-This now concludes this sequence about the link budget. We are now capable of sizing a service or system resources to meet a given service. This link budget tool is really important. It was worth spending some time on it. It is something that is really central to the design of satellite communication systems. Here is now a "Going Further" episode in the link budget sequence. When I introduced the link budget, I did not mention several things. It will not put into question what I introduced, but it will refine our approach. Let us start with a certain number of other factors that intervene in the link budget. As I already mentioned when we talked about attenuation on the up- or downlink, it can all be impacted by rain or snow. In France, in the Ku band, thus 12-14 GHz, attenuation linked to rain or snow can reach about 5 dB. It is quite limited. But in tropical zones, it can be totally different since rain is much more dense. It is the same for the Ka band. Remember that it is between 20 and 30 GHz for satellite communications. With an equivalent climate, when we use the Ka band, attenuation can be multiplied by 6 compared to the Ku band. Ka-band systems currently deployed must face this higher attenuation. Earlier during week 5, we also talked about intermodulation products. Those are products linked to the coexistence of several carriers in the same transponder for example. These intermodulation products will deteriorate C/N0. So we must also take them into account. What else can we say? We can talk about interfering signals. These interfering signals can be intentional interferences, someone trying to jam the system, or unintentional, and simply linked to several signals that are close to each other. Two neighboring signals will mutually jam each other slightly. Unfortunately, these interfering signals will also have an impact on C/N0. They can be compared to noise. Finally, there are deteriorations linked to going from theory to practice. One can imagine, for example, that because of the mechanical limitations of an antenna, pointing is not 100% accurate. So this will of course slightly decrease the antenna gain and have an impact on the link budget as we now know it. One can also imagine that a reflector has bumps. In that case, its gain will be smaller and it will also have an impact on the link budget. Finally, I must talk about two other performance criteria. The first is called C/N. It is a direct extension of C/N0. In this case, instead of considering N0, the noise power spectral density, we consider the noise power. We multiply N0 by the effective band of the receiver. So instead of getting N0, we get N. In our link budget it is the same as subtracting from C/N0 the receiver band expressed in dBHz. So the value we get, C/N, is actually a signal-to-noise ratio since it is the ratio between the power of C, the power of the carrier, as the numerator, and the power of noise as the denominator. There is a second factor called G/T, also called figure of merit. It will qualify performance at the level of the receiver. It is simply the gain observed at the level of the receiver. So it includes the gain of the receiver antenna but also the potential losses in the following connection cables. So it is a ratio between this gain and the noise temperature of the system. Once again, when we change for decibels, we will subtract a temperature expressed in dB/K from the gain expressed in dB. All of this is called G/T and it is really a figure of merit. It allows us to know if our system is actually efficient.