[ATM] mirror on the moon

[Douglas Hudgins]

Hi All:

In my opinion, one of the biggest failings of an optical or infrared  
telescope on the moon is that it has no advantage over the same  
telescope in space, but it costs a lot more.  First, as folks have  
noted, one has to deal with the problem of lunar dust contamination.   
Perhaps there are ways for dealing with this issue, but they all  
invoke new technology (= cost) not required to operate the same  
telescope in space.  Second, while both a space observatory and a  
lunar observatory have to be launched into space, only the lunar  
telescope has to be landed safely on another body.  Landing a  
monolithic instrument like a telescope on the moon and then deploying  
it represents a huge challenge--and it would add enormously to the  
cost of the observatory.

The other issue that has been discussed relates to exposure time.   
While It is true that Hubble's maximum exposure times are limited, it  
is not clear to me that, at the current state of the art, a single  
long exposure image has any real advantage over a combination of  
shorter exposures that add up to the same total exposure time.   
Moreover, I think that point is moot with regard to the advantages  
offered by a lunar observatory.  Hubble's limitation stems from the  
fact that it is in low Earth orbit (LEO; a choice that was made by  
NASA years ago to ensure that the Shuttle had something to do...er,  
to ensure that it could be serviced by the Shuttle).  Future space  
observatories will occupy orbits that are much more conducive to  
their operation.  For example, JWST will reside at the Earth's second  
Lagrange point (L2; see ngst.gsfc.nasa.gov/orbit.html).  Thus,  
residence on the lunar surface will offer no operational advantage  
for future observatories.

Of course, a cynic might suggest that the drive to put a telescope on  
the moon has more to do with the search for reasons to justify NASA's  
return to the moon than it does the intrinsic merits of a lunar  
observatory, but I'm sure no one is that cynical...

Doug



On Jun 24, 2007, at 2:13 AM, hermit wrote:

> I was a little disappointed though.
>
> http://www.reuters.com/article/scienceNews/idUSN2140065620070621
>
> Ken Lowther
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