In Figure 9, the link budget is shown for ground antennas of “0 dB”. Is that dBi, dBd, dBiC, or what?
dBd, I think. This question has prompted an update to the tools used to evaluate link budgets and future charts will be more precise. 6. In Figure 9, what is assumed about the spacecraft attitude? Does the link margin shown in Figure 9 assume that the spacecraft is perfectly nadir-pointing? If so, that’s unrealistic. The current crop of magnetically-stabilized Microsats experiences significant very-slow fading due to attitude changes. At my latitude, I often have to switch polarizations to optimize signal strength on the AO-16 downlink. If the link margin doesn’t take this into account, it is overly optimistic (like many other link budgets published pre-launch by AMSAT). Echo will be pointed approximately towards the ground over the northern hemisphere and away from the ground over the southern hemisphere similar to the other Microsats. The dynamics of this can be adjusted somewhat by the active magnetic attitude control system (the “torquer”) but Echo will generally point in the same
