Questions tagged [radio-communication]

Using radio wavelengths to communicate between multiple spacecraft or between a spacecraft and the Earth.

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54
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3answers
16k views

How did NASA prevent third parties from spoofing Apollo communications?

The Apollo crews transmitted footage to Earth using SSTV, a ham radio technique that amateurs and pirates can use to send similar messages around the world. Did NASA have any technical ...
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Why would GPS availability be reduced by high demand (or solar eclipse)?

This Newsweek article states that "GPS...will likely be nonexistent near the eclipse zone" because of all the people going to that area. While it makes sense that cell towers might be overloaded and ...
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Has any spacecraft ever had the ability to directly communicate with civilian air traffic control?

Should such a contingency become necessary, mission control centers have the ability to contact (e.g. by telephone) civilian or military air traffic control centers, even those located in other ...
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1answer
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Why were there beeps punctuating the voice communications during missions such as Apollo?

Voice communication between ground and spacecraft during missions such as Apollo seemed to be always punctuated by beeps. What was the origin of these beeps? Were they some sort of unavoidable ...
27
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2answers
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How will the closure of the Arecibo dish impact deep space communications?

Earlier today, the U.S. National Science Foundation announced that it is decommissioning the Arecibo radio telescope. The 305 meter dish is famous for the 1974 message for extra-terrestrial ...
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Is Quantum Entanglement technology possible for interplanetary communication in future to achieve low real-time latency?

There is a small debate over the comment session in NASA Lands InSight on Mars video uploaded by JPL. The 1 minute and a half video is about the essential part of InSight's EDL event cropped out from ...
22
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1answer
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Was “I have the farts, again” broadcast from the Moon to the whole world?

The BBC News article Apollo in 50 numbers: Medicine and health says: When Apollo 16 commander John Young walked on the Moon, he shared his feelings on the new diet with his companion Charlie Duke. ...
22
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1answer
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Why was Canberra able to listen to Voyager 2 but not talk to it?

The New York Times's When Voyager 2 Calls Home, Earth Soon Won’t Be Able to Answer explains that because Voyager 2's trajectory has taken it way below the ecliptic, of the three 70 meter dishes in the ...
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Apollo communication between the Earth and Moon

How was it possible for astronauts to send back tv/radio signals to earth from the moon? I have just been teaching my son about waves behavior and understand that radio waves are reflected back to ...
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3answers
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Why not send Voyager 3 and 4 following up the paths taken by Voyager 1 and 2 to re-transmit signals of later as they fly away from Earth?

Voyager 1 and Voyager 2 spacecrafts are on their journey out of solar system. They collected so much of important data that helped us understand our solar system. As these spacecrafts moving out of ...
17
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1answer
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What is carrier lock and bit lock?

I'm not sure if this question belongs here or in Amateur Radio, but during the acquisition of signal from New Horizons on New Year's Day, I heard the controllers call out "carrier lock", "symbol lock",...
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How much RF transmit power does DSN need to send commands to Voyager?

I recently looked up how weak the Voyager signals are when they get to Earth from the 22 W transmitters (as of September 2013, it was roughly -245 dBm). But that got me wondering how many watts of ...
15
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1answer
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Did USSR discontinue radio transmissions, relocate ships, to aid the US in response to Apollo 13?

In this article there is following statement by Dr. Ernst Stuhlinger: Let me only remind you of the recent near-tragedy of Apollo 13. When the time of the crucial reentry of the astronauts ...
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709 views

Why have four parabolas on a ground-side array instead of just a single large one

An article on RT: Russia to stop ferrying US astronauts to ISS from April 2019, is accompanied by a photo of a ground-side radio array consisting of four separate parabolas merged into one pointable ...
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5answers
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What's stopping space probe communication from being jammed?

Space probes use radio waves to communicate back to Earth - I would imagine a probe sent many decades ago, using very little energy and from very far away would be sending an incredibly weak signal ...
14
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349 views

What exactly do they look for when searching for extraterrestrial intelligence?

There are some experiments and projects that are searching for extraterrestrial intelligence.(SETI) I want to know what signs exactly are they looking for? Do they just look for monotone sinusoidal ...
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392 views

How is RF spectrum usage coordinated in Mars orbit?

