Digest Number 509

RE: "Microwave is great for returning power to earth, because it punches through the clouds, but there's no weather on the moon, and so it's going to be more expensive by the time you've laid out multiple square kilometers of rectenna. I mean, microwaves don't focus down worth a damn from any distance unless you have huge antenna at each end. Light is easy."
I do not agree with the above. It used to be true, but not any more. Antenna theory works equally well for transmitters and receivers. I don't have the reference, but radio antenna in the US south west have recently imaged stellar objects with a resolution of afew micro-arc-seconds. With out adaptive optics, perhaps 0.7 arc seconds (i.e. nearly a million times larger (where larger is worse)) is the best one can do with visible light. With continued development, one might predict that soon microwaves will be resolved (now think aimed) a million times more accurately. Microwave generators can be individually controlled in amplitude and phase, so a solar power satellite, Moon base or redirecting could accurately control the direction and size of their beams. This field, using microwaves, which includes radio astronomy, is advancing rapidly. Sincerely, Jay Huebner