Advantages of the Lunar Farside for Radiotelescopes

Will Cochran

A radio telescope could do many things on the moon's farside that it could not do on the Earth or in Earth orbit. The primary advantage is shielding from terrestrial noise, and sensitive access to more of the spectrum.

Interference and/or the opacity of the ionosphere are serious limitations in the HF regions for Earth or Earth orbit instruments; the moon's farside would be ideal.

Opacity of Earth's atmosphere limits observation at many millimeter wavelengths; the moon's farside would be ideal, but except for a very large aperture, Earth orbiting instruments can take care of this range, and a cost analysis might show that it would be cheaper to put a very large aperture in Earth orbit than on the moon's farside.

Also, the radio astronomy community is in a never ending battle to protect even very tiny slices (mostly common emission line wavelengths) of the spectrum from commercial gadgetry. So to a large extent, the spectrum outside these tiny slices is gone for sensitive radio astronomy, and the tiny slices may be going.

So it appears to me that a farside radio instrument covering a very broad spectrum, say 50 KHz to 12 GHz, would be capable of making obervations that are impossible either on Earth or in view of Earth. The key is interference-free coverage of large, continuous spectral ranges. It is also probable that there are specific wavelengths of interest that are currently polluted in Earth view.