From the link 'evilduck posted, it seems that's big indeed, but possibly big.

240km is a big thing, but within the realm of possibility; also I'm personally hoping someone will invent some magic mathematical trick around phased arrays or whatever, and cut that size by an order of magnitude or two :).

240km is also what's required to resolve a feature no smaller than 100km across. I'm no mathematician and I am not equipped at the moment to pretend to be one, but to resolve a feature an order of magnitude smaller, I suspect you'd need a much larger instrument.

If I did the math correctly, it turns out to be ~2400km for 10km across (changing 100 to 10 in the eq). This could very easily be wrong as I only glanced through the comment. Think of it as Kirkian mathematics.

I would file 240km under very do-able. It's nothing like, say, a solar system sized particle accelerator.

That simple? Well jeez, I don't know what I was even worried about. :D