Lunar Observatories: Grand Plans vs. Clear Problems

On 12/5/06, Combs, Mike wrote:
(...)
> Yeah, I know; I too have seen that same assertion, and in more than one place. Odd, then, that NASA is proceeding on an orbital mission which will indeed do optical interferometry in space:
>
> http://planetquest.jpl.nasa.gov/technology/formation_flying.cfm
(...)

Well, Terrestrial Planet Finder goals are in fact detection and
atmospheric caracterization of Earth-sized planets, and for this it
will use a relativelly small baseline - separations in the range of 40
to 100 meters between telescopes, perfectly achievable in space. That
is far different from what could be achieved by telescopes based on
Luna with baselines of hundreds or even thousands of *kilometers*.
Such geographic-scale interferometric telescopes could in theory image
continents and even weather systems in extrasolar worlds. As far as I
understand it is simple physics, resolutions using interferometry get
better as you increase your baseline.

So if your goal is just to say that there is a pale blue dot around
such star, you really don't need the Moon. If your goal is gather more
information from the pale blue dot, perhaps you should consider the
lunar alternative.