Xref: utzoo sci.space.shuttle:631 sci.space:5127
Path: utzoo!mnetor!uunet!husc6!mailrus!ames!oliveb!sun!moria!dunc
From: dunc%moria@Sun.COM (duncs home)
Newsgroups: sci.space.shuttle,sci.space
Subject: Re: Moon or Mars? Editorial in _Air & Space Smithsonian_
Message-ID: <48414@sun.uucp>
Date: 6 Apr 88 15:36:17 GMT
References: <47032@sun.uucp> <1290@hubcap.UUCP> <4076@whuts.UUCP> <1022@thumper.bellcore.com>
Sender: news@sun.uucp
Reply-To: dunc@sun.UUCP (duncs home)
Lines: 41

In article <1022@thumper.bellcore.com> karn@thumper.bellcore.com (Phil R. Karn) writes:
>                                  ...
>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.

There's no reason a relay satellite couldn't store and forward in exactly
the same way.

>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

On the surface solar panels are illuminated for roughly half the time too.
Yes, you have to store the energy longer, but you have planet worth of raw
materials to assist.  In return you get to make uninterrupted observations
for as long as you choose.  The orbital observatory spends half the time
with the Earth shouting in it's ears and half the remainder with the Moon
between it and whatever it's interested in.

>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.

Could you explain again why having the antenna cycle from sunlight to shade
every few tens of minutes provides better stability than having it happen
every two weeks?

>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.

Probably true.  On the other hand, it's probably easier to get all the bits
pointed in the same direction when they're mounted on a large common platform.

				--Dunc