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Cosmographia Important Details

Ephemerides of Solar System Bodies

The SPICE-enhanced version of Cosmographia comes with ephemerides (SPK files) for the planets, major planetary satellites, and two asteroids, covering the period of 1950 JAN 01 through 2049 DEC 31. See notes below about obtaining additional SPK files to handle bodies not contained in this default set.

The Cosmographia information provided here and in the on-line User's Guide applies only to the "SPICE-Enhanced" version of Cosmographia. To obtain full SPICE accuracy one should use this version of the tool.

Sizes, Shapes and Rotation Rates of Solar System Bodies

The planets and all regularly shaped satellites have their orientation, size and shape defined using SPICE Planetary Constants Kernels (PCK) data. The small, irregular satellites use spheroidal shapes.

Getting SPICE Kernels

If you don't already have the SPICE kernels (data files) you wish to use in your Cosmographia session, you may be able to get them from one of several sources.


NAIF maintains the SPICE archives for NASA's planetary missions. These archives are well organized, carefully constructed and as complete as possible. You can download all of a mission's SPICE archive, or a subset based on user-provided begin and end dates. You can also download a number of generic kernels—those not tied to a specific mission. You may read more about these possibilities and obtain the kernels from the Data page of the NAIF website.

Other Repositories

Other space agencies and individual flight projects maintain their own SPICE collections, some of which are open to the public. Pointers to some of these repositories are found here. NAIF is not able to obtain such data on your behalf.

Horizon's Comet and Asteroid Ephemerides (SPK kernels)

The NAIF or other agency repositories probably contain comet or asteroid SPK kernels for bodies associated with their mission archives. However, you yourself may create and download an SPK kernel for any comet or asteroid registered in the Horizons Ephemeris System maintained by JPL's Solar System Dynamics Group.

Make Your Own SPICE Ephemeris (SPK kernel)

Persons who are rather familiar with SPICE and celestial mechanics, and having access to an alternate source of spacecraft ephemeris (trajectory) data, might be able to make their own SPK kernel using the MKSPK utility program available under the Utility and Application Programs page of the NAIF website.

Kernel Types Not Used

Events Kernel (EK) - It might seem logical that the SPICE Events Kernel would be used to provide observation information to Cosmographia. However, the EK is rarely used today, and there is no connection between it and the "observation" JSON file used by Cosmographia.

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