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I am currently designing specifications for a human-inhabited station on Mars. Said station would require communications with Earth, to do so requires power. Apparently, a radio telescope is capable of transmission of data. But power is the main concern at the moment; I have not decided on a power source yet. To do so I need to know a radio telescope's peak power consumption to make sure that the lights on the rest of the station don't go out, or, more importantly, the lithium-ion cells are not overloaded (they are apparently combustible).

I would like to have communication speeds close to 256kbit/s (the average uplink speed for satellite internet), and a dish diameter of 30 to 50 meters (which should work for both Earth-Mars comms and some radio astronomy).

Alternatively, if you have suggestions about more effective ways of communication with the Earth from Mars, please let me know and I'll edit the question accordingly.

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  • $\begingroup$ The power you need will depend on many different factors. The biggest two are 1) nature of, size of, and cost of your broadcasting antenna (single dish, array, something clever, or possibly an optical comms system) and 2) the data rate. Higher data rate needs higher power if everything else is equal. If you think about it, there is already plenty of data being sent from Mars regularly from combinations of RTG and modest solar panel-powered rovers and orbiters. If you can live with the current data rate, then you don't have anything to worry about. And it will get even better with optical! $\endgroup$ – uhoh Jul 22 '17 at 16:27
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    $\begingroup$ Oh, 3) size of the receiver on Earth of course! Signals from orbiting spacecraft and sometimes from rovers are received on Earth because of large 30 to 70m diameter dishes. There are of course plenty of other factors, but you need to choose the aperture sizes at both ends plus the bandwidth before you can calculate power. $\endgroup$ – uhoh Jul 22 '17 at 16:32
  • $\begingroup$ @uhoh My idea was that the data rate as seen in satellite internet access is good enough. According to my calculations, at 256kbit/s, about 18.6 hours is needed to transmit a 2GB file of a 2-hour movie. As for the dishes, I am thinking of somewhere from 30m to 50m of diameter; both not overly heavy and (approximately) good for radio astronomy too. As for optical comms, I haven't seen many ideas on that. I think it would be effectively shooting lasers, but when we tried that last time, it didn't end well. $\endgroup$ – Danya02 Jul 23 '17 at 15:26
  • $\begingroup$ OK then, you should go back and put all of this into your original question in a clear & organized way. The more effort you put into describing exactly what it is you would like to do, the more likely you are to get a really helpful answer. You can look around here and get a feeling for how other questions are written. The short questions are usually very specific, but for the most part, people add plenty of information in their question in order to receive well developed answers. Welcome to stackexchange, and if you haven't already, take the tour! $\endgroup$ – uhoh Jul 23 '17 at 18:20
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NASA's Mars Reconnaissance Orbiter currently transmits data at up to 6 megabits per second using a 3 meter (10 foot) diameter dish antenna deployed from its stowed (not folded) position shortly after launch, and Traveling Wave Tube (TWT) amplifiers that transmit radio signals at a power of 100 watts, when communicating with the Deep Space Network antennas back on Earth. MRO gets all of its electrical power from two solar panels (folded and stowed for launch), each of which produces more than 1,000 watts of power at Mars. Where the entire spacecraft power budget is approximately 2kW, the transmitters have to be consuming considerably less than that.

MRO launch configuration
MRO launch configuration illustration

If you want to have a radio telescope to use for radio astronomy work, you would probably want to keep that separate from your communications antenna if you can (so they can be pointed independently), and have the two antennas as widely separated as possible, to minimize transmitter interference from affecting the observational work.

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    $\begingroup$ Good answer, but note that spacecraft often have components that use considerably more power than the solar array collects, for short periods of time. It's supplied by batteries that are gradually recharged from the solar or RTG power source. That said, I agree that MRO's TWTAs use well under 2 kW. Per this DESCANSO paper the X-band TWTA has 100 W RF output and they're usually in the realm of 40-50% efficient, so ~250 W input power is a reasonable guess. $\endgroup$ – pericynthion Jul 24 '17 at 20:24
  • $\begingroup$ @pericynthion That's a useful link. Thank you. (N.B. - the same link in my answer pointing to the antenna details is used as the amplifier data link on the page where I found it, the amplifier output is described below the antennas - but in a more "public oriented" fashion.) $\endgroup$ – FKEinternet Jul 25 '17 at 4:08
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DSN dishes (the largest of which are 70 and 36 m in diamter) use up to 20 kW to communicate with deep-space missions including Voyager and various Mars missions. On the DSN Now site, you can see how much power a DSN dish uses for each contact.

So that should give sort of an upper bound: if you use a 36-m dish, you can get away with using a tiny antenna on Earth. In practice, you want the biggest dish to be on Earth (construction is much cheaper here). For a simple manned mission, a 5-m parabola with a low-powered transmitter (100 W or less) should be feasible: you can build a folding construction that fits inside a reasonably-small lander.

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  • $\begingroup$ According to deepspace.jpl.nasa.gov/dsndocs/810-005/101/101E.pdf page 13 there is also a up to 400 kW transmitter for DSS-43 $\endgroup$ – Uwe Jul 24 '17 at 16:39
  • $\begingroup$ Yes. I ignored that because that's only used in emergencies, to contact deep-space missions via their medium-gain or low-gain antennas. $\endgroup$ – Hobbes Jul 24 '17 at 16:42

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