As of 2016 there are multiple operational missions in orbit around Mars. There are possibly more non-operational missions in orbit around Mars, simply because we do not know the final fate of all ...
13
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1answer
235 views

Does Mars Reconnaissance Orbiter require “reprogramming” when handling communications for newer spacecraft or landers?

While I was going through the question What happens to Insight's parachute? I learned of the role of the Mars Reconnaissance Orbiter to provide reliable communication between other Mars spacecraft and/...
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How to calculate data rate of Voyager 1?

I've read the following passage in the answer to the Quora question How can Voyager send a signal strong enough for us to receive, in spite of its enormous distance from us? And how can it have the ...
12
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1answer
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Has DSS-43 ever been used in high power mode (>>20 kW) for an emergency situation?

This answer notes that while most Deep Space Network transmitters are 20 kW of power or less, one dish (DSS-43 in Canberra) is equipped with a transmitter capable of 400 kW. As described in 101, 70-m ...
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860 views

Why doesn't thermal radio emission from a DSN “hot dish” completely swamp the benefits of a cold LNA?

The 70 meter DSN dishes are often used to receive the weakest signals, and so their receiver LNAs have cryogenic front-ends in an assembly that also contains a LHe refrigerator and vacuum system. If I ...
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2answers
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Why did Moon missions state their number in radio context?

I'm not sure if this still happens, so the question may be broader, but in the Apollo transcripts the astronauts would begin a call with something like "Houston, 13". I get that they may have been on ...
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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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What does “clearing of C-band spectrum” mean and why will it cost Intelsat a billion dollars?

From "Intelsat files for bankruptcy" One of the primary catalysts for restructuring the balance sheet now is Intelsat’s desire to participate in the accelerated clearing of C-band spectrum under ...
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Would an orbital Deep Space Network be more efficient?

Deep Space Network sites in California, Madrid and Canberra perform an excellent job, for example receiving from Voyager 2 (16+ billion km) at -150 dBm power. However, would it be more advantageous ...
9
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383 views

Do you need a “wire” on a Europa submarine to phone home?

In regards to Europa, what are the limitations regarding current data transmission technology. Say we were to have an orbiter circling Jupiter, a lander on the surface of Europa and a "swimmer" [...
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Could a smartphone really transmit to satellites in a space based internet system?

Space based internet systems, like the one recently proposed by SpaceX and Google, are said to use satellites to communicate directly with end users, without using cellular ground stations. But how ...
9
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1answer
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With the correct antenna and transmitter, could the Sojourner rover be reactivated?

The Sojourner rover was deployed as part of the Mars Pathfinder mission. At the end of the mission, the Sojourner rover was still operable. But the base station that the Mars Pathfinder carried failed....
9
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1answer
958 views

Why has the Earth's motion carried it out of view of Pioneer 11's antenna?

According to The Pioneer Missions, my emphasis, The Pioneer 11 Mission ended on 30 September 1995, when the last transmission from the spacecraft was received. There have been no communications ...
9
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1answer
565 views

How much power would an Alpha Centauri probe require for communication?

Project Longshot report (1988) says: A laser with an input power of 250 kilowatts would allow for a data rate of 1000 bits per second at maximum range." Yet Breakthrough Starshot website (2016) ...
9
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1answer
632 views

What is the highest practical data rate for a downlink from a spacecraft at a distance such as Pluto to Earth?

An answer to this question states that the expected downlink rate for New Horizons at Pluto encounter will be about 1,000 bits/sec. Understanding the issues of distant transmitters and data rates as ...
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Do satellite uplink/downlink signals spread or leak into space?

Satellite communication generally involves three types of nodes: the ground station (also known as teleport), the satellite in geosynchronous orbit, and the satellite receiver/transceiver. I am ...
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1answer
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When is a phased array antenna not a phased array?

This question is inspired by an answer to this question, where it is stated that: The real power of phased arrays is their ability to be steered electronically. This set me wondering about the ...
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2answers
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Encryption in radio system

We know that radio waves are used in communication with rockets, space crafts and satellites. Now, radio system basically consists of transmitter and receiver. If there is frequency match between ...
7
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1answer
347 views

Deep Space Network time budgets per spacecraft - is such statistics available?

