Re: Radar visibility
Hi, Phil!
I read that, too - in a pre-1980 NASA pub on SETI. Don't have it with to check citation info, but that might give interested parties a start on tracking it down.
I recall it also saying that, in that region of the EM spectrum, Earth is a far brighter source than the Sun - which implies to me that the Doppler effect of our orbital motion would make it much easier to decuce that our transmitters were orbiting a parent body and thus much more likely to be artificial. Besides, what natural object radiates preferentially at those wavelengths?
E'