How do I get ephemeris for comets or asteroids and load it into STK?

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QuestionHow do I get ephemeris for comets or asteroids and load it into STK?
Answer
If you need to load asteroids or comets into STK, you can download the ephemeris from the JPL Horizons system and then load them into STK using the attached reader
 

Download the data

  1. Go to the JPL Horizons web interface and use the following settings:
JPL Horizons settings
  1. Set the following table settings:
    User-added image
     
  2. Save the resulting file as a txt file.

Register the Ephemeris Reader

  1. Unzip the attached JplHorizonsEphemeris.zip files.
  2. Register the plugin using the steps from the "How do I register a .wsc type plugin" FAQ.

Load ephemeris file

  1. Start up STK.
  2. Create a new scenario.
  3. Add a satellite. After you change the propagator to StkExternal, you should see the new "JPL Horizons Ephemeris Reader" as an option. You can now load the file you had downloaded from the Horizons website.

STK Ephemeris GUi

 

Notes

  1. Horizons produces vector reports in Julian Data Barycentric Dynamical Time (TDB). Conversion to UTCG occurs when importing the ephemeris into STK, so reports from JPL Horizons in TDB will yield a ~70 second difference from UTCG.
  2. In Observer reports, Horizons considers an "Apparent" measurement to include the effects of light time delay and aberration, whereas STK defines "Apparent" as the effects of light time delay only. Aberration is available as a separate option. 
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