Is statistics available about time consumed by different spacecraft for communication wint NASA Deep Space Network (DSN)? It would be interesting to compare which space missions are more downlink-...
7
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1answer
879 views

What Soviet signals (if any) attempted to scramble communication and sabotage Apollo missions?

The NPR.org news item and audio podcast JoAnn Morgan: The Only Woman In The Firing Room During Apollo 11 features an excellent interview with JoAnn Morgan and other KSC personal. It's a short but ...
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How many stations could one hear with an AM/FM radio in front of the ISS' cupola window?

Propagation of AM and FM radio signals up into the sky would behave differently than propagation along the surface of the Earth. As a Gedankenexperiment, if you were on the ISS and had an AM/FM radio ...
7
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1answer
710 views

How much power does the Voyager radio dish draw?

I found here and here that Voyager transmits its main radio signal at 23 watts. In other words, the strength of the signal coming from its radio dish is 23 watts. However, what I want to know is how ...
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How much power do missions to other planets use for radio transmissions?

How much power did the voice and data radios have on the Apollo missions? Additionally how much broadcast power is used on data transmissions from the surface of Mars?
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1answer
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Why is TESS' high gain antenna made of undulating BLACK fabric rather than metal?

above: from Facebook, then annotated. There is an excellent review of the design of the TESS spacecraft in G. R. Richter et al. Journal of Astronomical Telescopes, ...
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472 views

How would the Voyagers finally die if allowed to transmit to the bitter end?

According to this answer and this question the Voyagers will run out of power to "operate a single instrument" in 2025 for Voyager 2 and a little longer for Voyager 1. It is purported to be the end of ...
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0answers
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Can anything at Mars speak 900 MHz ZigBee besides Ingenuity helicopter and Perseverance rover?

Interest is piqued by What could be strong arguments against Ingenuity following Perseverance at a safe distance when the flight test program has been a success? Question: Can anything at Mars ...
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Hijacked space data, notable instances of recovering images or other goodies from someone else's space mission?

These are images taken by a Chinese cubesat in lunar orbit, taken again by a Dutch radio telescope. The original of this GIF was tweeted here and I've reconstructed it because I don't know how to ...
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2answers
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How are phased array antennas used in spaceflight? Benefits and limitations

It would seem to me that a phased array antenna would be great for spacecrafts since it removes the need to turn the entire spacecraft around in order to point the radio dish towards Earth. Many ...
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1answer
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Why were the two Quindar tones so close in frequency and not apodized?

This and this answer explain the function of the Quindar_tones within Apollo mission comms. At 2525 and 2475 HZ they are only 50Hz or 2% apart in frequency, and the duration is 250 ms or 0.25 seconds....
6
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1answer
842 views

How is a space probe's antenna directed toward Earth?

I wonder how is it possible to direct the probe's antenna from enormous distances (like Pluto) toward the Earth. Because if even an extremely small inclination in antenna direction emerge, it will ...
6
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Feasibility of Interstellar Probe Communication

So, I understand that to transmit information across interstellar distances, you need to use a lot of power (or less bandwidth?), something for example a small space probe wouldn't exactly have. If we ...
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1answer
873 views

Why such a large observed doppler shift from Apollo 17 orbiting the moon?

Following the links in this comment by @Uwe I've found some interesting sources of information on Ham (amateur) radio operators trying to listen in on Apollo transmissions. One of them is Sven Grahn's ...
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2answers
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Have solid dish antennas on deep space spacecraft (as opposed to meshes) ever provided any other helpful function? As meteor shields perhaps?

This answer to Which deep space spacecraft had main dish antennas that were perforated or made from mesh? tells the tale: Galileo's troubled high gain antenna was made from "a gold-plated ...
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When scientific and engineering data are sent from space probes, are the signals repeated to minimize transmission error?

I would think that this would be the case. In any one transmission there will be a systematic error due to the fundamentals of the transmitter / receiver. Is there also a transient or stochastic error ...