The 11-Parameter propagator models geostationary satellites using 11-Parameter files. The propagator uses an algorithm documented in Intelsat Earth Station Standards (IESS) IESS-412 Rev. 2 (PDF), available at www.celestrak.com.
Analysis Time Period
Set the satellite's analysis time period by setting the Start Time, Stop Time, and Step Size. The Step Size is the interval between computed ephemeris output points.
Managing 11-Parameter Files
Click Add to browse to an 11-Parameter file and add it to the satellite's state definition. You can add multiple files to a single satellite, but they must all have the same identifier, which is displayed above the table once a file has been added. The table automatically sorts the file entries by their epochs. Click on an entry in the table and then click Remove to delete it from the table.