Flexible Image Transport System
(FITS)

The astronomical community has adopted the Flexible Image Transport System (i.e. FITS) format as the default standard for the exchange of data between institutions. The FITS file format is platform independent, supported by many institutions, and endorsed by both NASA and the IAU. For these reasons FITS is the recommended file format for archiving data at STScI. A description of the MAST data format recommendations can be found in the MAST Data Format Guidelines document.

MAST and the HST project, following the recommendations of the IVOA, has been developing a standard for storing spectral data in FITS format. As shown in our FITS File Formats table, spectral data has been stored in a wide variety of formats, making it difficult for Virtual Observatory developers to write programs for coplotting spectra from various missions. The proposed format uses binary tables to store vectors of flux, wavelength etc. with each row in the table representing a single spectrum. Once completed, this will become the recommended format for projects planning to archive spectral data within MAST.

For the latest documentation on FITS, see the FITS Documentation Page maintained by the FITS Support Office at Goddard Space Flight Center. The latest standard, the
FITS Standard Document Version 3.0 was adopted in July, 2008.

The somewhat out of date FITS Standard Document Version 2.0 and the even more out of date FITS User's Guide are both available locally. The User's Guide provides examples and infomation on the early history of FITS as well as a thorough description of the early formats, but does not include changes made after 1997. Note that although the Version 2.0 standard is now out-of-date, it may be more appropriate for describing archived FITS files created prior to 2008.