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The onus for Spectrum management lies with ITU. What little I know - Space communications (as against Satellite communication) are allocated frequencies out of the S, X bands. Other bands may be allocated too - the ITU Space Service document was unavailable/pay-walled

What I'm curious about

  • Are space communication frequencies allocated per-mission, or per-agency?
  • If allocation is per-mission, are the frequencies recycled after the mission is over? E.g. Giotto
  • What is the rationale behind the allocation of micro-wave bands to space communication? Instead of, for instance, HF/VHF why are some of the micro-wave bands used? Is it merely a matter of convenient antennas, or is there more to it?
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    $\begingroup$ The allocation is done on several levels: first, by function (based, inter alia, on atmospheric absorption on the wavelength, possibility of interference), second, by nation, and afterwards national spectrum authorities assign particular frequencies. $\endgroup$ – Deer Hunter Dec 16 '13 at 19:15
  • $\begingroup$ @DeerHunter Updated the last part of the question; I meant why use microwaves instead of a different part of the spectrum. $\endgroup$ – Everyone Dec 18 '13 at 14:25
  • $\begingroup$ The same frequency may be used for several missions if the directions to ground station are different. $\endgroup$ – Uwe Mar 28 '18 at 13:31
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As yet I am unable to reply to the former two queries raised i.e.

  • Whether communication frequencies are allocated on a per-agency, or a per-mission basis.
  • Whether allocated frequencies are re-cycled after the mission

To the last question on the rationale behind allocation of micro-wave bands, here is what I found

Space communications are effected mostly through the radio part (It extends from frequencies below 1 Hz up to around 3000 GHz) of the Electromagnetic spectrum. More recently NASA demonstrated LASER communication on the LADEE.

Part of the rationale behind the allocation of frequencies for various services are the following

  • Propagation changes with frequency
  • Signal generation techniques differ from one frequency to another

The article referenced writes to say

Not all of the electromagnetic spectrum can pass through the Earth's atmosphere... There are in fact only two main windows of the EM spectrum that are open to space ...

Windows in the E/M spectrum open to space

Briefly, the use of higher frequencies allows

  • Larger bandwidths,
  • Better tracking capability and
  • Minimal ionospheric effects

It also requires greater pointing accuracy. A higher frequency means a smaller antenna on board the craft that may be pointed with a limited amount of motive power.

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