Depending on the version of STK® digital mission engineering software you are using and the planetary ephemeris your instance of the STK application is set to use, the outer planets will be modelled for a period as specified below:
• 1950 to 2050 when using the JPL Developmental Ephemeris (DE) 421 File
• 1950 to.2150 when using the JPL Developmental Ephemeris (DE) 430 File
• 1950 to.2150 when using the JPL Developmental Ephemeris (DE) 440 File
To check which version of the DE file you are using and the duration of the data it contains, create a custom report of the
Planetary Eph Info data providers on your scenario level.
JPL releases new DE files periodically, either as general purpose updates or as updates targeted for specific missions. See the Help topic
Central Body Ephemerides for more information.
To model the outer planets for a period from 1900 and 2500, you can replace your default JPL DE with DE422, which is a long-term ephemeris that replaces the former long-term ephemeris DE406. Unlike DE406, DE422 includes lunar libration data when modeling the orientation of the lunar-fixed reference frame. Also unlike DE406, there is no degradation of accuracy to conserve space in DE422. The overall available span of DE422 is year -3000 to +3000, though the period of the file on the AGI Planetary Supplement disk/download (11.0.1 or newer) is 1900-2500.
For an overview of all planetary ephemerides available, you can visit the website for
JPL Planetary and Lunar Ephemerides. Additionally, JPL occasionally announces new DE versions in the
JPL IPN Progress Reports. An example is the
report for DE421.
To configure the AGI version of DE422, follow these steps:
1. Install the STK Planetary Data Supplement that matches your STK application version. This will copy a file named plneph.422 to:
C:\Program Files\AGI\STK 12\STKData\PlanetEphem\lendian\
2. Locate and open the _Default.ap file. Most users will find _Default.ap in their "User" folder.
C:\Users\<you>\Documents\STK 12\Config\Defaults\_Default.ap
If the file is not there, you can force its creation by changing any setting located under Edit > Preferences in STK.
3. Edit the _Default.ap file under the section titled BEGIN DefaultCentralBody. It should read as follows:
PlanetaryEphFile plneph.422
4. Restart the STK application.
5. (Optional) Create a custom report for the scenario object that includes the Planetary Eph Info data provider and run the report. It should indicate that the STK application is using the plneph.422 file and then report the available date range of the ephemerides in the format shown below.
Source Start Date (UTCG) :: End Date (UTCG) :: Contains Nutation :: Contains Librations
