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The Question

(Submitted May 28, 1997)

Would you have by any chance any information on possible NASA projects as regards observing from the Moon? Would the dark side of the moon be a good place for a telescope?

The Answer

There are many advantages to putting telescopes on the Moon. http://aerospacescholars.jsc.nasa.gov/HAS/Modules/Earth-to-Mars/6/4.cfm proposes an optical telescope on the Moon.

Optical telescopes can be on either the Nearside or the Farside of the Moon. (The term 'dark side' is no longer used because it confuses people into thinking that the Sun doesn't shine there. In fact, the Sun shines on both sides equally.) There is very little atmosphere to scatter light from the Sun or Earth, so you can use the telescope all day and all night (14 Earth days each).

Radio telescopes are best placed on the Farside, to block out the radio noise of Earth and its increasingly chatty retinue of satellites. Radio bends around small obstacles so it is harder to block out. Half a mile from the point where you can no longer see any of Earth would not be enough. (Besides which, an effect called 'libration' means that Earth wanders slightly in the sky over the course of a month.) Data communications from the observatory to Earth should be done by laser through a Lunar satellite to further avoid noise.

As for whether you would want a manned observatory, probably not. Even on Earth, there is a tendency to lower the staffing of telescopes for budgetary reasons, and let the astronomers control the telescopes through the international computer networks from their own offices. And it costs a lot more to send an astronomer to the Moon than it does to send her to Arizona. In addition to being expensive, people are noisy, smelly, and filthy. Even when she's not kicking dust onto the mirror, she'll be talking on the radio, stomping around, and venting gas. That's the sort of thing we're trying to get away from.

A good source of information on NASA's future plans is the following WWW page:

http://www.nasa.gov/missions/solarsystem/explore_main.html

In general, the idea of putting observatories on the Moon has been around for quite some time. A few years ago, the Bush administration suggested that NASA look into putting a man on Mars. One step in this process would be to produce a lunar station as a testing ground.

Assuming that this lunar station would happen, many astronomers discussed building observatories on the Moon. In their calculations, this would be cost-effective only because the prior infrastructure would already be there.

As it happened, it was later decided that manned missions would be too expensive, so the lunar station concept was abandoned (at least for the near future). Without an already existing lunar station, the cost of building lunar observatories becomes prohibitively expensive.

As I understand it, the only near-future missions to the Moon or mars are unmanned missions to study the Moon or mars respectively.

Sincerely,
Jonathan Keohane
and David Palmer for Ask an Astrophysicist

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