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Questions tagged [communication]

Questions regarding information transfer between spacecraft, and between spacecraft and Earth.

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What evidence would be needed to determine a signal was artificial in origin?

Humanity has received some odd signals in the past. We've also sent out some signals ourselves. How could we determine that a signal we'd received was artificial in origin? Or of course inversely, ...
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1answer
481 views

Has Earth ever sent out a repeating signal into space?

My understanding is that for us to confirm that a signal is of artificial origin, we have to get the same signal at least twice. However, as far as I can tell, most of the signals we've sent out to ...
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How does radar calibration using LEO orbited calibration spheres work?

On December 28, 2013 two Russian SKRL-756 calibration sphere satellites will be launched during the maiden flight of the Soyuz-2.1v, a brand new lightweight derivative of the Soyuz launch vehicle, ...
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1answer
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How many space-craft can a station on the DSN communicate with concurrently?

A bit of spin on Which LEO missions are currently supported by NASA's DSN (and why)? is what I have in mind. The Deep Space Network home-page writes to say Each complex consists of at least ...
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754 views

Which LEO missions are currently supported by NASA's DSN (and why)?

NASA's Deep Space Network, a collection of antennae throughout the globe, is sometimes used to support earth-orbiting missions: The NASA Deep Space Network - or DSN - is an international network of ...
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1answer
234 views

What is the rationale behind the allocation of micro-wave bands for space communication?

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 ...
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350 views

Do lunar landers communicate with ground stations during descent and landing?

In about one day China's Chang'e 3 will land on the moon in a fully autonomous way, which is pretty exciting and I think especially the autonomous hazard avoidance system is just amazing. However, I ...
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1answer
148 views

How would critical refractivity of radio waves on Venus be overcome?

Rereading my answer here and in particular, rereading the article Optical and Radio Refraction on Venus (Stratton, 1968) it is my understanding that there is significant refraction of radio waves, as ...
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3answers
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How did NASA achieve their live TV broadcast in 1969?

In 1969, NASA not only went to the moon, but broadcast the whole thing live on TV. How did they achieve the TV broadcast? What technology did they need to use to send a video and audio signal from ...
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2answers
470 views

Interstellar eavesdropping

For about a century, humanity has broadcasted noise to space in the form of TV broadcasts, radio, etc... The nearest star is 4.242 light-years away, so for about 90 years, aliens -- if they exist in ...
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262 views

Where can I find relevant papers describing the cryptographic algorithm(s) and/or techniques used within KY-171 and KY-172?

The KY-171 Audio Frequency Coder was used for the NASA Project Mercury (1958-1963) to encode radio traffic between ground stations, as well as between ground stations and the space capsule. It was ...
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2answers
864 views

What language does ISRO use for radio communication?

Wikipedia lists both Hindi and English as the official languages of ISRO. But what language does ISRO use for radio communication? Say they launch a manned mission, which language would they use to ...
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What is the procedure if communication with the ISS is lost for an extended period?

Between ground control and the ISS there is the occasional short communications loss which they are obviously able to deal with, but is there a procedure to follow if the communication is lost for ...
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1answer
724 views

Resilience to data transmission errors of the Juno spacecraft

What techniques have been employed for the Juno spacecraft to successfully transmit data packets back to Earth once she's in a polar orbit around Jupiter? Jupiter is a strong source of radio ...
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2answers
785 views

Commercial TDRSS alternatives?

NASA's Tracking and Data Relay Satellite System (TDRSS) is a space-based relay system at geostationary orbit. If one has, for instance, a LEO mission, and one's coverage requirements can not be met by ...
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988 views

Long range laser communication beam divergence angle values?

NASA has been working on demonstrations of laser communication with satellites. The motivation is simple, in that lasers see less power loss because they spread over a smaller angle. That raises the ...
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1answer
641 views

What, if any, mechanisms prevent unauthorized commands?

Since deep space probes and satellites receive commands from Earth via radio, what prevents unauthorized commands from being accepted by such devices? For deep space probes, the required power of ...
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3answers
2k views

How would we communicate over light years?

Anyone who has been in an email conversation where the chain split into different threads, or has been in chat where they receive two diverging comments requiring a response before a reply to the ...
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How much power loss does the LLCD suffer in transit?

Space.com writes to say (freeform improved quote): The LLCD (Lunar Laser Communication Demonstration) space terminal is designed to beam data from the moon at a rate six times faster than the best ...
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366 views

Does man send any signal to attract aliens?

Does man send any signal (such as electromagnetic radiation) to space to attract aliens?
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1answer
1k views

Decoding Russian ISS telemetry

While the American segment of the ISS has data published on-line (http://spacestationlive.nasa.gov), the same cannot be said about the Russian segment. It is known that telemetry is transmitted to ...
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What communication protocols are used with latencies going into hours? [duplicate]

What communication protocols are used to communicate with probes that are many light minutes or even hours away? Not only the signal will be weak and badly damaged by background noise, we can't just ...
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1answer
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Did Curiosity rover communicate to the ground station during its descent phase?

During descent phase and entering Mars' atmosphere, was the rover's descent controlled by the Earth based ground station, or by the rover itself? What are the technical challenges, when communicating ...
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What frequency wavebands are used for communication in LEO?

What are the most commonly used wave bands for communications between satellites in LEO and ground station, and what is the minimum frequency used?
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Do all satellites and space probes have high & low gain antennas and what are their functions?

What is the main function of high and low gain antennas? Do all satellites and space probes have high and low gain antennas?
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1k views

How is data transferred from interplanetary missions?

I'm trying to find out information about the mechanics of data transmission from planetary probes: techniques, devices, methods, software. In short, How reliable data transmission is undertaken in ...
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1answer
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How does Voyager 1 send signals to Earth?

I recently studied that Voyager 1 has traveled a distance of 125.01 AU as of August 3rd, 2013. I wonder, how would it be able to communicate with the Earth? How much time does it take for the signal ...
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Cubesats in lunar orbit and beyond - how does communication work?

Somewhere I read that there are serious plans to send a cubesat into lunar orbit. A few years ago, the ISS was also offering a launch opportunity for such a mission. I guess that it was actually ...
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627 views

Alternative data transfer channels for inter-stellar probes?

The problem how it is possible to receive data from Voyager I at all is dealt in this question: https://physics.stackexchange.com/questions/13227/how-earth-communicates-with-voyager-i However, there ...
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1answer
300 views

How to design a spacecraft to cope with redshift?

Redshift occurs whenever an observer moves away from (shifted to the red) or approaches (shifted to the blue; blueshift) an object that emits radiation and the other way around. Traveling towards ...
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489 views

Techniques for digital superluminal communication

Considering photons only travel at the speed of light (and cannot travel faster), our main technique of digital communication (at least I believe, but I could be wrong) is off the table. What ...
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2answers
1k views

What data compression algorithms have been successfully used in spacecraft?

Scientific spacecraft can generate very large amounts of data. However, both the storage available onboard the spacecraft and the bandwidth available to transmit the data to ground stations are ...
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3answers
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VLB interferometry in deep space - does it make sense for communication?

This is something I was thinking about right now when this beta was opened ... perfect! In radio astronomy, there is an technique which is called very long baseline interferometry. The idea is to ...