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From: karn@thumper.bellcore.com (Phil R. Karn)
Newsgroups: sci.space.shuttle,sci.space
Subject: Re: Moon or Mars? Editorial in _Air & Space Smithsonian_
Message-ID: <1022@thumper.bellcore.com>
Date: 5 Apr 88 18:56:41 GMT
References: <47032@sun.uucp> <1290@hubcap.UUCP> <4076@whuts.UUCP>
Organization: Bell Communications Research, Inc
Lines: 41
Summary: it's been done

> ... The dark far side of the
> : moon..." being a good place to conduct " ...sensitive radio astronomy...
> : without interference from terrestrial signals."

Yes, it's a great idea. In fact, it's already been done. Only it was an
unmanned probe in lunar orbit instead of a manned base on the surface. 
The spacecraft recorded its observations during the time it was shielded
from earth, and it relayed them back down when earth was visible.

I really wish people would stop clutching at straws, looking for every
possible application of their pet man-in-space project when many (if not
most) of the tasks can be done far more cheaply and effectively with
unmanned spacecraft. In the case of lunar-shielded radio astronomy,
lunar orbit makes a lot more sense than the lunar surface for several
very good reasons:

1. You need communications channels back to earth. A radio telescope on
the far side of the moon would need relay satellites in lunar orbit for
this purpose. These satellites would themselves have to transmit within
view of the far side of the moon, possibly polluting the very spectrum
you spent so much to view in a pristine state. On the other hand, a
telescope in lunar orbit can provide its own store-and-forward relay. It
need not transmit anything at all while it is actually observing.

2. You need power. This is much easier to obtain in orbit, since solar
panels will be illuminated for roughly half of each orbit. On the
surface, you will almost certainly need nuclear power sources to carry
you through the long 2-week lunar night.  Thermal control is also much
easier in orbit. Of course much of a surface station could be buried to
help level out the day/night temperature fluctuations, except for the
antennas -- and these are likely to be very susceptible to severe
thermal-induced distortions.

3. You need large antennas. You can build truly awesome arrays in zero-gee
that require very little mass. Not quite as easy even in 1/6 G.

Even Arthur C. Clarke originally conceived of his geostationary
satellite relays as being manned. Fortunately, technological
developments (and some economic common sense) have made that romantic
notion unnecessary.

Phil