Planet Properties

Defining a Planet

The options on the Definition page enable you to identify the ephemeris source for a planet. First, choose between using a Central Body (Sun, Moon, or a planet) or specifying the ephemeris with an external file. If you select a Central Body, then choose the desired Ephemeris Source. The set of available ephemeris source options depends on the Central Body selected.

Option Description
Central Body

Select a celestial body (Sun, Moon, or a planet) from the list.

To create a new central body, start by selecting the AsteroidTemplate, which has few mission-specific settings of its own. You can then rename the AsteroidTemplate object in the Object Browser and redefine one or more of its parameters.


Ephemeris Source Depending on the Central body, one or more of the following alternative sources is available:
  • Default - Use STK's internal definition of the Central Body (contained in the STKData\CentralBodies\PlanetName\PlanetName.cb) to generate ephemeris.
  • DE440 - Use the JPL DE file. The file covers a time span from 1960 to 2060 and is available for the primary planets, Pluto, Earth's Moon, and the Sun.
  • Analytic ephemeris - Use an analytic propagator. Available when orbital elements are known for the Central Body about its parent.
  • SPICE - Use the SPICE toolkit to generate ephemeris. Available only if a SPICE ephemeris file (*.bsp) has been loaded for the selected planet.
File Use a planetary ephemeris (*.pe) file to define the planet.
Filename Type the file path and name of the planetary ephemeris file or use the button to select a file.
Auto Rename The Auto Rename option saves time in naming planets. If you want the planet's name to be the same as that of the body it represents (e.g. you want to call Mars "Mars"), select this option when defining the object. The name of the planet in the Object Browser and visualization windows automatically changes to the name of the selected body.
Radius Radius values (see reference below) are read-only and update automatically.

Ames R. Wertz (ed.), Spacecraft Attitude Determination and Control, Kluwer Academic Publishers, 1990, p. 816, Table L-2.