I have just come across this wind sound coming from pressure sensor of Insight lander which is in Mars at the moment.

I know basically that AM, FM, PSK, FSK ect. all have disadvantages and advantages depending on the bandwidth, terrain, distance ect. I'm assuming between the planets or the moon the scenario is more likely pure line of sight with plane waves but have no information on the topic even in a basic level.

What carrier frequency and what type of modulation technique could they be using for such radio transmission?

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    \$\begingroup\$ This is far too broad, as there are multiple communication systems on such missions! But rest assured: the analog vs digital war was over in the 1980s, when we proved that under the same noise, one could get more out of a channel when using digital modes (allowing channel coding), not only on paper, but also practically. So, at least definitely no AM or FM. \$\endgroup\$ Dec 8, 2018 at 2:21
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    \$\begingroup\$ about 8GHz for downlink and uplink; the antennas need to be quite directional, for high speed; the Pluto downloads were only 100 bits/second and took weeks to send the many photos. \$\endgroup\$ Dec 8, 2018 at 3:05

1 Answer 1


For science data these days, the preferred frequency band for Earth-bound links is X-band for numerous reasons.

  1. Relatively unaffected by atmospheric conditions (on Earth), unlike Ku/Ka which are subject to severe attenuation through rain.

  2. Higher frequency yields higher antenna gain at the probe (rocket fairing constraints limit diameter of antenna, and nobody wants a repeat of what happened to the Galileo probe). X-band again is a decent compromise.

  3. For the Mars Menagerie there are multiple frequency bands in use from UHF to Ka band, primarily between the ground-based probes and the orbiters which can serve as store-and-forward systems. Again the primary Earth link is X-band.

  4. The X-band technology is pretty robust, but there have been tests of optical (laser) communications links, however no interplanetary probe has used this as the primary data link. The Psyche probe is scheduled to have optical capability for deep space testing. Again the problem with optical wavelengths is the atmospheric uncertainty, which would put such a station up on a mountain range such as Atacama desert for utilization. Most likely the practical configuration will be to have a satellite (network) receive the deep space signal and retransmit to the ground using a more powerful signal (since the path length is much shorter, and the local satellite can have rather large solar panel efficiency).

  5. It would be difficult to locate enough atmospherically clear areas around the world to provide the same coverage as the existing DSN system. On the other hand the sites would not take up nearly as much room.

  6. There can be other narrow-band links at other frequencies for telemetry, command and control, emergency operations.

  • \$\begingroup\$ If two points in space are very very far from each other a small movement will cause a huge angular distance error. If the directivity is very high isn't it very hard to achieve aligning the receiver and transmitter antennas where one here in Earth and the other in Mars? \$\endgroup\$
    – user16307
    Dec 8, 2018 at 3:20
  • \$\begingroup\$ For current systems the Earth-side antennas will have both high resolution (0.001 degree) position encoder systems, and will also have a monopulse feed structure which allows the control system to automatically follow the wavefront as it comes in. On the probe side, it's not nearly as critical, as a 2.4m dish will have a pretty wide beamwidth (relatively speaking); an optical system such as a star-tracker allows the probe to know which direction to point, for fly-by probes it's not a huge deal, but for orbiters the propellant consumption budget is always something you have to deal with. \$\endgroup\$
    – isdi
    Dec 8, 2018 at 3:39

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