How is the Worst Case Geometry Calculated?

The worst case geometry (WCG) uses the inputs to calculate the positions of the GSO satellite and ES that would cause the highest single entry EPFD level. If there are multiple geometries that give the same single entry EPFD level, then an assessment is done of which would occur most often by considering what is the angular momentum of the non-GSO satellite as it moves through the in-line geometry point. In cases where that is not available, the lowest elevation angle is used as that is likely to give a similar result.

The algorithm varies on direction (down, up or intersatellite) and can also vary depending upon whether the orbit repeats or is non-repeating and the type of orbit (equatorial or inclined).

For the EPFD(down) case the algorithm iterates over the PFD masks, the latitude of the non-GSO satellite and the (θ, Φ) angles as described in Section 6.3.