8.7.1 Intelsat eleven Parameter Prediction (I11)

The analytical propagation of a satellite in the eleven Parameter format was originally released by Intelsat IESS412 document. The calculations which are used in the sat-nms ACU are based on Review 3 of this document.

The calculation based on the given algorithm and the provided eleven parameters are very simple:

• Calculate from the I11-Data the satellite position for the particular time of interest.
• Calculate from the satellite’s prediction position and the earth station’s known position the geometric pointing angles.
• Finally theses pointing angles are corrected for the effects of atmospheric refraction.

To verify the satellite position calculation, there is also the satellite position after 170h available. The sat-nms ACU use this parameter to verify the correct entry of the data.

The data have to be entered in the menu ‘Orbital Data’ in the Section I11 Elements. There are 99 datasets possible. To activate a dataset it must be set in the Tracking Parameter menu in the Section Prediction Parameters I11 Ephemerides. To follow a satellite with the chosen dataset, the Tracking Mode have to be set to ‘I11’.

Remark:

• The parameter ‘max. prediction age’ will limit the execution time of the prediction Tracking. After the limit is reached the antenna will stop the execution and an alarm will be displayed in the pointing screen.
• If the calculation distinguish from the 170h prediction value an invalid I11 Alarm will be displayed.