Contents

• Contents
• List of Tables
• List of Figures
• 1 Overview
  • 1.1 Purpose
  • 1.2 Scope
  • 1.3 Applicability
  • 1.4 Organization of This Document
• 2 References
• 3 Definitions, Acronyms, and Symbols
• 4 FITS File Organization
  • 4.1 Overall
  • 4.2 Individual FITS Structures
  • 4.3 Primary Header and Data Array
    • 4.3.1 Primary Header
    • 4.3.2 Primary Data Array
  • 4.4 Extensions
    • 4.4.1 Requirements for Conforming Extensions
      • 4.4.1.1 Identity
      • 4.4.1.2 Size Specification
      • 4.4.1.3 Compatibility with Existing FITS Files
    • 4.4.2 Standard Extensions
    • 4.4.3 Order of Extensions
  • 4.5 Special Records
  • 4.6 Physical Blocking
    • 4.6.1 Bitstream Devices
    • 4.6.2 Sequential Media
      • 4.6.2.1 Fixed Block
      • 4.6.2.2 Variable Block
• 5 Headers
  • 5.1 Card Images
    • 5.1.1 Syntax
    • 5.1.2 Components
      • 5.1.2.1 Keyword (bytes 1-8)
      • 5.1.2.2 Value Indicator (bytes 9-10)
      • 5.1.2.3 Value/Comment (bytes 11-80)
  • 5.2 Value
    • 5.2.1 Character String
    • 5.2.2 Logical
    • 5.2.3 Integer Number
    • 5.2.4 Real Floating Point Number
    • 5.2.5 Complex Integer Number
    • 5.2.6 Complex Floating Point Number
  • 5.3 Units
  • 5.4 Keywords
    • 5.4.1 Mandatory Keywords
      • 5.4.1.1 Principal
        • 7.1.1.1 SIMPLE Keyword
        • 7.1.1.2 BITPIX Keyword
        • 7.1.1.3 NAXIS Keyword
        • NAXISn Keywords
        • 7.1.1.9 END Keyword
      • 5.4.1.2 Conforming Extensions
        • XTENSION Keyword
        • 7.1.1.7 PCOUNT Keyword
        • 7.1.1.8 GCOUNT Keyword
        • EXTEND Keyword
    • 5.4.2 Other Reserved Keywords
      • 5.4.2.1 Keywords Describing the History or Physical Construction of the HDU
        • DATE Keyword
        • ORIGIN Keyword
        • BLOCKED Keyword
      • 5.4.2.2 Keywords Describing Observations
        • DATE-OBS Keyword
        • DATExxxx Keywords
        • TELESCOP Keyword
        • INSTRUME Keyword
        • OBSERVER Keyword
        • OBJECT Keyword
        • EQUINOX Keyword
        • EPOCH Keyword
      • 5.4.2.3 Bibliographic Keywords
        • AUTHOR Keyword
        • REFERENC Keyword
      • 5.4.2.4 Commentary Keywords
        • COMMENT Keyword
        • HISTORY Keyword
        • Keyword Field is Blank
      • 5.4.2.5 Array Keywords
        • BSCALE Keyword
        • BZERO Keyword
        • BUNIT Keyword
        • BLANK Keyword
        • CTYPEn Keywords
        • CRPIXn Keywords
        • CRVALn Keywords
        • CDELTn Keywords
        • CROTAn Keywords
        • DATAMAX Keyword
        • DATAMIN Keyword
      • 5.4.2.6 Extension Keywords
        • EXTNAME Keyword
        • EXTVER Keyword
        • EXTLEVEL Keyword
    • 5.4.3 Additional Keywords
      • 5.4.3.1 Requirements
      • 5.4.3.2 Restrictions
• 6 Data Representation
  • 6.1 Characters
  • 6.2 Integers
    • 6.2.1 Eight-bit
    • 6.2.2 Sixteen-bit
    • 6.2.3 Thirty-two-bit
    • 6.2.4 Unsigned Integers
  • 6.3 IEEE-754 Floating Point
• 7 Random Groups Structure
  • 7.1 Keywords
