FITS's 80-character headers made it astronomy's universal data format

Astronomers in the 1970s shared data through a mess of incompatible formats. In 1981 Don Wells and colleagues described FITS — the Flexible Image Transport System — built on fixed 2880-byte logical records and 80-character keyword=value header cards, followed by the data blocks.

The initial description was deliberately minimal. As Eric Greisen later wrote, a detailed coordinate specification was seen as too controversial and risky, so the authors kept it simple to maximize the chance of wide agreement and use. That bet paid off: at the 1982 IAU General Assembly, Commission 5 recommended the FITS tape format for use by all observatories.

NASA endorsed FITS for its missions, and a NASA committee later codified the standard formally in 2001. Because FITS carried both the data and its descriptive headers in one file, it became the transport, analysis and archival format of astronomy — still in use for spectra, images and data cubes four decades on.

Keep the format simple enough for everyone to implement

80-character headers were trivially readable and writable on any machine.

A minimal v1 avoided the controversy that a complete spec would have triggered.

IAU and NASA endorsement gave agencies and archives permission to standardize on it.

Header keywords kept metadata with the data, so files stayed self-describing.

A format wins by making the first implementation trivial: ship the minimal spec, earn the endorsements, then extend it backward-compatibly.

FITS remains the standard data format endorsed by NASA and the IAU; the FITS Support Office maintains the definition, libraries and a conformance verifier, and extensions like world-coordinate-system keywords have grown the format without breaking old files.