Darkside observatory

I am unsure if we are thinking the same thing here
then. My idea of a lunar radio observatory is more
ala VLA then arecibo. Each dish exists with its own
independent power. For this model, RI generator would
be sufficient. OK, I see how one can get around the need for a full-up nuclear reactor, then. Still, I feel intuitively that the electrical requirements for even a single dish of the VLA ought to be greater than those for a small probe like Voyager or Cassini. And given all of the hullabaloo over Cassini's single RI generator, I hate to think what the backlash would be against a plan to launch several dozen.
Not sure on what this comment is suppose to imply.
There is a large difference between human colony and
an automated scientific outpost. I don't recall
anywhere in O'neil's writings that ALL things had to
be off planet. No, but O'Neill pointed out that any operation requiring electrical power can rely on solar energy if taking place outside the shadow of a planet or moon. He also pointed out the advantages of building large yet flimsy structures in 0-G.
For this scientific study, not seeing the Sun is
advantages as there will not be noise from it. This
has nothing to do with a high frontier perspective. If noise from the sun is a problem, then it will be a problem half the time on the moon.
As per my earlier comments, aero braking is unnecesary
if you use a landing similiar to that which pathfinder
used. Pathfinder had already been slowed by the atmosphere by a very significant amount before the balloons were inflated. I just can't see a Pathfinder type landing on the moon. I also can't see designing a radio telescope to fold up, crash to the lunar surface surrounded by balloons, bounce and roll for God knows how long (remember, no air resistance), and then open up and function.
An arecibo-class radio telescope I do not think is
practical. Most astronomers want to look at the very
low frequencies which you cannot see on Earth (10-10^4
m wavelengths). For this to happen, we are talking
about 100 km size area. Now Drake's original idea
called for a single dish made by lining a whole crater
with wire, the more modern approach to this is to use
an interferometer. It's good that they're moving away from the "lining a crater" approach. It looks tempting, but craters are actually the wrong shape for a dish.
I am not in a position to argue these points at this
time. I am way to unfamilar with the HEO concept to
even begin to estimate these costs and weights. The
biggest concern here is that this is a recurring cost. I'm not sure what you mean by "recurring cost". I would interpret recurring costs to be like the cost of ongoing maintenance. And here, a dish in HEO once again has the advantage over one on the lunar surface.
The big kicker would be if the weight of the shielding
required an even bigger rocket. This could boost up
the price of the launch dramatically. Not as dramatically as you might think. The shield can be even less substantial than the dish. But again,
without real numbers, this discussion is moot. True, without real numbers we can't draw hard-and-fast conclusions. But I have my expectations.
At this point, all we can say is that the weight would
be higher for HEO. Granted (unless the weight of the stiffeners required by 1/6th G vs. 0 G outweigh the shield). So the question becomes: Is the trade-off involved in the requirements for the shield worth the operational advantages? I expect it is.
The only other issue I have with the shielding concept
is the amount of station keeping required to make it
effective. This can be reduced to some extent using
ion thrusters but again, I would need to see a more
developed HEO plan to see the total affect. Another way it can be reduced is by extremely accurate position sensing, such that drifts are corrected early rather than later. And lasers enable extremely accurate position sensing.

I may be wrong, but this is what I suspect: The body of work which suggests the moon for astronomy did not start out with a blank slate and then ask the question, "Which is more advantageous: an orbital location or the lunar surface?", and then dropped the orbital option after weighing it's disadvantages. They started out with an assumption that an observatory needs to be on the moon because, as everybody knows, in order to build an observatory you first have to find a plot of land to build it on. This assumption was never once voiced out loud nor was it even on a particularly conscious level. Having then gone down the path to the moon, and only after being asked what advantage the lunar surface would have over an orbital location, they offer up a few arguments which sound plausible on the surface but don't bear close scrutiny, and in truth are ad-hoc explanations to justify automatic assumptions made far back up on the path.
Regards, Mike Combs