    • 7.1.1 Mandatory Keywords
      • SIMPLE Keyword
      • BITPIX Keyword
      • NAXIS Keyword
      • 7.1.1.4 NAXIS1 Keyword
      • 7.1.1.5 NAXISn Keywords (n=2, ..., value of NAXIS)
      • 7.1.1.6 GROUPS Keyword
      • PCOUNT Keyword
      • GCOUNT Keyword
      • END Keyword
    • 7.1.2 Reserved Keywords
      • 7.1.2.1 PTYPEn Keywords
      • 7.1.2.2 PSCALn Keywords
      • 7.1.2.3 PZEROn Keywords
  • 7.2 Data Sequence
  • 7.3 Data Representation
• 8 Standard Extensions
  • 8.1 The ASCII Table Extension
    • 8.1.1 Mandatory Keywords
      • XTENSION Keyword
      • BITPIX Keyword
      • NAXIS Keyword
      • NAXIS1 Keyword
      • NAXIS2 Keyword
      • PCOUNT Keyword
      • GCOUNT Keyword
      • TFIELDS Keyword
      • TBCOLn Keywords
      • TFORMn Keywords
      • END Keyword
    • 8.1.2 Other Reserved Keywords
      • TSCALn Keywords
      • TZEROn Keywords
      • TNULLn Keywords
      • TTYPEn Keywords
      • TUNITn Keywords
    • 8.1.3 Data Sequence
    • 8.1.4 Fields
    • 8.1.5 Entries
  • 8.2 Image Extension
    • 8.2.1 Mandatory Keywords
      • XTENSION Keyword
      • BITPIX Keyword
      • NAXIS Keyword
      • NAXISn Keywords
      • PCOUNT Keyword
      • GCOUNT Keyword
      • END Keyword
    • 8.2.2 Units
    • 8.2.3 Data Sequence
  • 8.3 Binary Table Extension
    • 8.3.1 Mandatory Keywords
      • XTENSION Keyword
      • BITPIX Keyword
      • NAXIS Keyword
      • NAXIS1 Keyword
      • NAXIS2 Keyword
      • PCOUNT Keyword
      • GCOUNT Keyword
      • TFIELDS Keyword
      • TFORMn Keywords
      • END Keyword
    • 8.3.2 Other Reserved Keywords
      • TTYPEn Keywords
      • TUNITn Keywords
      • TNULLn Keywords
      • TSCALn Keywords
      • TZEROn Keywords
      • TDISPn Keywords
      • THEAP Keyword
      • TDIMn Keywords
    • 8.3.3 Data Sequence
      • 8.3.3.1 Main Data Table
        • Logical
        • Bit Array
        • Character
        • Unsigned 8-Bit Integer
        • 16-Bit Integer
        • 32-Bit Integer
        • Single Precision Floating Point
        • Double Precision Floating Point
        • Single Precision Complex
        • Double Precision Complex
        • Array Descriptor
      • 8.3.3.2 Bytes Following Main Table
    • 8.3.4 Data Display
• 9 Restrictions on Changes
• A Formal Syntax of Card Images
• B Proposed Binary Table Conventions
  • B.1 ``Variable Length Array'' Facility
  • B.2 ``Multidimensional Array'' Convention
  • B.3 ``Substring Array'' Convention
• C Implementation on Physical Media
  • C.1 Physical Properties of Media
  • C.2 Labeling
    • C.2.1 Tape
    • C.2.2 Other Media
  • C.3 FITS File Boundaries
    • C.3.1 Magnetic Reel Tape
    • C.3.2 Other Media
  • C.4 Multiple Physical Volumes
• D Suggested Time Scale Specification
• E Differences from IAU-endorsed Publications
• F Summary of Keywords
• G ASCII Text
• H IEEE Floating Point Formats
  • H.1 Basic Formats
    • H.1.1 Single
    • H.1.2 Double
  • H.2 Byte Patterns
• I Reserved Extension Type Names
• J NOST Publications
• Index