The STK satellite database provides Two-Line Element (TLE) sets, which are not valid for interplanetary spacecraft. Ephemeris files for many interplanetary spacecraft are archived and continually updated, in SPICE format, at the NASA Navigation and Ancillary Information Facility, located at http://naif.jpl.nasa.gov/naif/. For more information about these file formats, consult the links at the bottom of this page.
Obtaining ephemeris for interplanetary spacecraft
1. Navigate to http://naif.jpl.nasa.gov/naif/.
2. Using the navigation bar on the left, select Data.
3. Click on one of the links under the Active Flight Project and Non-Archived SPICE Kernels section, such as Outer Planet Missions.
4. For the given mission, click the link inside the 'spk' column. This will launch an ftp folder view.
5. The ftp folder may contain many *.bsp files which are compatible with STK. Some folders may also contain text files, such as 'aareadme.txt' which explain the naming conventions and contents of each *.bsp file. Careful attention should be paid in order to obtain actual spacecraft trajectory 'spk' files and not planetary ephemeris or other related files.
6. Download the desired spacecraft ephemeris files into any directory on your computer.
7. To load these into STK, create a satellite using the SPICE propagator and browse for the saved file.
Note that SPICE ephemeris files may contain many segments and STK may not display all of them by default. Use the segment slider bar to view properties for all segments. Set a Start Time and Stop Time for the satellite to cover the period of interest.
Note that SPICE files use identifiers for a given spacecraft since a single SPICE file may contain information about multiple objects.
For more information on TLEs and the algorithms used to propagate them, consult the STK Help or http://celestrak.com/NORAD/documentation/.
The SPICE format supports many different kinds of spacecraft information besides ephemeris. For more information on SPICE, consult the STK Help or http://naif.jpl.nasa.gov/naif/aboutspice.html.