a planetary surface extension for FITS metadata

Chiara Marmo et al.

in the VESPA EUROPLANET 2020 collaboration

in collaboration with the USGS Astrogeology Center (Trent Hare)

May 2019 IVOA Interoperability Meeting

Just another new format in Planetary Science?

  • FITS is not new (Hayabusa, Akatsuki, Dawn, Rosetta, ...)
  • PDS metadata, are optimised for archiving, not for processing.
  • FITS provides interoperability during the entire processing chain.

Does FITS fit Planetary Science?

  • Compatible with PDS (version 3 and 4) archiving constraints
  • Ready for multi-digital objects (using Multi Extension FITS)
  • Open Source, stable processing libraries (e.g. CFITSIO, astropy, ...)
  • Efficient and well standardised World Coordinate System description (but for 3D systems)

How to fit Planetary Science even better?

  • Adding standard keywords for 3D reference surfaces
  • Adding standard keywords for linear (in meters) WCS
  • Mapping standard FITS keywords to PDS
  • Interfacing planetary software with FITS (in particular GIS)

keywords for 3D reference surfaces

Keyword Type Status Definition Unit
WGCCRECS string reserved DOI of the WGCCRE report
A_RADIUS real mandatory semi-major radius, usually equatorial meters
B_RADIUS real mandatory intermediate radius, usually equatorial meters
C_RADIUS real mandatory polar radius meters
OGCCODE string reserved OGC code (if any)

keywords for linear WCS

Alternate WCS description available in FITS

Need of CTYPE standardization (Coordinate types - projection type)

For angular coordinates the standard says xLON xLAT or yzLN yzLT, where x or yz correspond to the target body.

For projected coordinates in meters : yzPX as Projected X yzPY as Projected Y.

Target body codes

Body CTYPE Code
Earth EA
Moon SE
Mercury ME
Venus VE
Mars MA
Jupiter JU
Saturn SA
Uranus UR
Neptune NE
Satellites (other than the Moon) ST
Asteroids AS
Dwarf Planets DW
Comets CO

Projection codes

FITS Name FITS Code PDS4 Name
Zenithal Equidistant ARC Azimuthal Equidistant
Zenithal Perspective AZP General Vertical Near‐sided Projection
Plate Carre CAR Equirectangular, Miller Cylindrical
Equidistant Conic COD Equidistant Conic
Conic Equal‐Area COE Albers Conical Equal Area
Conic Ortomorphic COO Lambert Conformal Conic
Mercator MER Mercator, Oblique Mercator, Transverse Mercator
Polyconic PCO Polyconic
Sanson‐Flamsteed SFL Sinusoidal
Ortographic SIN Orthographic
Stereographic STG Stereographic, Polar Stereographic
Gnomonic TAN Gnomonic
Zenithal Equal‐Area ZEA Lambert Azimuthal Equal Area

FITS to PDS keyword mapping

FITS Format for Planetary Surfaces: Definitions, Applications, and Best Practices FITS Format for Planetary Surfaces: Definitions, Applications, and Best Practices

FITS GIS interoperability

Planetary WCS implementation in GDAL - Geospatial Data Abstraction Library: done in GDAL V3.0


  • Planetary WCS implementation in WCSlib (and astropy?)
  • Planetary WCS extension in IAU FITS standard
  • Planetary WCS extension as IVOA standard/recommendation

Planetary Data FITS conversion

References are available at

Example scripts are available at

Thanks for listening!