# A Framework for Assessing the Interference from NGSO Satellite Systems to a Radio Astronomy System
## 4 Simulation Results
### CDFs of Satellite EIRP  
In order to avoid interference from NGSO satellite systems to an RAS telescope, it is necessary to carefully consider the CDF of the NGSO satellite's EIRP. This function depends on various factors, including the satellite's radiofrequency parameters, the spatial distribution of users, and the constraints on beam scheduling. To avoid interference, NGSO satellite systems may need to take measures such as ensuring that the GSO arc avoidance angle of the NGSO satellite beam is not less than 18 degrees, as shown in Table 2. The mean values of EIRP in the field of view of the NGSO satellite at different latitudes and the CDF curve of the EIRP at different azimuth and elevation angles are depicted in Figures 6 and 7, respectively.  
As the subsatellite point moves from low to midlatitudes, a belt can be observed in the centre of the satellite's field of view. This belt shifts to higher elevations as the satellite's latitude increases until it is no longer visible. The formation of these belts is largely due to the requirement that the GSO arc avoidance angle must be at least 18 degrees, which limits the mean EIRP by preventing the beam from pointing into the belts. The latitude of this belt is generally higher than the latitude of the subsatellite point, except at zero latitude, where the inline interference event has the same latitude as the subsatellite point.  
The CDFs of the EIRP at different directions is given in Figure 7. In Figure 7, the direction corresponding to the elevation and azimuth angles of \(-2.5\) degrees and \(-2.5\) degrees, respectively, is located in the exclusion zone of the GSO satellite system; the direction corresponding to the elevation and azimuth angles of 57.5 degrees and \(-2.5\) degrees, respectively, is located outside the coverage area of the NGSO satellite. The EPFD levels corresponding to these two directions are small for the same probability. This is mainly due to the fact that the beam cannot be pointed to the directions and therefore, the radiated EIRP is small. From Figure 7, the CDF curves become tighter with different directions.  
\begin{table}
\begin{tabular}{c c c} \hline
**Parameter** & **Value** & **Unit** \\ \hline Orbit height of NGSO satellite & 1200 & km \\ Orbit height of GSO satellite & 35,678 & km \\ Radius of the Earth & 6371 & km \\ Bandwidth of satellite beam & 250 & MHz \\ EIRP & 34.6 & dBW \\ Centre frequency & 10.725 & GHz \\ Diameter of satellite antenna & 0.4 & m \\ Max gain of satellite antenna & 32 & dBi \\ GSO arc avoidance angle & 18 & deg \\ Minimum frequency of RAS telescope & 10.6 & GHz \\ Maximum frequency of RAS telescope & 10.7 & GHz \\ EPFD threshold & \(-160\) & dBW/m\({}^{2}\)/100 MHz \\ Allowable probability of exceeding EPFD threshold & 2\% & - \\ \hline \end{tabular}
\end{table}
Table 2: Simulation parameters.  
Figure 6: The mean EIRP of the satellite: (**a**) the latitude of the satellite is 0 degrees; (**b**) the latitude of the satellite is 20 degrees; (**c**) the latitude of the satellite is 40 degrees; (**d**) the latitude of the satellite is 60 degrees.  
This is mainly due to the natural separation between the NGSO and GSO satellite systems at high latitudes. There is no need to take any interference avoidance measures and the beam pointing within the satellite coverage is uniformly distributed. Therefore, there are similar CDFs of the EIRP within the coverage.