The Flexible Image Transport System (FITS) is an image format
invented by and primarily used by astronomers. One of the founding
principles of the format is that all records must be 2880 bytes long.
(2880 is divisible by both the byte and word lengths of all computers
available at the time the standard was proposed: 6,8,12,16,18,24,32,36,48,60 and 64.)
Thus a file size should be divisible by 2880. I just saved a JPG as
FITS using gimp 1.1.9 and the file size is 1175580 bytes. This violates
the FITS standard! Granted, most FITS readers will let this slip by
with no ill-effects. But, the data should be padded with zeroes to
fill out the record.
The original paper describing FITS may be found at:
More current information on the FITS standard may be found at:
http://www.gsfc.nasa.gov/astro/fits/fits_home.html and http://www.cv.nrao.edu/fits
University of Maryland, College Park