FITS (Flexible Image Transport System) is a bitmap image file format specified by International Astronomical Union (IAU). FITS files can store data in binary or text format.

FITS file applications

FITS files are manily used in astronomy for exchanging, archiving, and analysing scientific data. FITS file extension is commonly used for saving iamge frames captured with telescopes. NASA and IAU use FITS format extensively.

FITS is much more than a image format

FITS is more that a image format such as JPG or GIF. FITS files can be used to store scientific data formatted as N-dimensional arrays (e.g. 2D images) or tables with rows and columns. FITS also offers such features as saving data long with origin metadata.

FITS file structure

FITS offers a unique advantage – is stores image metadata in human-readable ASCII format in file’s header. Each FITS files contains at least one header in ASCII format of length up to to 80 characters with keyword/value data pairs. Header is followed by data block called HDU (Header-Data Unit). A file that contains a single HDU is called a SIF (Single Image FITS) file, and if it contains more tha one HDU, a MEF (Multi-Extension FITS) file.