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There are such things as moon-bounce communication whereby radio signals are 'bounced' off the lunar surface to a distant location on Earth. This mechanism may be likened to the way a mirror reflects light.

This article writes to say

it has been discovered that radiowaves, unlike light and infrared radiation, are reflected back to the Earth principally from a small region at the center of the visible disk

Radio communication on Earth is strongly dependent upon the ionosphere - a layer of the atmosphere comprised of charged particles sympathetic to radio energy. Luna does not have an ionosphere but lunar dust levitates. The dust is ionized by the Sun.

What I am curious about

  • Is long range radio communication possible on the lunar surface?
  • Was/Is radio propagation on the lunar surface part of any mission/programme to-date (or proposed)?
  • Could analysis of the signal quality on CSM/LM communication tapes of the Apollo program yield anything useful in this context?
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2 Answers 2

The lack of an ionosphere seems, intuitively, to mean great difficulty in propagating over-the-horizon radio waves, but according to this paper by Robert M. Manning, it should, in theory, be possible to radio to another point beyond your line-of-sight even without the use of a lunar communications satellite. From the abstract:

Two potential low-frequency propagation mechanisms characteristic of the lunar landscape are the lunar regolith and the photoelectron induced plasma exosphere enveloping the Moon. Although it was hoped that the regolith would provide for a spherical waveguide which could support a trapped surface wave phenomena, it is found that, in most cases, the regolith is deleterious to long range radio wave propagation. However, the presence of the plasma of the lunar exosphere supports wave propagation and, in fact, surpasses the attenuation of the regolith. Given the models of the regolith and exosphere adopted here, it is recommended that a frequency of 1 MHz be considered for low rate data transmission along the lunar surface.

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This is from logic and opinion, no references:

Is long range radio communication possible on the lunar surface?

No. The dust around the moon will be much more discrete than the ionosphere which acts more like a continuum. It would be a bit like trying to see your reflection in ground up mirrors dust. If you have the appropriate wavelength then it might be possible, but it would be dependent on a high enough number of particles levitating.

Was/Is radio propagation on the lunar surface part of any mission/programme to-date (or proposed)?

I assume this question is about long range propagation. I've had a look over everything I could think to look over and I haven't found anything substantial, I assume because it wouldn't work.

Could analysis of the signal quality on CSM/LM communication tapes of the Apollo program yield anything useful in this context?

Yes. This could be used to test if the frequencies used have the wavelength. It may also be used to predict to what which frequency would be required, since there would be a degree of Doppler shift in the frequency at times and you might cross into a frequency that produces some measurable 'bounce', after that you could extrapolate the best frequency.

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