats was made. Thus, the sample 'f09' used the 'F' format for single precision because it was allowed in the ASCII tables. The 'F' format is not included for binary tables and I will make a correct test file available shortly. Whereas it for ASCII table is an actual FORTRAN format, the BINTABLE extension only use it for the field type. It is therefore reasonable only to use 'E' in BINTABLEs. Preben Grosbol ESO From hanisch at stsci.edu Fri May 22 10:14:00 1992 Status: RO X-VM-v5-Data: ([nil nil nil nil nil nil nil nil nil] ["1613" "Thu" "21" "May" "1992" "20:28:19" "GMT" "Bob Hanisch" "hanisch at stsci.edu " nil "42" "AAS WGAS meeting, call for agenda items" "^From:" nil nil "5"]) Newsgroups: sci.astro.fits,sci.astro,alt.sci.astro.aips Followup-To: poster Organization: Space Telescope Science Institute From: hanisch at stsci.edu (Bob Hanisch) Subject: AAS WGAS meeting, call for agenda items Date: Thu, 21 May 1992 20:28:19 GMT To all members of the American Astronomical Society Working Group on Astronomical Software and other interested parties: I would like to have suggestions for agenda items for the forthcoming WGAS meeting. We have a program of 4 contributed papers in our morning session, and our `business' meeting is in the afternoon. So far, I expect to include the following topics in the business meeting: o FITS issues - Establishment of a formal FITS Committee - Status of recent FITS actions (binary tables, etc.) - Report from the NASA FITS Support Office o Communications - Pros/cons of establishing a newsgroup for the WGAS o Data compression - Relationship to FITS - Distribution/catalog of compression algorithms o Software distribution/catalogs in general Please let me know if there are other topics you would like to see included. I will distribute a more formal agenda within the next week or so. In case you've not read your AAS meeting announcement, the WGAS will convene on Monday June 8 as part of the Columbus AAS meeting. The details are as follows: Session 14: WGAS oral papers, McKinley room 10:00-11:30am WGAS Business Meeting, McKinley room 2:00- 3:30pm Bob Hanisch Chair, AAS Working Group on Astronomical Software hanisch at stsci.edu tel. 410-338-4910 -- Robert J. Hanisch Tel. (410)338-4910 Fax. (410)338-5090 Space Telescope Science Institute NSI: hanisch at stsci.edu [130.167.1.2] 3700 San Martin Drive DECNet: STSCIC::HANISCH [6549::] Baltimore, MD 21218 USA Bitnet: hanisch at stsci