Apparently the highest gain antenna NASA has is 61.7 dbi at the relevant frequency. If they used 5 watt transmitters, that would be like running 4.5 megawatts into a conventional dipole antenna. The reality is NASA probably used many tens or even hundreds of watts to contact the spacecraft. As an amateur radio operator I assure that is out of reach for most of us.

> Apparently the highest gain antenna NASA has is 61.7 dbi at the relevant frequency.

Don't forget angular resolution. Because of the antenna's geometry, it's misleading to describe its gain without also mentioning that the gain applies to a very small angle -- which, depending on the circumstances, may be a great advantage if it needs to reject interfering sources.

61.7dbi, while it represents a peak rather than a more descriptive statistic, does go a ways toward describing 'angular resolution', or rather, how tight you can make the beam of the transmitter.

It's easiest to think about it thusly: You steal part of the power that would normally go out equally to a sphere ("isotropic radiator") and you redirect that power to a smaller part of the sphere. If you can successfully redirect the entire power into only half of the sphere (1 hemisphere), you get +3db. Keep slicing that in half and you add +3db each time.

61.7dbi gain necessarily means that the power felt at the center of the target is 1545883 times as powerful as it would be if you were using an isotropic radiator, given the same number of input watts. If you have successfully concentrated the power that much, something at the target's range isn't going to detect sidelobes much at all.

This isn't a technical summary - radiation patterns are never absolute step functions and there is indeed a distinction between peak power and usable area... it's just not as relevant as the huge number represented by 61.7dbi, for any remotely gaussian distribution of signal.

Would you even need a 61.7 db gain antenna? It's going to be doing a near earth flyby.